SmallCaliberCentral

Anyone have experience demonstrating that the use of magnum primers diminishes accuracy?

I'm loading my AR with magnums so far, and am wondering about possibly switchning to the BRs that I use in my bolet gun.

Yes, I understand that magnums "should" be used in a semi-auto...

As the Remington 7-1/2 BR primer is considered their Small Rifle Magnum primer, and their 6-1/2 their "Standard" primer, and the fact that my personal very best 17 Mach IV groups (as well as many BR records), along with my 20VT, 204 Ruger, 223 Rem, and my 223 Ackley all thrive on the 7-1/2 primer, I'd say don't worry about it.

I use the 6-1/2 in all my Hornet-based cartridges (less intense ignition flame, thinner cup). Many gas gun guys like ball powder, and it is ignited best with "magnum" primers....is that what you heard in regard that semi-auto's should be used with magnum primers?

The Remington 6.5 is not supposed to be used in ANY high pressure centerfire cartridges. Hornet, etc, is the only low pressure centerfire cartridges the 6.5's are supposed to be used in.

For accuracy, I use Rem 7.5's or CCI 450's.

You should check out this guy's homemade primer tests. Can't tell you how recent it is but the reason I even mention it is the Winchester magnum primer had the lowest SD, lower even than the purpose-built match primers. How's that for a kick in the shorts!

RIO: yup, that's what I hear about the semi's and magnum primers. So far I'm using Benchmark. I've also heard tell that the magnums have a thicker cup and that is supposed to be better because... I don't know why.

I'm always hunting for a tad more accuracy, that's what's prompting my primer musings..

Currently recipie for the Rock river (24" bull) AR is:
32gn Sierra Blitz King
Nosler brass (fired 4x)
Trim 1.845 +/- .002"
COAL (appx) 2.250"
26.5 gn Benchmark
CCI small magnum primer
flash holes preppec (didn't need it)
weight sorted +/- < 1 gn (didn't need it)
VLD chamfered (didn't need it)
Primer pockets uniformed (didn't need it)
(can you tell I love Nosler brass? )

Regular 5 shot group: 2" @ 300y, (excluding one shot: 1.3" @ 300y)

I don't have bench gear, I'm shooting off a Harris with a crappy bass pro rear bag. I wish I had more scope power too. My Elite 3200 is supposed to be 24x but the bull looks the same to me at that distance as my Leupold at VXIII at 20x.

Check these photos out... this is part of what got me thinking. Some primers seem to flash in a hazy/plasma manner like a jet engine, and others throw sparks like a welder. Which is "better"... beats me, LOL!!

http://www.6mmbr.com/primerpix.html