TX_COWDOC said:

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I'm sharing my approach to trouble shooting an inaccurate gas rifle.
For perspective, here's a Grendel build with factory Hornady Black:

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Distance?

10 feet.


J/k 100 yards. Atlas bipod and a rear bag.

Still cannot get the upit app to work but here is a pic of the offensive beast from a few years ago.

Looks like it works ok to me

Need to move that front scope mount back
Recheck mount screws and scope screws

You took a 4 year break from reloading - gonna ask some dumb questions here, and remember that there aren't dumb questions, only dumb people that ask questions:

Assume you FL resized all of your brass
Assume you've checked headspace
Brass is trimmed to SAAMI standard?
What type of primers are you using?
Try different powder.
I know you've tried a few projos, but try different ones.
Have you lapped your bore? (I think you said you did, but can't remember)
Gas block - is it adjustable? If so, start with it fully closed and slowly work until it cycles.
Muzzle brake/flash hider - have you shot it without one? Check alignment to ensure your threads are cut right

Keep in mind that you are talking about a pistol here - shorter barrel, brace isn't he same as a stock, errors are going to be magnified as a result.

I thought the barrel was 18", unless I misread

I had issues with mine as well. At first we thought it was the barrel but finally found out it was the crappy rings used to mount the scope. Thanks to eyeguy they used better rings and now no issues.

tandy miller said:

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I thought the barrel was 18", unless I misread

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Aww snap, you are right. I was conflating this one with the post that has the Grendel pistol for sale. My mistake.

Measure your chamber. Some guns like close to the lands and some like a little more jump. Load 5 rounds close and then load 5 more .004 shorter. Do this for 4 different loads and one will perform much better than the other 4. A friend told me years ago that many chambers are reamed with the same reamer. The first chamber will be longer than the 20th chamber. I do this with my rifles and have found this to make a difference.. Hornaday makes a tool that you put a case and bullet in and you push the bullet to the lands and then mic it. Keep reducing .oo4 for 4 different length loads. One will perform better than the other 3. Hope that helps.

I have a LaRue Grendel and it's very accurate. The factory Hornady Black 123ELDM shoots pretty dang well. When I worked up some loads, I personally had the best luck with XBR 8208 and 120BT and 120ELDM bullets. My node was 28.0-28.3 grains of powder. I think I tried 3 different powders and 8208 was the best for me.

I also load for a buddy that has a Ruger Ranch Grendel and his rifle liked the 8208 as well. Basically the same load as my LaRue. I didn't really fiddle with depth. They shot well at 2.26" COAL.

I've only tried 2 loads out of mine:

PSA stainless barrel, hodge podge of other parts and what not.

Nosler BST, 120 gr, G7 Drag Coefficient
22.6 gr Hodgdon 4198
Wolf SR Primer
Starline brass
2.20" COAL
1.730" Ogive length
.60" group @ 100

Hornady 123 SST, G7 Drag Coefficient
23.6 gr Hodgdon 4198
Wolf SR Primer
Starline brass
2.25" COAL
1.780" Ogive length
.50" group @ 100

Just as an update. I do many of the suggestions above. I have the Hornady Tool to check chamber length, cases are fully sized and trimmed each time. Annealed every second or third firing. I shoulder bump .004, have .003 neck tension and seat bullets lightly crimped with a Lee factory crimp die. I have used both CCI 450 and WSR primers but usually use the 450s because the powders I have been using are all ball type and the magnums are supposed to provide more consistent ignition. I have not lapped the bore as it was hand lapped at the factory but I might give some J-B a try.

I built this gun in about 2009 and have taken the upper completely apart and put back together 3 times in the last 5 years. First to check for gas tube interference, second to lap the receiver ring and last spring I bedded the barrel extension. Always torqued back to specs when put back. I'll try the J-B and I'll move the forward scope ring back as suggested. I'm not sure what that will do because it sits on a full length rail. If I get no result with that I will try a different handguard, I'm pretty sure I have a spare PEPR mount laying around. I have some 2015 powder and some Varget that I might try as well. Thanks for everyone's thoughts.

Seems like you've gone through a painstaking process on the gun itself.

No one here has mentioned just swapping the scope and mount from a gun you know shoots well to see if it's an optics or rings issue. Burris isn't a top of the line scope. It should more than do the trick but maybe it's a dud.

Surely you've already tried that?

In OP no. 4

Why do so many people skip half the OP?

And Burris as a brand is fine

Buck Compton said:

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Seems like you've gone through a painstaking process on the gun itself.

No one here has mentioned just swapping the scope and mount from a gun you know shoots well to see if it's an optics or rings issue. Burris isn't a top of the line scope. It should more than do the trick but maybe it's a dud.

Surely you've already tried that?

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Yes... mentioned in OP.

CactusThomas said:

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In OP no. 4

Why do so many people skip half the OP?

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I read it and missed it. My bad. Touchy today with football sucking I guess.

swampstander said:

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Buck Compton said:

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Seems like you've gone through a painstaking process on the gun itself.

No one here has mentioned just swapping the scope and mount from a gun you know shoots well to see if it's an optics or rings issue. Burris isn't a top of the line scope. It should more than do the trick but maybe it's a dud.

Surely you've already tried that?

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Yes... mentioned in OP.

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Then honestly it sounds like you just have a dud. Might just be time to cut your losses on this one.

tandy miller said:

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Looks like it works ok to me

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That was a long night. Four came out and I popped the biggest one from about 150. The other three scattered with one running up to about 50 yds so I popped her. I got down and I loaded those two up. The other two were hanging around still watching me so I popped the third resting across my truck bed. The forth was still standing in range as I drove off by I gave her a pass.

OP - where are you located?

TX_COWDOC said:

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OP - where are you located?

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Anderson County, hunt in Leon/ Freestone Counties.

Update on my Grendel.

I moved the scope ring and scrubbed the bore with J-B as suggested above with no result. I took the gun back apart and swapped out gas block, scope mount and handguard. Yesterday I was able to keep Hornady factory SSTs and some Nosler BT reloads all inside an inch at 100. I still want better but I guess my issue is solved. I had enough confidence with it to back up into some bushes and pop a fat doe under her chin from about 75 yds yesterday evening. Not sure what the problem was other than as Cactus suggested, sometimes quality parts just don't play nice together. I swapped a $250 handguard for a $60, a $100 gas block for a $40 and a set of $60 scope rings for a $20 Chinese PEPR knock off.

On a side note, I was shooting yesterday using a pond dam as my back stop. I noticed as I was setting up my target that there was a small water moccasin curled up at the base of a bush. He ignored me so I ignored him. When I got done shooting the Grendel I decided to shoot my Contender in 7mm TC/U. I was able to put 3 rounds into .8 inches from that same 100yds. I wondered if I could pick up that small moccasin in that 4 power scope Sure enough there he was. The contender group centered about an inch high and 1/2 inch to the right. I made score adjustments, loaded another round in the contender an sent it. Definitely my furthest water moccasin kill ever but 100yds with a pistol is pretty cool.

Still cannot get upit app to work or I would post pics.

I have had best luck with 120gr bergers with 8208 xbr and lapua brass. Shot sub .25" through JP barrel. Fairly finnicky getting there. I'll post recipe when I find in book.