My new 6.5 Grendel Piston AR build

[mwroseberry]

Just got her slapped together and wanted to post up some pics. Have a couple rounds out for a function check and will have to shoot it this weekend for groups.

I'll post up specs later tonight.

Thanks,
Merritt

 

[Gildoom]

Looks really nice, can't wait to see how it shoots and what that piston system is. Congrats!

 

[mwroseberry]

Seekins upper and lower
Stoner 1 in 8 twist 24"
4 port break
Adams piston system
ALG mil spec trigger
Ace Skeleton stock
Samson hand guard
BCM gril
BCM charging handle

 

[savages]

Nice setup!
I'm betting 1/2 moa average at 100yds once you get the load work done.

 

[CastleRocker]

That's real nice. I've built two for my wife and both of them are amazing shooters. Factory ammo shoots under 3/4" and it's a one ragged hole rifle after load development. Thinking of building one for myself!

 

[mwroseberry]

Thanks guys. Had an interesting issue this weekend. Was having feed trouble and couldnt figure out what was going on. When the rifle fed normally it was shooting 5/8" groups with factory hornady amax ammo but whenever I had a feed issue it was opening up to 2". Packed it up and went to the house. Once there I noticed that my piston gas block had shoved forward. I didnt use lock tite when I originally installed it and I payed for it. So ive since put red lock tite on the barrel, slide the block over it and installed blue lock tite on the screws. Now a 3 day wait and try again.

Also noticed the rounds were into the lands when I went to extract. Is this normal with factory ammo on these grendels?

Thanks,
Merritt

 

[plong]

Nice!! One question: where the @$#&*!! did you find a barrel? I've been looking high-n-low for about 3 months...

 

[mwroseberry]

Nice!! One question: where the @$#&*!! did you find a barrel? I've been looking high-n-low for about 3 months...

Gunbroker. Ive had two barrels on order since october. Neither delivered so I got one off gunbroker. Now got to decide which order to cancel. Both quoted me 4-6 week waits and both are triple that so I gave up on them.

Good luck,
Merritt

 

[BigBlue&Goldie]

What were your impressions of the barrel? Any flaws? Did it come with the bolt?

 

[mwroseberry]

No flaws. It came with the bolt. Everything seams to be within spec. The M4 feed ramps even fit together well, no polishing required to mate them up.

Thanks,
Merritt

 

[LRRPF52]

Thanks guys. Had an interesting issue this weekend. Was having feed trouble and couldnt figure out what was going on. When the rifle fed normally it was shooting 5/8" groups with factory hornady amax ammo but whenever I had a feed issue it was opening up to 2". Packed it up and went to the house. Once there I noticed that my piston gas block had shoved forward. I didnt use lock tite when I originally installed it and I payed for it. So ive since put red lock tite on the barrel, slide the block over it and installed blue lock tite on the screws. Now a 3 day wait and try again.

Also noticed the rounds were into the lands when I went to extract. Is this normal with factory ammo on these grendels?

Thanks,
Merritt

The factory ammo is engaging the lands because the Midway AR-Stoner barrel wasn't cut with a Grendel reamer, which is a SAAMI spec'd, open-source chamber now. We actually see this a lot on the Grendel Forum. A Hide & Grendel member who does barrel work used an ogive comparator, and saw anywhere from .020"-.030" of COL shorter on the AR-Stoner barrel than his Shilen Grendel barrel.

All factory ammo, from 90gr TNT's, to 129gr SST's have fed and extracted fine in my Grendel chamber, and I can actually load out to 1.300" with the 129gr SST in my gun. I just wish everyone in the industry would use the SAAMI chamber, rather than a derivative of a chamber that was built around the 123gr SMK. You don't know what you're getting with many of the barrels on the market, which is why AA was so insistent that barrel-makers adhere strictly to the Grendel chamber diagram. It makes sense to have one datum, so all the factory ammo makers know where to seat their bullets with different ogives.

Right now, it's hit and miss with barrels that weren't cut with a Grendel reamer. Another thing to think about is start pressure. With the projectile jammed into the lands, you're most likely in territory over 50,000psi chamber pressure. We have seen cases where guys are getting soot flow out the primer pocket, wondering why their "Grendel" is doing that with factory 123gr AMAX, only to learn the barrel was cut by an unknown source, or someone who thought their chamber was better, that didn't want to be held to the QC standards spec'd by the Grendel chamber dimensions.

In the 6.5 Grendel Reloading Handbook, this aspect of chamber variants is addressed in detail, to include chamber drawings. Know thy chamber, and load/feed for it.

 

[mwroseberry]

In the 6.5 Grendel Reloading Handbook, this aspect of chamber variants is addressed in detail, to include chamber drawings. Know thy chamber, and load/feed for it.

Yeah I had a bad feeling this was the case. I have some 120g A-max in hand and 123smk on the way. Sounds like I need to get to reloading faster than I planned to. I don't have any major pressure issues as of right now with primers getting blown out but I'll make sure to inspect the brass well.

Thanks,
Merritt

 

[LRRPF52]

Yeah I had a bad feeling this was the case. I have some 120g A-max in hand and 123smk on the way. Sounds like I need to get to reloading faster than I planned to. I don't have any major pressure issues as of right now with primers getting blown out but I'll make sure to inspect the brass well.

Thanks,
Merritt

Your throat will slowly erode to where this might not be an issue. I personally would just have it reamed and move forward, and here's why:

When I got into the Grendel, I thought I would exclusively hand-load for it. As factory ammunition resources have grown to the point where there are 25 loads, going on more, I realized how much more fun it is to shoot ammo out of the box, which I can just grab and go. The Hornady 123gr AMAX is very hard to beat for accuracy, as are many of the loads from AA and Precision Firearms, and even the el cheepo $13 a box Wolf 120gr MPT, which is 1MOA or better from most people's guns, and a surprisingly deadly hunting bullet to boot. (It has a tapered jacket thickness, so as you go deeper into the jacket cup, it gets thicker and thicker, helping retain bullet mass through game.

Someone just posted some links to sources for the reamer that will address this issue for you. You should not be forced to hand-load for the Grendel, although many enjoy it.

 

[mwroseberry]

Your throat will slowly erode to where this might not be an issue. I personally would just have it reamed and move forward, and here's why:

When I got into the Grendel, I thought I would exclusively hand-load for it. As factory ammunition resources have grown to the point where there are 25 loads, going on more, I realized how much more fun it is to shoot ammo out of the box, which I can just grab and go. The Hornady 123gr AMAX is very hard to beat for accuracy, as are many of the loads from AA and Precision Firearms, and even the el cheepo $13 a box Wolf 120gr MPT, which is 1MOA or better from most people's guns, and a surprisingly deadly hunting bullet to boot. (It has a tapered jacket thickness, so as you go deeper into the jacket cup, it gets thicker and thicker, helping retain bullet mass through game.

Someone just posted some links to sources for the reamer that will address this issue for you. You should not be forced to hand-load for the Grendel, although many enjoy it.

This is going to be a medium range competition rifle so I planned to hand load everything anyway. And I was planning on using it in a sniper match the beginning of next month so it looks like I have no choice. no big deal I just have 160rds of Hornday match I need to pull the bullets on and hand load then adjust the seating depth.

Off to the gun room to see about getting some done.

 

[mscott]

Looks good. I think that will make a very good rifle for the Rayner's match.

I've kicked around the Grendel as it is a cool round, but just barely have time to load for the calibers I already have.