Posts Tagged ‘mainspring’
by B.B. Pelletier
I recently started writing more reports about the fundamental things that many airgunners would like to know. These are things you don’t have to know to shoot an air gun; but if you do know them, they can often help you recognize why your gun does what it does. You also don’t have to know what makes an automobile work; but when it stops working, sometimes knowing how it’s supposed to work can help you find the problem and fix it.
Today, I’m going to show you how a brand new mainspring is set to its operational length before installing it into a spring-piston airgun. It’s not necessary to do this; because, over time, the mainspring will automatically reduce in length after being in the spring gun under some tension and being compressed many times. If you do this first, it makes the job of spring installation easier in some cases.
When a coiled steel spring is wound, it ends up being longer than it will after some use. Robert Beeman wrote that the surface of the wire in the spring is oriented like strands that run along the axis of the spring wire and twisting the wire into a coil twists those strands unevenly.
As the spring is used (compressed and released), it shortens (the coils get closer together); but until they do, the spring coils will be separated a little farther than they should be. If the spring has many coils and each is separated a little more than it should be, the overall length of the spring can be up to several inches longer than it should be. Once it assumes its final length, it will still have the same strength as when it was longer. It will just be easier to work with.
Not all scragging is done as I’m describing it, so please focus on what I’m presenting here because it applies to spring-piston mainsprings. Scragging is the English term for what many spring makers call “set removal.” Set removal, or scragging, means compressing the spring to its solid length (i.e., all coils are touching, and the spring cannot be further compressed). Once it’s done, it allows the spring to operate at a higher load capacity without overstressing.
Spring-piston mainsprings are almost coil-bound (fully compressed) every time the gun is cocked. In fact, measuring the potential overall length of the compressed spring and determining whether it can be further compressed is an aspect of spring-gun tuning. Tuners often install washers that decrease the length that a mainspring has to compress, just to get the spring closer to its coil-bound state when the gun is cocked. They’re trying to wring out all the power the spring has to give when they do this.
This practice will put the operational length of the spring very close to the stress limit of the spring. If the spring is scragged, the stress limit is set at the spring’s fully compressed length; so if the spring never gets compressed quite that far during operation, it stays within the bounds for which it was made. It will, therefore, last a long time. While it’s impossible to compress a spring that has been scragged past its operational limit, you can compress it right up to the limit. I personally like staying on the safe side of that limit.
We learned how to measure the length of a compressed mainspring in the recent report titled The spring-piston power plant. You learned a technique that tuners use to determine the compressed length of the spring by measuring the wire diameter and counting the number of coils. The method I showed is not absolutely precise, but it will get you within a few hundredths of an inch, which is usually close enough. However, if you want to go all the way to coil-bound, you may have to adjust the length of the spring by adding washers to take up some of the space in which the spring exists. You can then fine-tune this length by removing some washers or even by thinning one of them, if you choose to go all the way to the coil-bound limit. If you stop just shy of that limit, your mainsprings will always fit inside your gun.
A scragging tool
In industry, scragging is usually done with a hydraulic press, but there’s an inexpensive way to do it. Just use a long piece of threaded rod with two washers and two nuts, and tighten the spring between the two washers. I showed that tool in the blog last week.
A simple tool for scragging coiled steel mainsprings.
When you tighten the nuts, you’ll notice that the spring really wants to twist. You have to hold both nuts with wrenches, and they will try to get away from you as you try to tighten them. This is spring torque, and sometimes it can be felt when certain spring-piston guns fire.
This is important!
Look at the photo below of the spring-piston powerplant. The compressed mainspring has to fit inside the piston and between the end of the piston and the base of the spring guide. That is the entire length in which the compressed mainspring must fit.
The mainspring fits inside the piston and goes back to where the trigger begins — minus the base thickness of the spring guide that isn’t visible in this picture.
What you cannot appreciate from the picture above is what the mainspring looks like when it’s compressed. But when you scrag the spring, the shape jumps out at you. The spring tries to squirm away from the force that compresses it.
Here is the mainspring before it’s in the scragging tool.
The spring has been installed.
The spring is compressed almost as far as it’ll go. Notice how it wants to curve away from the in-line force that compresses it? That is what happens inside your spring-piston airgun. Only the piston and spring guide prevent the spring from looking like this.
The mainspring is completely compressed. There’s still a slight curve to the spring, which the inside of the piston and the outside of the spring guide will remove. Leave the spring in this tool fully compressed for four hours and it will be scragged.
What’s happening inside your spring-piston gun is that the mainspring is being held compressed between the piston and the spring guide. The more room there is, the kinkier the spring will be when compressed, and the more room it will have to shudder and shake when it expands. You will feel that as vibration. Remove the extra room, and you remove the vibration.
A word on springs
There have been comments on this blog in the past about stretching springs to increase their power, and I want to address that now. You can’t stretch a spring and increase its power for more than a couple of uses. What will happen if you try is that you’ll cause the premature failure of the spring. One or more of the coils will collapse, resulting in a canted spring. The results will be greater vibration and less power.
The metallurgy of a coiled spring is very precise and has not been covered in this report. There are things like forming techniques, heat-treatments and stress relief that are part of what make a spring capable of doing what it does; and while it’s possible to change the characteristics of hot-formed springs, we use springs that are wound cold and cannot be changed. When they reach the end of their life, they’re done and are not suited for reclamation except through scrapping.
It’s important to get all the performance a spring has to offer since there’s no way of adding life at the end. Scragging normally does that; however, in the case of the spring inside a spring-piston air rifle, the scragging process can occur naturally during operation since the spring is nearly coil-bound every time it’s cocked. So, scragging doesn’t really add life to an airgun spring.
What it does is make the spring shorter so it’s easier to stuff inside the powerplant. But if you don’t want to do it and can get the spring into the gun anyway, you can either cock the rifle and leave it cocked for about four hours or else you can just use the gun normally and the scragging will take care of itself over time.
One final thought
Manufacturing being the imprecise process that it is, every airgun powerplant will have slightly different dimensions — even within identical models. So, the length of the spring that fits inside the powerplant will change from one gun to the next. That’s why manufactured airguns cannot be held to tolerances as close as those that are tuned by hand. Some of the “slop” we see in off-the-shelf spring-piston guns is there to account for these small differences. That’s why an individually tuned gun can usually be made smoother and more powerful than one made by a factory process.
by B.B. Pelletier
Is this Custom Match the best HW 55 ever made? Read the report to find out.
In the last report, I tuned the rifle and got rid of the objectionable firing cycle. It’s always a great pleasure to return to a classic air rifle like this one after testing so many modern airguns, because these oldies are so reserved and well-behaved. I know it’s not going to kick, roar and fight me at every turn. It may only be suited to shoot 10-meter target, but sometimes — and by that I really mean often — that’s exactly what I need.
I had to remove the sights during the tuneup, so the rifle needed to be sighted-in again. It wasn’t that far off, but the indices are so dark on a 55 rear sight and my eyes are so bad that I had to play around until I discovered which way to adjust the sight to go right. In this respect, a modern 10-meter rifle has it all over a vintage one.
The first pellet I tried was the H&N Finale Match Rifle pellet. I haven’t had a lot of recent success with this pellet in target rifles, but in the past this was one of two to contend with — the RWS R-10 Match Pistol pellet being the other. This time was different, though. Although the first group wasn’t what I wanted, it showed enough promise that I shot a second and a third. By the third group, I could tell this pellet likes this rifle.
Next, I tried the RWS R-10 Match Pistol pellet, and I gave it the same number of chances, but it never showed me anything. That was a surprise, because I think this pellet is one of the more accurate pellets in several of my other 10-meter rifles.
Following the R-10, I tried the RWS Hobby pellet, because in my HW 55 SF — the 55 that has no barrel lock — Hobbys do surprisingly well. Again, there was no joy this time. I’m showing the group to contrast with the others in this report.
At this point, I was satisfied that this rifle is accurate, though it won’t give an FWB 300S any competition. But why stop there?
I next mistakenly loaded some obsolete and nondescript European diabolos that I mistook for JSB S-100 competition pellets. Boy! If you ever wanted to see a comparison between good pellets and cheap ones in a good gun, this was it! How about a three-quarter-inch five-shot group?
Back to serious ammo. The next pellet I tried was the H&N Match Pistol. This is not a Finale Match pellet, and I find that these sometimes vary in weight a lot more than Finales tend to, but there can be surprises. Not this time, though. The best group looked like Hobbys. Oh, well!
After that, I tried H&N Match Rifle pellets. They’re the same as Match Pistol, only heavier. But for some reason that nobody understands but everybody believes, they shot great! These are the pellets for this rifle — until I find something better.
The rifle is shooting fine with the new tune. I could live with less power, but what I have isn’t bad. The trigger is a joy, because it breaks at just 7 oz., and that’s as light as I need it to be. Shooting from a bench in the rested position doesn’t give you the full feeling of the rifle. All it shows is the potential for accuracy, and this one’s got it.
by B.B. Pelletier
Is this Custom Match the best HW 55 ever made? Read the report to find out.
This is a special Part 3 for the HW 55 Custom Match target rifle. It will be a retest of velocity, following a strip-down and lubrication with black tar to get rid of some uncomfortable vibration when the gun fires. When I tested it for velocity in Part 2, I discovered the rifle was shooting way too fast for an HW 55. Probably the Beeman Company replaced the mainspring when it went back to them for an overhaul. At any rate, when RWS Hobby pellets average 694 f.p.s., as they did for this rifle, you know something is wrong. I’ll try to remove as much of the harshness as I can with this tune, and I really don’t care how much velocity is lost.
A word about the Part 2 report is needed here. I combined it with Part 2 of the report on Mac’s Diana model 60 target rifle because I don’t want to crowd the blog with too many reports about vintage air rifles. Since the velocity report goes pretty quick, I just put the two of them together. But, today, the 55 CM gets its own report, because as well as testing velocity I’ll be disassembling the rifle and applying a tune. There will be some observations for that, as well as the velocity results afterward, so this work rates a report of its own. Of course, there will still be a Part 4 accuracy test to come.
There were no real surprises when disassembling the rifle, except to find a very canted mainspring. That was where the vibration came from — of that there can be no doubt. I rooted around in my collection of replacement mainsprings and found one that Jim Maccari made for a TX 200! Talk about inappropriate for an HW 55 — but the dimensions of this spring were so great that I had to try it.
I discovered that the trigger was still coated with a drying, tacky layer of factory “tractor grease.” I kidded Hans Weichrauch, Jr., about this years ago and he had no comeback. From his perspective, the grease is always fresh and new. I removed everything I could from the trigger but expected no change in performance. This was more of a conservation step than a restorative one.
The new spring was very liberally buttered with black tar, and the rifle was assembled once more. However, when I cocked it the first time, I knew that wasn’t the solution. The cocking effort started out light but quickly stacked until I was pulling back around 30 lbs. of effort. That’s way too much for a 55 target rifle.
On the plus side, I probably added at least another 50-75 f.p.s. to the velocity. But, with a target rifle, who needs velocity?
So, once more, the action came apart. This time I used a spring that had very similar dimensions to the one that came from the gun — only this one is straight. It got buttered with tar, too and then everything went back together.
How does the rifle feel?
The rifle now requires 26 lbs. of force to cock, compared to the 20 lbs. before — so that part isn’t good. The firing cycle, however, feels lighter and much quicker. Gone is the objectionable vibration that came from the canted mainspring. This rifle will now be easier to shoot accurately.
The first pellet tested was the RWS Hobby that was such a speed demon with the old tune. Back then, the rifle averaged a blistering 694 f.p.s. with this pellet. That’s way too fast and does nothing for the potential accuracy. The extreme spread was 17 foot-seconds with that pellet and tune.
With the new tune, Hobbys average 603 f.p.s., ranging from 602 to 610 f.p.s. for an 8 foot-second spread. That’s more like what I wanted, and maybe even on the low side of what I was looking for. But with that tight spread, I know the rifle is doing well with this tune.
Next, I tried H&N Finale Match Pistol pellets. The old tune gave an average 632 f.p.s. velocity with a 14 foot-second spread.
The new tune gives an average of 573 f.p.s. with a 12 foot-second spread that runs from 567 to 579 f.p.s. The spread is pretty close to what we had before, but the velocity is now down where I expect it to be.
The last pellet I tested was the RWS R-10 Match Pistol pellet. With the old tune, the pellet averaged 632 f.p.s. with an 18 foot-second spread that went from 619 to 637 f.p.s.
The new tune sends this pellet downrange at an average 565 f.p.s. with the total velocity spread that runs from 560 to 567. Only 7 f.p.s. separates the slowest shot from the fastest.
The rifle now seems much more calm and settled when it fires. I can’t be sure until I shoot for the record, but I think I’ve tamed the beast.
Am I satisfied with this tune? Yes, except for the extra cocking effort. An HW 55 should cock at around 15 lbs. of force, and this one takes 26 lbs. That’s heavy, even though it doesn’t set off any alarms. I would still like to get it back under 20 lbs., but I’m not going to hold up the show just for that.
Accuracy testing is next, and then we’ll have complete tests for five popular 10-meter spring-piston target rifles: the HW 55 SF, FWB 150, Diana model 60, Walther LGV Olympia and this HW 55 CM. Guns I haven’t yet tested (that I own and have access to) are the FWB 300S and the Haenel 311.
by B.B. Pelletier
2011 airgun show calendar
Before I get to the report, here’s a calendar of all the 2011 airgun shows I know of. If you want to go to an airgun show, here they are.
March 5 & 6
Pacific Airgun Expo
Placer County Fairgrounds
Contact Jon Brooks @ 707-498-8714
Flag City Toys That Shoot
Lighthouse Banquet Facility
10055 S.R. 224 West
Findlay, OH 45840
Duane Shaferly @ 419-435-7909
Dave Barchent @ 419-423-0070
Dan Lerma @ 419-422-9121
To register contact:
April 15 & 16
2nd Arkansas Airgun Extravaganza
Fairgrounds, Exit 98A on I-30
1605 Martin Luther King Blvd.
Malvern, AR 72104
Contact Seth Rowland
June 11 & 12
5th CT Airguns Airgun Show
Windsor Elk Lodge
Contact Kevin Hull @ 860-649-7599
July 15 & 16
Airgun Show and Shoot
American Legion Post 113
Contact Larry Behling @ 315-695-7133
Daisy Get Together
Kalamazoo County Fairgrounds Expo Center
Wes Powers @ 517-423-4148
Bill Duimstra @ 616-738-2425
St. Louis Airgun Show
Stratford Inn Garden Room
800 S. Hwy. Dr.
Fenton, MO 63026
Contact Gary Anthony @ 636-861-1103
This is the 14th report I have made on the FWB 124. In all that time, I was mostly tracking a single 124 — the one I obtained that had been packed for eternity in a wooden case like an Egyptian sarcophagus. We went through many tunes with that gun and saw what each one did. Then, I tuned a 124 for Mark Taylor, a shooter I met at Roanoke. That one wasn’t planned, but it did give us a look at a later and different rifle.
Today, I’m reporting on the bluebird buy I happened upon while registering a firearm several weeks ago. The guy at the gun store owned this 124 that had suddenly stopped shooting, a fault that is common with this model because of a bad formula of synthetic used in the piston seal. You’ll also see it in FWB 150 and 300 rifles, Walther LGV air rifles and probably a lot of other airguns made back in the 1970s. The fix is to install a new seal. You’ve already seen me do this several times in this series, but the one thing I haven’t shown you is what the old seal looks like when it’s broken up inside the gun, and that’s something all airgunners should know.
I originally thought I was going to tune this for the guy at the store, but he wound up selling me the rifle, so I’ll do both a velocity test after the tune and an accuracy test using the curious little Bushnell scope that came on it.
How the new gun differs from the old
Before I tear into the action, let me report on how this later 124 differs from the ones I have already shown you. The Deluxe models weren’t made when this one was built. It’s called a Sport, but it has a checkered grip and sling swivels, two features from the older Deluxe class. Gone, however, is the Wundhammer palm swell, and the cheekpiece that’s on the left of the butt of this later rifle is so small and ill-formed as to make the rifle nearly ambidextrous. With the ambi-style safety and the ease of breakbarrel loading, it should have been an ambi from the start.
When I tore into the gun, I initially wondered if it had ever been apart. The serial number is 42,648, which places the gun very late in the production cycle. So, it could have been a virgin rifle, but it wasn’t. The mainspring was coated with moly grease, a sure sign that someone has been inside, because the factory used only clear grease. From the look of the tune — moly on the mainspring, an FWB mainspring instead of an aftermarket spring, a replacement FWB piston seal (a Beeman trademark, even though they knew about the disintegration problem) and the trigger adjusted very nice — I believe this rifle was last tuned by Beeman. All those characteristics are the ones Beeman would do. As good as they were, even Beeman could not prevent that piston seal from decomposing. And, that’s what I want to show you.
This is what a decomposing FWB seal looks like. The brown particles you see used to be hard, tough synthetic. Now, they’re soft, waxy particles that break apart easily.
In this view, you see hundreds of smaller particles in the tube; and at the bottom (the end farthest from you in this picture), the top of the piston seal has broken off and wedged itself against the end of the compression chamber. The small hole at the lower right inside the compression chamber is the air transfer port. All of this mess must be removed before the rifle can be tuned.
There isn’t much left of the piston seal after it disintegrates. Most has been left inside the compression chamber, but this root has to be cut out of the piston top. Like most of them, this one popped out easily.
I won’t say anymore about disassembly and reassembly except for one thing. Installing the bolt that holds the trigger assembly in the gun is a tricky job. The trigger assembly has the spring guide and is what keeps the whole powerplant together. The bolt is hardened steel, but the trigger housing into which it threads is softer aluminum. You can easily cross-thread the bolt if you aren’t careful. If you do, the trick is to remove the trigger housing from the gun and carefully thread the bolt into the hole, keeping the head aligned straight. It’ll reset the threads in most cases and you’re home free. You can then assemble the gun, and the bolt will not cross-thread anymore. This is the biggest reason you need a mainspring compressor to do this job.
This large bolt with the two flats for gripping is what holds the 124’s powerplant together. It threads into the soft aluminum trigger housing and can easily be cross-threaded. This photo shows an older 124 trigger assembly, not the one from the newer gun I’m testing in this report…which has an aluminum trigger blade.
Many tunes — final satisfaction
I tried several combinations of springs and piston seals until I settled on the Maccari Mongoose spring and seal. At first, the seal was way too tight, as it’s supposed to be, so I sized it by hand-sanding until it had just a little resistance in the compression tube. The spring was lightly lubed with moly grease, and the seal also got a coat of moly before going back into the gun.
Crosman Premier 7.9 lites
The first pellet I tried with the new tune was the Crosman Premier 7.9-grain “lites.” They’ll be among the most accurate in this rifle; history has proven many times. They averaged 761 f.p.s., with a spread from 752 to 770 f.p.s. The average velocity produced a muzzle energy of 10.13 foot-pounds. All pellets were tight in the breech
Next, I tried RWS Hobbys, a 7-grain pellet that’s the speed-demon of the lead pellet world. They averaged 821 f.p.s., but a curious thing was happening as I shot them. The velocity kept increasing! Shot one went just 767 f.p.s., but the fastest shot among the 10 I fired went 832 f.p.s. With the average working out to 821, you can see that velocity was climbing all the time. I think this tune will wear in to the point that the Premiers will go about 800 f.p.s., and the Hobbys will get up to 860 or so. At the average velocity, the muzzle energy was 10.48 foot-pounds.
Beeman Silver Jets
The last pellet I tested was the vintage Beeman Silver Jets that are no longer available. They were the No. 1 go-to pellet when the 124 was in its heyday. Back in Part 10 of this report, I tested them against the best of today’s pellets, with the result that they weren’t far from the leaders.
The 8-grain Silver Jets averaged 732 f.p.s., with a range from 721 to 747 f.p.s. At the average velocity, they were generating 9.52 foot-pounds.
I mentioned that this rifle has a nice trigger. It’s sort of a single-stage, by which I mean that pressure is there immediately when you begin the pull, and there’s no obvious hesitation. It breaks with only 26 oz. of pressure, and it feels like less than a pound. I have to be very careful, because I’m used to three-to-five-pound triggers on the rifles I shoot the most. This one feels like nothing to me.
Most 124 triggers have more creep in them than this one. When I owned Mrs. Beeman’s personal custom 124, the Queen Bee rifle, I found that the Beeman company could really adjust a 124 trigger very finely. Whenever I feel a good one, I always suspect someone from Beeman has been inside.
Well, that’s it for this test. Next time, I’ll see about sighting-in the rifle with that unusual scope.
by B.B. Pelletier
The November podcast has been posted.
Before we begin, my buddy, Randy Mitchell, who was also the outlaw, Dakota, from Frontier Village (an amusement park in San Jose, California, from 1961-1980) sent me a photo from over 40 years ago. I was Casey Jones, the engineer who ran the railroad at the Village, and Dakota had put an obstruction across the tracks out in the badlands. When I stopped the train, he jumped me at gunpoint and forced me to clear the rails. Then, he stole my boots and drove the train back to the station himself. How time flies!
Dakota forced me to clear the obstruction, then stole my boots and drove the train back to the station himself. I had to walk back!
Now, on to today’s report. Well, well. How the tide turns when you go to an airgun show! I went to Roanoke hoping to score an FWB 124 to tune and instead I picked up one to tune for somebody else. That’s usually a good thing, because when I tune for other folks I do a better job. I’m like the cobbler whose children are barefoot.
You’ll remember from Friday that this rifle is Mark Taylor’s, and I gave you an idea of how it performed. The cocking was too hard, plus there was a scraping or grinding feel to it. Well, once I got the guts out I found out what that was and why it happened. But, I’m getting ahead of myself.
The first comment I’ll make is that Mark’s rifle hasn’t been apart many times. The mainspring I removed looked like a 124 mainspring, except that it had 39 coils — and a standard spring I have has only 35. So, the spring I removed was much longer than standard. At least I think it’s longer. Heck, it’s been so many years since I tuned a 124 that I doubt I know anything for sure anymore.
Looking through the cocking slot before disassembly, you can see that the mainspring has been coated with moly grease.
The second comment is that Mark’s rifle had the strangest lubrication I’ve ever seen in any spring rifle, and I include my older San Anselmo rifle in that observation. My gun was tuned back in the day when it was standard practice to use an entire jar of Beeman’s moly grease on the mainspring of a 124. When I took that gun apart the first time, I was scraping grease from everywhere! Had I known how full it was, I could have called Mike Rowe and gotten him to put it on his Dirty Jobs TV show.
In contrast, Mark’s rifle was almost dry inside! Only the mainspring was coated with moly, and it looked like a smear of lithium grease might have been applied to one spot on the back of the piston. As a result, the piston was touching the top of the spring tube when the gun was cocked and had galled (made shiny by removing a small amount of metal) a large area that wasn’t too deep. It wasn’t serious, but it also was never going to get any better.
This is how the piston looked immediately after removing it from the gun. There’s no lube on the seal!
This is the back end of the piston, called the skirt. As you can see, it has next to no lubrication.
The scraping, grinding feel came from this area. Those two bright lines are galled metal, where the piston skirt scraped against the inside of the spring tube. The damage is minor and correctible with the proper lubrication.
I discovered this lack of lube when I cleaned the inside of the spring tube. It was practically dry and grease-free in there. If I had tuned it, there would have been a lot of moly burnished into the metal and the cleaning patches would have come out black instead of white.
Using moly grease on the mainspring isn’t the best thing when you want a smooth shot cycle. That’s where Maccari’s Black Tar comes into play. A dry piston isn’t the right thing for this gun, as evidenced by the galled metal. I lubed the front and rear of the heavy 124 piston with moly grease. Gene Salvino, Pyramyd Air’s tech manager, recommends using lithium grease on their piston seal, but I used moly on this one because of the galled metal.
The piston seal that was in the rifle looked to be in fine shape. Since this was supposed to be a test of the new Pyramyd Air seal, I removed it anyway. I’ve never seen another one like it and have no idea where it came from.
I also noted that the baseblock bearings weren’t lubricated with much of anything, which might have added to the cocking effort. Also, the barrel pivot pin was dry. I spread moly grease on both the bearings and the pivot bolt before installing them in the rifle again.
I selected an old Maccari Deluxe tune kit for the rifle. This kit drops in, but is made so perfectly that the mainspring goes on the spring guide like it was nailed on. That’s tuner’s slang for a very tight fit. The spring diameter expands when it’s compressed lengthwise, so the fit isn’t as tight as it seems when you install it. There was also a Delrin spacer for the spring guide that put a little more tension on the spring.
This is how to lubricate a 124 piston correctly. Both the front and rear of the piston can contact the other metal surfaces inside the gun. The center of the piston is smaller and cannot touch anything. Besides this, I also burnished moly inside the spring tube before installing the piston.
All metal-to-metal contact surfaces except for the outside of the mainspring got a coat of moly grease before the gun was assembled. The outside of the mainspring was buttered with Black Tar. Then, the gun was assembled in reverse order from disassembly.
This is how I “buttered” the mainspring with Maccari’s Black Tar mainspring dampening compound.
On to shooting
The proof is in the shooting, and the first time I cocked the assembled rifle it worked as it should, which doesn’t always happen. I noted that the cocking effort didn’t seem to have decreased much, but the cocking cycle was now as smooth as it should be. Then, I shot the rifle.
Wow! What a beautiful tune this is. Not only is all vibration gone, but the forward recoil I had noticed disappeared, as well. The gun just sort of pulses when it’s shot.
I then measured the cocking effort and was stunned to find it had increased a pound to 28 lbs. of effort. Personally, I think it’s too heavy for a 124, but the smooth shot cycle is too nice to ignore. Let’s see what is does over the chronograph.
Crosman Premier lites
The 7.9-grain Crosman Premiers averaged 744 f.p.s. with this tune. The spread ranged from 736 to 750 f.p.s. That’s a little tighter than the original tune, and much smoother. The average muzzle energy was 9.71 foot-pounds.
RWS Hobby pellets averaged 784 f.p.s. The spread went from 776 to 793 f.p.s. Again, a slightly tighter spread than before. The average muzzle energy was 9.56 foot-pounds, and a super-smooth shot cycle.
JSB Exact 8.4 grains
JSB 8.4-grain Exact domed pellets averaged 723 f.p.s., a surprisingly low figure. They ranged from 713 to 730 f.p.s. and produced an average muzzle energy of 9.75 foot-pounds. They shot just as smooth as the other two pellets.
What to do next?
This is a toughie. The rifle is cocking and shooting extremely smooth right now, but the cocking effort is a bit high. Mark, the owner, says he doesn’t mind that, as long as the gun shoots smooth, which it definitely does. I’m at the point of a decision that I’m going to let Mark make. I feel certain that the Black Tar on the mainspring is what’s slowing down the gun just a bit. As tight as the mainspring fits, it probably isn’t necessary. Still, the gun does shoot very smoothly, and almost all of the forward recoil seems to be gone, as well. From a shooting standpoint, this is a fine tune. I’ll let Mark decide.
If he wants more power for the cocking effort, I would remove the Black Tar and lube the mainspring with moly grease. But, if he wants a super smooth shot cycle, we have that right now.
Mark, what would you like me to do?