Die Selection and Reloading for Reliability in AR10s
By Dennis Santiago
Competition teaches you things. Compared to loading for benchrest bolt guns, producing ultra-reliable and accurate ammo for tight-chambered, semi-auto .308 target rifles requires a different approach to case prep. Smoothness of operation is much more important in a field course gun. Reliability trumps everything (even case life) for these types of guns.
In the photo below, there’s a Redding small base body die for bumping the shoulder and making sure the case body is at SAAMI minimum. This body die is not just nice to have. It is vital. There are also a full-length sizing die and a Lee Collet neck-sizer in that turret holder. One or the other gets used after the body size die depending on what rifle the ammo will be used in. The semi-auto rounds always go through the full-length sizing die. After that comes trimming and finally cleaning — then loading can begin. The cases are trimmed using a Gracey trimmer so everything’s the same each and every time. I use an RCBS Competition Seater Die to seat the bullets. One nice feature of this RCBS die is the open side slot that allows you to place bullets easily.
It’s a long path methodology but uniformity is accuracy. More important for safety, controlling “stack-up” errors in the system solution is how one achieves reliability. The chamber-hugging philosophies of benchrest bolt guns do not apply well to AR-10s. Like most things, the right answer is context-dependent. Success is about accepting and adapting.
Dennis Talks About Using a Semi-Auto in Tactical Competitions
I have succumbed to the Dark Side — deciding to put an AR-10 together. For tactical competitions you want a bolt gun most of the time but there are times the course of fire favors the use of a semi-auto. I was using an M1A that gives me 0.75 MOA performance but I heard people were getting almost bolt-gun-level, half-MOA accuracy out of their AR-10s — so I wanted to see if that was really achievable. A quarter-MOA difference in accuracy potential may seem tiny in practical terms but it will make a difference in competition. In a match, the difference between 3/4-MOA and 1/2-MOA can alter your hit probability on a small target by 20-30%.The AR platform also lets you tinker with triggers, stock ergonomics and muzzle brakes that help in managing the dynamics of a long distance shot better. Well I found out you can get the incremental accuracy but there’s more work to do to get the same reliability. Being a curious sort, it’s worth it to me to explore it. It’s a far cry from as-issued M-1 shooting with whatever HXP is handy. This is definitely swimming in the deep end of the pool.
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Tags: AR10, Dennis Santiago, Field Course, Lee Collet, M1A, Tactical
I agree that reloading for a gas gun is different than your average bolt rifle, I don’t think the small base die is vital to the reloading process. I have loaded more 223 and 308 ammo than I can count over the years for both M1A/M1 and AR type platforms. Never once have I used a small base die. I have used Redding, RCBS and even Lee dies, and when set up properly to size the case, I have had no problems that were the cause of improperly-sized brass. The trick to gas guns is properly sized brass, but your load and fitting it to your gas system are more important. The biggest piece of advice I can give for AR shooters is to avoid military surplus brass unless it is virgin brass. Most of the “cheap” surplus stuff has been fed through M249 SAWs and the SAW is unbelieveably tough on brass (as are most machine guns). I highly recommend biting the bullet and getting new brass and keeping it separated for each rifle. I don’t mean to dismiss the author’s idea that small base dies are good tools, but I don’t think they are essential when you are a careful reloader.
R/S, JW
Editor: Thanks for the comments JW. I’ve chatted with Dennis and he agrees that if one has a good FL-die that is an excellent match for the chamber this could eliminate the need for the small base die. Your advice regarding keeping brass for each gun separated is smart.
New to the AR308 reloading game and my (match) chambered 308 won’t accept brass that HASN’T been run through a full length sizer and a small base die. Just another step in brass prep.
JWT,
I’ve also reloaded ammo for .223 and .308 semi-autos including .308 M-1’s and M1A’s for years and never ran into a problem like this until the AR-10/LR-308. My issue was not an isolated one. The internet is full of notations about failure to feed problems with these guns. Naturally, I tried full length size dies with the AR-10. No dice. A vanilla FL die leaves dimensions ever so slightly fat – we’re talking as small as 1/1000th – and it seems that’s enough to interfere with the bolt carrier from going all the way home reliably with these guns. And they get dirty quickly owing to direct gas impingement with further adds to friction.
I found my rifle consistently failed the pull on the charging handle after loading a round and the bolt should come open easily test. I checked everything until all that was left was a tolerance mismatch between the clearances in a common full-length sizing die and the dimension of the chamber. Not just any small base sizing die but specifically the Redding Small Base Body die is what it took.
For this model of rifle, it looks to be critical to both bump the shoulder and squeeze the main body of the case to minimum with a small base die to ensure proper clearance. Knowing what this does to work hardening the case, yes it goes against my instincts. But, if that’s what it takes to ensure reliable operation that’s what you have to do.
The discussion I had with Paul was about whether at some point the two die sizing process could be replaced by a tailor made full length sizing die. Essentially that’s going from the Redding approach of a body die + neck size die to a Whiddon single size die made to a match chamber print. The answer is of course yes for competition purposes.
However I’d also posit that for the many non-competition users of AR-10’s out there experiencing failure to feed issues, the observation that a $27 small base body die may be a low cost solution to improving reliability might have utility for this somewhat finicky platform.
Indeed, I wonder if a good question to ask is if there is a need to develop a Wylie type chamber for these AR-10/LR-308 type guns to improve reliability without degrading accuracy. After all, it works for their smaller AR-15 cousins.
– Dennis
Wylde type chamber. Darn auto spell got me again. Apologies.
I realize I’m blaspheming yet a second time but I’ve not really found surplus cases to be that problematic if properly prepared prior to first use.
Here’s the story of how I first discovered the utility of the Redding Small Base Body die. I got hold of three sets of once fired brass where I knew what chambers they came out of and had sample rounds of unfired ammunition to measure.
Set #1 was M118-LR Lake City cases from a single known lot number of ammunition – that’s like finding golden eggs – that were fired from a mix of bolt and semi-auto rifles I could go back and check against.
Set #2 was a mixture of 168gr Federal Gold Match cases that came out of around two dozen police sniper rifles from five different agencies with about half those rifles built by Tac-Ops in Beverly Hills, Ca.
Set #3 was a lot of Remington cases that were once-fired through an M134 Mini-Gun belonging to Independent Studio Services (ISS) for a sound recording session with Activision for the video game “Call of Duty”.
The bottom line is that regardless of source chambers, the cases got fat. I think it’s a myth that one should feel more confident with once-fired stuff that came out of bolt guns versus once-fired machine gun brass. I saw just as much variability in set #2 all of which came out of $10,000 sniper rifles. In fact, once-fired brass from some match chambers tended to get fatter. I think the cases were fire forming to their first use chambers particularly at the shoulders.
I used to full size brass as part of taking it out of the storage pile and getting it ready for my own active use. What the AR-10/LR-308 has taught me is this likely not enough. I now body die as the first step when initializing use of brass. The full size die is sort of a detector for when you “need” to do it again. You can feel it gets less easy to run the case through the full sizer as it grows again. Personally, it’s a lot better to do preventive squeezing for the AR-10/LR-308 rather than discover the bolt carrier group is being uncooperative at a match.
Anyone who’s had that happen to them knows the meaning of that angst.
Accuracy is one of the requirements to become a sharpshooter. This can only be obtained by using these tools. I am glad to read your site. Not many guns and ammo enthusiasts are very willing to share this kind of info. Thanks a lot! http://www.fsibrass.com/
Ive reloaded and fired tens of thousands of rounds in .223 for AR service rifle with a Forster standard FLS die without issue. Bumping the shoulder .002. I like the Lee collet die, use it with the body die when needed and a Forster seater for .308 Palma. Loaded rounds show very little run-out. Both the collet die and bump die can be bought for about 50 bucks total.