I've loaded for bottle-necked cartridges for years, I learned from my father and countless writers. I have never crimped my hunting loads, I have read that they will be more accurate without a crimp, but now I own a .454 barrel for my Encore and I've read that I absolutely must crimp this monster for consistent ignition and accuracy, and it seems to me that the same principle would apply to my bottle-necked cases. I get sub-MOA with all of my stock hunting rifles, and I'm a firm believer in "if it ain't broke, don't fix it" mentality. I don't intend to start crimping my bottle-necks for this reason, but why are they crimped by some?

I crimp all of my reloads, from .22-250 to .500 for 2 reasons:
To keep the bullet in place on a heavy recoiling cartridge/gun combo, like a .454 in a revolver, and
To get consistant powder ignition and consistant velocity.
Most of what you read for crimping a .454 is for revolvers, but if you are going to use ball powder, I would suggest that you crimp the bullets for your encore. You will get better ignition.

To get the obvious out of the way, you crimp loads that will go through a tube magazine, an autoloader, or guns that will develope very high recoil with that load. You can't depend on neck tension alone to hold the bullet in place.

I've run into pistol loads using very slow powders (296, H110) that had to have a very heavy crimp to get uniform burning. I expect that's true in your .454.

I'll leave the great crimp-don't crimp debate in other instances for others.

Leftoverdj, that's the way I understand it to, so I guess I'm back to "if it ain't broke, don't fix it", but I plan on crimping all of my .454 reloads, I bought a Lee factory crimp dies specifically for it.
Yardbird

I'm pretty much with Leftover. I've loaded zillions of rifle and pistol cartridges and not crimped any of them unless for one reason or another I had to.

There is a danger for many new reloaders who may try to do a "roll crimp" with their reloading dies that they will actually push the shoulder of the case back and create headspace.

However, with the arrival of Lee's excellent "factory crimp" dies, I think crimping has become a very safe, easy and "case friendly" process that I am starting to use.

Saeed has done some interesting studies and posted the results on this website which do indeed point to improved accuracy with crimping.

Conclusion: Properly done...there ARE probably some benefits to be reaped from this process. But be careful how you do it and use the Lee "factory crimp" dies where possible.

For my single-shot 6mm Rem - no crimp.

For .308 for a self-loader - Lee Factory Crimp.

For .416 Rigby magazine rifle - Lee Factory CRIMP!!

I crimp anyathing that has a cannelure on the bullet.

I use a Lee factory crimp on most every caliber that I load. Feel that it makes a more consistant round for me.

Lately I too have been using the Lee Factory Crimp on all my loads. I'm convinced that doing so improves the accuracy of those loads.

(See Saeed's tests on this question. His tests also show a small but significant increase in accuracy with crimping using the Lee Factory Crimp Die.)

Only for my tubular fed cartridges and handgun cartridges.

I've found crimping of any bullet w/o a cannelure to be very detrimental to accuracy. I never crimp any thing but pistol cartridges, cartridges for tubular magazines, and heavy recoiling cartridges.

I have loaded some very accurate rifle ammo without crimping and I have loaded some very accurate rifle ammo with a crimp. My Dillon dies come with a taper crimp, for the others I use a Lee factory crimp. Those that are crimped seem to have better overall accuracy. Taper crimping also means the length of the case isn't as critical, so I don't have to trim as often.

I have a Redding 3-die set that I have used to crimp, but only 275-grain A-Frame bullets. because of their deep cannelure. I followed the Redding instructions on how to crimp bullets, and is was very easy.

I noticed an increase in velocity from the crimped ammo, so I decided to reduce the powder charge a little. Other than that, I am not sure if a crimp or not would make a difference, but I don't think I will crimp the next batch, since I only load a few "heavy ones" every now and then.

XWind,

I've reloaded for my wifes M14 with alot of different bullets and I never had a problem with bullets moving in it or anything else I've ever loaded for, including my Ruger 416Wby with slick 400gr XLC's too. I have always had .003" neck tension and not less with them all too, so if you have less it may be a problem for you.

The Sierra bullets have a thin jacket and crimping will deform it certainly, this isn't good for accuracy at all and probably explains why most target shooters DON'T do it. I also use GI mags so I can seat bullets out to 2.845".

180gr Scirocco's shoot great in it over 43gr of varget, psi is fairly low at about 50k psi on the Oehler 43 at about 2550 fps too.

I use the Lee Factory crimper on my 454 as well, nice die.

I've been wondering the same thing. I recently loaded 45Colt for the first time, and crimped very lightly. I got very inconsistent ignition, actually one of the bullets was tossed out of the gun by primer alone! I had loose powder coming out of the empty cases and there was soot all over the cases and the gun. I used the same load again with a really good crimp, and the problems went away. I had way more velocity and cleaner burning. So I've been thinking about this in relation to my .308. May not be important for some, but I'm using a very short barrel, and thought maybe more powder would burn before bullet exit. Of course, it has to increase dwell time before the bullet lets loose, which could in itself decrease accuracy the same way lock-time does.

As for the accuracy question, virtually no competition shooters that I know of use crimping. I know of people that have experimented with it. All abandoned it.

I only crimp my big bore dangerous game rounds as they might sit back and cause me problems..I use a very light crimp with the bullet seater and a full case of powder, but not a compaction of powder.....no problems so far, and its been about 50 years of no failures. I also take the expander ball out of my DGR dies and turn down about 3 thousands off them for a tighter fit of bullet.

Ray,

Wouldn't you get about .002"-.003" more tension buy just not using the expander at all? That seems about what mine open them back up by, I'm guessing yours are barely even touching at that point?

I have turned necks to true them up some to get .003" tension back without the expander using my normal dies. No need for the expander after this unless necks get dented though. Case necks are looser in the chamber so unless you have a tighter chamber than SAMMI the necks definatly get over worked.