6.5 History: Why do some variants have 0.295" neck diameters

[nincomp]

[pinzgauer]

Why are there .295” diameter (and smaller) chamber necks?

OK, I'll say it... some want to be able to claim a differentiation from stock Grendels. And there may well be some differentiators, but I've seen enough to decide that .295 vs .300 is not one of them!

My experience has convinced me that stock grendel chamber with decent ammo in a bull barrel, free float tube will shoot at the limits of AR accuracy.

Not saying that's the optimal setup for 600+ yards, but the folks I've heard who do shoot at that range have not jumped in swearing by.295 either. One very vocal person was building a spec gun for long range, and he spent months fighting neck & other chamber issues trying to "improve" on the grendel. Rand into lot's of compatibility issues. At his last report, he was just getting the same accuracy many are seeing/reporting with box stock chambers.

So my read is that it's just marketing hype to claim a perceived high ground. With the downside that it puts reliability at risk.

All that said, if there was an advantage to .295, you'd see AA and others move to it, publish why, which loads, etc.

[nincomp]

http://www.accurateshooter.com/cartr...rtridge-guide/ and
http://www.accurateshooter.com/guns-...ser-by-speedy/= bad tooling life and lots of out-of spec parts (rejects). In general, crisp angles at junctions of diameter-change (case neck-to- shoulder, for example) get less crisp as tools wear. Rounder junctions at diameter changes, along with generous tolerances at points of maximum tool wear= good tooling life

[txgunner00]

Good post. Lots of good information.

[Whelenon]

History class was always my favorite, thanks for sharing all that information.

[mongoosesnipe]

On a side note I don't know any one who runs a tight neck chambered gun with out using a concentric gauge and neck turning every case... If one were trying to set up a bench rest bolt gun chambered in Grendel I suppose I could see a point to running a tight neck but not in an ar platform it just seems prime to cause reliability issues

[pinzgauer]

Pinzguaer,
Originally, the comments on the smaller neck diameter were part of a longer post. I wanted to point out that there can be legitimate reasons for a smaller neck (long case life and perceived accuracy). I started to point out disadvantages of the smaller neck, but in editing, left out the following:

“If you want to reliably shoot “off the shelf” Grendel ammunition, you need a Grendel chamber. The larger tolerances for 6.5 Grendel chambers and ammo exist for reasons, including reliable functioning in poor conditions and the ease of manufacture of the ammunition; not infinite case life. If you want to use one of the variants, be prepared to handload. Not all Grendel ammo fits all variant chambers.”

Pinzgauer, I followed your saga of trying to get a batch of Hornady Grendel ammo to function in your AR. It appears that your chamber did not have the gentle transition from the neck to the shoulder that is one of the design features of the Grendel chamber. Bill Alexander tried to explain this, but in all the hoopla, his explanation was poo poo’ed by some.

Understood, and to be clear, it was not me who had the issues with the non-standard chamber and Hornady. My point was that many people trying to "improve" the chamber have encountered significant difficulties, with very little tangible advantage. Lot's of perceived advantages, but very few documented.

And if it was the hot setup, many more would be using it, even if it compromised Full Auto, etc.

About the only semi-legit issue that the .295 would help address is work hardening of the neck on repeated reloads. And that one is probably nominal and will require use of button dies and tuned expander balls. IE: You won't see that advantage without some additional effort/expense.

I'm getting 7-8 reloads out of IMI brass with Forster dies in a .300 bog stock grendel chamber. With the price of Lapua & Hornady coming way down, I'd have to get many, many more reloads to justify the expense of custom chamber & associated dies to break even.

And I'm usually retiring the brass due to primer pockets, not neck splits anyway. If I do get a neck split it pretty much always started as a scratch from sharp feedramps/etc.

So I'm with you on the history lesson, and core points. Just not convinced even the "legit" reasons for .295 are worth the problems & risk.

[bwaites]

I've only shot standard Grendel chambers, and I have 20+ reloads on some of my brass. I lose 1-3/100 on each reload over 10, but the number has come down since I switched to better dies.

[nincomp]

Pinzgauer,
I agree with you given the current brass and ammunition situation. Why tempt fate?
By the way, what is the range of loaded neck diameters with your IMI brass? I know that IMI brass has a good reputation, but don't know the relative difference between the necks of "factory" 6.5 grendel and converted 7.62x39 brass.

Note that in my earlier posts, I said "perceived accuracy" of tighter necks. I just wanted to point out that for serveral years the Grendel's reputation for long-range accuracy was linked to essentially match-quality Lapua brass. I imagine that some of the "knock-off" chambers were designed around that brass, which we now know was relatively undersized. The loaded neck diameter of the early brass was about .291", as I recall. Given this, the early brass and factory-loaded ammo fit the .295 CSS and later, the .264 LBC chambers. With the spotty availability of the brass, long life was paramount, so some shooters did indeed utilize bushing dies (without expander buttons) and recommended them to others. The first batches of Wolf ammunition generally had even thinner neck walls and some reloaders complained about having to buy tighter reloading bushings. With any of this brass, standard Grendel dies with expander buttons worked just fine for .295" variants.

This is all just history, but it partially explains why some of the attacks on Alexander Arms and Bill Alexander were so heated. The previous 6.5 Grendel ammunition fit the non-Grendel chambers, I guess that some people assumed that all future Grendel ammunition would fit their non-Grendel chambers. Nope.

Mongoosesnipe:
I don't recall folks complaining about stuck cases with the .295 necks. The quality and consistancy of the Lapua cases may have made this a non-issue. On the other hand, I think that some bolt guns with a .292 neck were made, and I am pretty sure that they neck-turned.

[Variable]

Thanks Nincomp. You seem to have summed up the big picture pretty nicely as far as I can tell. Your long view synopsis does a good job of stitching the big picture together better than I had ever thought about it. I (and probably others as well) get lost in the board minutiae, and haven't looked at it quite like that. I think your take on the issue is spot on.

[rasp65]

Nincomp Since the Grendel was a proprietary cartridge and copyrighted the chamber drawing were never public. With the acceptance of the Grendel by SAMMI at the end of last year it may be a while yet before they publish it.

[LR1955]

Nincomp Since the Grendel was a proprietary cartridge and copyrighted the chamber drawing were never public. With the acceptance of the Grendel by SAMMI at the end of last year it may be a while yet before they publish it.

Nothing proprietary about the cartridge, chamber design, etc. The name 'Grendel' is the thing that is apparently proprietary. I have been shooting various 6.5 AR chamberings for years that used different chamber reamers. Every single one of them accepted standard 6.5 Grendel Brass (Lapua, Hornady, and Wolf), several different brands of 7.62 X 39 brass, all factory loaded 6.5 Grendel ammunition, and all (except for Lee) brands of reloading dies. You could not have determined any difference between them and the several 'Grendel' chambers I have owned over the same years.

Also, I believe that Lothar Walther will make anyone a barrel that has the same chamber design as a AA Grendel and a person can get this barrel with a 'Grendel' bolt.

LR1955