Help with cheap 6.5 Grendel upper accuracy issues

solidarmy

Private
Belligerents
Mar 27, 2010
39
3
12
39
MD
I recently purchased an 18 inch 6.5 Grendel complete upper from PSA. The fit and finish are good as well as reliability, however I can’t say the same for its accuracy. With Hornady Black 123 gr ELD I was getting about 3 MOA. Basic build info is CMMG lower receiver parts kit and a Viper Vortex 4-16 HS LR scope.

I have seen a couple of reports indicating PSA barrel accuracy gets better over time, but I would like to use the rifle for hunting now. I don’t want to wait until I’ve put thousands of rounds through it before it’s useable. On my next trip to the range I plan on changing up a few things to test accuracy.

Use a different lower with a Geissele trigger.

Try different ammo

Work through the proper barrel braking procedures.

Is there anything else I can try out to improve accuracy?

These will be my last few tests before I give up and purchase a new barrel.

Any thoughts on a bore lapping system?
 
  • Like
Reactions: Arkansas shooter

Romeo458

That Guy
Belligerents
Minuteman
Sep 20, 2019
220
218
49
NEIA
Palmetto State armory as excellent customer service. Try a different scope, that was my issue with a rifle recently and if you continue to have issue yet ahold of them and they will make it right.

Try different ammo also. I have had good luck with hornady black but I've also had good accuracy from the Wolf ammo too.

They also are on Facebook with groups. With the AKV group I have seen a lot of comments that if anyone has any kind of an issue they have been Johnny-on-the-spot to help fix it
 
  • Like
Reactions: Greg Langelius *

Lawless

Pessimistically Optimistic
Belligerents
Minuteman
Feb 11, 2018
5,244
21,576
119
49
NC
Even milspec PSA barrels with M193 shoot better than that. I have built over 30 for family and friends. Grendel is typically a good shooter in PSA guns. Look at the scope and mount. Check barrel nut, there have been a few escape loose from SC.

All this assumes good semi auto fundamentals, not accusing bro just mentioning...driving an auto means follow through has to be perfect.

I once spent $100 on sight in ammo for a second hand Remington pump 30-06 only to finally figure out the barrel was loose in the receiver. Probably why I got it so cheap LOL. Tightened it up (made sort of like an 870 shotgun) and the thing shot well.
 

jphil108

Private
Belligerents
Jul 21, 2010
40
43
24
I have a PSA upper in .300 BLK I bought a few years ago and the forend rail was loose the first time I shot it, it was throwing large groups (5-8 moa) when I was sighting it in off of bags. tightened that up and they all land within the size of the reticle. This is with about the cheapest lower and gritty battle trigger you could get in 2010. Might also be able to lap the barrel some. As mentioned, their customer service is awesome and they'll have help you with anything you have a problem with.
 

bfoosh006

Sergeant
Belligerents
Jun 13, 2007
803
253
69
PNW
Double check that everything is tight... including the barrel nut.

Years ago I bought an upper that shot about the same group size as yours... I also decided a better barrel was warranted .

After getting to the barrel nut part of the swap ... the wrench , just placed on the barrel nut, moved the barrel nut.... it was finger tight and had been held in place by the gas tube.

After tightening it, properly , precision was much more in line with my expectations. ( it wasn't a match barrel, Lol )
 
Last edited:

solidarmy

Private
Belligerents
Mar 27, 2010
39
3
12
39
MD
Thanks for the great recommendations. I'll be checking tightness on everything and trying a different optic and ammo. If that doesn't help I'll reach out to PSA.
 

Gatorshark

kaboom
Belligerents
Minuteman
Apr 16, 2018
147
90
34
Many times its loose scope mount or rings. The lower assy does not affect accuracy that much usually.

Do some research on bedding the barrel extension. Especially if your going to check the barrel nut anyway.

I wouldn't just try to tighten the barrel nut, I'd try to loosen it and retighten/torque at a minimum.
 

101stinfantry

Full Member
Belligerents
Feb 14, 2017
1,593
894
219
AR
Check the easy stuff first, scope base/rings, check that the muzzle device isn't torqued on at 150 ft. lbs. Then try different ammo/loads if your a reloader. I'm gonna bet it just didn't care for that particular ammo.
Rakkasan! :D
 

Greg Langelius *

Resident Elder Fart
Belligerents
Aug 10, 2001
7,648
3,201
219
73
Arizona, good place for me...
Are you using a bipod? If so, how is it mounted?

I had installed a Magpul M-Lok bipod mount on a homebuilt (from AR Stoner components) 6.5G Upper, and due to the narrow handguard diameter, the M-Lok mounting screw protruded inside the handguard deeply enough to be in solid contact with the barrel.

Accuracy (inaccuracy) paralleled yours.

I removed the Magpul mount by turning the mounting screw just far enough out to get the Internal pad to rotate the required 90 degrees. I then broke out the dreaded Dremel and ground down the screws where they protruded until they are flush with the pad.

When remounted, the barrel and screws have adequate clearance, and accuracy immediately improved, a lot.

Greg
 

solidarmy

Private
Belligerents
Mar 27, 2010
39
3
12
39
MD
Quick update. I checked my rifle for all the suggested issues that were brought up in this forum and I think Greg Langelius wins. The M-lok mounting screws for the bipod were touching the gas block. I moved the bipod back a few inches, I'll be headed to the range next weekend. I'll post an update whith results.
Thanks again for all the help.
 

Yondering

Sergeant
Belligerents
Mar 16, 2017
574
196
49
Skagit Valley, WA
Double check that everything is tight... including the barrel nut.
This, especially with a PSA. Verifying the barrel nut tightness is one of the most important things you can do on their uppers.

I've used a handful of their uppers and lowers and always consider them a parts kit that happens to be mostly assembled. I've learned it's best to strip them down and go through everything, assembling everything the right way so I know it's good.

Bad accuracy as the OP described usually comes from something loose - scope rings & bases are the most common, but a loose barrel nut will do it too.
 

solidarmy

Private
Belligerents
Mar 27, 2010
39
3
12
39
MD
I went out for a short while today. Some improvement, but still needs more work. I checked the barrel nut, and scope mounts, everything was good. It seemed as the barrel warned up the accuracy got worse. The bottom group was the first. I then made some adjustments on the scope. The second group opened up more.
 

Attachments

Gatorshark

kaboom
Belligerents
Minuteman
Apr 16, 2018
147
90
34
I went out for a short while today. Some improvement, but still needs more work. I checked the barrel nut, and scope mounts, everything was good. It seemed as the barrel warned up the accuracy got worse. The bottom group was the first. I then made some adjustments on the scope. The second group opened up more.
That's just not at all Grendelish. Maybe you can get it swapped out? May just be dud.
 

Slowshot18

Private
Hessian
Minuteman
Aug 8, 2018
28
3
6
Houston, TX
I recently purchased a PSA 6.5 grendel 12" pistol kit. I threw it together on a stripped lower I had an away I went. I took it to the range for initial shooting and the groups sucked. take a look at the first white and green target. I was using Hornady black and the factory Hornady SST ammo. I chalked it up to the shitty trigger that came with the kit, the barrel was breaking in, or I was shooting bad that day (I do not usually shoot gas guns often). A buddy of mine found this thread and brought up the loose barrel nut. He had the proper tools to tighten it and while he was taking a look at the gun, he discovered that there were burrs on the inside of the barrel, from the cutting of the barrel. He never did check the barrel nut as the handguard was on pretty damn tight so we assumed the barrel nut was good.
He suggested I send it back to PSA but I do not like to wait.
I used a small file that I had and de-burred the muzzle. Took it out again and had great 3 round groups at 100 yards with the cheap wolf ammo and Hornady black ammo.
 

Attachments