Originally Posted By LRRPF52

SAAMI Grendel chamber is .300" neck with compound throat starting from the neck at .5 degrees, then at .153", it hits a 1.5 degree target leade. It shoots all bullet shapes well, is easy to load for. No matter what bullet I have tried with this cartridge, I get boringly similar results, namely ~.75 MOA to 1.2 MOA for 5rd groups measured at 200yds, from a production button rifled ER shaw/AA cut 16" barrel.

From 20" high end cut-rifled or button barrels, we typically see .5" or better accuracy for 5 rounds. Some of the AA/Satern barrels will shoot 8rds into less than .25". Many have contacted me and wished they could still get a Satern barrel with an AA provided reamer like they used to be.

6.5 CSS is Arne Brennan's chamber, which is a tighter neck, but still has the compound throat to be able to shoot VLD's from the mag without jumping them. It's an excellent chamber if you hand load for it and full-length size your own brass, ensuring the necks are at a point where they will still feed in a gasser.

.264 LBC-AR is a .295" neck with parallel freebore at .120", 1.5 degree target leade.

This mentioning of "Grendel II" is total hogwash BS to address a problem that never existed, unless you consider running a ragged turd reamer with no freebore through untold numbers of barrels, then sending them to Midway and Brownell's advertised as "6.5 Grendel", then blame AA for it. We took a chamber cast and did bore scope analysis of some of those. The rifling literally started in front of the neck of the case-absolutely no freebore at all, which is why projectiles were jammed way into the lands, bullets being pulled, primers piercing and blowing. Accuracy was great because there was no jump at all, jammed thoroughly into the lands like a bench gun. Pressures to blow primers are usually in excess of 70,000psi. Some morons actually advocated people to keep shooting those barrels, and ignore the "hype" from guys like me and others who have been reloading and shooting for decades.

Here's the comparison between the chamber cast of one of the Liberty barrels that were chambered with a severely worn reamer:



Now you see why factory ammo was jamming into the lands, piercing/blowing primers, pulling bullets, but shot very accurately.

Especially as the steel case now hits the market, you definitely want to ask for an actual SAAMI chamber if you plan to shoot it. Certain reamer makers don't like cutting the SAAMI reamers because it actually requires them to put attention to detail in the reamers that will show up quickly if they don't. Many ask, if the Grendel compound throat is such a good design, why aren't other cartridges using it?

Easy answer: Pressure. Since the Grendel operates at lower pressures, you don't erode the throat like you do with 58,000psi and higher designs. The next question then naturally is, why can't we just ramp up the pressure in the Grendel/AR15?

Easy answer again: AR15 upper receiver and barrel extension dimensions restrict us from using a larger diameter extension like on an AR10. Once we try to enlarge that, we just eliminated parts commonality with upper receivers and barrel extensions. Once we start looking at a redesign, we say, "Why not totally redesign the upper, lower, bolt, extension, and mags?"

Right now, the difference in performance between Grendel and .260 Rem for me is 200yds comparing 16" Grendel to 22" .260 Rem with a 123gr. With 22" to 22", it's more like 90-150yds difference.

Is it of any value to attempt a total redesign of the AR15 so I can close that 150-90yd gap? We're talking about effective ranges that are outside of over 98% of the consumers' capabilities or practical uses in the market. My little 16" stays supersonic out past 1300yds right now with just factory ammo at my lowest elevations in this State, and past 1000yds at sea level in other States.

If I go to a 20" or 24" Grendel, it's even farther, but I'm quite happy with the shorter barrels.

An 18" barreled Grendel will exceed the hunting and target uses of most consumers easily. Those who have very specific requirements will have their rifle built for them exactly how they want anyway. The 18" Grendel really offers a wide range of real performance advantages for the first time in firearms history if you think about it:

* Lightweight (8lbs or less base rifle)
* Small package/AR15 compatibility/ easily fit to the user, by the user
* Very low recoil for a centerfire rifle ~50% of a .308 Winchester, friendly to youth, small-framed, and injured shooters
* Medium to large game killing capability (Mule deer, large hogs, caribou, elk, moose)
* Excellent hunting system for stalking elusive game, with farther reach and less wind drift than many common hunting cartridges/rifles that require larger actions
* Semi-auto
* Trajectory like .308 or better, with less wind drift for hitting steel targets at distances up to 1000yds or more, depending on atmosphere and user skill
* Over 30 production factory loads available, all of which are meant to function in a gas operated AR15
* Affordable, readily available magazines
* SAAMI-approved & certified cartridge, with relatively low operating pressure

I can't think of another caliber/rifle that can fill all those bullet points, and the Grendel does each of them well.