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should I crimp or not

Re: should I crimp or not

I just stopped crimping ammo for my bolt guns and haven't seen anything get worse! Accuracy is improving but then I just bedded my stock and installed a new, lighter trigger so that may have more to do with it.

I think skipping the crimp on match rounds avoids the introduction of additional randomness in the reloading process and thus would lend to greater consistency.

 
Re: should I crimp or not

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: queequeg</div><div class="ubbcode-body">I just stopped crimping ammo for my bolt guns and haven't seen anything get worse! Accuracy is improving but then I just bedded my stock and installed a new, lighter trigger so that may have more to do with it.

I think skipping the crimp on match rounds avoids the introduction of additional randomness in the reloading process and thus would lend to greater consistency.

</div></div>

+1
I ran a little personal experiment with a collet crimper...
It decreased accuracy in the stuff I did... (some various 308 and 243 loads)
YMMV
 
Re: should I crimp or not

For rifle, I don't crimp unless the bullets have a cannelure.
 
Re: should I crimp or not

Right now i only load .223. I crimp loads for my ar. Just started loading for my new Rem 700 in .223. Did a little test when loading for it and no crimp groups better. A buddy's likes them with a crimp so YMMV.
 
Re: should I crimp or not

The other thing here is that there are 3 different types of crimps, and nobody mentioned which crimp they were using. A bayonet crimp or factory crimp uses a collet on the case neck, a roll crimp rolls the neck of the case around the bullet, and a taper crimp slightly tapers the mouth of the case in a similar manner as the roll crimp.

You wouldn't roll crimp without a cannelure, a taper crimp or bayonet crimp is more appropriate for those bullets.

You don't roll crimp any brass that headspaces on the case mouth, a taper crimp or bayonet crimp is more appropriate.

On heavy recoiling rounds like some revolver cartridges a heavy roll crimp is almost mandatory to prevent bullets from unseating during recoil.

and like I said before, crimp only out of necessity and when it is necessary as little crimp as you can get away with.
 
Re: should I crimp or not

I never thought about crimping my rounds, and from what I'm reading here I don't need to worry about this. I KNOW LOOKING AT THE FNG.

Any way I'm loading .45 ACP, and .308 win. Using an RCBS rockchucker, and the standard 3 and 2 die sets. I'm assuming that there is no need to crimp in this situation right? I hope not else I have a lot of crimping to do.
smile.gif

 
Re: should I crimp or not

Don't worry about the .45, and unless your .308 is a tube fed lever action (which i doubt) I wouldn't worry about crimping those either.

The .45acp headspaces on the case mouth so a roll crimp would push cartridges into the chamber further than they should be.
 
Re: should I crimp or not

Using jacketed bullets in the .45 probably no crimp. With lead bullets, a taper crimp is appropriate. You are concerned with pushing the bullet deeper in the case when it is fed from the magazine, which destroys accuracy (if your gun and trigger puller are accurate) and increases pressures, perhaps destroying the gun. And your hand. JMHO
 
Re: should I crimp or not

A light taper or factory crimp on lead or jacketed pistol bullet with no cannelure is my practice. Lightly tapping or pushing the the nose into a firm, no marr surface until it won't push the bullet into the case is a yardstick for me as enough crimp. Not scientific to be sure, but better than trusting the neck tension of thousands of X times fired brass cases!
 
Re: should I crimp or not

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">semi...yes
bolt gun ....no </div></div>
+1
I probably should crimp but I don't for my ar15.
For fun I Over crimped some rounds pretty harshly with a Lee Factory crimp die and found the accuracy dropped about a 1/4inch if I remember correctly(100yrds). I'm quite sure at longer ranges they wouldhave wondered around quite a bit.
Not realy sure.
smirk.gif
 
Re: should I crimp or not

Neck tension should be enough to ensure the bullet does not set back into the case.

If the round is in a magazine, any magazine, recoil can cause the cartridge to rebound back and forth in the magazine, so a more significant crimp is called for.

After some years to think about it, I believe that bullets without cannelures don't accept a crimp well. Bullets crimped without canelures that have been pulled and reused without further crimping have clearly demonstrated an accuracy loss in my experience. I believe this indicates that crimping a non-canelured projectile distorts it in some way that degrades accuracy.

For bolt guns, my experience indicates that the less neck tension, the better the accuracy; with the caveat that a bullet that sets back before firing becomes a wild card. Accuracy is not as good. In order to make light neck tension work well, the bullet needs to be hand chambered, and care taken to avoid inadvertant bullet setback.

Some handloaders deliberately load their bullets long with minimal neck tension, which allow the chambering process to touch the rifling, and then ride back into the case while being held in contact with the rifling. This works rather well, until one needs to extract such a round unfired. There is about an even chance that the bullet will stick in the rifling as the case is extracted, spilling the propellent charge into the action.

This we call a mess; and it must be cleaned out before the rifle can be safely fired again.

A more effective way to extract such rounds is to have a second person apply pressure to the forward end of the bullet with a cleaning rod inserted through the muzzle, pushing the bullet out of contact with the rifling and into the case, and then slowly withdrawing the bolt to complete the extraction. In a pinch this can be accomplished by a single person, but the entire process is tricky and serves as a good lesson against taking unnecessary chances. Imagine this happening in the middle of a match stage.

In situations where significant neck tension is called for, and the bullet does not possess a canelure, I believe it makes better sense to avoid crimping, and to resize the necks to a smaller diameter, thus increasing the neck tension without distorting the bullet. My means of accomplishing this is to provide an expander ball that has been shaped to a slightly smaller diameter by placing the stem and ball in a drill and turning the ball with its side in contact with fine emery.

Greg
 
Re: should I crimp or not

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Neck tension should be enough to ensure the bullet does not set back into the case.

If the round is in a magazine, any magazine, recoil can cause the cartridge to rebound back and forth in the magazine, so a more significant crimp is called for.

After some years to think about it, I believe that bullets without cannelures don't accept a crimp well. Bullets crimped without canelures that have been pulled and reused without further crimping have clearly demonstrated an accuracy loss in my experience. I believe this indicates that crimping a non-canelured projectile distorts it in some way that degrades accuracy.


Greg </div></div>
Hi Greg,I havn't been on here in a while
smile.gif

Ive been using a lee FCD once in a while and havn't noticed a terrible decrease in accuracy unless I get careless with it and over crimp the bullets(Non cannelure).With magfed 75gr Horn BTHP,and sierra 77gr mag fedammo and a firm neck tension I havn't had any issues with bullet setbackand the only proof I have of that is accuracy on paper.
I have considered crimping for added safety but wonder if it will be that effective considering I havn't had any issues and I don't have any bullets with cannelures. Ive basicly done what you mentioned and resized my expander.

Maybe I'm gambling a bit by not crimping,But with the tighter neck tension,,I havn't had any problems .
 
Re: should I crimp or not

I feel that in the case of bullets without cannelures, using a properly set up lee factory crimp die or other collet style crimp die could produce more uniform neck tension as well as solving the problem of bullet set-back. I have nothing to substantiate that claim with though.
 
Re: should I crimp or not

Some believe, at least with rifle cartridges, normal full length sizing provides adequate neck tension to prevent bullets from being driven inward, except for semi-auto magazine fed cartridges, or those that generate lots of recoil.

Another reason for crimping that I don't see discused here is uniformity of ignition; bullets are held more tightly than when no crimp is employed, so powder and bullet are not driven into the bore by the primer prior to ignition. This may assure, or at least improves the chances, that the powder will be ignited within a chamber volume that is uniform from one cartridge to the next.

Some reloaders claim they can see a consistency with a chronograph when checking velocities. This is one of my favorite reasons for using the Lee Factory Crimp tool, compared to uncrimped cartridges. This may not seem like much, but the velocity difference has been measured by others. So crimping does alter something, even if only increasing pressure.
 
Re: should I crimp or not

I do not crimp but do make sure that when using the redding com dies with bushings for an M21 I have theat I change the bushing to .001 or .002 smaller than the bolt guns. just to be sure there is enough tension to hold the bullet in place when using the M1A
Bill
 
Re: should I crimp or not

I was a huge fan of the Lee FCD, thinking it was a neat way to control neck tension. As I experimented with it, I found myself setting it for less and less crimp, and the accuracy improved accordingly, Taking it to the logical extreme, I skipped it completely, and accuracy improved yet again. So I decided that the best LCD crimp was no LCD crimp.

My next experiment was to use partial neck sizing, where one backs off the die so it only sizes a portion of the end of the neck. This also yielded positive results, with a technique where only the final 1/16" of the end of the neck was getting resized. My theory has evolved to where it is now; no more neck tension than is absolutely necessary, and if crimping, use the method that is least likely to deform the bullet in any way.

My shooting technique involves single feeding and hand chambering, and I can get by with a lot less neck tension than the average guy who loads from the magazine, so use my advice accordingly.

Greg
 
Re: should I crimp or not

I went back and forth on this issue myself.

My primary gun in .308 is an AR10. I thought I would crimp for the extra peace of mind and picked up the LFCD so that I could crimp non-cannelured bullets. For me to get any kind of noticeable crimp though I definitely had to adjust down far enough for it to imprint a ring on the bullet and thus deform it. I decided that for "match" type ammo with SMKs, Scenars, and A-maxes this would be unacceptable and stopped crimping them. You pay a premium for match bullets with a high level of consistency and I didn't like the idea of ruining that. I then noticed that my sizing die was only giving me .001" neck tension so I switched to using a SB FL "S" Bushing die from redding and got the appropriate bushings to give me .003" with my AR10 and .002" when I load for my bolt gun. I will still use my LFCD when I load ball rounds with cannelures. When I had just .001" neck tension I did see if I could forcefully set the bullet back and it was hard to just get it to move in a few thousandths. I don't think setback would really be a problem with a compressed load of Varget but I've read reports of the bullets moving back out a few thousandths when neck tension is insufficient on highly compressed loads that are stored for long periods of time.
 
Re: should I crimp or not

I found that .001" was the most crimp that offered any useful effect, and that using even that light a crimp with a non-cannelured bullet distorted the bullet enough to degrade accuracy, and made the resulting cartridge nearly impossible to disassemble with a kinetic bullet puller. It was by doing that disassembly and re-using the bullets without crimp in new cartridges that I discovered the accuracy degradation, so I'm pretty certain it's real.