Re: AI AW vs 700 style actions ...which fails mor
This is the thread in which I speculated about the mechanics of the problem
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1630204
Note that I am not generalizing this problem, just noting that it happened to both my .260 and my 6.5x47 barrels.
It is also not meant to be a discussion of reloading practices in general-- it is just a discussion of a very specific type of pressure issue.
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In my guns, shooting .260 since 2006 and 6.5x47 since 2007, primer piercing would occur during load progression after significant primer cupping, to the "volcano" level. Thus my hypothesis is that eventually the primer cup material cannot be stretched anymore and the volcano "plug" simply breaks off (and is left loose in the bolt head).
I speculate this happens due to firing pin retraction fast enough during firing to allow the primer material to move. However, this is just a guess with no direct observation, measurement, or instrumentation.
One could always blame this on pressure, but that's kind of a cop out because:
(1) it is caused by pressure and if you reduce pressure it goes away - the same can be said for any pressure symptom, and
(2) we are running high performance loads in high performance guns, and other rifles (with different bolt assembly designs) do not have the piercing issue.
But the point is that the AW exhibits this problem before other rifles do, and this limits the performance I can wring from the AW.
I know for a fact that some of my fellow competitors are shooting .260 and 6.5x47 loads in other rifles that caused extreme primer cupping or piercing in my AWs, and I can't match their velocities using the same recipes without those issues.
The first 6.5x47/AI-AW article was published by me in 2007 and I detailed the limitations I found with this combination with regard to primer piercing. This happens to be the same limiter I had with the .260, although I didn't mention that in an article until the 6.5mm Shootout, late 2007.
I realize this is off topic for this sub-forum, and I don't mean to divert an industry for-sale post; however, some things I said were quoted and I wanted to make it totally clear what my experience was with regard to the issue.
FWIW, I still stand by my statement that this is not a big handicap, just an annoyance, and that any practical field match can be won with a 139gr Scenar at 2900 fps. I shot 1st and 2nd place at the last two Sporting Rifle Matches in 2009 using my my .260 AW with its original barrel from GAP (from 2006).
I also think that .260 is a better choice than the 6.5x47, and specifically on the AI-AW platform in light of the issues detailed here.</div></div>
The original reporting of it was here
http://demigodllc.com/articles/6.5-shootout-260-6.5x47-6.5-creedmoor/?p=2
and here
http://www.6mmbr.com/gunweek084.html
and here
http://demigodllc.com/articles/6.5x47-lapua-tactical-rifle/?p=3