Thread: 500 Yard Rifle
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Old May 16, 2013, 07:22 AM   #39
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 5,464
Metal god asks:
would the tightness of the mag and accuracy issues have more to do with making the receiver and or complete platform more stable or ridged when using tight fitting mags and not so much how the mag is sitting in the well pre-say ?
I think it has more to do with the magazine. The receiver's fixed in dimensions; magazines vary a few thousandths. So, to me, the big variable's the magazines.

Could a tighter mag change the vibration of the barrel or whole rifle which intern would change POI per mag change.
I don't think a magazine will change the resonant frequency the barreled action vibrates at very much (it does add mass to the barreled action, though), but moreso how it fits will change the amplitude and axis those vibrations have. Just like an out of square case head slamming against an out of square bolt face when the round's fired; the barrel vibrates differently compared to when square case heads slam against square bolt faces. New cases have reasonably square case heads so their effect on accuracy is minimal as the bolt face issue remains constant; one reason semiauto M1 and M14/M1A rifles shoot new cases so darned accurate with their out of square bolt faces. A given metal shape has a given resonant frequency it vibrates at. So a barreled action without a DBM installed will have a different one with the DBM installed.

With M14's and M1A's, zero's shift up to about 3/4 to 1 MOA across a batch of magazines. I've no data on these modern bolt gun's accuracy issues except what happened not too long ago when the military was comparing internal box magazine .300 Win Mag sniper rifles to DBM .338 Lap Mag ones and the Win's out performed the Lap's at ranges from 1000 to 1500 yards for accuracy. But that may have been 'cause the Win Mag's easier to shoot accurately hand-held in prone off ones shoulder than the Lap Mag's are.
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Last edited by Bart B.; May 16, 2013 at 02:55 PM. Reason: Zero shift, not accuracy degrading
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