9.3x62 - Large or Large Magnum Primers?

[Hilux01]

I use Cci250 Magnum Large Rifle - with both my ball and extruded powders due to the volumes

 

[amschind]

My experience is that EVERYTHING in reloading except for your own data is a rule of thumb. Primers vary primer to primer, as does powder, as do rifle throats. The jump on 6.5 PRS rifle at the end of the match is measurably longer than it was the day before. My best personal example is working up loads for a .50 BMG: I confirmed that the mil surplus 639 gr Silvertips were far from the rifling, resized them all anyway (a burst from a Ma Deuce doesn't need MOA precision and it appears that Lake City is well aware of that fact) started 10% below listed load, and got a sticky (as in it took effort to get the gun open) bolt 15 grains below the posted max. There are only two Hodgdon 50 powders and only one commercial primer, and everything is standardized on military brass.....so what gives? I don't know, and it isn't important that I find out.

What is important is taking data as guardrails that will generally keep you safe (though as in the example above, blindly starting at the published load would've pierced the primer in my AR50 and could've been a very bad day in a semi auto), not as a baking recipe. To that end, the answer to the question on LRM vs LR primers is the same answer as to all reloading questions: don't take anyone's word on it, carefully accumulate data in your own firearms with the exact components that you plan to use. LR and LRM primers are completely interchangeable, BUT that is true if and only if you follow the universal rule, which is to develop loads for them as though they are completely different. This is the exact same procedure as is necessary for two different LR or two different LRM primers, different lots, et c.

Of all of the things that I have learned over many years of reloading, the single most important is only trust yourself. There is plenty of great knowledge and you're wise to accumulate it, but it is still your job to filter and test it because some of it will be 1) inaccurate or 2) specific to circumstances that differ in tiny, potentially undiscoverable but still very meaningful ways from your own.

I hope that's helpful.

 

[mooze]

Anything with around 70 and more grains of powder my rule of thumb is magnum primers

but the 9.3 only need arounds 60 gr...

 

[amschind]

but the 9.3 only need arounds 60 gr...

Primer Reference.

Note that they are up front that these are unitless numbers, so purely for comparison within the list. But the big take-aways to me are 1) Federal Match and CCI primers are much more consistent than anything else and 2) Most of the LR primers have a non-zero chance of being "hotter" than a magnum primer. LRM primers are supposed to burn longer than LR primers, which makes sense and is harder to measure without expertise and equipment that basically nobody outside of the industry would have, but for our purposes the end result of "did this load generate overpressure?" matters infinitely more than any intermediate number. I use GM215Ms on just about everything, while for my 6.5 CM practice rifle it doesn't seem to care what I feed it. That cartridge is the pig of the precision rifle world.