Grendel II chamber

[LRRPF52]

so the gap rifles you mentioned you still call them 308 and 260 but the throats are specific to the bullets you shoot are they not still 308 and 260 chamberings?? I am not defending liberty barrels in fact I returned my barrel for a shilen. The problem centered around not being able to chamber factory ammo and that is a valid problem.

The .308 AR10 I had built pulls 168gr and 167gr factory ammo, and dumps powder everywhere. If you light one off, it craters or blows the primers.

The .260 Rem will never see a factory round if I have anything to say about it. I only fire hand-loaded ammunition through my .260 Remington. Every .260 Rem gas gun I've seen, as well as 6.5 Creedmoors, spit out brass with either:

* ejector swipes
* thrashed extractor rims
* Cratered primers
* flattened primers
* pierced primers

Here is what JP has posted on their website about the .260 Rem in a gas gun:

LRP-07™ rifles chambered in .260 Remington

[SIZE="3"]The LRP-07™ chambered in .260 Remington is designed primarily for the skilled hand loader[/SIZE], as there is little available in accurate factory .260 ammunition. Best accuracy is usually achieved at about 10% below recommended maximum load data in recognized loading manuals. Be aware that canister powders can vary significantly in burn rate from one lot to another and if you start a new lot of powder, it may be necessary to work up a new load. Do not assume that a “factory“ load for the .260 will perform satisfactorily in your LRP-07™ and assume that there is something wrong with the rifle if a particular ammo fails to function or exhibits high pressure signs. Available factory ammunition is designed for rifles with 1:9 twist barrels. We use a 1:8 twist barrel for improved accuracy with certain high BC-type projectiles. This may not be compatible with some factory loads. You may experience high pressure failures such as dropped primers and excessive bolt velocity resulting in extraction/ejection failures or even possible ruptured cases. If high-pressure signs are evident with any ammunition, discontinue use of that ammunition immediately.

Remember that gas-operated semi-automatic rifles in any caliber are much more ammo sensitive than manually operated rifles. You must find or load ammo that is compatible with the rifle, not expect that the rifle can be made compatible with the particular ammunition that you have chosen.

Every factory load I have shot through my 6.5 Grendel has fired, extracted, ejected, fed, and chambered correctly without these pressure signs, and it's fun to shoot. I honestly got into the Grendel thinking that I would only hand-load for it, but I ended up shooting a lot of factory ammunition in it from AA, Precision Firearms, and Hornady. What's not to like?

It makes it much easier for me to take it out shooting than my .260 Rem, which a very kind forum member has sent me an improved firing pin for to address primer piercing and cratering issues of the 60,000psi SAAMI .260 Rem. When you drive long bullets with slow powders and those pressures, and have a gap between the firing pin and the hole, the primer likes to fill in there. I've already bent & ruined at least 2 firing pin retaining pins with my .260 Remington AR10. Hopefully this new pin will solve the cratered primer issue.

When I describe the AR10's I have had custom built, I usually explain that the chambers were cut for specific bullet profiles. My .260 Rem will shoot all the bullets I had it throated for into very tight little clusters. Guess what? Trying to get the 140gr A-MAX to shoot that way has never worked, no matter what powder and combo I have tried. 139gr Scenars first 5rd group I ever shot looked like this: