AR Accurizing

[LVLAaron]

I always think all of the voodoo with service rifles is of diminishing returns. Do nothing but use good parts and a good quality well machined barrel with decent ammo and 3/4 moa 20 shot groups from a rest is pretty achievable. That’s kind of the gold standard for high power competition. I’ve had some better but could never quantify why.

That "attitude" (no offense at all) is why I find the topic interesting. Lots of into out there about bolt rifles. Almost nothing in regard to gas guns. We just expect them to shoot how they shoot and never investigate what we can do to tighten them up.

Most conversations about AR15's are incredibly toxic (arfcom) - I really just want to win matches, or build guns that win matches.

I shot a lot of 5 shot groups like this with my AR Tac F-Class gun. I want to dig in and understand why, and repeat it.

 

[Bamban]

What clearance are you targeting Nez?

About a thou

 

[Bamban]

I always think all of the voodoo with service rifles is of diminishing returns. Do nothing but use good parts and a good quality well machined barrel with decent ammo and 3/4 moa 20 shot groups from a rest is pretty achievable. That’s kind of the gold standard for high power competition. I’ve had some better but could never quantify why.

I built my own service rifle topped off with a special order 1 moa dot March scope with all the best parts considered to be the golden standards in the community. I chambered the barrel with my own reamer and did all the mods I know. In testing at 200 from the bench, the rifle shot 5 shot groups at 3 different days no larger than 0.8 inch.

This was before the plandemic. I loaned my rifle and ammo (virgin brass, and 80 vld) to a friend to shoot at our mid range championship. He dropped 11 points across 2 days, but posted 61 Xs. The highest X count for all sling shooters including the any any winner.

The shooting system worked fine that day. The trigger monkey - the biggest contributor. The other two in the system - rifle and ammo enabled him to perform at his best.

Edit: Forgot to add that the gas port was timed to the groove the way Dave Tooley showed me how through our email conversation.

 

[whatsupdoc]

About a thou

That seems really tight, I am surprised there are no reliability issues.

 

[Bamban]

That seems really tight, I am surprised there are no reliability issues.

You are right. I had a problem with one right off the bat. It did not even go in the upper. I fixed the process. BCG to buffer tube clearance is more.

 

[SKWERLZ]

It was shot with front bipod and rear bag. I guess I should also note the groups were only at 100yds. I have not shot it further than that.
I tune the gas tube by making small bends so that the tube can enter the gas key without it making contact as it enters the key, lots of bend, test, bend involved. It probably took me an hour and a half to get it adjusted to where I like It. The upper and lower were tightened by using the Accu-shim. I also bedded the rear lug on the upper to help with any side to side movement.

That’s a double win as it keeps the gas’s tube from being abnormally worn early and leaking excessive gas.

 

[LVLAaron]

Got the tube bored out today. Hone arriving tomorrow. It's gonna be slick. If anything it feels a lot nicer cycling it without stuff slopping around.

 

[tobnpr]

View attachment 1649845


This is an interesting no name upper for the project. The bore is 1.012+- (Spec is 1.000 +.006)

Curious- what's the "+/-" on the raceway consistency (did you check with gage pins)?

 

[LVLAaron]

Curious- what's the "+/-" on the raceway consistency (did you check with gage pins)?

I don't have pins that big (Thought about making some that are "good enough" for gauging uppers). It's 1.012 plus or minus a half thou. I turned the bolt between centers to 1.010- It's still a LITTLE snug in a spot, but I'm sure that will wear in quickly.

 

[Precisionhunter417]

Do you have a tight fitting barrel extension or does it have end play? I recommend the match level accuracy videos from the CMP/NRA service rifle community.

 

[LVLAaron]

Do you have a tight fitting barrel extension or does it have end play? I recommend the match level accuracy videos from the CMP/NRA service rifle community.

I've always been a big advocate for bedding the barrel with loctite, or using a shrink fit upper

 

[urbanrifleman]

I don't think the parts are as good as they used to be. At one time you could buy chrome A1 bolts at gun shows. Pair that with a DPMS upper and they would easily shoot 1/4 inch groups with a good barrel. Mine did. At least.

My space gun is an old slab side upper bedded to the lower. The trigger is an early JP set up by John. Barrel is a Kreiger 7.7 made by Kreiger.

 

[jelenko]

I don't think the parts are as good as they used to be. At one time you could buy chrome A1 bolts at gun shows. Pair that with a DPMS upper and they would easily shoot 1/4 inch groups with a good barrel. Mine did. At least.

I think the quality of the parts depends on who makes them.

 

[urbanrifleman]

I think the quality of the parts depends on who makes them.

Sure. I think the old mil spec parts were (on the whole) from consistent vendors that held tolerance.

I think the earlier specs on the M16 were much tighter clearances than later when they opened everything up for sand and dirt.

 

[LVLAaron]

If you can tolerate him, Chad at School of the American Rifle has some interesting stuff. The guy gauges everything. He's been doing a mystery shopper series where he buys 10 of the same rifles from Ruger, M&P, etc and checks them all in great detail. Spoiler; the results aren't awesome.

 

[jelenko]

earlier specs on the M16 were much tighter clearances than later when they opened everything up for sand and dirt.

I'll be darn!

 

[CSLR grandpa]

I’ve had a few AR’s the first Colt I had I didn’t spend any time with it, a work friend rebarreled it and it shot fine.

The first really accurate AR I owned was an Olympic Arms ultra match probably shot 15000 rounds through that barrel.(a lot of Blackhills blue box) it was cheap back then.

Older Aero, Bushmaster lock up good, lower to upper fit, New Alexander Arms Upper is very good, 6.5 Grendel shoots very good for a 18” barrel. Older krieger set up by Derrick Martin is still very good.

New Wilson uppers and lowers I own are not as tight as I was expecting but they shoot very good, WOA 20P on one and Krieger 6Arc on the other.

Most are set up for squirrels and targets, The Grendel is light enough to carry.

Load development is done mainly with the Aero lower with a Jewell trigger.
As stated above the Barrel Extension to upper fit is very important.
This has been my limited experience I haven’t owned all brands but a few

CSLR grandpa

 

[urbanrifleman]

I’ve had a few AR’s the first Colt I had I didn’t spend any time with it, a work friend rebarreled it and it shot fine.

The first really accurate AR I owned was an Olympic Arms ultra match probably shot 15000 rounds through that barrel.(a lot of Blackhills blue box) it was cheap back then.

Older Aero, Bushmaster lock up good, lower to upper fit, New Alexander Arms Upper is very good, 6.5 Grendel shoots very good for a 18” barrel. Older krieger set up by Derrick Martin is still very good.

New Wilson uppers and lowers I own are not as tight as I was expecting but they shoot very good, WOA 20P on one and Krieger 6Arc on the other.

Most are set up for squirrels and targets, The Grendel is light enough to carry.

Load development is done mainly with the Aero lower with a Jewell trigger.
As stated above the Barrel Extension to upper fit is very important.
This has been my limited experience I haven’t owned all brands but a few

CSLR grandpa

My Derrick Martin service rifle is an absolute hammer even with the supposed worn out Douglas barrel.

 

[AccelR8]

Two methods to reduce or eliminate bolt droop. In my experience the two-screws way as described in the CMP/NRA videos is equally effective as the sleeve method but doesn't require work on the buffer tube.

I have never been able to get an upper to close down on an accu-wedge but I use hot glue as a quick fix on those receiver combinations that have a little play. Works quite well and is durable. Another quick fix is an o-ring over the upper receiver front pivot stud before mating the upper and lower. Works to eliminate play but usually the o-ring has to be replaced each time because it gets smashed and cut.

I create my own heat-shrink fit upper to barrel extension by using .001 or .002 shim stock around the barrel extension. I'm afraid to use locktite because I do like to take things apart. I used green once on a gas block and I needed a whole lot of heat to get it off again. More heat than I'd want to use on an aluminum upper.

 

[AccelR8]

By far I find the single most important thing is a good barrel. No surprise there. I have seen lots of barrels with sub-par chambering jobs and I believe this is the major cause of accuracy not meeting expectations.. I don't know whose barrels to recommend although I think White Oak has a good reputation. I make my own barrels from blanks. Usually do a Wilde chamber, being as careful as I can to ensure a concentric chamber.