by Tom Gaylord, a.k.a. B.B. Pelletier
Today’s report is both an object lesson, and a summary of what we’ve been studying for so long — the fact that ballistics, though often difficult to understand, are also precise and repeatable. It may not sound like that until I summarize at the end; but trust me, this is a lesson for all airgunners.
As the title says, this report is about my new AR-15. If you’re just finding this report for the first time and are interested in the AR, you owe it to yourself to read the first three parts of the report, linked above, before reading today’s message.
It was another very calm day at the range — perfect for testing a little experiment I’d cooked up. As you know, I do not shoot factory ammunition of any kind in my rifle. I did prove that it will function with standard factory 55-grain Remington .223 rounds in the last report, but the accuracy was horrible. I put 10 shots into about three inches at 100 yards. So I use the word “function” here to connote that the rounds fed through the magazine and action smoothly, as designed. I would never consider shooting them, other than for this test!
My load has been a 77-grain pointed bullet and a load of Varget gunpowder. That has demonstrated the ability to put 10 shots into less than one inch at 100 yards on many occasions. But another bullet — a 68-grain Hornady Match hollowpoint — produced the best 10-shot group I ever got with the rifle. It measures 0.562-inches between the centers of the two bullet holes farthest apart.
Ten bullets went into 0.562 inches at 100 yards.
So, I dreamed up a little experiment. I would shoot another group with the same load, only this time I would also do some other things to improve the group. For starters, I would only select cases that had the same headstamp. Different companies make .223 ammunition, and their cases differ a little. Even though they all meet the specifications for the .223 Remington case, there are tiny variations that occur from the differences in the manufacturing processes each company uses. Add in the possibility of different materials at the beginning of the manufacturing process and you get small variations. The specifications allow for this, as long as the gross tolerances and performance specs are satisfied.
These cases were picked up off the ground at the range, so they came from several different manufacturers and were made at different times. They’re not uniform at the lowest level.
Reloading cases with different headstamps, therefore, sets up the possibility for small variations in performance. Those differences probably don’t matter to a deer hunter; but to a guy trying to put 10 bullets in the same place, they can matter a lot.
So, I pulled 10 cases with the Federal Cartridge headstamp and set them aside for special treatment. Then, I selected a second lot of Federal cases and put them into a second group. A third group was comprised of cartridges with random headstamps.
Next, I trimmed all the cases to the same length — 1.760 inches. To this point, I hadn’t trimmed a single case, and semiautos like the AR-15 are known for stretching their cases.
Following that, I reamed the inside of the necks of the 10 special FC cases. I then loaded them with the 68-grain bullet and Varget powder that had produced the best group. The other cases I loaded with 77-grain bullets and Reloader-15 powder that has also shown a lot of promise. I wouldn’t call them control groups because they were reloaded with a different charge and bullet, but I was certainly interested in how well they did.
The moment of truth!
After warming the barrel with the 10 mixed cases (which got a 1.225-inch group), I started shooting the select cases with the good bullet and reamed case necks. The second bullet went into the same hole as the first. So did the third. When the fourth bullet enlarged the hole only a little, I suspected I was finally onto something. Shot 5 didn’t seem to make the hole any larger and I almost stopped shooting at that point. Never in my life had I ever put 5 shots from any rifle into 1/8 inch, which was what I estimated this group to be through my 30x scope sight. But fair is fair, so I pulled the trigger on shot 6. It went into the same hole, but enlarged the group noticeably. It was now about 1/4 inch between centers.
I was on a roll, and what a story this was going to make. So I lined up the crosshairs and fired shot 7.
“Oh somewhere in this favored land the sun is shining bright;
The band is playing somewhere, and somewhere hearts are light,
And somewhere men are laughing, and somewhere children shout;
But there is no joy in Mudville — mighty Casey has struck out.”
[From the poem Casey at the Bat by Ernest Thayer, 1888]
Shot 7 landed apart from the first six and thumbed its nose at me through my powerful scope. So, I put my head down and finished the group. Two more shots were also apart from the main group and had the ironic audacity to land together, as if to say they were in the right place and all the rest were wrong. And one bullet managed to nick the main group, enlarging it by a considerable amount. In the end, I’d put 10 shots into .859 inches — a decent group; but when compared to the 0.198 inches of the first 5 shots, not that respectable.
The first 5 rounds went into 0.198 inches at 100 yards. Seven of the 10 shots went into 0.43 inches. But the 10-shot group measures 0.859 inches because of those 3 shots that strayed.
Here was yet another group that contained within it a smaller group of respectable size. But why had at least 3 of the 10 bullets gone so far astray? Hadn’t I done everything in my power to make these cases identical and as perfect as possible?
I had to wait till I got home to sort the 30 cases because my eyes were not good enough to discern those with the reamed necks. They were reamed on the inside and now the tiny scratches were filled with burned powder ash. But under the magnifying hood and strong lights at home I found them, one at a time. They all had the tiny scratches from reaming. But there was a problem. There were only 7 cases with the FC headstamp on them. None of the rest of the FC-stamped cases showed the signs of having been reamed. I looked among the odd headstamps, and there I found the remaining 3 reamed cases. Somehow, I’d mixed them up during the reaming operation and the non-FC-stamped cases got mixed in with the others.
Three! An interesting number, because it matches the number of bullet holes that are not in the main group. And that’s today’s lesson. It’s not a lesson about how to do something — it’s a cautionary tale about what not to do. That’s what we learned today. You can’t be too careful when you test things, and you have to check things twice and even three times before you pronounce them as good.
That is what I failed to do this time. And you know what comes next, don’t you? I have to rerun this test and next time make sure everything is done correctly.
I’ll make a prediction. If I do everything correctly as I’ve said here, I predict that this load will be able to put 10 rounds into a group that measures under 1/2 inch at 100 yards.
We shall see.
by B.B. Pelletier
You know that dream where you remember at the end of the semester that you signed up for a course that you forgot to attend, and the final exam is today? And you just walked out the front door without your keys and the door locked behind you? And you’re in your underwear? And you live on Main Street? Well, something similar really happened to me!
Two years ago, I spent some time in the hospital, and the best-laid plans….Actually, my buddy, Mac, drove out from Maryland and spent a week testing airguns and taking pictures to help Edith and me keep the blog going. When he left, Mac left me with a pile of targets and photos that I continued to use to write blogs for two weeks after I was finally discharged but still not back on my feet.
Mac did test the .25-caliber Benjamin Marauder for accuracy and left me with the test targets, but in the post-hospital confusion I threw them out! Then, when I recovered enough to finish the report and discovered I’d disposed of the targets, I looked for the .25-caliber Marauder so I could finish the test. But couldn’t find it. I figured Edith might have returned it while I was out of action.
However, last week I was packaging some guns to return and found the .25-caliber Marauder standing just where Mac had left it. So, today, I am doing the accuracy test of the gun that was last reported nearly two years ago.
Actually, the rifle and you readers do benefit from my mistake, because there are now two great .25-caliber pellets available. When Mac tested it, there was only one — the .25-caliber Benjamin dome that I’m so tempted to call a Premier. It weighs 27.8 grains, and Mac got an average velocity of 797 f.p.s. with a tight spread from 791 to 802 f.p.s. That’s an average muzzle energy of 38.94 foot pounds.
The other pellet wasn’t available when Mac tested the rifle. But I discovered during the test of the TalonP pistol that the .25-caliber JSB Exact King is another superior .25-caliber pellet. Weighing 25.4 grains, it should be a trifle faster than the Benjamin dome but produce slightly less energy.
Long time, no shoot!
When I set about to test the Marauder for today’s report, I was reminded how long it’s been since I shot one. There was a guy at the recent LASSO shoot who was shooting a .177 Marauder, and I remember being surprised by how quiet it was. But his rifle was the only one keeping up with my Talon SS on the smallbore range! And he was shooting out to 75 yards! So I admit there was a lot of anticipation at getting to shoot a Benjamin Marauder once again.
So, here’s a quick impression of the rifle before we get to the accuracy report. The Marauder is a big gun. I’d forgotten how large the stock feels. It isn’t heavy, but it fills your hands. The trigger is one of the best on the market, but the trigger in the rifle I tested has not been adjusted. It’s exactly as the factory sent it. The first stage was surprisingly heavy, but stage two was light and very crisp. Once I figured out where stage two was, I found the trigger very crisp and responsive; and of course, it would be no trouble to dial off some of the first-stage pull weight.
The rifle was set to operate on a 3.000 psi fill from the factory. I say that because the Marauder will function with any fill pressure from 2,000 to 3,000 psi — it’s adjustable by the owner. But the .25 screams to be set up for the full 3,000 psi. That’s because this big .25 is a real thumper that uses a lot of air for each shot. I got three good 8-shot magazines from each fill, but after that the pellets started falling lower on the target. So, 24 shots to a fill.
I mounted two-piece medium-height rings on the rifle, and that was when I discovered that the receiver of the Marauder is not very high. Usually, the receiver on a precharged rifle is much higher than the barrel, but the Marauder is different. The barrel is shrouded for quiet shooting, which makes it fatter, and the low receiver means mounting a scope takes some thought. You can’t just slap on a scope with a 50mm objective lens, because it will hit the shroud. So, I used an old Bushnell 6-18×44AO Trophy that I used to use in field target competition. It provided plenty of magnification and a very clear image.
If I wanted to use a scope with a larger objective, I could have used high mounts, of course. But the medium mounts were much better for natural eye placement.
Okay. What will she do? Quite a lot, actually. This big quarter-inch bore is accurate! At 25 yards, it managed an 8-shot group that measures just 0.287 inches between the centers that are farthest apart. That was with the Benjamin domes. Why 8 shots and not 10? Because that’s the magazine’s capacity in this caliber. I actually shot a couple such groups, and they were all pretty much the same, much to my surprise. This big Marauder wants to lay them into the same hole, shot after shot.
Next, I tried the JSB Exact King pellet. It’s a little lighter than the Benjamin dome, but also has a wider skirt — and I could feel the pellet entering the breech every time the bolt was pushed home. This time, I went to the trouble of loading a partial magazine to get the full 10 rounds in the target.
From just this evidence, I would have to say the JSB pellet isn’t right for the Marauder; but because I took such a long break in the report, I’m not going to let it end here. I want to mount a better scope on the rifle and try it again. And I want to adjust the trigger next time. I think the Marauder has more to show us.
One more thing
The pellets for this big .25 cost as much or more than .22 long rifle ammo. That’s correct — they run $20 to 25 for 500. So why shoot an air rifle? First, because it’s more accurate than the average .22 rimfire shooting budget ammo. Second, because this rifle has a better trigger than all but the more expensive target rimfires. Third, although this air rifle produces pretty close to 40 foot-pounds at the muzzle, it’s still shooting diabolo pellets that are safer at distance than a .22 bullet. Fourth, because unless you spend $400 and more, you aren’t going to get a .22 rimfire that’s this quiet.
Scale is why you shoot a Marauder. You can drop woodchucks at 50 yards and not bother the cattle in the next pasture. Make no mistake, the .177 and to a lesser extent the .22 Marauder are both well-suited to plinking and general shooting. The .25 is not, unless you don’t mind the additional cost of the pellets. The .25 is a hunting airgun, plain and simple. But it’s a hunting airgun that can hit the target without weighing 12 lbs. or requiring 50 lbs. of effort to cock.