22" JP Barrel at 5k and dispelling 2 myths

[StoneHendge]

Another thing I'll mention here instead of on a prior thread given the direction it took was that I had sheared a Maxim bolt on my 16" ARC, so I took the JP bolt from this Grendel to use in the ARC for a match. It had been in a Toolcraft carrier in the Grendel and went into the ARC's JP LMOS carrier so I didn't have to fiddle with it. When I did this test, I just used the bolt in the LMOS carrier as it was in the ARC and didn't touch the gas, so there was a significant change in mass (6.7 oz carrier vs 9.5 oz) but no meaningful difference in POI since 1/10th mil up or right wouldn't get it closer to the aiming point. Not exactly the same as changing a buffer, but still a significant change in reciprocating mass.

[LR1955]

Thanks everyone and sorry - I didn't abandon the thread - just busy.

I certainly do think that annealing would have extended the case neck lives. Thing is, this lot of Lapua brass is the only brass I've owned where the primer pockets haven't started going first. I'll add that I purchased 300 pieces of Alpha 6.5CM brass that is over a buck apiece and all the rage in some circles. The primer pockets were so tight at first that I couldn't even get a Fed LR primer into them - only a BR-2 which has a slightly smaller diameter. After 5 firings they still don't fully accept a no go gauge, but some are getting close and the Feds fit easily. I'm pretty dissapointed and although I'm at a near max load (2850 with a 123 Scenar with H4350 out of a 22"), I'm not over it. So what I grapple with is investing the money and time in something that might not get me any additional brass life at the end of the day

Klem and others, I don't disagree that a clean bore will shoot faster than a dirty bore - I've tested myself and I'm sure others have and the first one to three always run a bit faster than once its fouled (20 fps for the first if I recall in my Grendel), so that will affect vertical dispersion at range, but it should have an insignificant effect on POI at 100 yards which is what I was referring to. The heat shouldn't have an impact on zero either provided a temp insensitive powder is being used. A faster bullet does tend to go lower as barrel dwell time is less as the barrel is following its natural rise - and for me it also goes slightly right - I don't know if that's normal or a function of my shoulder structure or my form. I debated about whether or not i should clean this time and did decide to for exactly the reason you said, Klem - who knows what the time and temp fluctuation could do with the residue over 6 months. Normally, I wouldn't have since its a barrel that can go to at least 150 before a cleaning is needed.

By cold shooter I mean that we get on our rifle, we run through our checkdowns and we blame the cold barrel when the shot doesn't go where we thought it should. And then we have the feel of that first shot and our muscle memory takes over and we're more relaxed and the next rounds go where we know they should go. I think that group was so good because I didn't overthink it and part of me was kind of looking forward to having it be shot out so I could buy an ARC barrel. So I think I was truly perfectly relaxed.

It would be interesting to document one's cold shots to see it there is a pattern - be it first shot pulls due overgripping or maybe pushes from too much shoulder, or maybe a little of each.

I put my remaining 13-14x brass in the tumbler and have about 3/4 lb of the lot of powder I was using left. I'm interested to see what the SD's are like and if the more brittle necks will have an impact. My 5 shot SDs were in the 5-7 range when I worked the load up when the brass was at 9x. If anyone has any ideas of any other sort of test that could be run on brittle necks, let me know!

SH:

It used to be the rage in Army sniper courses. Not sure if it still holds true but it was viewed as kind of a religion. After seeing a whole lot of guys carefully record every possible variable and carefully making their 'cold bore' shot, and recording it, my conclusions are like yours and your buddy. I never saw a pattern that a guy could dope for to ensure his 'cold bore' shot went to center. In fact, if you looked at their data books you saw their cold bore shot was within their average group size and location. A lot of time from a training day to fire a couple of shots from 600 that very few shooters ever really looked at over time to see if they could dope for it and make a better shot the next time. And we are taking shooters whose calls were questionable.

I also witnessed a lot of very top end prone shooters fire their first sighter shot into the X ring at 600, and repeat it over and over again throughout their record fire.

I figure it probably makes a difference for bench rest but those guys shoot fowlers so it doesn't matter.

Yes, more cold shooter than cold bore for the majority of shooting situations.

I think my question would be this. For everyone here who believes the cold bore stuff, do you adjust zero for that first shot and does the shot go into the middle? And, following that shot will you return to your previous zero and does that shot and those that follow go into the middle?

LR-55