Posts Tagged ‘moly grease’
El Gamo 68/68-XP — A futuristic airgun from the past: Part 6
by Tom Gaylord, a.k.a. B.B. Pelletier
Part 1
Part 2
Part 3
Part 4
Part 5
El Gamo 68 is a futuristic breakbarrel from the past.
I last reported on this rifle on August 8 of last year. And that was Part 5! I had just tuned the rifle with a new mainspring and proper lubricants and was wondering what the changes would be. I was ready to report on it several months ago when I discovered that it wouldn’t cock. After fiddling with the trigger adjustments awhile with no success, I set it aside and moved on — thinking that the gun would need to be disassembled.
I disassembled it last week and discovered there was nothing wrong! The sear was working properly, or at least it seemed to be when I played with it as the gun was disassembled. I relubricated everything and put it all back together and was going to write Monday’s report on it. But the trigger still didn’t work! ARRGH!
This time, I remembered that when I got the gun the trigger was also a bit iffy, so I fiddled with the adjustments WAY outside the normal realm and, presto! I got it working again. Oh, it took a couple hours and there were some accidental discharges when the barrel was closed (direct sear!), but I solved all that by giving the sear way more contact than it needs.
Now the trigger releases at about 12 lbs., but at least it’s safe. Today, I’ll share with you how the tuned gun does at 25 yards — heavy trigger and all.
One other thing I did to the rifle was lubricate the leather piston seal with 10 drops of 3-in-One oil, leaving the rifle standing on its butt for two days afterward. The oil was allowed to slowly soak into the leather, which it did, but to protect the carpet and walls (Edith–Are you listening?) I put a long drop cloth in front of the rifle when I shot it.
Today’s test is a deviation from my normal pattern. I’ve tuned this gun and not yet reported the new velocities, and yet here I am shooting for accuracy. I decided to do it that way; and if I got good results, I would test the velocity next. I’m not changing the usual way of doing things — this is just an exception.
RWS Hobby
The first pellet I tested was the RWS Hobby. I chose it for its light weight and because it’s often accurate in lower-powered spring rifles and pistols. Sitting 25 yards from the target, I have to admit that I was wondering if the rifle had enough power to hit that target — let alone shoot a decent group.
Five of the first 10 pellets were detonations from the oiled piston seal. And the smell of burning oil was in the air. The Hobbys landed in a vertical group that was pleasingly tight from side to side. I was prepared to blame the verticality on the dieseling, but the truth is, that wasn’t the problem. The gun just doesn’t want to shoot Hobbys at 25 yards. That’s not too surprising since 25 yards is about the maximum distance for any wadcutter pellets, in my experience.
Ten Hobbys made this 2.151-inch group at 25 yards.
Air Arms Falcon
The second pellet I tested was the Air Arms Falcon, a 7.3-grain dome that’s often accurate in spring rifles. I used the spotting scope only on the first shot, which was a detonation, to make sure it was on the paper. There were 4 detonations in the 10 shots. I didn’t look at the target again until I walked down to change it. Boy, was I surprised by what I saw! To paraphrase Crocodile Dundee, “Now, THAT’S a group!” For open sights at 25 yards and 65-year-old-eyes, it ain’t too bad!
Ten Air Arms Falcons went into 0.898 inches between their two widest centers. This is an acceptable group for this rifle at 25 yards.
Remember, I’m shooting 10 shots — not 5. So this kind of group really proves the rifle can shoot. It also proves this old man can still hit things when the rifle does its part! So much for the problems of the droopers and gas springs! I needed this validation after some of the disappointing tests I’ve done recently.
The heavy trigger apparently is not causing much of a problem for me. I think that’s because the rifle is rested. If I were shooting offhand, I’d want a lighter trigger-pull.
JSB Exact RS
Next, I tried JSB Exact RS pellets. This is another 7.3-grain dome from JSB (JSB also makes Air Arms Pellets) and is very often accurate in many different airguns. And this is one of them. The group is slightly larger than the Falcon group, but the two are so similar that I would call it a tie.
Ten JSB Exact RS domes went into 1.028 inches. Though not quite as small as the Falcon group, I would rate both pellets about equal in this rifle.
RWS Superdome
The last pellet I tried was the RWS Superdome, which often does well in lower-powered spring rifles. This time, however, it didn’t. Ten pellets produced a 1.765-inch group. It didn’t disappoint me, though, because the Falcon and JSB RS groups looked that much better. It showed that the earlier Hobby group wasn’t just a fluke of bad luck — the gun simply likes what it likes.
Ten RWS Superdomes made this 1.765-inch group.
Evaluation
This test was calming for me. It was slower than many of the tests I’ve run in the past month, and the results were more based on me as a shooter rather than on the equipment. I find that I like that a lot!
The El Gamo 68 XP is operating well right now, except for the heavy trigger that I’ll probably keep just as it is for a while. The tuned powerplant is now smoother with less of a jolt. I noticed in this test that each pellet has a firing characteristic of its own. The two JSB pellets were definitely the smoothest of the four tested, and the Hobbys were the roughest.
This is such an odd airgun, with the fat heavy butt and no forearm to hold. Yet, it shoots like a thoroughbred. With the new tune, it cocks smoothly and just feels good to shoot — I don’t have any better way of describing it. I wish you could all try one, but since you can’t, I will, again, recommend the Air Venturi Bronco, which is the closest thing still being made today.
What is a tune?
by B.B. Pelletier
Announcement: Bill Cardill is this week’s winner of Pyramyd Air’s Big Shot of the Week on their airgun facebook page. He’ll receive a $50 Pyramyd Air gift card. Congratulations!
Bill Cardill submitted this week’s winning photo for BSOTW.
Tune is slang for tuneup, and in airguns a tuneup can range from a quick lubrication all the way to a major overhaul of the powerplant and trigger. Everything in between these two extremes is also fair game. So, lesson one is that a tune can be anything that changes and hopefully improves the airgun’s performance.
I’m going to address a breakbarrel spring gun in today’s report. Other powerplants can also be tuned; but the steps are different, and the results will differ from what you get with a spring gun tune. Since the majority of airgun tunes are performed on springers, it’s appropriate to look at them first. And the breakbarrel is the No. 1 type of spring gun.
Victor asked what was meant by a tune, but I suspect that others would like to know what’s involved, as well, so today we’ll look at airgun tuning in all its complexity. Let’s begin with a brand-new spring gun and see why we would tune it and what might be done.
Smoothing the edges
Most new spring guns have sharp edges on all the mating powerplant parts. Sometimes, these edges interfere with the movement of the parts. These edges are worn down during a long break-in period, which is why a gun gains velocity as it wears in. But you can also remove these edges and burrs with small files, and that is one thing that a tuneup can do.
Key places to look are the cocking slot, the piston slot, the cocking linkage and, if there’s an interface between the linkage and the piston, that’s a prime place to look for burrs and sharp edges. The forward edge of the cocking slot is especially important, because it can slice a new piston seal when it’s installed…and that will ruin the seal. The end cap and sides of the trigger mechanism should also be checked.
The action forks that the pivot bolt passes through is another place to look for burrs and sharp edges, as well as the sides of the baseblock that the barrel is pressed into.
There are also burrs and sharp edges that don’t affect the operation of the powerplant. These do not go away with use and they can be left alone if you like. However, if you plan to take the powerplant apart in the future, these edges and burrs will be waiting to cut you.
Lubrication
Probably the most common thing done during a tune is lubrication. New guns can have either too much grease or not enough. And most of them have the wrong kind of grease. The factories use a general machine grease, but there are much better greases that can be used.
For metal-to-metal contact, nothing is better than grease that contains a high concentration of molybdenum disulfide. Moly isn’t a grease — it’s a solid particle that’s ground very fine and mixed with grease for application. When it comes in contact with metal under some pressure, the particles bond with the metal on the surface, forming a layer of extreme low friction. That layer is durable and allows other metal to slide across the surface it’s on.
We don’t appreciate how low-friction moly is, because the grease it’s in raises the coefficient of friction. But custom tuners are known to burnish certain parts of a gun — like the inside of the compression tube — with dry moly particles. This process takes a long time, as the moly doesn’t want to cooperate; but once it’s, done you have a surface with very low friction. Jim Maccari and I split a pound of moly powder, and my half was in several large bottles. It’s a lifetime supply for a full-time tuner!
Another place where moly powder comes into play is on the mating trigger sear surfaces. I’ll have more to say about this in a moment, but this is a custom tuner’s trick. The action fork and baseblock can also benefit from a burnish of moly.
I don’t burnish anymore, though. Moly grease, such as Air Venturi Moly Paste, will do the same thing over time as it gets worked into the action through the process of shooting.
But not every springer needs moly grease. The older guns with leather piston seals actually do better with a white lithium grease. The grease serves as fuel for the constant dieseling of all spring-piston guns, and leather seals burn more fuel than synthetic seals do. For this same reason, I lube the mainsprings of the lower-powered springers like a Diana 27 with the same white lithium grease.
Does it bother you that I said all spring piston guns diesel? Well, they do. Don’t confuse dieseling, which is normal and even good, with detonation — which is when you here a low bang. That’s too large an explosion for your gun, and you don’t want to do very much of it.
The barrel pivot and the forks through which it passes is another place to grease. The right grease (moly) applied here reduces the cocking effort by 10 pounds!
The mainspring is the other place that gets lubed, and often it’s to stop the vibration, though I’m going to tell you in a moment a better way to do. For this, people use black tar, or what Jim Maccari calls Velocity Tar. It’s just a very viscous grease with a high adhesion that feels tacky to the touch. Farmers and heavy equipment operators know it as open gear lubricant. Most of the different greases like this will slow your gun to some extent, but there are products like Velocity Tar which, if used sparingly, seem to not phase the velocity at all.
Remove all the play
Okay, lubricating a gun to smooth the firing cycle is a redneck approach. Many people, including me, do it that way. But there’s a more elegant way if you’re willing to work. That way is to remove all the play in the various moving parts. The piston and mainspring are the primary parts involved.
The piston in a factory gun fits well inside the spring tube, but there’s a looseness to allow for manufacturing tolerances. The piston seal takes up a lot of the slack, but it’s located just at the front of the piston. The rear is free to move in all directions. While the space is small, this is where some of the vibration comes from.
To tighten the piston, it’s possible to put small bearings at the front and rear of the piston. These are usually small, round spots of synthetic material such as Teflon or nylon. Typically, three are placed at the front and three more at the rear. They are spaced evenly around the piston body, and the front ones are offset from those in the rear. If they fit the spring tube exactly, the piston rides on them, and then a moly coating really does its work.
The next critical fit is the mainspring, and here it’s sometimes possible to buy a spring that fits the spring guide in the rear and the piston rod in the front very tightly. Tuners call this close fit being “nailed on.” When you have a close fit like this, good moly lubrication is essential, or the close fit of steel on steel will cause galling, which is a form of burnishing that causes friction, vibration and excess heat.
If you can’t find a spring that fits this tight, you can always have a custom spring guide made that does fit the spring you have. Then, inside the piston, you can put a steel shim that fits between the mainspring and the inner walls of the piston. It’ll look shoddy; but once the powerplant is together, it’ll stay in place. And moly is essential here for the mainspring and the guide. This is called a “beer can” tune, because people often use cans to make the shim.
Another trick people use is to put shims behind the mainspring on the spring guide end. This puts the mainspring under more tension and gives more power. You have to make sure there’s enough room to cock the rifle when doing this, because it’s possible to shim the spring too much.
New airgunners assume that the stronger the mainspring, the more powerful the airgun. That isn’t always the case. Piston stroke has more to do with power than the spring rating. I always look for a weaker spring because I know it won’t subtract that much power from the gun. A coating of tar will do more to slow down a gun than a weak spring, as long as the spring fits well.
A final word on the mainspring is to notice that each end is usually a different size. Try to match the end with the spring guide or piston rod that fits best.
Piston seals
Piston seals used to be a real big reason for tuning a spring gun, because they wore out or melted from friction. Today’s seals are pretty well made, though there will always be some cheapies that come to market from time to time. The thing about the piston seal is to ensure that it fits the bore of the compression tube without adding too much additional friction. Some is unavoidable, but it’s easy to go overboard. The modern parachute piston seal that expands as it compresses air is very sophisticated, and shouldn’t be too difficult to size correctly. To reduce the diameter, put the seal on the piston and rotate the piston against sandpaper. Be careful to keep the sides of the seal parallel to the compression chamber bore while doing this. It usually only takes a minute or two for this job.
Trigger
The trigger can be adjusted and lubricated during a tuneup. I lubricate with moly grease, because a trigger is not a part that works by friction. No matter how low you get the friction, the trigger should always be safe…but this is a place where home tuners often have problems. They either stone or file the mating sear surfaces and put a dangerous angle on them. Then, they lubricate them with moly. These are the triggers that slip when cocked.
People are also known to adjust a trigger to have too fine mating surfaces, and once more, they’ll slip when cocked. My advice is to lube first, then let the trigger work for several hundred shots before you adjust it. I would keep stones and files away from triggers unless you’re certain that you know what you’re doing.
Breech seals
This part is often overlooked and can sometimes give you a large boost in power. The breech seal doesn’t have to stand proud of the breech to work well. It all depends on how the gun is designed. But don’t overlook the possibility of improving performance by raising the breech seal a few hundredths of an inch.
I hope this report answers most of the questions you have regarding tuning an airgun. As I said at the start, a tune can be any of these things, or all of them. A professional tune is usually all, but you should discuss the specifics with your airgunsmith before letting him start the work.
Crosman’s 160: Part 2
by B.B. Pelletier
Fresh from the closet, another fine Crosman 160 emerges into daylight. We’ll watch this one blossom.
Today, I’ll report on the cleaning of Jose’s Crosman 160 and the adjustment of the trigger. This rifle was quite rusty when I got it, so today it came out of the stock for a thorough cleaning. The barreled action comes out of the stock by removing one nut on the bottom of the forearm and by removing the safety switch. To remove the switch, it must be turned toward SAFE while you push it out of the triggerguard. It will pop right out when you get it in the right position.
The broken safety has been pushed out, and the nut removed from the stock. That’s a new safety to the left of the broken one. The barreled action is now ready to come out of the stock.
Once the action was out of the stock, I could see that it was far rustier than I originally thought. The rust that could be seen when the rifle was intact was just surface rust, but the stock was hiding deep active rust that had to be removed.
This was under the stock — heavy, active rust that must be dealt with!
I used Ballistol and a special scrubbing pad I bought at a recent gun show. A friend of mine says this pad looks like a stainless steel pot scrubber. All I know is that it removes all the rust and doesn’t harm the blue.
I used Balistol in a spray bottle and a special metal scrubber to remove the rust.
I was surprised at how fast the rust was removed. In all, it probably took no longer than 15 minutes to completely clean all the metal parts.
The trigger
With the gun finally clean, it was time to address the trigger. I mentioned in Part 1 that this trigger is one of the finest ever put on an inexpensive air rifle, and it can be adjusted to a very light, crisp pull. When I got the gun, the single-stage trigger had lots of creep and was breaking at 5 lbs., even. Something had to be done about that.
The Crosman 160 trigger is an adaptation of a 15th century crossbow trigger, where a rotating piece called a nut forms the sear that releases the hammer — in the case of the pellet rifle. The nut is a lever that’s shaped like a circle. It allows a small force (the sear) to overcome a greater force (the hammer spring) through leverage. No filing or stoning of the trigger contact surfaces is necessary, because the trigger doesn’t work like a conventional one.
From Sir Ralph Payne-Gallwey’s book, “The Crossbow,” (published in 1903) this illustration of a 15th century crossbow nut shows how a great force can be overcome by a smaller one.
But the Crosman 160 trigger is more sophisticated than the crossbow trigger. It allows the adjustment of the sear contact area and also the point at which the trigger stops. This gives the shooter a safe trigger that breaks cleanly, yet feels like an expensive precision target trigger.
The trigger in the subject rifle was about as filthy as I’ve ever seen. This trigger has a sideplate that allows the user to watch the adjustments of the parts and even to cock and fire the trigger with the parts exposed. Normally, this sideplate keeps the parts inside pretty clean, but you can see from the photo what I saw inside this one.
I’ve removed the trigger unit from the action here. It isn’t necessary to do this, and in fact you must be able to cock the rifle when you adjust the trigger, so leave it connected. I did this for cleaning purposes.
Compare this photo to the previous graphic, and you’ll see all the important trigger parts. This is before cleaning. The rusty red part at the upper right is the nut that’s the sear.
I removed the trigger blade from the trigger assembly and cleaned it outside the trigger box, but all other parts were cleaned where they were situated. Ballistol on cotton swabs worked wonders at removing the rust, dust and dirt. And it left all the parts with a lubricated surface.
The two trigger adjustment screws were stuck in place by dried grease, so Ballistol had to dissolve that before I could clean the threads. The final touch was to apply moly grease to the mating surfaces of the trigger blade and the rotating nut that serves as the sear. Then it was time to adjust the trigger.
Trigger adjustment
The first step was to back off the trigger return spring, which is located at the bottom rear of the trigger box. With this spring relaxed, you can feel the engagement of the sear much better.
Next, I adjusted the top screw, which adjusts the trigger/sear contact area. I set it very quickly because I’ve adjusted dozens of these triggers over the years and I know what they need. You may have to adjust the screw then cock the rifle and fire it several times to get the engagement you want. The engagement needed is very narrow, and it looks like the trigger is about to slip off the sear; so I always give the cocked rifle a bump test after adjusting the trigger, just to be safe. If I can’t jar the trigger off the sear, it’s safe.
The final screw to adjust is the trigger stop or overtravel screw. It stops the trigger blade after the sear has released, and the closer this is to the release point without impeding the trigger-pull, the better the trigger feels. Once the engagement area is okay, it’s easy to set this screw to stop the trigger immediately following trigger release.
With that done, I put the cover plate back on the trigger and shifted my attention to the S331 sight. By the way, Robert of Arcade explained in a comment that the S331 sight was actually made by Mossberg and not by Williams, as I originally said in Part 1. I changed the maker to Mossberg in Part 1, and now I’m telling you.
The rear sight on this rifle was loose when I examined it, so I removed it from the rifle and disassembled it for cleaning. Most of the parts are aluminum, but a couple are blued steel and suffered from rust to the point that there were pits left on their surfaces after the rust was removed. The detents are very crisp and easy to feel as you make the adjustments. This is a simple peep sight assembly, but it works very well and adjusts precisely, which is all you can ask of a sight.
Once the sight was clean and back on the rifle, I put the barreled action back into the stock. I had to use the old broken safety switch because the replacement I have is slightly too large to fit the hole. I’ll trim it down in a separate session so the gun has a complete safety switch. For now, I’ll just keep the rifle off safe.
How does it look?
Because the bulk of the deep rust lies below the stock line, the deep pits that appeared from cleaning do not show. What was above the stock line was mostly just surface rust that’s now completely gone. The metal on this rifle now appears to be 80 percent or better. The stock finish is still flaky and needs to be taken down all the way with sandpaper and reapplied, but it doesn’t detract from the rifle’s appearance.
And the trigger?
The trigger now breaks at one pound, even. It’s glass-crisp, and you would swear that it releases at just a couple ounces if you didn’t see the trigger-pull gauge. I think the owner will be amazed at the transformation this rifle has undergone.
Yet to come
I won’t bore you with the other mundane jobs like the safety and the stock finish, but I’ll test this rifle for accuracy. So, there’s one more report yet to come. We already know the velocity is in the right ballpark — 656 f.p.s. for a 14.2-grain Daisy pellet on a 90-degree day. But I want to show you the accuracy these old rifles can give with modern pellets.
El Gamo 68/68-XP – A futuristic airgun from the past: Part 5
by B.B. Pelletier
El Gamo 68 is a futuristic breakbarrel from the past.
I’m sure many of you imagine that I’m immersed in airguns all the time, which is true. That my office is filled with all sorts of models (it is) and that my workshop bench is strewn with parts of projects in process. There’s just one problem with that view. I don’t have a workshop. When I really need a lot of room, such as for today’s report, I usually move to the kitchen, where I do my work on that time-honored bench — the kitchen table!
The other thing most readers don’t appreciate is how whipsawed I am with time. I can’t afford to spend a week or even two days on a project anymore. Back in the days of The Airgun Letter, I had one month to crank out the stories that are now written in about four days! If I spend more than three hours on a project before starting to write about it, I’m working on a 12-hour day because the writing and photography take so much more time than the actual testing. And so it was with some trepidation that I approached today’s report, which is a disassembly, evaluation, cleaning and lubrication of my Gamo 68 breakbarrel air rifle.
I wanted to do this because the 68 shoots very suddenly. It doesn’t vibrate like many spring guns, but the thump when it fires is very heavy — way out of proportion with the power of the gun. The trigger is very heavy, and I wanted to see what might be involved in bringing it down. It’s crisp enough, just too heavy for the release.
Because of the potential time element and the fact that I have no room for another disassembled airgun, I studied the rifle carefully for two months — the way a diamond cutter examines an important stone. And with all that study, I still did not recognize the way the gun is assembled. But one look at a schematic sent by David Enoch showed me what to do.
Only three screws have to be removed to take the action out of the stock. That’s no different than any other breakbarrel, but the location of the third screw is certainly different! It’s at the back of the spring tube.
This photo shows the action out of the stock. One extra screw was removed. The one below the triggerguard does not hold the action in the stock. It’s one of two screws that hold the trigger unit to the stock, and it doesn’t have to be removed to get the action out of the stock.
With the action out of the stock, you have access to disassemble the mechanism and do what I ended up doing to the rifle. The trigger is really a complex bullpup unit that’s entirely separate from the barreled action. By “bullpup,” I mean that the trigger blade does not directly contact the sear. It’s located many inches forward of the true sear and is connected by a long lever inside the trigger unit. If I want to improve the trigger-pull beyond what simple adjustment can do, I need to remove this unit from the stock to get access to the pins and levers.
I decided to leave that task for another day, as working on the powerplant was all I had time to do in this session.
You’re looking down into the aluminum stock that holds the spring tube. The trigger unit runs from almost all the way on top, where the trigger blade is located, to all the way on the bottom, where the true sear releases the piston. It’s a complex bullpup unit that must be removed as a unit for work. You can see the steel channel that holds all the trigger parts.
Because of the way the Gamo action is designed, I could set the trigger aside and go to work on the powerplant. The end cap is held in the spring tube by a single large pin that must be drifted out. The action was installed in a mainspring compressor for this next step.
Here you see the barreled action in the mainspring compressor with the large pin drifted out. The pin is on the table, next to the hammer handle. The spring tube is ready to come apart.
Moment of truth
Taking a spring-piston powerplant apart for the first time is always a surprise. You never know how much compression the mainspring is under, even when relaxed, and how far it will come out of the gun before it’s fully relaxed and the gun can be removed from the mainspring compressor. It was a real surprise this time, for the spring came out several inches before fully relaxing. If I had just drifted the pin and tried to hope I could hold the end cap with my body, I could have broken bones!
Like a python that swallowed a telephone pole, the mainspring just kept coming out of the spring tube until it was this far! As you can see, I didn’t have much more room on my adjustment screw.
Once tension is off the mainspring, the rifle can be removed from the compressor. The end cap, spring guide and mainspring can now be removed. The piston, though, is still held in the rifle by the cocking link. You must disconnect the link from the piston before it will slide out of the gun.
The 68 has an articulated cocking link, and I noticed a spot at the front of the cocking slot that was enlarged for the removal of the cocking link. That told me that I did not need to remove the barrel from the action to disconnect the link from the piston. Just line up the link end with the enlarged hole, and the end pops right out.
The cocking link is two pieces.
The end of the link can be removed from the spring tube through the enlarged hole at the end of the cocking slot. The two-piece cocking linkage helps you do this.
The mainspring and piston both told me this gun had probably never been apart before. The grease looked like factory grease, and there were many years of accumulated dirt and grime on all the parts.
The piston has a leather seal that looks brand new. It was a bit on the dry side. After I assembled the rifle, I lubricated it heavily. I’ll continue to do that many times over the next few months, until I’m satisfied that the leather is oily and supple once more.
Leather piston seal looks good.
The piston itself is a very strange duck. It has to be, because the trigger is autonomous from the powerplant. There’s a window on the side of the piston at the rear where the sear catches it when the gun is cocked.
Here you see the entire piston, which is a machined steel part. The rectangular window at the end of the piston skirt is where the sear catches and holds it when the gun is cocked. Only the piston seal and the machined section at the rear touch the inside of the spring tube, so that’s where the moly lubrication goes.
The inside of the spring tube was as dirty as the piston and mainspring. I put paper towels over the end of a long-bladed screwdriver, dipped the paper in alcohol, and cleaned the inside of the spring tube and compression chamber. This would also be the time to remove any burrs from the cocking slot, but there weren’t any on this one.
After the entire powerplant was cleaned, I examined that long mainspring. After all those years, I thought it had to be canted — and it was, though not as much as I’d imagined. Rolling it on a flat surface revealed a wobble at one end, which translated to a jolt during firing. Hopefully, I had a suitable replacement.
I found several possibilities, but the best one proved to be a replacement spring for a TX200, of all things. It’s a special spring Jim Maccari made some years ago and it has collapsed coils in the center and at one end. As you can see in the picture, it’s a lot shorter than the spring that was in the 68. The wire is thicker, but there are so many fewer coils that I knew it would fit. The fit inside the piston was about the same as the factory spring, and the fit on the spring guide was tighter. So, this is a good replacement.
Factory spring above, replacement below. The new spring will certainly be under less compression when the gun is not cocked!
I coated the new spring with a thin layer of black tar and inserted it back into the piston. The front and rear of the piston were then coated with a heavy layer of moly grease and installed back into the spring tube. The cocking link was inserted back into the enlarged hole, where it contacted the piston for cocking.
The spring guide was coated with moly and slid inside the mainspring as far as it would go. The end cap was placed over the end of the spring guide, and the barreled action was installed in the mainspring compressor, once again. This time, the amount the spring stuck out was drastically reduced.
The spring guide is steel. It was coated with moly and slid back inside the mainspring.
The new mainspring has just begun to compress. It’s a lot shorter than the old one!
The gun went together without a hitch! And that was when I noticed for the first time that the entire job from start to finish had taken me only one hour — including photos! That’s as fast as I could tune a TX200 (assuming I would, which would never happen), and it doesn’t require a mainspring compressor. This wasn’t the time-killer I thought it was going to be.
How does it shoot?
The rifle cocked with 22 lbs. of force before this tune. Now it takes 28 lbs. to cock it, and the final sear lockup takes a final crunch that wasn’t there before.
The gun fires with 70 percent less jolting than before, but its just as quick as it was before the tune. The feel of firing is atypical of a lower-powered breakbarrel, just as it used to be. I can now feel a little vibration in the powerplant that I think was previously masked by the heavy firing jolt.
I still don’t know the gun. It will take a session of velocity testing and shooting for accuracy before I can finish this report. Since I’ve already tested the gun extensively before, I’ll combine both of those things in the next report.
Tech Force TF79 Competition Rifle – Part 3
by B.B. Pelletier
The Tech Force 79 Competition rifle is a lot of value for a very low price.
Well, the best laid plans of mice and men….I was supposed to be at the SHOT Show today, but the night before my flight left I went to the emergency room with what I thought might be appendicitis. It turned out to be a small but painful hernia, which cancelled all travel plans and heavy lifting for a while. So, no SHOT Show this year! Apparently, my extended hospital stays and being fed intravenously for so many months last year resulted in too much muscle loss. The doctors believe it will heal up shortly without any surgery.
That’s sad, because Crosman is unveiling a brand new kind of big bore air rifle. Named the Rogue, we called it the electronic PCP during development, because it uses computer control of the valve to get far greater efficiency than has ever been possible.
The idea of an electronically controlled valve isn’t new. Daystate has been doing it for several years and getting great results. But, no other airgun will get the performance this new gun offers. The computer senses the remaining air pressure in the reservoir and holds the firing valve open long enough to extract highly consistent velocities. Instead of 2 shots or 6 good shots from a big bore, what would you say to the possibility of 10 high-powered shots? Or, change the programming and get 20 lower-powered shots at a level that’s still impressive.
This new system was invented by one of our own blog readers, Lloyd Sikes. He signs in here as Lloyd. He first showed me his design at the Roanoke airgun show several years ago, and I was so blown away with the possibilities that I set up a meeting with Crosman. Of all the airgun companies in the world, Crosman is the only one open to new and radical ideas, as well as having the engineering and production capability to act on it. Lloyd initially demonstrated his invention by video, followed by several live demonstrations at the Crosman plant. They made the decision to take his idea and make it into a producible airgun system, and I use the word system advisedly. Although the initial offering is a rifle in .357 caliber (imagine the hundreds of lead bullets now made in this caliber!), a barrel change allows conversion to .30 caliber and even .410 gauge! For the first time in history, we may have an air shotgun with power identical to a firearm! I’m talking about sending a half-ounce of shot out the muzzle at over 1,100 f.p.s.!
Imagine filling to 3,000 psi and still firing shots at the same velocity when the pressure has dropped below 1,500 psi. This will be the most flexible, most adaptable big bore airgun ever conceived.
Crosman has poured their corporate heart and soul into this project, knowing that they have a technology unlike any that’s gone before. The future may hold .50 caliber buffalo rifles, real usable shotguns, smallbore rifles that have incredible velocity uniformity…and the list goes right on out to the horizon. And, you, my dear readers, are the absolute first set of airgunners outside the development team to learn about it. This is the big bore that many people guessed would be some kind of Marauder on steroids. It’s nothing of the kind. It’s a brand-new technology that has never been seen before.
I’ll be getting a rifle to test for you this year, so the future bodes well for more great new toys.
Today, we’ll look at the velocity of our .177 caliber Tech Force Competition Rifle, as well as the endurance of two 12-gram CO2 cartridges. Don’t be confused because this is Part 3. I did a special report on the trigger in Part 2.
Pyramyd Air rates this target rifle at 550 f.p.s., which is right where a 10-meter target rifle ought to be. But, the test rifle proved to be more powerful than that. Before I get into the velocity numbers, though, I’d like to share some more info on the trigger.
Sweet trigger
At the end of the trigger report in part 2, I told you that the trigger was almost creep-free. Just a hint of creep remained in stage two because I insisted on more sear contact area for safety. I also lubed the sear and the trigger contact with moly grease. Within just a handful of shots, the moly had erased all hint of creep, and I now have a target trigger worthy of the name. I cannot emphasize too strongly what an incredible value this trigger is in such a low-priced airgun.
Velocity
The first pellet I tested was the RWS R10 7.7-grain target wadcutter. It seems RWS has dropped this pellet in favor of an even lighter 7.0-grain R10. But, it was the heavier pellet that I tested. They averaged 613 f.p.s. and the range stretched from 608 to 617 f.p.s. for a span of 9 f.p.s. They average 6.43 foot-pounds of muzzle energy.
Next, I tried the H&N Finale Match Pistol pellets. They weigh 7.56 grains and they averaged 617 f.p.s. in the test rifle. The range went from 614 to 619 f.p.s., so a tight spread of only 5 f.p.s. The average muzzle energy was 6.39 foot-pounds.
I cannot emphasize too strongly what an incredible value this trigger is in such a low-priced airgun.
Gamo Match pellets were next. They weigh 7.71 grains and averaged 613 f.p.s. in the test rifle. The velocity spread went from 610 to 617 f.p.s., so only a 7 f.p.s. spread. Average muzzle energy was 6.43 foot-pounds.
The last pellet I tested was the RWS Hobby. They were the fastest pellets, at an average of 632 f.p.s., and the range went from 629 to 636 f.p.s. The spread was 7 f.p.s. The average muzzle energy was 6.21 foot-pounds.
After this testing, a total of 40 shots had been fired with the two CO2 cartridges. I continued shooting Hobbys to see what the total number of shots would be. The velocity fell off immediately. By shot 48, it dipped below 600 f.p.s for the first time. This particular rifle has a total of 40 good shots on a set of two CO2 cartridges. That might be extended a few rounds in the hot summertime, and in cold weather it might be a few less. I shot in my office with the temperature at 70 degrees F.
A plinker could go on for several additional shots, but a target shooter wouldn’t want to. That’s where the degasser comes into play. When CO2 is in the reservoir, the o-rings press against the walls of the reservoir so hard that no amount of effort short of vice grips can turn the end cap off the gun. The degasser lets you dump the remaining pressure and start all over again.
The degasser slips into a hole on the left side of the gun and works just as the name says.
I’m going to get a setup for bulk-filling in a future report. For now, know that the TF79 is even more efficient than the classic Crosman 167 (the .177 caliber version of the 160). Coupled with better overall design and a finer trigger, that’s saying a lot. Accuracy will be the next thing we look at.
