Accuracy Woes

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fancygunz
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Accuracy Woes

Post by fancygunz » Thu Apr 23, 2020 2:27 pm

Hello All,

This rifle has been giving me issues since day 1. The current issue is that I cannot, no matter what I have tried, get below 2 MOA (1 inch at 50 yards) on this rifle. I don't know what else to try at this point, but I find it very difficult to believe there is not something very wrong with the system!

This rifle is a semi-auto AR with a Ballistic Advantage 8.3" Hanson profile barrel (which has a sub-MOA guarantee) w/pistol length gas, bare muzzle for testing purposes, and a Primary Arms 1-6x24 scope (on a 1-piece cantilever mount, tightly screwed down and loctighted). I have an accu-wedge in there to take up any slack between the upper and lower receiver, so there is no wobble. I am shooting from the bench supported with a rest at the front and a bag at the rear. I consistently shoot 0.4-0.5 MOA handloads out to 300yd with my 308 bolt rifle so I doubt technique is the issue. I just replaced the barrel with an identical brand new one with NO significant change in accuracy before and after with the same loads. I was convinced it was a barrel issue but I now have no idea what could be going on. The gas port is 0.093" diameter and clean, the gas tube is clean, rifle is well lubed.

Shooting factory ammo at 50 yards, 5-shot groups:
Remington OTFB 120gr: 1142 fps, 30 SD, 77 ES, 2.9 MOA
Remington OTFB 220 gr: 1031 fps, 16 SD, 38 ES, 3.7 MOA
Sellier & Bellot 124gr: no velocity info, 4.1 MOA (YIKES!)

Shooting handloads at 50 yards, 5-shot groups, no less than 2.0 MOA (consistently 2-3 MOA) out of 65 variations of the following:
125gr Speer TNT
130gr Hornady SP
150gr Speer gold dot blackout
150gr Hornady Interlock SP
200gr Hornady ELD-X
212gr Hornady ELD-X
220gr Hornady ELD-X

H110
Shooter's World Blackout
CFE BLK

CCI #41 primers

Some single digit ES/SD numbers still with 2+ MOA. The velocity differences don't account for the accuracy issues. It's also not vertical stringing, it's all over the place. I attached a couple images of the "best" groups I can expect at 50 yards, those are 1-inch squares. Any help would be GREATLY appreciated!

Image Image
Last edited by fancygunz on Mon Apr 27, 2020 3:52 pm, edited 1 time in total.

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rebel
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Re: Accuracy Woes

Post by rebel » Thu Apr 23, 2020 4:59 pm

Try a different optic and take that out of the equation. Worth a try. 2 barrels, same problem so it is probably another issue.
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Re: Accuracy Woes

Post by BlogSarge » Thu Apr 23, 2020 6:03 pm

I second Rebel’s suggestion. Try another optic on this rifle and maybe also try the PA 1-6 on a known-to-be-sub-MOA rifle.

Also, is your one-piece mount attached entirely to the receiver, or is it partially attached to the rail on the hand guard? I’ve experienced accuracy issues due to slop and movement in the hand guard When I had a front mount attached there.

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Re: Accuracy Woes

Post by cdl » Thu Apr 23, 2020 9:56 pm

I have an 8.3" BA barrel and the 125gr TNT's consistently shoot extra poorly for me too. I've also swapped scopes when I get extra frustrated.

Try the 125gr SST's with 17.8gr H110 @ 2.100", 1922 fps.

Then grab some Hornady 208gr BTHP's. Load them with 10.4gr A1680 @ 2.095", 1030.5 fps.

The 110gr V-Max's shoot well too. 20gr H110 @ 2.055", 2141.3 fps.

These three loads stand out in a long list and will shoot one hole at 50 yds with my 8.3" BA barrel. The 208gr, maybe a little less so, but still great for a sub.  

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Re: Accuracy Woes

Post by certifiable » Fri Apr 24, 2020 6:01 am

Did you true the face of the upper receiver? I have not come across one yet that was perfect out of the box.
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Re: Accuracy Woes

Post by fancygunz » Fri Apr 24, 2020 10:30 am

rebel wrote:
Thu Apr 23, 2020 4:59 pm
Try a different optic and take that out of the equation. Worth a try. 2 barrels, same problem so it is probably another issue.
BlogSarge wrote:
Thu Apr 23, 2020 6:03 pm
I second Rebel’s suggestion. Try another optic on this rifle and maybe also try the PA 1-6 on a known-to-be-sub-MOA rifle.
Also, is your one-piece mount attached entirely to the receiver, or is it partially attached to the rail on the hand guard? I’ve experienced accuracy issues due to slop and movement in the hand guard When I had a front mount attached there.
Yeah it's definitely another issue (i.e. not the barrel). The mount is completely on the upper's rail and not the handguard. I'm hesitant to change out the optic because my only other one is sitting on a very accurate bolt action which I have spent a lot of time honing to perfection, so I don't want to mess up zeros or accidentally break something during the swap. I have removed and reinstalled the same optic twice already though, so unless it's something broken inside the scope itself (?) I can't see how it could be the cause. I swapped back and forth between rings and a single piece mount with no effect. I'll leave the scope swap test for later.
cdl wrote:
Thu Apr 23, 2020 9:56 pm
I have an 8.3" BA barrel and the 125gr TNT's consistently shoot extra poorly for me too. I've also swapped scopes when I get extra frustrated.
Try the 125gr SST's with 17.8gr H110 @ 2.100", 1922 fps.
Then grab some Hornady 208gr BTHP's. Load them with 10.4gr A1680 @ 2.095", 1030.5 fps.
The 110gr V-Max's shoot well too. 20gr H110 @ 2.055", 2141.3 fps.
These three loads stand out in a long list and will shoot one hole at 50 yds with my 8.3" BA barrel. The 208gr, maybe a little less so, but still great for a sub.
This is a very interesting reply. There is also a guy on youtube (Johnny's Reloading Bench) who reloads quite a bit of 300blk that could not get this barrel to shoot. He has 70 videos dedicated to 300blk, many of them are him struggling with this barrel. The same loads on a 16" barrel were shooting cloverleafs while the 8.3" BA would shoot wild all over. I know this is only anecdotal evidence with only 3 people's experiences but I haven't really seen any positive results yet from this 8.3" barrel :lol:

How sensitive to powder variations and OAL are the loads you listed above? You said they stand out in a long list of loads, how far off from the nearest bad load are they? I'm wondering if this barrel just has extremely narrow accuracy nodes. Unfortunately I don't have any of those bullets and finding some now might be difficult...I will try to get some 125 SST's or 110 V-Max's.
certifiable wrote:
Fri Apr 24, 2020 6:01 am
Did you true the face of the upper receiver? I have not come across one yet that was perfect out of the box.
No, what would this involve? I'm not sure what truing the face of the upper receiver means.

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Re: Accuracy Woes

Post by rebel » Fri Apr 24, 2020 1:23 pm

Facing or truing a receiver involves buying the tool, mine was from Brownells, and some medium valve lapping compound. Chuck the tool in a drill, apply the lapping compound to the front surface of the receiver and true it. It might be an issue with your build. I was going to ask what you torqued your barrel nut to as well.
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Re: Accuracy Woes

Post by cdl » Sat Apr 25, 2020 2:04 pm

fancygunz wrote:
Fri Apr 24, 2020 10:30 am

..., how far off from the nearest bad load are they? ...
How bad can bad get? It can get pretty darn bad.

In my 8.3" BA I mostly found OAL critical to reliability. Note also the loads I gave you will run fine in a GI mag. Pretty near every bullet that's fed out of a magazine needs to "jump" to get to the lands. I'm sure the manufacturer's liability carrier insists. So I mostly use OAL in 300 Blk to fine tune for reliability and velocity.

I spent a lot of time trying to get the 125 TNT to work. As a concept, they're cheap and look fragile in a good kind of way. I have a bunch. But they were never quite accurate enough to make me smile. Ok for fodder I suppose. 

The best 125gr TNT load I came up with was 18gr H110 @ 2.100" using Tula 556, Rem 7 1/2,  Win, Rem 6 1/2 and Fed 205M, in that order. CCI 41's didn't make the top 5. No CCI primer did. Standard deviations always seemed too high. (I actually track MAD instead of SD because "sum of the squares" and all, tend to pull the number toward the fliers. For me MAD is closer to what I expect to get.) Anyway, when I go to that trouble, it's a lost cause.

Now those other loads I gave you are awesome in my gun. They say the good barrels will shoot any bullet well, the budget barrels just take more work. That's not to say a budget barrel can't be good, there is just a higher chance it'll take more work. I own 3 BA barrels and they have a place. I don't spend $300 or $400 on every barrel.

Wish I knew who "they" always are.

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Re: Accuracy Woes

Post by fancygunz » Tue Apr 28, 2020 3:15 pm

cdl wrote:
Sat Apr 25, 2020 2:04 pm
fancygunz wrote:
Fri Apr 24, 2020 10:30 am

..., how far off from the nearest bad load are they? ...
How bad can bad get? It can get pretty darn bad.

In my 8.3" BA I mostly found OAL critical to reliability. Note also the loads I gave you will run fine in a GI mag. Pretty near every bullet that's fed out of a magazine needs to "jump" to get to the lands. I'm sure the manufacturer's liability carrier insists. So I mostly use OAL in 300 Blk to fine tune for reliability and velocity.

I spent a lot of time trying to get the 125 TNT to work. As a concept, they're cheap and look fragile in a good kind of way. I have a bunch. But they were never quite accurate enough to make me smile. Ok for fodder I suppose. 

The best 125gr TNT load I came up with was 18gr H110 @ 2.100" using Tula 556, Rem 7 1/2,  Win, Rem 6 1/2 and Fed 205M, in that order. CCI 41's didn't make the top 5. No CCI primer did. Standard deviations always seemed too high. (I actually track MAD instead of SD because "sum of the squares" and all, tend to pull the number toward the fliers. For me MAD is closer to what I expect to get.) Anyway, when I go to that trouble, it's a lost cause.

Now those other loads I gave you are awesome in my gun. They say the good barrels will shoot any bullet well, the budget barrels just take more work. That's not to say a budget barrel can't be good, there is just a higher chance it'll take more work. I own 3 BA barrels and they have a place. I don't spend $300 or $400 on every barrel.

Wish I knew who "they" always are.
So, OAl is important... just how important?

I am compressing CFE BLK for 150gr Gold Dot loads with some pretty good velocities (~1850fps out of an 8.3" barrel).

Even with identical processed brass there are some differences in bullets and powder settling which causes slight variations in both COAL and CBTO (cartridge base to ogive). How how crazy should I get with this, meaning what tolerances are "good enough" for 100 yard shooting? Should I be adjusting the seating die for each cartridge, or just set it once and leave it for the whole batch? Should I be looking at COAL or BTO? Are these variations small enough that they don't really matter? I would normally just shoot and check the results but I don't have enough bullets right now to perform extended testing. I will post velocity results for the below 20 bullets next time I have a chance to get out.

Load 1, 21.0gr CFE BLK, 10rd, (~1625 fps from previous testing)
COAL CBTO
2.103 1.521 min
2.140 1.532 max
0.037 0.011 ES
2.112 1.527 avg
0.011 0.004 StDev

Load 2, 24.0gr CFE BLK, 10rd, (~1850 fps from previous testing)
COAL CBTO
2.242 1.662 min
2.253 1.671 max
0.011 0.009 ES
2.249 1.666 avg
0.004 0.003 StDev

Is 0.037" variation in COAL or 0.011" in CBTO important?

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Re: Accuracy Woes

Post by cdl » Tue Apr 28, 2020 8:42 pm

0.011" is a lot for base to ogive, especially within the same bullet lot. Did those bullets come out of the Philippines?

Within a 5 shot group for accuracy, OAL and component consistency are material, but don't get hung up on a few thousandths batch to batch. Just use quality components.

The good loads are loads you can be sloppy with and they still shoot great. They exist. When things aren't going right, many times it just seems like some of those little things might matter. It's the brain trying to justify the effort...

Most of the "blueprinting" stuff is for people whose mission is to turn a 0.1 mill group into a 1/4 moa group. They're already starting with a great load and a useful form of a compulsive, obsessive disorder.

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