Is it necessary to crimp certain High Powered Rifle Cartridges?

[gamestalker]

For most bottle neck cartridges the question is rarely raised and for good reason being, it's not necessary, and it can cause accuracy issues. But before I indulge this further, I would like to elaborate on a couple of questions about the percieved effect a crimp would have on two particular cartridges of current discussion. The 300 Winchester magnum and the 338 RUM, both are cartridges that deliver a good deal of recoil.
Some say a crimp is likely to cause pressures to spike noticably, but either one of those two cartridges will not react any different than any other high powered rifle cartridge in this respect. Normal working pressure produced by a listed SAMMI charge is more than sufficient to release the bullet from a crimp without producing an excessive pressure spike.
More importantly is the question of necessity to crimp. Experienced hand loaders, expert sources such as bullet manufacturer's, and even competitive bench rest shooters, are all consistently in aggreement that crimping either of these cartridges is unnecessary. In addition to it being unnecessary, it is clearly a method that is going to effect accuracy negatively.
So the final expert opinion I've gathered from the hourses mouth is treat them no different that any other high powered rifle cartrdige. Certain exception could present when being used in an auto loading rifle under extreme conditions, amybe. But if loading for daily shooting as with any hand load, target shooting, bench rest, or hunting purpose it isn't necessary at all to crimp. My .270 has bullets available for hand loading that have a canelure and many other's I've loaded ofr over the years. In conclusion, I simply accept the advice of those who manufacture bullets and other hand loading components and have never gone wrong. A lot of us here at this forum have a good deal of background atake the time to nd experience based on trial and error, but with no disrespect to those of us who have invested decades finding what works best for us, we are not qualified or certifiable experts. When in doubt or if hearing too many varrying opinions, one should begin to realize it is time to consult a confirmed and certified expert. Firearms produce an enormous degree of pressure that is easily capable of causing a great deal of bodily harm, or even death. With this said consult your loading books, and talk to experts.

 

[ArchAngelCD]

I'm in the minority here when it comes to crimping rifle cartridges. I put a LIGHT factory crimp on all my rifle rounds. I know many feel it's unnecessary and it well may be but I have always gotten good results applying a factory crimp on my rifle ammo so I will continue to do so...

Point: If a crimp could cause pressure spikes factory's would apply a crimp on their commercial ammo. I can't see the harm in applying a light crimp on your ammo either.

 

[JimKirk]

If I am loading for a heavier caliber rifle and the bullets have cannelures... then yes I crimp.
All others are not crimped even though their bullets may have cannelures.

Jimmy K

 

[gamestalker]

And that was my point, it is a personal preference more than a necessary standard. I think if I had a FCD I would probably give it a try. Who knows, it may produce some favorable results beyond what I'm already getting? I'm an old dog though, and don't take well to new tricks, and that is certainly a new trick for me. But for those of you that crimp, continue doing so with confidence, it won't change pressures to any noticable degree, or at all.

 

[jem375]

I have yet to crimp a rifle bullet and I shoot some fairly big calibers, in my opinion there is no need unless it makes you feel better.

 

[suzukisam]

I shoot 223, 308, 243, and 6.8 in the AR platform. Run a couple bullets into a case and you'll start crimping. But for my 300 wby mag and other bolt calibers, a light crimp if any. I sometimes turn down the expander ball if I don't feel I like the neck tension.

 

[P-32]

The only rifle cartridge I crimp is 30-30 used in a lever gun with a tube magazine.

 

[rcmodel]

Run a couple bullets into a case and you'll start crimping.

Or, I would turn the expander plug down to the right size so you have proper neck tension to keep the bullets in place in the first place.

I crimp for handguns and tube magazine rifle calibers.

I don't crimp .223, 25-06, 30-06, etc.

If I had a .458 Win-Mag eliphant gun, I would probably crimp for that.

rc

 

[suzukisam]

Or, I would turn the expander plug down to the right size so you have proper neck tension to keep the bullets in place in the first place.

I said that too. I just like my auto loaders to be crimped. we can argue all day if it's needed, but the fact is if it is crimped it won't give you any problems. unless you just like smashing your forward assist, or leaning on your bolt to close the action.. at that point crimping is the least of your problems!

 

[Kawabuggy]

Since there is no scientific data available in this thread to prove one way or the other, I would like to add that serious shooters should do their due diligence and load both crimped, and un-crimped rounds and shoot them comparatively to see what works best in their case.

I personally have found that a light crimp as provided by the LFCD (Lee factory crimp die) produces better accuracy than non-crimped. As such, I lightly crimp EVERY round in every caliber I load for.

Further, there was a study done and the results published which showed the exact same loads, developed at the same time, with the same materials, with 1/2 of the rounds crimped, and the other half non-crimped, and guess which ones shot better?
Crimped.

 

[blarby]

Just to throw in ..... There is another thread with almost this same direction started yesterday.... maybe a combo thread ?

"Do I need to crimp "

 

[blarby]

Maybe a little history of the cartridge courtesy of remington, winchester, Norma, and last but not least wiki might help you make your decision :


The .300 Winchester Magnum was designed with a neck which is shorter than the diameter of its bullet. If Winchester had released the cartridge prior to 1960 the cartridge would have been similar to the .30-338 Winchester wildcat cartridge.

However, by the time Winchester got around to designing their own .300 the .308 Norma Magnum and the .30-338 were already on the scene. To help differentiate it from the other .300 magnums and to allow for the chambers of the standard length .300 magnums to be rebored to the .300 Winchester Magnum chamber dimensions, Winchester moved the shoulder forward and lengthened the cartridge slightly. This created the long criticized short neck of the .300 Winchester Magnum.

The short neck was thought to hinder accuracy because it would prevent the alignment of cartridge to the bore but this is rarely an issue either today or when the cartridge was designed. The fact than the cartridge has gone to win many 1,000 yd (910 m) matches puts this criticism to rest.

However, the short neck with the shoulder moved forward does cause some real problems. Since the .300 Winchester Magnum is designed to work out of a standard length action heavier bullets will need to be seated deeper into the case. Since many heavier .30 caliber (7.62 mm) bullets have a long taper, and these bullets will be required to be seated deeper into the case, the neck will end up being positioned in the ogive rather than on the shank of the bullet due to the fact that Winchester had moved the shoulder forward.

( Here comes the important, crimp necessitated part in rifles incorporating a magazine... If you fire only single rounds from a bolt action non mag'd rifle, whether or not you crimp is up to you)

This prevents the case from having a good grip on the bullet. Under recoil such loosely held bullets in the magazine will be pushed back into the case. Also, if using a highly compressed load the cartridge might “grow” in length and may not be able to fit into the magazine. For these reasons bullets weighing over 200 gr (13 g) are not recommended. Norma goes further recommending that bullets heavier than 180 gr (12 g) not be used with the cartridge.

So, with that said... Do you need to crimp ? I think this question falls neatly into another question we run into all the time : Does chambering the same round continually in an auto-loading pistol eventually force the bullet further into the case ?

I would say yes. Some would not say "no", but that it would take a lot of re-chambering to do it.. some would say "NO" Those who would say "NO" in this instance, would have been proven wrong in a number of instances... Sometimes it happens on the first re-chamber....sometimes it happens on the 51st re-chamber...but it can happen.

Now, consider the recoil bullet re-seating in your magazine: Will it happen every single time ? Probably not. Will it happen eventually... More than Likely. Is it preventable using a very basic technique, which when applied properly provides a wide margin of safety whilst effecting accuracy at a minimum : Definitely.

Magnum rounds are not to be trifled with.... either on the receiving end, or the firing end. Play safe kiddies.

 

[gamestalker]

Blarby has hit the nail on the head, and stated it with a good fact orientated history. We are all practicing a hobby that can be risky even on a good day. In this respect, all we can do is reduce the risk by trying to control the variables of human interaction and error. I'm certain the number of mistakes I've made reloading, are only the ones I'm aware of.

 

[30Cal]

I only crimp where I have to (leveractions). Uncrimped rounds are less likely to create stoppages.

 

[EddieNFL]

Or, I would turn the expander plug down to the right size so you have proper neck tension to keep the bullets in place in the first place.

Treat the problem, not the symptom. Works ever time

 

[Walkalong]

Uncrimped rounds are less likely to create stoppages

Please explain, or did you mean improperly crimped?


I crimp .30-30 & .35 Remington for obvious reasons. I lightly taper crimp .223 for added reliability/resistance to set back, unless it is target stuff, which I do not load right now. I also crimp .458 Win Mag. I do not crimp .30-06 for my Garand.

 

[elwoodm]

for auto loaders check to see how hard they load a round. fire the gun let it load and pull the round out to see if there is a mark on the bullet. guns like the fal load hard so i crimp fcd on all those rounds. but if they load good without bullet impact on anything like the sks or the svt i dont bother.

 

[Offfhand]

This is from an earlier post, see above:
"Further, there was a study done and the results published which showed the exact same loads, developed at the same time, with the same materials, with 1/2 of the rounds crimped, and the other half non-crimped, and guess which ones shot better?
Crimped."
Written my whom? Published where? Probably just an ad (Lee?) promoting crimp dies.

The most exacting and expert handloaders on the planet are benchrest shooters and they load fantastically accurate ammo. Visit a bench tournament and ask any of the competitors if they crimp their ammo and if they think it will improve accuracy. They will probably think you are just kidding, that is after they stop laughing at the question.

 

[jim243]

I'm in the minority here when it comes to crimping rifle cartridges. I put a LIGHT factory crimp on all my rifle rounds.

Same here, no effect on accuracy if done right. Allows the powder to develop full pressure on inital burn. (or so it is my opinion)

Jim

 

[elwoodm]

my only wish is why cant crimping on mag revolver rounds be easy to get right the first time. the trial and error of working those up is a pain. rifle rounds with light crimps just make it seem a little more reliable as with factory stuff being crimped. every auto loader loads with some degree of abuse. its up to the owner of the gun to know how much the round is getting banged up and crimp what you need to feel safe.

 

[788Ham]

All calibers I reload for get a slight crimp. Using the FDC die, such a light crimp doesn't hurt anything as far as I'm concerned, I reload for .223, 22-250, 250 Savage, 30-06 and 375 Win., never heard anything wrong so far! The factory rounds all have a slight crimp, do they shoot okay?

 

[Offfhand]

Quoted from above post:
"The factory rounds all have a slight crimp, do they shoot okay?"

Check out Federal's .308 Gold Medal Match and Lapua .308 Aficionado Match, they are NOT crimped, and for good reason.

 

[tcj]

I put a light crimp on 30.06 shot through an M1 Garand. If it were for a bolt action then I woudn't bother.

 

[Andrew Leigh]

I have heard that on very heavy calibres it is possible for the recoil to cause the bullets in the magazine to seat deeper. Any opinions on this?

 

[helotaxi]

I have heard that on very heavy calibres it is possible for the recoil to cause the bullets in the magazine to seat deeper. Any opinions on this?

Only possible if the bullet contacts the front of the magazine under recoil and the case has so much mass that neck tension can't overcome its inertia.

Crimping for "safety" is pretty much only needed on lever actions that feed from tube magazines where the recoil and magazine spring are conspiring to push the bullet into the case, and double rifles where the rim on the case causes the rifle to act like a kinetic bullet puller on the second round.

I've seen plenty of crimped 5.56 rounds get pushed back into the case. When the bullet comes out of the magazine funny and catches the feed ramp, the mass of the bolt carrier is going to overcome any crimp you put on the round. If the rifle is working correctly, neck tension will more than suffice, if it isn't, nothing will suffice.