Large primer vs small

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Bigfoot
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Large primer vs small

Post by Bigfoot » Tue Apr 28, 2015 8:54 am

So a friendly conversation took place recently that had me scratching my head.

A couple of us were talking about 6.5 cartridges and the differences. What got me befuddled was one gentleman stating that because the 6.5x47 had a small primer it was capable of generating higher velocities. This didn't make sense to me. I confess to not liking small primers as I find them harder to work with but I have always been under the belief that large primers in like cartridges created higher velocity.

I guess I'm hopping Bob McAlice has tried an experiment with this as looking through some of my reference materials I couldn't find anything written to support my understanding.

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Bob Mc Alice
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Re: Large primer vs small

Post by Bob Mc Alice » Tue Apr 28, 2015 10:23 am

Sorry Mark, I have no actual experience on the matter. Here is some related info:

http://riflemansjournal.blogspot.com/20 ... ll-primer-


308.htmlhttp://riflemansjournal.blogspot.com/2009/06/primers-large-rifle-primer-study.html


http://www.6mmbr.com/primerpix.html
Last edited by Bob Mc Alice on Sat May 02, 2015 8:06 am, edited 3 times in total.

Jerry G
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Re: Large primer vs small

Post by Jerry G » Wed Apr 29, 2015 11:58 am

A large mag primer will start a bigger fire than a small primer. That would translate to a quicker pressure spike. A quicker pressure spike means the recoil would be quicker. In theory, you want the last grain of powder to burn in the last inch of your barrel. That would be easier on you and your equipment.

A freind of mine got a 6.5x47 the same time I did. I used small mag primers on recommendation of the gunsmith that did my work. My friend used small benchrest primers and he had about 3% to 4% misfires and I had none. He switched to mag primers and his problem went away. To me, the small primers are a pain in the butt. The large ones are much easier to handle.

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Re: Large primer vs small

Post by Snake » Wed Apr 29, 2015 12:32 pm

I can only give the perspective from our club's benchrest guys. They like small rifle primers because they claim they are more reliable and more consistent. They claim that large rifle primers even the so called match grade just aren't consistent enough. They also seem to think that the small primer takes pressure better....so they say. O'Malley and I did some testing a few years ago dealing with which brand was a) more accurate and b) produced the best velocities. In two different 7-08s we found that the differences in velocity with either Varget or XMR 4064 were insignificant (50fps) except with Winchester primers...they produced the highest velocities exceeding the others by at least 100 fps. Sadly there were just ok in the accuracy department. The worst results and most inconsistent results came from magnum primers and CCI's military primer no. 34 I think. Remington' had the thicker cups, produced good consistent velocities and acceptable accuracy. CCI bench rest primers had the lowest standard deviation in velocity, very consistent velocities although slightly lower velocities in general and good not excellent accuracy. Federals displayed no differences between their match and standard primer ...the match primer isn't worth the extra money. Their cup is softer and has good velocities fairly consistent, and OK accuracy but better than the Winchesters with the test powders. The BR CCI primer has a hard cup, of correct diameter but if your primer pocket are loosening best use another primer like the Federal with the soft cup. They don't leak but accuracy falls off....and I can't tell you why. :| :-? :ympeace:

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Re: Large primer vs small

Post by Jerry G » Wed Apr 29, 2015 3:22 pm

Good info snake. Thanks.

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Re: Large primer vs small

Post by OldRanger » Thu Apr 30, 2015 7:54 am

Thanks snake, I love when a problem comes up on this board and someone has already taken the time to do a study on it!
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