Accuracy Troubleshooting

[mac86951]

OK I'm starting this thread in an effort to predict what I'm doing wrong and to manage my plan going forward in finding the lost accuracy from my rifle. I'm guessing most of this is something I'm overlooking and will apply to any rifle, but some of this is rifle specific so sorry if it isn't directly useful to all.

Rifle: AR15 assembled by me (weee). White Oak Armament Varmint upper, meaning Wilson barrel 1:7 twist 20" long 223 Wylde chamber. ~2k rounds (+/- 10%) fired.

It used to be 3/4MOA when new and I started hand-loading for it at round 50.

Problem. I just completed load testing for two loads that used to shoot decently, which came out 4-5 MOA instead of the sub MOA I'd expect. Of course there have been a few changes to the rifle which I'll diagnose in a minute to determine problem.

Load 1: Nosler 77gr CC with 22.6gr Varget (2.260"). This was nearer to 2MOA than 5, however, it used to perform far better with same batch of bullets/powder.

Load 2: Hornady 75 A-Max single loaded (2.390"). I did 5-round groups from 23.5gr to 25.3gr Varget with no pressure signs (nor case head swipe meaning no marks of early ejection). I was lucky to hit a 12" plate at 209 yards with any of these loads.


Changes Made to Set-up:
Accuwedge installed
Sightmark Tactical scope installed (replaced Barska Varmint) please don't laugh the Barska did well for me for a while.
Default match load of 77gr Sierra and 23.4 Varget was not tested (supplies on order).

Plan of attack:
1. Full cleaning and disassembly along with looking for anything loose. Note scope rings, scope, and 20MOA rail are all tight ( I checked that already).
2. Load Default match load and try again
3. Change scope back to Barska and try match load again
4. Try newer brass. All previous loads tested with old set of brass (10 reloads on it)

Any other ideas?
I should say my reloading process, so to summarize.

Charges weighed on Chargemaster 1500 and loads pre-developed there using ladder testing at 200Y. Shoulders bumped 0.002" back on sizing and all brass trimmed to 1.750" when any in the batch measure over 1.760" Primers are R 7.5s seated with lee hand tool. Concentricty of loaded rounds is within 0.005" which is my old loading spec, this has narrowed thanks to RCBS competition seater die. Loads all fed from Magazine as the previous 2k rounds have been (except long seating for 75 A-Max).

-Mac

PS reading through this I realize I'm a happy reloader for someone who started 18 months ago. I'll also ask the AR guys. I have the same bolt, but might have mixed up the Bolt Carrier, would you expect this to shift accuracy this much? Naturally I'll test this theory, but opinions here would help too.

 

[pacificman]

Sounds like it might be the scope. Check scope with 4 point test. Your plan of attack seems reasonable. I would consider reversing the changes you made one at a time to see if one of those changes caused your problems.

 

[mac86951]

Sounds like it might be the scope. Check scope with 4 point test. Your plan of attack seems reasonable. I would consider reversing the changes you made one at a time to see if one of those changes caused your problems.

Aww now you tell me...
I'll put the pile of parts back together and hope I don't leave something out (just kidding)

I'm thinking scope too, which bites, cause it was mid-priced. Not cheap, but Not $$ either. Well, wait and see.

-Mac

 

['Freak]

Do you check and record distance to the lands and save the projectile used in the initial check so it might be done again later on to see what them 2K rounds fired been doing to your barrel?

 

[mac86951]

Do you check and record distance to the lands and save the projectile used in the initial check so it might be done again later on to see what them 2K rounds fired been doing to your barrel?

Good point, and yes I did do this.

Lands are still at the same point. Interesting note: My barrel hasn't performed well with VLDs ever aside from Hornady A-Max. I tried JLK 75gr, Berger 70gr and got only marginally ok plinking performance. It has done very very well with JLK's conventional 77gr as well as Sierra's and Hornady 75gr.

Mag-Length loading 2.260" is my requirement for our local match, and the lands are at 2.450" for that bullet. That is a bit more than a jump, but it used to shoot great. I'll do some loading this week and provide results early next (77gr SMK arrives Saturday)

-Mac

 

['Freak]

May be you’re stuck with not going over a fixed maximum length but also could be you’ll find something better by moving the ogive even further from the lands, incrementing the seater in steps of ~ .003”.

 

[mac86951]

May be you’re stuck with not going over a fixed maximum length but also could be you’ll find something better by moving the ogive even further from the lands, incrementing the seater in steps of ~ .003”.

That is a good point, I would try it, but 77gr SMK in a .223 at 2.260" is already seated quite far into the case, but theoretically there could be some room for adjustment there, but I'll stick to the minimum recommended loading for the bullet/cartridge.

-Mac

 

[mac86951]

OK, I have my answer

Details: I cleaned my rifle before starting the experiment. Finding was that it cleaned quickly with less than 6 patches.

First load: Nosler CC 77 gr. I had previous good results at 22.8gr varget, but those results were not repeatable. Today I shot the remainder of my 23.6gr varget load for testing scopes.

Shot a 5 round group at 100y first. Result was far better 1.5MOA.
Shot 2 shot groups at 100 for the box. Scope tracked back to center of initial group. 5 shots at 210y and back to 4-5 MOA. Switched to competition load.

Comp load: 77sierra 23.4gr varget.

Sub 1/2MOA 5 shot group at 100. 1/2 MOA at 200. Swapped scopes
And shot a one holer at 100y.

Done. Found out how important testing in reference to old loads is. I will keep some comp loads for reference before I switch to anything else.

-Mac

 

[pacificman]

Glad you found the problem...I think that is a good idea to keep a known load and target for reference. I do the same with my rifles. I'll tell ya that when yer rifle is not shooting the way you know it should...nothing will be right till you get it shooting. : ;D