Here is a good page describing the essential components and design considerations in an AR-15 action. In this post I summarize some research I did focusing on the tail end of the system: The recoil spring and buffer. In order to see exactly what goes on in there I cut a viewport into a buffer tube, clamped rifles into my test fixture, and recorded high-speed video of the action cycling.
I had the good fortune to meet Kyle Paaren, proprietor of Paaren Firearms, who specializes in rebuilding classic machineguns – often by rewelding demilitarized receivers. Many of these are brilliant pieces of engineering whose reliability and durability were proven in the mass military conflicts of the twentieth century.
I think the MG42 is the most impressive: It shoots full-power .30-caliber ammunition at a rate exceeding 1100 rounds per minute. It uses a roller-locked bolt mechanism that is unlocked by muzzle pressure (captured in its distinctive muzzle device) pushing back on the barrel itself. Its barrel can be changed in under five seconds.
I was allowed to take photos of some of these recent rebuilds.
Continue readingI’ve written a number of posts over the years in which I test the precision of various firearms. Some readers have asked about the particular methodology I use.
When testing guns for accuracy it is common practice to look at the Extreme Spread of a group of 3 or 5 test shots. I will explain why this is a statistically bad measure on a statistically weak sample. Then I will explain why serious shooters and statisticians look instead at some variation of circular error probable (CEP) when assessing precision.
Over the winter I accumulated a bunch of new factory ammo, and a few handloads, I was waiting for a nice day to test. That day finally came! Suffice it to say that with four rifles, two of which I switched in the field from .338LM to also test .308, this was an all-day affair. Now I need to find time to analyze all the targets and radar data….
This Remington R51 is a really great gun. I bought it at the end of 2017 for $500 (including the Crimson Trace laser sight) while Remington was offering a $100 mail-in-rebate. I have to applaud Remington for going through the significant trouble of launching a pistol based on the Pedersen “hesitation lock.”
Previously, pocket guns with such a low profile were only available with simple blowback actions, which limits them to .380ACP or lighter cartridges. The R51 is rated for 9mm +P, which puts it in the realm of “full-power” defensive handguns. At one time I owned a Sig P232, which is a very slick .380ACP pocket gun, but I sold it some years ago during a caliber consolidation. Subsequently my only gun that really fit a pocket holster was the S&W 642 revolver. Lacking the cylinder bulge, the R51 is easier to carry in a pocket. If you’re looking for an “everyday carry” gun, you could end your search here on that basis alone.
“Full-power” Sub-compacts: S&W 642, Remington R51, Sig P239
Interesting announcement today: The Summit toggle action 10/22 will now be manufactured by Volquartsen!
Dean Sylvester, PWS President and Summit designer commented “The Summit has been one of our most requested products over the years. We feel combining the unique features of the Summit design with the impeccable manufacturing standards and reputation of Volquartsen Firearms will allow both companies to focus on our core markets and ensure all customers are getting the best product possible.”
Here’s a .22LR bullet that went through my paper target at 50 yards and then somehow ricocheted back to hit me on the forehead. (It then bounced onto the bench in front of me, leaving me scratched and bewildered, but nothing more serious.)
I’m well aware that bullets can do surprising things, and I’ve even researched some of them in depth. I’ve seen videos of people supposedly getting hit by ricochets of their own bullets fired into conventional backstops, but this is the first time I can offer a first-hand account of such an event.
I was doing more precision testing with a rifle in my machine rest, which meant that I was firing tight five-round groups very quickly. The last shot in one group made an unusual impact sound in the earthen berm behind the target, and as I lifted my head from the scope I heard a snap in the trees to my left and then something like a small pebble hit me in the forehead hard.
I was alone on a private range, and as I rubbed my head feeling for blood or a welt (and finding neither), I saw this slug on the bench in front of my machine rest. It was too hot to hold, so I set it aside while I finished shooting my test plan. After photographing it back in my shop I weighed it at 40.7gr, so if it shed any lead during its trip it appears to have made up for it by catching dirt in its crevices.
Does this story come with a lesson? Well, for one thing, wear eye protection! If this had hit me in an eye it would have produced a serious ocular injury. Another: Unlikely things can happen! I would still say it’s extremely unlikely for an unjacketed, subsonic bullet fired into an earthen berm to ricochet a full 180 degrees and cover another 50+ yards. (And, in that rare event, the bullet would not have enough energy to cause serious injury, unless it hit someone in the eye.) But however unlikely something may seem, just realize there’s probably somebody who’s going to have an astonished look on his face when it eventually does happen. Do what you reasonably can to make that the worst consequence!
There are various reasons to take up handloading ammunition, including:
But the last benefit depends in large part on how one values one’s time.
Continue reading
Following some review of the recent Buckmark accuracy test, some readers wondered if the suppressor was hurting precision. Others, noting that Buckmark barrels are well known for their accuracy, wondered how the stock 5.5″ barrel would fare.
I ran the standard barrel through the same procedure as before. The aggregated data and analysis are in this Excel workbook, and the summary results with links to the 50-yard targets are here:
| Ammunition | CEP Radius (MOA) | Average fps | fps Standard Deviation |
|---|---|---|---|
| CCI SV | 0.9 | 930fps | 17.1 |
| Eley Contact | 1.0 | 973fps | 17.8 |
| Eley Club | 1.0 | 958fps | 13.5 |
| Gemtech 42gr | 1.0 | 941fps | 13.8 |
| Federal AutoMatch | 1.2 | 1053fps | 19.0 | Federal Champion HV | 2.1 | 1073fps | 20.5 |
This pistol shot everything well. In fact, the best four loads tested would all be expected to hit inside a Bullseye 10-ring virtually 100% of the time.
Running the Tactical Solutions barrel without the suppressor seemed likely to help its score also, at least with some loads. At 4″, it gives up 40-50fps vs. even the 5.5″ barrel. But the accuracy of CCI SV went from CEP of 2.0 MOA to 1.3 MOA. Groups of Eley Club (essentially the same performance as Eley Target) showed CEP under 1.4 MOA. However, it was not able to tighten performance of the Gemtech load. (Detailed data were added to the spreadsheet from the previous test.)
How accurate is a typical rimfire pistol? Out of curiosity I mounted my Buckmark, with its 4″ Tactical Solutions barrel and 5″ AAC Element II suppressor, on my test stand and recorded shots simultaneously at 25 and 50 yards.
As usual, I digitized the paper targets using OnTarget TDS, and followed the statistical analysis outlined at ballisticaccuracy.com. The aggregated data and analysis are in this Excel workbook.
| Ammunition | CEP Radius (MOA) | Average fps | fps Standard Deviation |
|---|---|---|---|
| SK Plus | 2.0 | 904fps | 20.0 |
| Eley Target | 2.0 | 952fps | 11.9 |
| Gemtech 42gr | 2.0 | 910fps | 15.0 |
| CCI SV | 3.1 | 914fps | 16.2 |
| Federal Champion HV | 4.7 | 1037fps | 14.6 |
I was surprised at how much more dispersion this gun shows than the 10/22 rifles I have tested. It’s certainly nothing to brag about: The 10-ring on NRA Bullseye Pistol targets (shot competitively with autoloading rimfire pistols) typically has a radius of 3MOA, and even with zero shooter error the good ammo here would only hit that 80% of the time.
