Crimping

[tes1900]

Perhaps my question is so obvious that I just cannot see it for the trees.
How do you know when you have enough crimp?
9 mm, 40 S&W, 357, 38 special, 44 special, 44 mag, 45 ACP then .22 Hornet (for a pistol), 300 Win. Mag and .223 Rem.
But starting out on 9 mm.
Tom

In time I will also be doing the the 454 casull, 45-70 Govt (for pistol). and the 50 AE.



I cannot thank you all enough for all the advice you have given me. I have read so many books that were conflicting that I have gotten nerves!

Tom

[chris in va]

9mm is easy...just TAPER crimp enough to take out the bell from loading the bullet. It doesn't take a roll crimp like revolver rounds do.

To the naked eye it'll look like the shell is straight and not 'biting' into the bullet.

[kraigwy]

In reloading manuals they have drawings of the case. If you were to crimp you case to match the measurements the manual says for the mouth of the case, then you are good to go.

For roll crimps (38, 357, 44s etc) I use cast bullets which have a crimping grove. I like to get as much crimp on the case as I can without deforming the bullet.

Sometimes you will notice bulges in the case where the bullet sets, or wrinkles because roll crimping pushes down on the mouth of the case every now and then. Thats where the Lee Carbide Factory crimp die comes in handy. It has a carbide ring at the bottom of the die to completely resize the round as you pull it out of the die, makes for some nice smooth loading in cylenders, and really shines (great feeding) in my Smith Model 52 wad cutter gun.

[jmortimer]

+1 for the Lee Factory Crimp die. I crimp everything but I only shoot revolvers.

[SL1]

Crimping is different for different types of cartridges because it serves somewhat different purposes against different forces from different directions. You know you have enough when it is serving its purpose. So, let's review the purposes.

For semi-automatic pistol cartridges that headspsce against the mouth of the case, a taper crimp is used that leaves the mouth of the case flat against the bullet, but NOT dug-into its surface. Some folks use a caliper to measure the diameter of the case right at the mouth, and you will see specs for that for a lot of cartridges. But, so long as the cartridges feed OK, you have enough taper crimp. For this type of cartridge, the crimp is NOT what is used to keep the bullet from moving (case neck tension is needed to do that).

For revolver cartridges, there is usually a groove in the bullet that the case mouth can be turned into with a roll crimp. For low-power loads, it doesn't need to be much of a roll crimp, and even a taper crimp (with the case mouth against a flat part of the bullet) will generally work as well. But, when the recoil gets heavy, the roll crimp is necessary and needs to be rolled in pretty far to make sure that the bullets don't pull forward in the cases when the recoil jerks the cartridges by their rims. Generally, rolling the case mouth in so that it just touches the bullet in the deepest part of the goove is all you need. Less is OK with mildeer loads. Remember, the harder you crimp, the faster you will work-harden the brass and the sooner you will get a crack in the case mouth and have to discard it. However, with some of the new super-powerful cartridges like the .500 S&W Magnum, there have been some modifications to the roll crimp, called a "step-down-crimp" that only works well in bullets that have flat-bottomed crimp gooves. You didn't list any of those in your post, so I won't go into details about that.

For rifle cartidges that are loaded into tubular magazines, the crimp needs to be there to stop recoil from driving the bullets deeper into the case. In REALLY heavy recoiling rifle loads like used for hunting dangerous game in Africa, the recoil is bad enough even in box magazines that there needs to be a crimp to keep the bullets from being set-back. And, in some similar power double-barreled guns, the crimp is needed to keep the bullet from pulling out in the barrel that was not fired first just like in a revolver. These are usually roll crimps.

For lower power bottle-neck rifle cases, people usually do not crimp the bullets, especially not in bolt-action rifles. For auto-laoding rifles what the bullet is being slammed against the feed ramp pretty hard, some people find that they need a crimp to prevent setback, for example, in AR type rifles firing .223 or .308 ammo.

Some "slow" powders need a lot of resistance to the bullets starting to move so that they can succeed in buiding-up pressure enough to burn well. Without that, they can stop burning and cause a "squib" load that can leave a bullet lodged in your barrel. Usually, the load data will say something about a powder needing a firm roll crimp when that is an issue.

And, some folks argue that crimps on some cartridges that don't normally require them will still make the cartridge more accurate. Lee's "Factory Crimp Die" for bottleneck rifle cases is often advertised on that basis.

So, the best way to be sure you have enough is to test your loads and see if the crimp is serving its purpose.

SL1

[Sevens]

I can't imagine helping much after SL1's comprehensive post... but here's a little CHEAT method that some of us have used in the past!

Grab some decent factory ammo that you trust (quality from one of the big makers, not some low brow re-man stuff in a plain white box!) in each of the different calibers that you intend to load and look at them with a close eye. If you grab a piece of .44 Mag factory ammo, you will see a pretty obvious roll crimp where the brass is gripping that bullet. Grab some decent 9mm FMJ and you won't see that at all, but a nice flat edge on the end of the brass/case mouth to facilitate a perfect fit in the chamber.

Try and see how the pro's do it, and then see if you can replicate it. Not scientific, but it may help a bit.

[Sarge]

The purpose of a crimp is to retard the bullet's movement against the forces of impact, inertia and in some cases, magazine spring tension.

I check mine by taking a finished round, placing the bullet against the bench and pushing against it, as if I intended to move the bench; maybe 10-15 pounds of force. If the bullet doesn't set back, it's enough for my purposes.

[vladan]

For auto loaders the thumb test - measure OAL then stand the finished round on the bullet and press with your thumb on the base od case and apply moderate pressure (10-15 lbs) and measure OAL again - bullet shouldn't move. Another test ( but i would recommend to remove firing pin from your weapon ) would be to lock the slide in back, load the round in mag and release slide. then remove ( slowly) round from the chamber and measure OAL, again, bullet shouldn't move more than 0.001-.002 inch.
For the revolver and semi auto rifle I use lee factory crimp die to crimp into bullet cannelure. For bolt action no crimp needed

[vladan]

Sarge beat me to it ...

[robc]

I don't think anyone said it yet, so I will. Take the bbl out of your gun. Insert a few factory rds into the chamber. Pop them in and out with your finger. Feel how they "click" in there, then easily fall out when you tip the bbl and let the rd fall? Also, look at how far into the chamber they go when you push them in. This is exactly how your reloads should work. If you're anything like me, your first attempts will: 1) not go in, 2) go WAY in, or 3) not fit in the mag., which they also must do

[Lost Sheep]

Tom, tes1900,

Thanks for asking our advice.

Answers given so far leave little room for improvement, so I will expand on SL1's mention of the needs of heavy-recoiling revolver rounds. (SL1, your post should be in every loading manual I have ever read.)

I know of two instances where a 454 Casull revolver was rendered inoperative after shooting dangerous game (Grizzly/Brown Bear) because bullets "jumped crimp", sticking their nose(s) out the front of their chambers and tying up the cylinder. One happened to Craig Medred, a columnist for the Anchorage Daily News (probably 20 years ago) and one just last August when a desperate Brownie tried to make lunch of a Soldotna man who, fortunately, was carrying a Super Redhawk. Three shots put the bear down, but the fourth shot had to wait until a second gun was summoned (by cell phone). The gun was jammed up, reportedly by insufficient crimp allowing the recoil-loosened bullet to work its way out of the casing and chamber to tie up the cylinder's rotation. (web site: peninsulaclarion.com/stories/080709/out_478669517.shtml)_

The acid test, of course is to load up a cylinderfull of full-power ammunition and fire off all but one. Then reload and fire off all but that same one, and do it again. Then compare the length of the one cartridge after all that recoiling to what it's length was before the test (did I mention to measure it before you started?). If it is still the same length and the crimp is just as deep as it was before the test, then that round is a good one. Do that 4 or 5 more times and you will have collected enough "battle tested" rounds to carry in the field for self-defense against large predators. (Just kidding, you can safely assume that if one round of factory ammo passes this test, its box-mates will, also. But, inspect each one's crimp carefully, anyway.) Even with expensive ammo, it is cheap insurance if you are depending on only one gun.

Another point; In semi-autos, (pistol and rifle, but more so in pistols because the cartridge is shorter for its diameter than for rifles, thus makes it travel more angular) when the bullet nose hits the feed ramp, it can be pushed deeper inside the case, reducing the volume for the powder's burning gasses to expand, elevating pressures. You want to ensure a bullet will not be set back in the case, even if it is chambered and removed several times before it is actually fired (as many rounds are in duty guns, loaded and cleared many, many times without ever being fired.

Lost Sheep

[tes1900]

Another point; In semi-autos, (pistol and rifle, but more so in pistols because the cartridge is shorter for its diameter than for rifles, thus makes it travel more angular) when the bullet nose hits the feed ramp, it can be pushed deeper inside the case, reducing the volume for the powder's burning gasses to expand, elevating pressures. You want to ensure a bullet will not be set back in the case, even if it is chambered and removed several times before it is actually fired (as many rounds are in duty guns, loaded and cleared many, many times without ever being fired

Would I be correct that because a 9 mm or other semi-auto case being that the head spaces is on the rim of the case that having such case a bit short would not really be a problem?
Tom

[vladan]

Would I be correct that because a 9 mm or other semi-auto case being that the head spaces is on the rim of the case that having such case a bit short would not really be a problem?
Tom

No. Because of relatively small internal volume of pistol cases any bullet setback raises pressure. Some high pressure cartridges as .40S&W loaded with long 180g bullets have such a small margin that going from 1.140" OAL to 1.050" OAL ( only 0.090" setback) raise pressure from 26000psi to 51000psi. That is reason why most of 180g .40S&W are loaded on "milder" side than say 155g or 165grainers

[Bud Helms]

Would I be correct that because a 9 mm or other semi-auto case being that the head spaces is on the rim of the case that having such case a bit short would not really be a problem?
Tom

I'm pretty sure it headspaces on the mouth of the case, not the rim.

[Lost Sheep]

Originally Posted by tes1900

Would I be correct that because a 9 mm or other semi-auto case being that the head spaces is on the rim of the case that having such case a bit short would not really be a problem?
Tom

Tom,

I don't understand your question. Are you talking about the case or the cartridge?

The length of the case is highly critical to headspace. The length of the cartridge (which includes the bullet), not so much. Cartridge overall length is still important (for the reason vladan pointed out as well as others) but not quite so critical as the case length.

So, you see my confusion reading your post. "Having such case a bit short" would be a major problem with headspace.

By the way, 9mm cases do not have a rim, per se. The base of the cartridge in back of the extractor groove may LOOK like a rim, but since it is the same diameter as the case body and does not extend past the case body, it is not properly called a rim, and even if it were, you still could not headspace on it.

Would you care to re-state your question if my little dissertation has not answered it?

Lost Sheep

[Tim R]

What Tom is talking about is there are a few reloaders of auto pistols who will argue with you that the case head spaces on the rim of the case. (or more correctly the extractor groove) The reason they think this is because as the cases are used again and again they shrink with use. The extractor does hold a case enough to fire the round. A careful reloader knows the head space on most common auto loaders do head space on the mouth of the case and proper head space does lead to better shooting ammo.

Arguing with some of these incorrect thinking reloaders are like trying to tell an anti gunner the 2nd A is a good thing. They won't listen to reason or fact.

[tes1900]

Thank you everyone for you help, it give me a lot more to digest. I value everything you have said and beleve it or not give it more weight than some of the major books, you are answering direct queston with direct answers, something a book could never do.
As I have not yet recieved my powder and primers I have spent my time with case preperation and even loaded a few dummy rounds.
When I have another newbee type question I will call up this site again screaming for help.
By the way...anyone in Nevada?
Tom

[tes1900]

Would I be correct that because a 9 mm or other semi-auto case being that the head spaces is on the rim of the case that having such case a bit short would not really be a problem?

Please excuse my lack of proper terminology; as you can see I am not good with the terminology as of yet – still learning.
I understood about how critical the case length is, but my second quest was suppose to be referring to how critical is the OCL, that is as long as the cartridge still chambers. As long as it is under the max length am I correct that it would be acceptable? I have been having an impossible time trying to keep them consistent and within a few thousands of each other.
Perhaps I am too much of a perfectionist.
Again thank you for all your help!

[Lost Sheep]

Originally Posted by tes1900

my second quest was suppose to be referring to how critical is the OCL

You ask very probing questions. Good on you.

Cartridge length is impo9rtant for two reasons

1) One is very easy to describe. If a cartridge is too long, it won't fit in the magazine or feed properly through the gun's mechanism, or in the case of revolvers, a cartridge too long will stick out the front of the cylinder and not allow the chamber to rotate into firing position (or perhaps, to even to close the cylinder). For single-shots or bolt actions, a too-long cartridge can impinge on the rifling and cause bolt closure problems.

2) has to do with internal ballistics. The important measure of a handload is the available volume underneath the base of the bullet. This cannot be measured directly in a loaded round. Even the linear measurement from the base of the bullet to the cartridge base is unavailable while the primer is in place.

Bullets of the same weight, but different shape (e.g. long, spitzer point-or spire point) will have less volume for the powder and for combustion than a flat-point or round nose, EVEN THOUGH THEY HAVE THE SAME OVERALL LENGTH. Other things being equal (and with few exceptions), the cartridge with the lesser volume will have higher pressure than the one with more volume.

The exceptions are beyond my ken, but have to do with flame front speed in compressed loads vs loosely packed loads and other arcane or esoteric factors organic to internal ballistics.

Keep asking questions, keep learning, keep enjoying the shooting sports. I predict you will be a mentor to new reloaders before long.

Lost Sheep

[Lost Sheep]

Originally Posted by Lost Sheep

a rim, and even if it were, you still could not headspace on it. (the extractor groove, sometimes referred to as a "rim" on "rimless" autoloader cartridge cases)

As Tim R pointed out,

The extractor does hold a case enough to fire the round.

you CAN "headspace" on the extractor/extractor groove. But it is not reliable, therefore, not advisable.

In an autoloader, if the cartridge is short, the extractor may , instead of going over the "rim" and engaging the groove, may simply push the cartridge deep into the chamber (as the cartridge is short enough to go). Then, you have a chambered cartridge that the extractor will not extract (not engaged) and which the firing pin probably cannot reach with enough momentum to ignite. A jammed gun that the typical "Tap-Rack-Bang" clearance drill will not cure.

I stated "could not" which is wrong. You should not, except for certain guns designed for that functionality. (e.g. the Medusa revolver, designed for it and maybe Ruger's double action revolvers designed for the 9mm MIGHT be reliable enough because they had spring-loaded extractors that pretty positively engaged the grooves.

Lost Sheep

[Lost Sheep]

Originally Posted by Lost Sheep

a rim, and even if it were, you still could not headspace on it. (the extractor groove, sometimes referred to as a "rim" on "rimless" autoloader cartridge cases)

As Tim R pointed out,

The extractor does hold a case enough to fire the round.

you CAN "headspace" on the extractor/extractor groove. But it is not reliable, therefore, not advisable.

In an autoloader, if the cartridge is short, the extractor may , instead of going over the "rim" and engaging the groove, may simply push the cartridge deep into the chamber (as the cartridge is short enough to go). Then, you have a chambered cartridge that the extractor will not extract (not engaged) and which the firing pin probably cannot reach with enough momentum to ignite. A jammed gun that the typical "Tap-Rack-Bang" clearance drill will not cure.

I stated "could not" which is wrong. You should not, except for certain guns designed for that functionality. (e.g. the Medusa revolver, designed for it, and maybe Ruger's double action revolvers designed for the 9mm MIGHT be reliable enough because they had spring-loaded extractors that pretty positively engaged the grooves.)

Lost Sheep

[tes1900]

In an autoloader, if the cartridge is short, the extractor may, instead of going over the "rim" and engaging the groove, may simply push the cartridge deep into the chamber (as the cartridge is short enough to go). Then, you have a chambered cartridge that the extractor will not extract (not engaged) and which the firing pin probably cannot reach with enough momentum to ignite. A jammed gun that the typical "Tap-Rack-Bang" clearance drill will not cure.

Please excuse my ignorance; but it has been my understand that the mouth headspaces against the chamber and as long as the cartridge is not below the minimum length then what was said above cannot happen. I'm sorry but I just do not understand how the extractor has anything to do with the COL.
Gettng more confused - Tom