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+--- Thread: Ar accuracy problems (/showthread.php?tid=23995)
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Ar accuracy problems - jdd - 11-29-2021
I built a Ar for the grand kids. 18 fluted barrel medium weight 8 twist 5 r rifle long. Dpms match up adj gas block, match trigger, dual spring captured spring buffer spring system. Factory ammo will only do 4 at 100. Hand loads about 1 at 50 with 130 tsx and hot loads of tsx and h4895. 95?makers at 31.5 of tac approach 1 at 50 . Disappointed in accuracy. My 11 year old has arthritis problems and I want to shoot light bullets . I tried 3,shots of internet of 4198 near top end at 50 was a 2 group. What do I need to look at. Barrel was well reviewed but not a major brand , I dont recall the name , any suggestions.
Ar accuracy problems - Stugotz - 11-29-2021
I remember reading (and found) a website that was very specific to the subject of accurizing an AR platform.
Click on this hotlink:
http://www.majorpandemic.com/2021/06/how-to-build-crazy-accurate-ar15.html
The only thing I have ever done (to all of my AR upper receivers) is square up the fave of the upper receiver. I have a friend that owns an Upper Receiver Lapping Tool that I borrow when I'm doing a new build.
Ar accuracy problems - fmyellowj - 11-29-2021
Stugotz Wrote:The only thing I have ever done (to all of my AR upper receivers) is square up the fave of the upper receiver. I have a friend that owns an Upper Receiver Lapping Tool that I borrow when I'm doing a new build.
Receiver lapping is something I also do regardless of upper or barrel manufacturer. I also use a little but of Blue Locktite between the barrel extension and the upper receiver, not on the threads but where the extension meets the upper.
Is the gas block installed straight? I've heard that can affect accuracy. Other than that I'd check to make sure the barrel wasn't contacting the handguard during firing, assuming it's free floated.
Ar accuracy problems - VASCAR2 - 11-29-2021
Make sure you have good clearance for the gas tube and gas block. Ensure the scope mount and rings are tight. I have a Friend lap the front of my upper receiver and I use blue Loctite on the barrel extension and upper receiver. The upper to barrel fit has always been good enough I didnt need shim stock to tighten the barrel receiver fit.
Just to eliminate one cause check any muzzle device (flash hider or muzzle brake). If still poor accuracy shoot with no muzzle device.
In my experience Nosler 100 grain Ballistic tips, 107 grain SMK, 120 grain SMK or Pro Hunters are very consistent bullets in various barrels of mine. Many members report very good accuracy with 85 grain Sierra Varmint and Speer 90 grain TNT.
You didnt mention the brand of barrel but with cheaper barrels it is luck of the draw on accuracy. Usually with higher priced barrels the company has an accuracy guarantee and dont want unhappy customers.
Ar accuracy problems - grayfox - 11-30-2021
Like Vascar said you are probably somewhat limited by the barrel itself.
That being said the lighter bullets would I think have the best chance of some accuracy.
I know factory loads are expensive these days but do you have at least one box of factory you can shoot? that would help break in plus at least factory stuff should work and give you an idea of performance. Not perfect but it's a start.
I like these light wt bullets.
100 gr Nosler BT or Hornady eld-whatevers.
95 gr Hornady Vmax.
90 gr TNT (speer).
107 Sierra SMK.
Do you have a chronograph?
For powders the good ones for lighter bullets are H335, 8208 xbr, and TAC. Others I'm sure but these work well.
For a rack-grade barrel don't expect any good groups until 50-100 rounds down the tube. So you might still be in that initial period.
You want to do a load ladder of 1 powder, 1 bullet and various weights based on Mfr or published data, to look for a good grouping.
Example: 95 gr Vmax and H335, from the book, 28.0 is min I would start maybe 29.0, 29.3, 29.6, 29.9, 30.2, 30.5, 30.8, 31.1 (31.2 is max but watch your own gun's response).
First set, use 1-shot per load, so you can get a graph of how your powder jug and bullet work in your barrel (each barrel is unique, and powders differ from lot# to lot#, so load data is just a guide).
Then for second round, Use 3 or 4-shot groups at each load.
I would also use just a regular carbine buffer weight, start simple and work up from there.
If the line graph of the first ladder looks weird or none of the load-sets group, then you can get into troubleshooting.
I will help you with charting but without a chrono it's a lot of shooting in the dark so to speak...
I've got grandkids so I'm with you...
Ar accuracy problems - LR1955 - 11-30-2021
jdd Wrote:I built a Ar for the grand kids. 18 fluted barrel medium weight 8 twist 5 r rifle long. Dpms match up adj gas block, match trigger, dual spring captured spring buffer spring system. Factory ammo will only do 4 at 100. Hand loads about 1 at 50 with 130 tsx and hot loads of tsx and h4895. 95?makers at 31.5 of tac approach 1 at 50 . Disappointed in accuracy. My 11 year old has arthritis problems and I want to shoot light bullets . I tried 3,shots of internet of 4198 near top end at 50 was a 2 group. What do I need to look at. Barrel was well reviewed but not a major brand , I dont recall the name , any suggestions.
JDD:
What does '3 shots of internet of 4198 near top end' mean?
Before you start going down a path that will lead you to buying stuff that won't work, maybe you ought to say a bit more about your position and test procedures. Three shots is almost meaningless at any distance and your shooting position means a lot to outcome.
Also, although you can use those powders and bullets, they probably are not ideal. The powders that will give you the best chance of consistently decent performance are historically, TAC, 2520, BLC-2, and 748. The bullet weights that historically seem to give the most consistent overall performance have been in the 115 to 125 grain weight. Consistent means that most loads with these powders and decent bullets in that range of weights will perform dependably well. Right around 3/4 minute with match grade bullets and under 1 1/2 minute with more traditional hunting bullets.
The true Grendel stepped throat is more forgiving to ogive style and overall cartridge length than a conventional throat so if you have a true Grendel chamber and throat, it means you have a better chance of consistency than not.
LR55
Ar accuracy problems - PVBoom - 11-30-2021
Who is the barrel manufacturer?
I don't build without an upper requiring a thermal fit (BCM blems).
Ar accuracy problems - jdd - 12-01-2021
Thank you , a great article , apparently I did everything wrong . Over torqued the barrel nut and the muzzel break. I will be ordering a lapping tool tonight
Ar accuracy problems - jdd - 12-01-2021
Spell check got me that was 3 shots of IMR 4198 near a top end load did not show any potential!
Shooting off of a one piece benchrest grade rest. 6x18 Nikon with parallax adjusted, testing being done at 50 yards . If its not shooting a 1 group at 50 why bother at a 100. I have 95 makers. 100 nosler bt. 130 barnes tsx. 31.5 of tac gave best groups with the 95 maker 11/2,@50, h4895 27 gr with 130 printed at a 1 at 50 yards but showed signs of pressure. Factory hornady in 123, 120 2 at 50 4 or worse st 100. I tried different holds on the rifle and it likes a firm grasp. I going to break it down , lap the upper glue the barrel in. I know that factory brass grows 10 thousand in headspace. I bump shoulders back 4 thou but havent tested enough to say it makes a difference.
Ar accuracy problems - Stugotz - 12-01-2021
jdd Wrote:Thank you , a great article , apparently I did everything wrong . Over torqued the barrel nut and the muzzel break. I will be ordering a lapping tool tonight
My friend (that I have been borrowing) is a Wheeler brand lapping kit. It does a great job. It may even be a little cheaper than the Browning version.
Ar accuracy problems - LR1955 - 12-02-2021
jdd Wrote:Spell check got me that was 3 shots of IMR 4198 near a top end load did not show any potential!
Shooting off of a one piece benchrest grade rest. 6x18 Nikon with parallax adjusted, testing being done at 50 yards . If its not shooting a 1 group at 50 why bother at a 100. I have 95 makers. 100 nosler bt. 130 barnes tsx. 31.5 of tac gave best groups with the 95 maker 11/2,@50, h4895 27 gr with 130 printed at a 1 at 50 yards but showed signs of pressure. Factory hornady in 123, 120 2 at 50 4 or worse st 100. I tried different holds on the rifle and it likes a firm grasp. I going to break it down , lap the upper glue the barrel in. I know that factory brass grows 10 thousand in headspace. I bump shoulders back 4 thou but havent tested enough to say it makes a difference.
JD:
You can take out parallax down to fifty yards with the optic?
You really ought to shoot a couple of groups at 100 and 200 (if possible). You may be surprised.
LR55
Ar accuracy problems - jdd - 12-02-2021
LR1955 Wrote:JD:
You can take out parallax down to fifty yards with the optic?
You really ought to shoot a couple of groups at 100 and 200 (if possible). You may be surprised.
LR55
Yes I can, I am not boasting but I spent two summers as a RSO and volunteer instructor at a 1100 yard range. With my precision bolt rifle I shoot sub moa groups at 1100 Yards AR are a different beast to rest. I spent a lot of shoulder time shooting them fast. But no prs type matches
Ar accuracy problems - jdd - 12-02-2021
Thank you guys for the suggestions. I have ordered the lapping tool, a gas block alignment rod , a set of fat wrenches to re-torque the barrel nut . While I have it off I will clean the bore and slug it to check quality. Tempted to replace it but I am interested in the accuracy work. I built a few bolt guns and ppc pistol, apprenticed as a gunsmith 50 years ago , always thought of Ar 15 as plumbing work and more about tuning for function and speed , they either shot moa or didnt.
What do I need to know about cases .
The fired cases are running 1. 223 factory measure 1.116 down to 1.114
What should I hope to buy? If I get lucky enough to find some. All I have is hornady.
Running hornady dies again not my favorite.
Ar accuracy problems - ported45 - 12-03-2021
Set your dies to bump the shoulder back down 0.003" from your fired case length.
Ar accuracy problems - PrecisionFirearms - 12-05-2021
Being this is for your kiddo with health issues, send it to me and I'll look it over, do the lapping, check for issues with barrel. All labor will be free, any parts will be discounted by at least 25% including barrel if required. Email me at pf15@pf15.com if interested.
Ar accuracy problems - Lastrites - 12-06-2021
PrecisionFirearms Wrote:Being this is for your kiddo with health issues, send it to me and I'll look it over, do the lapping, check for issues with barrel. All labor will be free, any parts will be discounted by at least 25% including barrel if required. Email me at pf15@pf15.com if interested.
To think in this day and age that such a nice offer would come from a premium shop, hat's off to you!
Ar accuracy problems - jasper2408 - 12-06-2021
Lastrites Wrote:To think in this day and age that such a nice offer would come from a premium shop, hat's off to you!
+1
Ar accuracy problems - HKGuns - 12-06-2021
Lastrites Wrote:To think in this day and age that such a nice offer would come from a premium shop, hat's off to you!
+2
Ar accuracy problems - Zeneffect - 12-09-2021
Try to avoid using the drill attachment for the lapping tool and do it by hand. Sure it's slower but you can be far more precise in material removed. Takes about 10 min by hand.
Ar accuracy problems - jdd - 12-12-2021
That is a very kind offer. I just tore it down and posted a update what I found. I know after the next visit to the range if the barrel worth playing with. Crown was washed out. Poorly polished. I no longer have access to a lathe. Gave it to a buddy to recrown. His range rod went in deeper than he is a custom to. We did not slug the bore, the scope did not show any major faults. The feed ramps were denting the shoulders and causing severe bullet runout problems verified on my Sinclair Bullets runout gage . A bullet with .004 going in ejected with over .025. And dents and gouges that could interfere with the round sitting correctly in the chamber. A little reprofile and polishing solved that. Thanks for the kind offer, I may very well take you up on it.