Snug Crimp?

[Jeff H]

OK, here is a real newbee question. I often hear about giving your round a "snug crimp", but I never hear what that actually measures.

Essentially, what is a "snug crimp" or a "real firm crimp" vs. a "normal crimp" ?

 

[45flattop]

Basically to me, a snug or tight crimp is one that anchors the bullet
in the case sufficiently that under repetitive recoil, the bullet doesn't
creep forward slowly until it protrudes beyond the cylinder mouth or
in a semiauto, doesn't do the same and get too long overall so that
the slide won't lock at the rear. In the case of a revolver case having
a rim, it is a firm roll crimp and for anything with a rimless case, it
is a FIRM taper crimp. There are exceptions such as a 38 Super case
but I have no experience with them since they're semi rimmed.

 

[Rick Courtright]

Essentially, what is a "snug crimp" or a "real firm crimp" vs. a "normal crimp" ?

Hi,

I 'spose that's one of those things that means something different to each of us.

To me, it's a term I use most w/ ammo that has some form of "roll" crimp (revolver, rifle, shotshell.) If you look at a factory round of a particular caliber, that would represent a "normal" crimp to me. A crimp that shows noticeably more "roll" (w/o actually "pinching" into the bullet) would be MY "snug" one.

Some of our members have posted pictures in the past of THEIR versions of a "snug" crimp. If any of them post pictures again, you'll notice a wide range of interpretations of the term!

Rick C

 

[flatgate]

Look at these 300 grain jacketed bullet loads for this ol' clunker .44....

I was experiencing "bullet pull" until I gave my Lee Factory Crimp die a little twist.....

flatgate

 

[pvtschultz]

^^^That there is a VERY firm crimp!^^^

I do like the Lee Factory Crimp Die for finishing off my bullets. You'll never have to worry about crushing a case with it and it can create a crimp groove where one didn't exist.

 

[J Miller]

Here is a little thread I did some time back about the Lee FCD. There's several pics of different crimps in it.
http://forums.handloads.com/forum_posts ... W=J+Miller

Flatgate's crimps in the above picture are HEAVY. For most purposes they would be considered excessive, by me at least.

Here is a picture I post occasionally showing a good solid roll crimp and a taper crimp. Opposite ends of the spectrum.

Here is another picture showing heavy crimps:

Hope these pics help explain some.

Joe

 

[gerryb158]

The value of a "snug" "firm" or even a "normal" crimp is to hold the bullet in place against various forces that may act on it. Recoil, magazine feeding, loading in a tubular magazine under spring tension, etc. The amount of force it takes to "move" a crimped bullet out of the case mouth, no matter how well crimped, is relatively small. Probably about 25 to 50 psi of pressure will do it. This is evidenced by how many "squib" firings occur with reloaded ammo when the primer alone moves the bullet into the barrel. Is a crimp necessary? I guess that depends on the use of the particular ammunition. Bench Rest rifle ammo may be loaded without a crimp and relatively light neck tension as the cartridge is handled one-at-a-time and not through a magazine. For most applications, rifle or pistol, I'd agree a nice "firm" crimp is a good idea. I too like the Lee FCD.
Gerry

 

[Steve C]

I've never found any need to over crimp a round. For handguns and revolvers I consider any flattening of the case mouth to be excessive since you've gone past the maximum inward roll the die was designed to give. A firm crimp only needs to engage the bullet with the end of the case mouth in the crimp groove if one is proviced. The picture below is what i would consider a full or heavy crimp on a LSWC .357 mag load.

 

[tomiswho]

Here's a sample of what I consider a heavy crimp. I did this on some 300g .45 Colts with 22g WW296. They seem to work just dandy.
Tom

 

[flatgate]

I certainly agree that the "heavy for calibre" bullets, especially when loaded at "near max" velocities, darn well benefit from a firm crimp. The bullet pull situation is stopped and the increased resistance, in my experience, makes a definite difference in the combustion of the powder column.

I've seen "dirty" loads turn into "clean" loads via a firm crimp.

I usually only shoot powders that approach (or reach) 100% loading density, though. None of this "a pinch" in the bottom of the case....

JMHO,

flatgate

 

[sturmenater]

flategate thats a very nice clunker

 

[Driftwood Johnson]

Howdy

Believe it or not, mild or light loads in large capacity cases like 45 Colt will benefit from a heavy crimp. Most Smokeless powders need to achieve around 5000 psi before they begin to burn efficiently. Under 5000 psi, burns can be erratic. With a light load, a heavy crimp will retain the bullet in the cartridge for an instant while the powder gets a good burn going, exceeding the 5000 psi minimum. With a light crimp, the preliminary pressure needed to begin to shove the bullet out of the case may not be enough to get the powder burning consistantly. That is one reason why light loads usually exhibit soot on the outside of fired cases. The powder never built up enough pressure to expand the case enough to completely seal the chamber.

A good rule of thumb for crimps is to compare your crimps to commercial ammo. If the crimp looks like a commercial crimp, it is good. My own definition of a firm crimp is one that is not quite enough to create a 'bulgy' crimp. If the crimp die is screwed in just a little bit too much, the crimp will bulge and the cartridge may not chamber properly. Backing off the crimp die just a tad from that amount will result in a nice firm crimp.

I never use a crimp die for most of my revolver rounds, I simply seat the bullet and crimp in one step in a conventional seating/crimp die. It has worked for reloaders for a long time before the current fascination with crimp dies.

 

[Rex Driver]

Howdy

Believe it or not, mild or light loads in large capacity cases like 45 Colt will benefit from a heavy crimp. Most Smokeless powders need to achieve around 5000 psi before they begin to burn efficiently. Under 5000 psi, burns can be erratic. With a light load, a heavy crimp will retain the bullet in the cartridge for an instant while the powder gets a good burn going, exceeding the 5000 psi minimum. With a light crimp, the preliminary pressure needed to begin to shove the bullet out of the case may not be enough to get the powder burning consistantly. That is one reason why light loads usually exhibit soot on the outside of fired cases. The powder never built up enough pressure to expand the case enough to completely seal the chamber.

A good rule of thumb for crimps is to compare your crimps to commercial ammo. If the crimp looks like a commercial crimp, it is good. My own definition of a firm crimp is one that is not quite enough to create a 'bulgy' crimp. If the crimp die is screwed in just a little bit too much, the crimp will bulge and the cartridge may not chamber properly. Backing off the crimp die just a tad from that amount will result in a nice firm crimp.

I never use a crimp die for most of my revolver rounds, I simply seat the bullet and crimp in one step in a conventional seating/crimp die. It has worked for reloaders for a long time before the current fascination with crimp dies.

Driftwood, I am with you on the crimp and seating bullet in the same action. I have loaded many thousands of rimmed straight wall pistol rounds with Lee Carbide Three Die sets and have not had a problem. The only problem I have had with hand loads was the one that got me to reloading over 35 years ago. I bought some hand loads from a gun show (first and last time, big mistake) and took them to the range and had problems from the start. Unburned powder in the barrel and the last problem was some of the bullets slipped so far out of the cases that they locked up the cylinder. I ran, did not walk, to a sporting goods shop and purchased several manuals about reloading and after about a month of reading, I purchased my first single stage press, scale and powder measure and attempted to make ammo of a better quality than those I had purchased at the gun show.
Lee Carbide Three Die sets have served me well in my ammo production since then and I see no need to change to the current fad for my target shooting, cowboy shooting and just general plinking.