10-22-2020, 12:36 PM
txrider15 Wrote:Hi all,
I'm hoping maybe someone can give me some insight on a precision issue I've been dealing with since I got my first AR and 6.5G about a year ago. The problem: from one range trip to the next and sometimes on the same day I experience a wild inconsistency in my group sizes. They'll go from ~0.8in one day or group to ~1.25in to the next with no changes in the load etc. It's pretty much done this from day one at first I blamed the factory ammo Hornday Black 123 ELDs for the inconsistency. So I started hand loading and every time I thought I'd found a load where I was achieving ~0.75in groups, I'd load more go shoot to end up with 1.25in groups yet again. The best potential so far was 123 SMK with CFE I'd often get one tight clover leaf of 3 and 2 fliers that almost always landed in the same hole. Frustrated, I took the upper apart found the barrel was bedded (yes purchased assembled), removed it any ways and lapped the receiver face and reinstalled bedding with loctite 620. I took it back to the range. Factory ELD Black, 1.2in, 123 SMKs with 2520 ~1.3in, 123 SMKs with CFE one group 0.8 with 4 in <0.5in and then the 2nd group 1.3in only difference about 30 min later in the day. Exact same load within 0.04gr powder wise, within .001 CBTO, Hornady cases, chronograph says the average of each group was within 9fps of the other. Clean barrel with only ~15 rounds before the CFE groups. (Pic of CFE groups attached, 1.3in group was single fed, 0.8in group was mag fed at 3 and then 2 in the mag) (As an aside feeding from the mag use to really effect accuracy, this seems to be less prevalent since remounting the barrel. I also found the receiver bore was misaligned with the carrier bore and had to lap the carrier bore open to allow my face lapping tool to enter the receiver.)
Barrel is a 18in TBox, 1-7.5 twist
Additionally, I've replace the scope and mounts during all this with zero effect on the results. Running Vortex scope mount with Vortex Diamond Back Tactical.
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I'm not sure what to do with the gun at this point. I really just want it to shoot sub-moa but, consistently. Depending on the responses I get here if there's anything else to try before I give up on it, I'm thinking about selling and building from scratch or putting on a new barrel, like a proof research SS, Shilen, Douglas, or maybe trying Criterion or Wilson Combat? (Looking at 18in or 20in)
Sorry for the long post, trying to get the info out there up front. Thanks!
TXR:
There is no reason a rifle will shoot a group of 'X' number of shots and the next try, not shoot near or equally as well. The rifle doesn't know the difference. You do.
So, I believe it is you more than your equipment or ammunition.
Everyone wants to focus on the gear. Although I am suspicious of this 'TBox' barrel, even crappy barrels hold a group -- even if it is bigger than their false expectations of consistently shooting under 1/2 minute.
Now that you have conditioned yourself to shoot a couple of bad shots after shooting many good ones, you will have a hard time fixing it but it can be fixed.
You can buy a new barrel and if it is a top end one like you state, it will be better than this TBox thing. If you are convinced a new barrel will solve the problem, it probably will -- for a little while.
Most guys would be pretty happy if on demand they could hold 1 1/4 minute day in and day out. That is not bad performance at all. Very, very few guys here can hold one minute for shot after shot after shot. They may shoot a winning group during a shooting session but my bet is for every excellent group they shoot a bunch of average ones and a few that are bigger than what they would like.
So, my opinion it is primarily you and not your gear.
LR55