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Help… my Grendel pistol isn’t accurate - Printable Version

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Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-19-2022

[Image: cro9krb.jpg][Image: vH3lZ5s.jpg][Image: 1V6ilzI.jpg][Image: jaCZKYb.jpg]






odinworks barrel and with gas block and matched BCG

APF side folding lower

kaw valley linear comp

larue MBTS trigger

and lots of good stuff

Best I manage is about 2in at 100yards and Odin works said they have no guarantee on accuracy from their short Grendel barrel

Help… my Grendel pistol isn’t accurate - Klem - 11-19-2022

JH,

What makes you think your group size is all down to the gun? Where the bullet goes is a combination of factors: position/rest, conditions, ammunition, you, and the gun.

Your mount is back-to-front.

That ocular is too far back - it needs to be roughly level with the charge handle, fine tuned to where your natural cheek weld and eye-relief is best.

No offense, but all the aftermarket fruit on that gun is a clumsy proxy for precision. Precision is all down to the barrel, scope and trigger - in that order. Everything else just holds it together and makes it work. To be fair I have never heard of Rudolph and judging by their prices it might be the limiter in your accuracy system. Or it may be the ammo, or the barrel, or your ability to shoot. But something will be the limiter in your accuracy system, or in other words the weakest link. You just need to find it, improve or eliminate it, find the next one, and so on as your groups improve. It won't all be down to the gun.

And practise makes perfect.

Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-19-2022

I have a friend who owns a Gunshop and has a great relationship with their rep. They don’t have a strong American presence.

I’ve shot hornady black, sst, and Barnes.

The larue trigger isn’t my favorite, my other larue trigger feels better.

I’ve called Odin works and they said they have no accuracy guarantee on their pistol length Grendel barrel.

I’m shooting off a lead sled and can hold MOA or better with my bolt guns. The mount is backwards but it is to get more eye relief at higher power because the stock has the built in side folding mechanism.

Help… my Grendel pistol isn’t accurate - Klem - 11-19-2022

JH,

I strongly recommend pushing that scope forward (I've used side folders). Your folded unit is longer than it could be with that [fragile] scope sticking out one end. In a pack it is asking to get damaged. Use the collapsible stock to manage optimum eye relief - that is what it's for.

If the scope is repeatable to 1MOA, and you are capable of shooting that well with similar factory ammunition in bolt guns, then you could swap out the barrel for a better quality one. What branded scopes are on your bolt guns?

My earlier advice still stands.


['Repeatability' is the scope's ability to retain zero in the recoil. Cheaper scopes are less able to manage the G-forces of recoil]

Help… my Grendel pistol isn’t accurate - Bigs28 - 11-19-2022

It's also a semi short barrel. I wouldn't expect sub moa unless you get a quality barrel and reload. I can constantly get 0.6 moa 8 shot groups from my 12 inch krieger barrel with my own loads but i paid for that.

Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-19-2022

[Image: CsTN5FE.jpg]

My 300 win mag with a Rudolph scope

I’m pleased with it

Help… my Grendel pistol isn’t accurate - grayfox - 11-19-2022

Like Klem said.
Barrel, scope, trigger.
By the way, did you say what length the barrel is, or the gas length? I don't see it.
I'm guessing 10.5, pistol length barrel...

Might be, with factory ammo, 2" is best you can get, that is minute of deer btw...

I reckon there's a reason why Odin has a guarantee on regular length barrels, but not the short ones.

edit to add. If you're satisfied with those 3, then the next thing is the shooter.

Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-19-2022

https://www.odinworks.com/6-5-Grendel-Barrel-12-Carbine-with-a-BCG-p/b-6.5-12-ul-c-tg-bcg.htm

My barrel

Help… my Grendel pistol isn’t accurate - LRRPF52 - 11-19-2022

It is much easier to shoot bolt guns when going for tight groups since they don’t have a hammer swinging inside the action, followed by a lot of reciprocating mass slamming back and forth.

If you’re free-recoiling an AR-15 pistol, it won’t group.

Same is true with my lightweight AR-15 rifles. If I free-recoil them, I’ll get 1.5 - 2” groups.

When I man-up on the rifle and apply gas gun fundamentals with straight, rearward pull of the stock into my upper body, with aggressive rear bag support, I can rapid-fire ~ 1 MOA 5rd groups with the light-barreled guns, and anywhere from .3 to .6 MOA with the heavy-barreled Grendels.

Here’s an example of groups I shot rapid-fire back-to-back, starting with a loose-hold/free recoil from a field position, then hunkered down using gas gun technique:

[Image: 20201207_135258.jpg?width=590&height=590&fit=bounds]

That’s with my 17.6” Wasp profile Lilja barrel, which has a .650” thin profile under the handguard, then steps up to a .750” gas block journal, .740” fore end.

Load is 31.5gr of CFE223 under 123gr A-MAX in Lapua brass.


Here are some groups shot with my 12” 6.5 Grendel using gas gun fundamentals:

[Image: 20180727_170156_zpsurtmn8ob.jpg?width=48...fit=bounds]

From the other 12” Grendel I built with the same type of 12” Faxon barrel from the initial group buy we did here, different shooter:

[Image: 20190301_170115_zpsmgluejeu.jpg?width=59...fit=bounds]

Then me with the same gun:

[Image: 20190301_161744_zps9ge7vm8n.jpg?width=59...fit=bounds]

Help… my Grendel pistol isn’t accurate - LRRPF52 - 11-19-2022

Next I will ask what the assembly process was for installing the barrel, and was your upper receiver face square?

I true or check that all my receiver faces are square, then find the best barrel extension-to-upper fit among a handful of uppers I have at-hand.

I do not buy uppers anymore and just hope that they fit ok, but mate up the barrel in question with that upper to reduce and eliminate slop.

I also don’t let the barrel near the upper until it passes a series of dummy cartridge checks I have to see where chambers are at in terms of distance to the lands.

I also record what the gas port diameter is, and measure the diameter of the gas block journal so I can mate the gas block tightly (slop is the enemy for reliability, but friend of ease of installation for DIY builders, not a good combo).

All 3 of the Grendels listed above have bedded or thermo-fit barrels, where the barrel is mated to the upper tightly. One of the 12” barrels took me at least 45 minutes to pound into the upper with the tightest interference fit I’ve ever experienced with an AR-15. The others are bedded with Blue Loc-tite.

For optics mounting, I use a torque wrench to ensure all fasteners are consistent to the recommended specs from the mount and ring manufacturer.

Rings get Blue Loc tite on fasteners.

I think applying gas gun fundamentals will tighten your groups though.

I noticed what Klem was talking about first thing as well, with the backwards Warne mount.

If you set the optic up for ideal eye relief, it will be easier to shoot. The Warne mount (and any cantilever mounts) are designed to locate the optic for optimum eye relief on AR-15s.

Help… my Grendel pistol isn’t accurate - Zeneffect - 11-20-2022

Here is something that isn't mentioned, nor have I mentioned on my builds....

Your bolt catch/release/bad lever is going to wear out the ears of the lower eventually.

I shimmed mine! I forget who sells shims for like $20 but a set of feeler gauges on Amazon is $6.

Make shims from feeler gauges, then it will have to chew through the shim first before damaging your lower receiver. I measured the gap, grabbed a feeler gauge that is 1/2 the value and then drilled 2 holes and cut it to fit with scissors. Fixture to hold down the shim was packing tape and a wood block.

Help… my Grendel pistol isn’t accurate - stonehog - 11-20-2022

Jaeger - I’ve had two of these barrels and both shot better (in general) than my 18 and 20 inch (Faxon and PSA) but all will do MOA with the right loads. I agree with Klem and LRRPF52 in the recommendations.

Help… my Grendel pistol isn’t accurate - montana - 11-20-2022

Zeneffect Wrote:Here is something that isn't mentioned, nor have I mentioned on my builds....

Your bolt catch/release/bad lever is going to wear out the ears of the lower eventually.

I shimmed mine! I forget who sells shims for like $20 but a set of feeler gauges on Amazon is $6.

Make shims from feeler gauges, then it will have to chew through the shim first before damaging your lower receiver. I measured the gap, grabbed a feeler gauge that is 1/2 the value and then drilled 2 holes and cut it to fit with scissors. Fixture to hold down the shim was packing tape and a wood block.

https://triggershims.com/ar_15_shims.php#S25

Help… my Grendel pistol isn’t accurate - Zeneffect - 11-20-2022

Yea that's it. By the time you get the shims you want, it's way over the cost of a set of stainless feeler gauges.

Help… my Grendel pistol isn’t accurate - Klem - 11-20-2022

JH,

All this talk about the fixes to the external ambi slide locking lever. You're better off getting a dedicated lower with a thru button.

Help… my Grendel pistol isn’t accurate - montana - 11-20-2022

Zeneffect Wrote:Yea that's it. By the time you get the shims you want, it's way over the cost of a set of stainless feeler gauges.

Mill tolerance is .014 to .030 slop, so one washer from McMaster Carr should be sufficient. I have used the BAD lever for years and the most slop I have seen on any of my rifles was .01

These no. 2 stainless steel washers come in a thickness range of .018 to .032 for $2.73 per hundred https://www.mcmaster.com/washers/washers-3/general-purpose-washers-9/

As long as you keep the space between the min .004 and max .030 you should be good to go..

Spring tension with the bolt catch spring is what I focus on..

Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-20-2022

Im hoping to pick up a lower for some kind of Black Friday sale. I really like the aero m4e1 a friend has. Also want to get a trigger tech adaptable.

Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-20-2022

Would also like to get a 12in Rainer ultra match. The emails we have exchanged they guarantee sub MOA

Help… my Grendel pistol isn’t accurate - imaguy3 - 11-20-2022

Zeneffect Wrote:Here is something that isn't mentioned, nor have I mentioned on my builds....

Your bolt catch/release/bad lever is going to wear out the ears of the lower eventually.

I shimmed mine! I forget who sells shims for like $20 but a set of feeler gauges on Amazon is $6.

Make shims from feeler gauges, then it will have to chew through the shim first before damaging your lower receiver. I measured the gap, grabbed a feeler gauge that is 1/2 the value and then drilled 2 holes and cut it to fit with scissors. Fixture to hold down the shim was packing tape and a wood block.

First I'm hearing about this.. how does it wear the ears on the lower and any pics?

Help… my Grendel pistol isn’t accurate - Jaeger Heisen - 11-20-2022

The only ears I hear about are the ones on the trigger guard so I’m curious too