Ar accuracy problems

[jdd]

[Stugotz]

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.

[fmyellowj]

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.

[VASCAR2]

[grayfox]

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...

[LR1955]

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

[PVBoom]

Who is the barrel manufacturer?

I don't build without an upper requiring a thermal fit (BCM blems).

[jdd]

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

[jdd]

[Stugotz]

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.

[LR1955]

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

[jdd]

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

[jdd]

[ported45]

Set your dies to bump the shoulder back down 0.003" from your fired case length.

[PrecisionFirearms]

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.