Questions about Crimping

[bassfishindoc]

Hello all, I am relatively new to handloading and have a few questions about crimping. I am reloading .45 colt rounds for a new Ruger Blackhawk, using RCBS carbide dies and the seating die is able to do a rolled crimp. In looking through the reloading manuals for various loads I have noticed that some loads say a crimp is necessary, while others do not mention a crimp at all. I just have a few questions about crimping:
1. Do all loads need to be crimped, or just the ones that the manuals specifically say need to be crimped?
2. What are the benefits of crimping?
3. Are there ever any times when crimping should not be performed?
4. Should I crimp with the seating die or go ahead and get a die specifically for crimping?
5. Difference between a rolled crimp and tapered crimp?
6. As a beginner, one of the tough things is figuring out what I need to know so if there is somethings you all think are beneficial for me to know that I haven't asked please tell me.
Thank you everyone in advance, this is a great forum!

[Doodlebugger45]

There have been a few threads about crimping just today and hundreds over the past couple years. They can probably explain it better than I can, but I'll take a stab at some of your questions anyway.

1. Not all loads need to be crimped, but for your 45 Colt, yes, you need some kind of roll crimp. Whether it's a heavy roll crimp or a light one depends on the load level. The terms "heavy" or "light" are subjective, therein lies part of the problem. Generally though, revolvers and lever action rifles need at least some level of roll crimping.

2. Crimping serves 2 purposes. For lever action rifles, it prevents the rear cartridge from getting the bullet pushed inward in a tubular magazine due to the pressure exerted when the rifle is fired. To some extent, that is true on fairly heavy revolvers. The cartridges are just sitting there as round after round is fired. If the recoil is harsh enough, there is nothing to keep the bullets from working forward while they are just sitting in the cylinder. A different benefit though from roll crimping is that when the cartridge is fired, a roll crimp will provide a bit of resistance for maybe a few microseconds before the bullet exits out of the case. This will cause the pressure to build slightly even before the bullet starts its journey down the barrel. That helps ensure more complete ignition of the total powder charge. It's more important in slow burning powders like 296/110 and their ilk.

3. Bottleneck rifle cases are rarely crimped. The exception is rounds like 223 or those fired from other auto rifles with a relatively violent cycling action. Perhaps on very light handgun rounds it is also not the norm to do any crimping, especially on light target rounds in auto loaders like 380 or even 9 mm sometimes. There is just not that much force on some of those rounds during the firing and cycling.

4. LOL. That is debated here every day. I have some of the crimping dies and they do a great job. When I first started reloading, it was confusing and vexing trying to seat and crimp in the same step. I bought a couple FCD's and felt good about it all. Nothing wrong with them in the right application. Later on, I got the hang of seating and crimping in the same step with the same die. You can also do the crimping in a separate step just using the same seating die adjusted a bit different. In the meantime though, there's nothing wrong with buying a separate crimp die. Some people swear by them and technically, they can give a bit more precise seating and crimp doing it in separate steps with separate dies. It's kind of personal preference. Once I got comfortable (at the expense of several messed-up attempts and cases), I became too lazy to do a whole nuther step.

5. A roll crimp actually deforms the top of the brass into the crimp groove (cannelure) of an appropriate bullet. It doesn't have to be a whole lot and is easy to overdo, but you can see it and feel it. Take a look at a factory loaded 45 Colt or 44 mag cartridge and you can see the top of the brass actually bend inward into the crimp groove. Taper crimps are not visible typically. The crimping die in that case puts some pressure on the top of the brass and exerts extra tension on the bullet, thereby giving it a firmer grip on the bullet. Taper crimps are typically applied to auto pistol rounds like 9 mm, 40 SW, or 45 ACP. It is hard to tell after a case has been taper crimped. Maybe the brass is contracted a few thousandths of an inch in some cases, but basically it is just "tightened up" to get a better grip on the bullet.

6. Figuring out the proper crimp is tough because it is largely subjective. My advice is to use a factory round as your model (or maybe a loaded round from a very experienced reloader). If you have a "mentor" to assist you in getting the right feel, it will help immensely. Otherwise, just do some experimenting using a factory load. You might waste a few pieces of brass, but keep trying until you get the same overall length and the same look as your model round. It won't take long to figure it out if you have some common sense. Just don't be intimidated by this step is all.

[Uncle Buck]

When I am reloading my .45 LC brass I always crimp. I probably do not need to crimp every load I do, but I was taught to crimp, so I do it.

You probably have a bullet puller (hammer). Take a factory crimped round and put it in the hammer and try to remove the bullet. Now do the same thing to one you just reloaded. The hammer will show you the force needed to unseat the bullet.

I have several monsters (Ruined brass) that I made trying to set the seating plug and crimp at the same time. I would recommend getting your calipers out and using the seating plug, practice setting your die/crimp. You might ruin a few pieces of brass, but once you get the feel for it, you can always pull the bullet and run them through the expander die again.

Welcome to the forum and the wonderful world of reloading.

[Sevens]

You probably have a bullet puller (hammer). Take a factory crimped round and put it in the hammer and try to remove the bullet. Now do the same thing to one you just reloaded. The hammer will show you the force needed to unseat the bullet.

I see where you are going with this, but it's not completely accurate because most rounds of factory ammo have a sealant applied and this greatly affects the removal of the bullet. Better comparison would be to load two rounds on your press... one with little or no roll crimp and the other with a firm roll crimp and yes, you will feel the difference.

I agree with most everything that's been said.

When loading cast lead bullets, many of us seat and crimp in separate operations because the die is trying to do two things at once. When the case is far enough in that the crimp has begun -- and yet the bullet is not yet fully seated -- you've got a bullet being squeezed by the crimp while it's still moving. This will not help accuracy. I tend to separate the steps when I'm loading cast LSWC in .45. When I'm loading LSWC in .38 Special, I do them in the same step because I feel that the crimp is being applied after the bullet is fully seated.

Mostly, I do it because that's how I do it and the ammo turns out well, so I'm confident that it works!

[bassfishindoc]

Thank you for all your help! Information on crimping seems to be rather hard to come by in manuals and searching the internet (or maybe I'm just not looking in the right places) but all of you have been great. I do have one more question however, which companies make separate crimp dies and who should I go with? Also, what exactly is a Lee "factory crimp" and what are the pro's and con's of it compared to a roll or tapered crimp? Thanks again for the responses.

[Tim R]

Taper crimp is used for auto loader pistols because most head space on the mouth of the case.

Roll crimps are used when there is a cannelure in the bullet. The cannelure is what most use to crimp into to hold the none fired bullet in the case under recoil. Could be a wheel gun or a tube fed lever gun.

The roll crimps don't always have to be heavy, just enough to hold the bullet.

If I have to crimp, (I don't for most rifle) I do it in two steps. Seat the bullet then crimp.

I have never had the need to use a Lee FCD.

[AlaskaMike]

The Lee factory crimp die that I have for .45 ACP is a die with an adjustable tapered sleeve that gives a nice taper crimp. What makes the die controversial is that it has a carbide ring at the mouth which is sized for minimum SAAMI chamber spec. I've found that if I have thick walled brass (like mil surp) and cast bullets (which usually are .452" instead of .451" like most jacketed) then the carbide ring swages the round down.

I've been very happy with my factory crimp die--it's solved virtually all my jamming issues in my .45 autos. Some are worried that by swaging the finished round down like it does, it may squeeze the bullet down to too small diameter, resulting in leading. Others think it's a solution to a problem that doesn't exist. In my experience however, those rounds which the die swages down in diameter would typically jam my Sig P220. Prior to the factory crimp die I would readjust my RCBS seater die (since I seated and crimped in separate steps) to give a .470" or .469" taper crimp, but I still got jams periodically (failure of the slide to fully go into battery).

I can't comment on the factory crimp die for revolver or bottleneck rifle cartridges however--for roll-crimped revolver I use the Redding profile crimp die, and I'm equally happy with that one.

Mike

[James R. Burke]

I crimp for most pistols, and I do not crimp for most rifes;