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  #1  
Old 05-15-2021, 09:23 AM
SharpShooter82 SharpShooter82 is offline
 
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Posts: 102
Default Case crimping

I read a recent post and crimping was brought up but I did not want to hijack that post so I am just gonna start another one.

I know that this will probably open a can of worms so I apologise in advance.

I have been reloading pistol for about five years and rifle just over a year. When reloading revolver rounds I roll crimp just enough to get the case mouth into the crimp groove and taper crimp auto rounds just a touch. With rifle I have been crimping "medium" (setting Lee dies as stated in the directions without further adjustment).

I think that I understand the reason for crimping, basically to keep the bullet from moving under recoil, but some of the things I have read just don't make sence to me. I will try to explain and keep it short. Obviously I will leave out "to keep the bullet from moving".

I also understand that crimping at some point will affect chamber pressure, but if it is consistent and does not show excessive pressure does it really matter?

Auto pistols,,,the crimp is to just to taper the case mouth just a bit to allow it to feed easier.

Revolvers,,,the only thing I have read is to keep the bullet from moving.

Rifle,,,the crimp is used to "seal" the mouth of the case. The crimp makes the rounds more consistent.

I am sure the "consistancy" claim could be applied to all types of ammo but I think consistency in loading is the key more so than crimping. Sealing the case mouth,,,there is a .001" interference fit so I would think that would seal the case unless the case was in a higher pressure environment, say at 500' under water.

I have also read that the military crimps the bullet and primer to keep them from moving because apparently there was a concern of the rough handling of the ammo in transport. Not something most of us have to deal with.

The main reason given, to keep the bullet from moving, seems to be the most valid. So it is my opinion that there are two or three instances that may causethe bullet to move.

1,,,recoil, the bullet would move further out of the case. I have actually read that depending on the action type the bullet would move into the case.

2,,,round being moved from the magazine/clip. Bullet would move further into the case. This would be caused by the sudden acceleration of the round as the bolt engages the round to load it.

3,,,round stopping when chambered. Bullet would move further out of the case. Due to the speed of chambering the round.

So I would think that the following action types would be affected the most as followes,,,

Autoloaders = 1, 2,and 3.
Bolt = 1
Revolvers = 1
Lever = 1
Pump = 1

I left out single shots for obvious reasons. I suppose that if a bolt, lever, or pump could be operated with enough force or speed they could be affected by 2 and 3 as well. However single loading of any autoloader where the round is first placed in the magazine/clip and the action cycled would be affected by 2 and 3.

Here is what I have found to be true with my reloads (as loaded as explained above) for my firearms.

I have checked the last round in the magazine after firing from a full magazine several times and I have not noticed any measurable movement, and then checked that round after chambering it, same result. I have not yet loaded any ammo without the traditional crimp method, guess I should to make my own conclusions.

I have heard that crimping is not needed in bolt gun ammo. This does not make sence because ammo in a bolt gun is still subject to recoil unless single loading.

So I guess I am asking if anyone has tested the crimping issue? If so what have you found?

Eric

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  #2  
Old 05-15-2021, 09:37 AM
rcolarco rcolarco is offline
 
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Rifles: If crimping makes the rounds more "consistent," (whatever that means), benchrest shooters would do it. If you asked a benchrest shooter to crimp his rounds, he would look at you like you were the devil incarnate.

Sierra says do not crimp unless there is a mechanical reason to do so (tube magazines, dangerous game loads in big double rifles, etc.). Crimping does affect accuracy, in a negative way. But if it makes you feel better, go ahead and do it. You do not need to crimp to "seal" the cartridge.

Recoil is not going to pull a bullet out of the case in any .223, .308, or .30-06 load, if your bullets, cases, and expander plugs are properly dimensioned. If any of these are not so, crimping is not the solution.

Revolver loads in straight cases, roll crimp. If you are not crimping enough, you will find out very quickly.

Auto pistol loads, taper crimp. If you are not crimping enough, you will find out very quickly.

No new science here.
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Last edited by rcolarco; 05-15-2021 at 09:40 AM.
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  #3  
Old 05-15-2021, 11:19 AM
Pinecone Pinecone is offline
 
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Taper crimp on auto pistol is to remove the flare from the expanding die.

You should not reduce the diameter, as the case may headspace on the mouth.

If you look, match bullets do not have a cannular, so you should not crimp them.
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  #4  
Old 05-15-2021, 11:39 AM
Nikkineaux Nikkineaux is offline
 
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Location: DFW area
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I just started reloading .308 for my M1A & AR-10 & have found that unless I use new brass that I have to crimp the crap out of a round to keep the bullet from moving forward when the bolt "slams" into battery. I even bought an annealer which helped a little but a Sierra boattail would still move forward a few thousands when "slammed into the chamber so I tightened my crimping die and now I have a "bottle neck" around the bullet at the neck of the round.
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  #5  
Old 05-15-2021, 02:28 PM
luigi luigi is offline
 
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Location: NW Arkansas
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I will occasionally get a jam in my semiauto rifles/pistols and a slight crimp will keep the next bullet from being pushed back into the case by the jammed round. PS I have shot < 1 MOA w/ slight crimp so it ain't that bad.LOL

Last edited by luigi; 05-15-2021 at 05:23 PM.
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  #6  
Old 05-15-2021, 03:06 PM
X Hunter X Hunter is offline
 
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No competitor that ever taught me a thing recommended crimping rifle rounds.
What rcolarco says +1

Last edited by X Hunter; 05-15-2021 at 06:26 PM.
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  #7  
Old 05-15-2021, 03:56 PM
rcolarco rcolarco is offline
 
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Quote:
Originally Posted by Nikkineaux View Post
I just started reloading .308 for my M1A & AR-10 & have found that unless I use new brass that I have to crimp the crap out of a round to keep the bullet from moving forward when the bolt "slams" into battery. I even bought an annealer which helped a little but a Sierra boattail would still move forward a few thousands when "slammed into the chamber so I tightened my crimping die and now I have a "bottle neck" around the bullet at the neck of the round.
Try a smaller expander button. You should not have to crimp at all, certainly not enough to show a bulge at the neck.

Measure your expander button. If it is larger than 0.307, you need a smaller one. If it is a steel button, spin it in a drill and apply crocus cloth. If it is a carbide button, buy a new one.
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  #8  
Old 05-15-2021, 07:29 PM
navyrifleman navyrifleman is offline
 
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I crimp all rifle rounds that are loaded with cast lead bullets. Without crimping, the bullet will easily push back into the neck. This is particularly true of tubular magazine lever action rifles.

With pistol rounds, my bullet seater dies have a taper type crimp incorporated.

For most jacketed rifle bullets, I generally do NOT crimp the case necks, but do crimp them for tubular mag type rifles such as the .30-30.
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  #9  
Old 05-16-2021, 07:38 AM
SharpShooter82 SharpShooter82 is offline
 
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Thanks for the comments y'all.

I think I will load some .308 and .30-06 with no crimp and see how it does. Not crimping will remove another round of handle pulling, even though there is little to no effort in pulling the handle it is the motion that bothers my shoulder. That is the main reason I got a progressive for loading pistol ammo.

I will keep doing the pistols as I have been since that seems to be the correct way.

Eric


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Quote:
Originally Posted by rcolarco View Post
Rifles: If crimping makes the rounds more "consistent," (whatever that means), benchrest shooters would do it. If you asked a benchrest shooter to crimp his rounds, he would look at you like you were the devil incarnate.

Sierra says do not crimp unless there is a mechanical reason to do so (tube magazines, dangerous game loads in big double rifles, etc.). Crimping does affect accuracy, in a negative way. But if it makes you feel better, go ahead and do it. You do not need to crimp to "seal" the cartridge.

Recoil is not going to pull a bullet out of the case in any .223, .308, or .30-06 load, if your bullets, cases, and expander plugs are properly dimensioned. If any of these are not so, crimping is not the solution.

Revolver loads in straight cases, roll crimp. If you are not crimping enough, you will find out very quickly.

Auto pistol loads, taper crimp. If you are not crimping enough, you will find out very quickly.

No new science here.
You mention that crimping rifle bullets will negatively affect accuracy, how or why does it do this?

I agree that there is really no new science involved with reloading.

Eric


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  #10  
Old 05-16-2021, 08:15 AM
rcolarco rcolarco is offline
 
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Quote:
Originally Posted by SharpShooter82 View Post
You mention that crimping rifle bullets will negatively affect accuracy, how or why does it do this?

I agree that there is really no new science involved with reloading.

Eric


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I am quoting Sierra, who make a lot of match bullets.

Here is my speculation. Match bullets do not have a crimp cannelure, so any crimping must deform the jacket somewhat. This could not be good for accuracy, and may be bad.

If case lengths are not uniform, neither will be crimping. This could not be good for accuracy, and may be bad.

Benchrest shooters (who care about accuracy and nothing else) do not crimp.

If everything is sized correctly, you do not need to crimp to produce durable ammunition. You do not have to worry about sealing the round unless you plan to submerge it.
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