LR .308 Deminishing Accuracy! I'm Puzzled

[Hi Speed]

I finally fitted the JP trigger in the DPMS and went to the range earlier today. The rifle had 5 rounds put through it last time out after cleaning. The first 2 shots were touching and the last 3 were 2 inches low. I pulled a boresnake twice through the barrel and once again the first two shots touching at poa and the last 3 were 2 inches low. Would a dirty gas tube cause this? The scope is mounted in warne tactical rings with blue loc-tight and I checked them for torque. they are good to go. The gun has been set up for 5 years and has been a tac driver. I was using BHG 168's with like lot #'s as previously used. I have not ever changed the gas tube but do check the gas block every cleaning and can't think of anything else it could be.

The scope is a Mark 4 leupold 4.5X14-50AO MD.

I have both yellow springs in the trigger group even though it is reccomended to use thr red hammer spring to avoid misfires. I'm punching paper so a misfire would not bother me even though it did not happen. Could this cause the problem?

 

[cz777]

Re: LR .308 Deminishing Accuracy! I'm Puzzled

i had my ap4 do this trick to me too i found bore tech cleaner till no blue/green patchs followed brake cleaner and lightly oil with Mobil oil /slip2000 ....3 other things to check is barrel nut loose and head spacing ,muzzle end damage/ carbon built up!

 

[pupdawg]

Re: LR .308 Deminishing Accuracy! I'm Puzzled

Try and shoot it more with the same ammo. See if it tightens up those last 3 shots.

How are you shooting? Off the bench w/rear bag, prone with rear bag and bipod, benched off front and rear rest?

I don't think the trigger is the problem nor the barrel being dirty. If you did give it a good cleaning then maybe the barrel just needs to foul a little more to get consistent.

 

[Hellbender]

Re: LR .308 Deminishing Accuracy! I'm Puzzled

First, clean the barrel properly with a good copper solvent and use a real rod and brushes, not just the bore snake.

Second, (probably the source of the problem) put the proper heavy springs in the trigger group. Just because it goes bang does NOT mean you are getting proper, consistent ignition.

Your gas tube never needs cleaning, it is fine.

 

[Hi Speed]

Re: LR .308 Deminishing Accuracy! I'm Puzzled

I agree the barrel does need 13 shots after a good cleaning to season. Especially after some 7.62 has been used. The boresnake has never caused this problem. Prone bypod and bag is the only way I shoot after making a change. I've spent my lifes savings in this position!LOL. I guess I'll change barrels or crown it for giggles. I would rather not say how many rounds have been put through it. I'm on my third one. Many many thousands.

 

[Howie Feltersnatch]

Re: LR .308 Deminishing Accuracy! I'm Puzzled

I'd take it to a smith and check throat erosion. If you have that many shots down the barrel it makes sense to check it out and get it re barreled. Since the barrel has had that many shots down the tube theres a chance the explanation for your shots is because the first two shots the barrel is still "cold" but after that it heats up and throws the shots off. Could be something to look at.