How Much Crimp on Rifle Rounds?

[WR Moore]

About the comments that "crimping isn't necessary". In an earlier post, I noted that .222 Remington factory ammo was crimped. The factory (Remington) had a reason or they wouldn't spend the time & money to do so. I'll also note they certainly weren't daintly about the amount of crimp.

About ten years ago I became aware that several noted benchrest shooters (guys who try to put a bunch of bullets into one hole), had started crimping their loads. Don't recall their exact specs, but they found it increased accuracy. The theory being that it resulted in a more uniform bullet pull (the force necessary to get the bullet moving) and more complete powder combustion. While I'm certainly not in their class for accuracy, I did a very slight taper crimp (I don't happen to be in a location where I can get to my notes from that time.) on my long range match ammo. I can't swear that it helped, way out yonder the shooter is a much greater influence on the bullet, but it didn't hurt.

Finally, it 's a real good idea in semi & full auto weapons to prevent bullet setback that could greatly increase pressures. Not to mention possible powder spillage and other difficulties that are not easily cleared.

 

[tappedandtagged]

"The government does it, so it must be a good idea." LMAO !!!

BTW . . . you are likely to find that the cannelure is not where you want it. I.e., the COAL will be wrong if you crimp into the cannelure.

Cannelure was in the perfect spot. Accuracy was top notch (shot 0.65" at 100 yards). So laugh if you want at my reasoning but I am satisfied.

Thanks to those that responded with helpful suggestions in a more tactful manner.

 

[Gamecock]

Cannelure was in the perfect spot. Accuracy was top notch (shot 0.65" at 100 yards). So laugh if you want at my reasoning but I am satisfied.

Thanks to those that responded with helpful suggestions in a more tactful manner.

I'm glad it worked out for you.

 

[Prof_Fate]

I just read in an article about crimping - the ballpark is bullet plus .02 (twice the thickness of the brass in case you want to measure it, .01 being avg) minus .004.
So .224 plus .02 is .244 less .004 so .240.
And the author prefers to crimp separate from bullet seating.
He also says that the bullet is held by neck tension and he likes to see a 'coke bottle shape' in the brass where the bullet is seated.

If you can feel the edge of the case you've not crimped enough.

9mm and some others are very picky on crimp. I crimp my 9mm to .3795 for my XDm and have had no issues. According to the above info that's a tad too tight, but it matches the factory ammo I had to measure and meets the specs listed for the cartridge. But then it headspaces on the case mouth. I was getting the coke bottle shape but others looking at my rounds says that wasn't right so I upped the bell on the cases to do away with it. Can't say I notice anything one way or the other.

I'm about to start reloading 30-06 for a garand and have been reading a lot...it's rather different than pistol. I plan to crimp, just a little I think, probably in a separate step but I've not made a final decision on that yet.

I don't think I'm over thinking at all. I plan on crimping my AR rounds and asked how much crimp. The overall response was that I am being ridiculous for even wanting to crimp them.

The bullets have a cannelure and I want to crimp them. Right wrong or indifferent, I am going to crimp them. All I want to know is how to tell they have enough crimp. I have never crimped a rifle round before. I understnd the premise behind crimping ( I own and load for a S&W 629 mountain gun). But a rifle round is a whole new critter. I'm not overthinking, I'm just trying to weed out those that insist no crimp is best for every rile except tube fed.

The military crimps theirs, so there must be a benefit, otherwise the government would cut it out to save costs.

Ok, enough of my rant.