Crimping for a semi is it necessary?

D

delboybc

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I have been reloading for a 30-06 using hornady interlock that have a cannelure for crimping. Given that every reloading book I have says to crimp in a semi and they have a cannelure I have just been crimping them without giving it much thought.

I just bought some nosler partitions that do not have a cannelure which has led me to think about crimping for a semi a bit more.

I know people will have different opinions on the matter but I just wanted to have a discussion around some of the points when compared to reloading for bolt actions were I do not crimp the bullets.

My bolt and semi both have a 4 round magazine so no 30 round firings that may affect the bullets in the mag.

When I look at the feed ramps on the bolt and semi they look very similar.

When I hold the cocking handle on my semi there is a degree of pressure not sure how many lbs force and it chambers the round fast. My bolt action does not chamber as fast but I have had a few range sessions were I have fired the magazine as fast as possible and the force that I put pushing the bolt handle forward is not gentle.

Interested in some discussion on what people think about having to crimp bullets with no cannelure in a semi.
 
I never have with my T97 / .223 loads.. It's known to have issues ramming the feed ramp but it's never caused any problems for me. I'll occasionally pop a round out of the chamber without shooting to check and none have been effected yet.
 
I crimp everything except target loads that I single load into bolt guns. I use the Lee Factory Crimp Die and I don't see any negative effect on accuracy by crimping.
 
I would put some crimp on it. Too many horror stories around to make it worth not. Less about crimp/no and more about having some neck tension. As has been said, everything but single shot target rounds I do get some.
 
ShawnC6 said:
I'll occasionally pop a round out of the chamber without shooting to check and none have been effected yet.
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I look carefully at the type of ramps and the type of firearm. Pistols I always use a slight taper crimp.

My M1A platform rifle gets a very, very minor crimp: there is never a mark on the bullet from feeding if I use my USGI pinned mags.

5.56 / .223 in an AR platform with M4 feed ramps: USGI metal body mags are not bad but I find Pmags have a different angle. I always use a well cam-ed over Lee Factory crimp on them: otherwise there is signs of the bullet shifting in the case, first due to the ramps, then back from the chamber.
 
I don't crimp, but I use "small base resizer" dies for my semi autos. Actually I just use them for everything. It doesn't hurt for the bolt guns
 
what Hitzy said. I have spoken to some long time local reloaders who say that in semi auto mag fed rifles its a really good idea. I also use the Lee Factory crimp die on my AR-15 loads.

apparently, the shock of the rifle firing will slap the rounds around in the mag, end to end. This can loosen or even move the bullet deeper in the case, changing pressures.
 
I only crimp for my shorty .223 AR15. I want 100% reliability when competing in CQB matches. I don't crimp in my long range precision AR15. I don't crimp for my Norc M14, M1 Garand or my CZ85 9mm pistol
 
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