Armory Sponsor
Posted: 6/6/2012 6:01:23 AM EDT
|
i can find all kinds of info on how to remove a primer crimp, what exactly is it meant to do?
keep a primer from popping out under high pressure? how is it added? before or after primer insertion is there any reason to try and duplicate it with sealants/epoxy or metal? |
|
Quoted: There was a thread here a few weeks ago about how there's no load data to duplicate military loads.i can find all kinds of info on how to remove a primer crimp, what exactly is it meant to do? keep a primer from popping out under high pressure? how is it added? before or after primer insertion is there any reason to try and duplicate it with sealants/epoxy or metal? The pressure is high enough that it's not something they want you duplicating at home. I'm not speaking from experience, just parroting what I read. The military can't afford to have soldiers reduced to using their weapons as clubs because there was a primer jammed in the trigger during a firefight. |
| The primer crimp is to keep the primer from falling out or being knocked out during rough handling or in automatic weapon feed systems. It is NOT intended to keep it in when exposed to high chamber pressures (the locked bolt face against it does that). If the primer was crimped tight enough to hold it in at even normal chamber pressures (50,000 psi), you would not be able to punch it out to reload the case. |
|
Quoted: This is why. Good answer.The primer crimp is to keep the primer from falling out or being knocked out during rough handling or in automatic weapon feed systems. It is NOT intended to keep it in when exposed to high chamber pressures (the locked bolt face against it does that). If the primer was crimped tight enough to hold it in at even normal chamber pressures (50,000 psi), you would not be able to punch it out to reload the case. |
|
Quoted:
Quoted:
This is why. Good answer.
The primer crimp is to keep the primer from falling out or being knocked out during rough handling or in automatic weapon feed systems. It is NOT intended to keep it in when exposed to high chamber pressures (the locked bolt face against it does that). If the primer was crimped tight enough to hold it in at even normal chamber pressures (50,000 psi), you would not be able to punch it out to reload the case. I have had a few popped primers. If what your saying is true popped primers couldn't happen but they do. Dryflash, I am in no way trying to say I know as much as you cause I don't but I like other people have also heard that military primer crimp is used for a couple of reasons. One being to hold the primer in under full auto fire and two to keep it in with the high case pressures that the military rounds use to avoid the occassional popped primer that can sometimes happen when flirting with the limits of the case pressure maximum. Are you saying that this isn't true ?? If so , can you show me where you read it so I will know for sure that it's just hear say. |
| The crimp doesn't hold the primer in during case expansion under pressure, I should think that would be obvious, it does however sometimes help to keep the primer from falling out after the case has contracted if the case head has expanded enough due to pressure that the primer pocket won't contract enough to itself hold the primer, as sometimes happens with high pressure loads. This is a side effect of the crimp and not the origional intent, which was as stated to hold it in place during rough handling/cycling. 5.56NATO is high pressure, .30-06 and 7.62x51mm loadings intended for M1s and M14s both of which are intolerant of high pressure were, (in the case of the M14 are) also crimped, I'm sure there are other examples. |
|
Quoted:
If the primer was crimped tight enough to hold it in at even normal chamber pressures (50,000 psi), you would not be able to punch it out to reload the case. you had a good answer but... you should have stopped while you were ahead. 
I agree with the thought but there may be a technically inaccurate concept underlying it. There is no way brass of any type (crimped or otherwise) can contain pressures of 50 ksi. 50 ksi exceeds the yield and ultimate strength of cartridge brass (and many steels, too). It isn't a matter of being able to crimp it harder or crimp it more, even up to the point where a press and die can't punch it out. If the case or primer were asked to sustain that pressure differential, they would fail catastrophically. Barrels and bolts are made of steel to supports the brass case and primer which flow like putty at those pressures. The crimp prevents the primer from falling out under adverse conditions. |
|
Quoted: Popped primers? Your loads were too hot for the primer.Quoted: Quoted: This is why. Good answer.The primer crimp is to keep the primer from falling out or being knocked out during rough handling or in automatic weapon feed systems. It is NOT intended to keep it in when exposed to high chamber pressures (the locked bolt face against it does that). If the primer was crimped tight enough to hold it in at even normal chamber pressures (50,000 psi), you would not be able to punch it out to reload the case. I have had a few popped primers. If what your saying is true popped primers couldn't happen but they do. Dryflash, I am in no way trying to say I know as much as you cause I don't but I like other people have also heard that military primer crimp is used for a couple of reasons. One being to hold the primer in under full auto fire and two to keep it in with the high case pressures that the military rounds use to avoid the occassional popped primer that can sometimes happen when flirting with the limits of the case pressure maximum. Are you saying that this isn't true ?? If so , can you show me where you read it so I will know for sure that it's just hear say. Some primers have a thicker cup than others. A crimped primer will not solve your hot load or wrong primer for the pressure issue.
|
|
Quoted:
... once the cartidge functions it has outlived its usefulness. It's not going to add any more retention than a boltface would do. I'm not sure that's true. During firing, the brass flows, for sure. But it takes time to flow out. That delay is one of its functions. If the pressure were present for an extended period of time, the brass would flow a lot more than it does and the gas would vent. What the brass is doing is containing gas just long enough for the internal pressure to drop when the bullet exits the bore. It is also "sealing the leaks" or preventing the leaks that would occur if it were not present. That's an important function. Remember the ammo with plastic cases? Same deal there. The darned plastic just has to hold off the pressure long enough for the bullet to exit the bore. It won't hold it off forever but can do it just long enough. Does that make any sense? I hope it helps. |
|
Quoted:
Quoted:
Popped primers? Your loads were too hot for the primer.Quoted:
Quoted:
This is why. Good answer.
The primer crimp is to keep the primer from falling out or being knocked out during rough handling or in automatic weapon feed systems. It is NOT intended to keep it in when exposed to high chamber pressures (the locked bolt face against it does that). If the primer was crimped tight enough to hold it in at even normal chamber pressures (50,000 psi), you would not be able to punch it out to reload the case. I have had a few popped primers. If what your saying is true popped primers couldn't happen but they do. Dryflash, I am in no way trying to say I know as much as you cause I don't but I like other people have also heard that military primer crimp is used for a couple of reasons. One being to hold the primer in under full auto fire and two to keep it in with the high case pressures that the military rounds use to avoid the occassional popped primer that can sometimes happen when flirting with the limits of the case pressure maximum. Are you saying that this isn't true ?? If so , can you show me where you read it so I will know for sure that it's just hear say. Some primers have a thicker cup than others. A crimped primer will not solve your hot load or wrong primer for the pressure issue.
I should have clarified what I meant by popping primers. Yes it was definately with too hot of a load but I made this comment based on someone saying the bolt face will keep a primer from coming out and that's not true it does happen. Did you ever find in any manual where it definitively says what the reason or reason's are for using crimped primers on military ammo. I haven't been able to find anything other than hearsay. Plus in my experience not every primer cup has the same amount of tension to hold a primer in. Some are tighter some are less tight than others. You don't have to have a hot load to pop a primer. Granted most new brass will most likely not have loose primer pockets but I have found quite a few. I would imagine with the amount of brass that is made for the military it happens a lot more often than they would like to admit. If a pocket is loose it won't take a very hot load to pop it. With the military loading it's 5.56 ammo to extreme pressures anyway I would imagine it would be possible to pop one without an overly hot load. I know almost everytime this has happened to me it jammed my trigger up and wouldn't fire anymore. I would imagine that would be another reason the military uses the crimped primers also wouldn't you. I mean it sucks bad enough that it jams up my gun at the range let alone in a fire fight. |
|
So, am I reading you correctly? You are asserting that the crimp holds a loose primer in the primer pocket AFTER firing so it can be ejected with the case. That is, if the case head expansion allows the primer to become loose, the crimp will at least retain the now-loose primer and prevent it from jamming up the action during extraction and ejection.
That's an interesting idea. Sounds plausible to me but I'm no expert. I have to say, I've never once had a primer fall out on me on uncrimped brass, even after many reloads and certainly not on unfired brass. I've never pierced a primer, either, and I have fired some seriously hot rounds during testing. I'm not saying it can't happen, just that the round would have to be worn out brass or be using a damaged firing pin or have an insanely high powder charge/pistol powder. |
Armory Sponsor