crimping and its effects light v heavy

WhelanLad

WhelanLad

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im wondering has anyone got any info on what the difference is in a crimp ?

i use a lee factory crimp die on straight walled round an i crimp it down good....

is a lighter crimp v heavier crimp a pressure thing? does it create different pressure?

loaded Question but a projectile that is seated deeper into the case, will often create ? higher? pressure than the case with more air space??? given same charge ?
 
WhelanLad said:
loaded Question but a projectile that is seated deeper into the case, will often create ? higher? pressure than the case with more air space??? given same charge ?
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^Yes.

With regards to crimping, the theory is that it creates a more consistent start pressure because it takes a little more effort to get the bullet moving. If crimping is causing you pressure signs you were loaded too hot to begin with.

I'm not convinced it makes a huge difference. Consistent neck tension is probably more important. Bruce/H4831 hated crimping, saying it had a detrimental effect on accuracy. I go on a case by case basis; my .30-30 rounds are all crimped because of the tubular magazine.

A lot of bullets I load don't have a cannelure , and when it does, I often ignore it anyway and seat further out.
 
9.3mauser said:
^Yes.

With regards to crimping, the theory is that it creates a more consistent start pressure because it takes a little more effort to get the bullet moving. If crimping is causing you pressure signs you were loaded too hot to begin with.

I'm not convinced it makes a huge difference. Consistent neck tension is probably more important. Bruce/H4831 hated crimping, saying it had a detrimental effect on accuracy. I go on a case by case basis; my .30-30 rounds are all crimped because of the tubular magazine.

A lot of bullets I load don't have a cannelure , and when it does, I often ignore it anyway and seat further out.
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thanks mate, reason was-
before the storm today i had itchy fingeritis, an was scanning the interweb for lever gun froff , i had some rounds which had slipped in the case , rather than pulling, i just crimped em best i could an single loaded them...
i lined up on a 100m gong with a target infront looking to produce a group LOL
one a mile high-- seated deepest-
2 not so high, but high..

then with more normal seated an crimped it started getting closer to my aim.... figured ive either loaded an old Recipe - or the above combo upset the applecart.

i'll pop out for another shot with the right good ammo an re try that group i spoke about
 
I crimp all my "hard kickers" mainly. When rounds are sitting in the magazine, hard recoil launches the gun backwards. The bullets dont move back at the same speed and usually hit the front of the magwell. With poor neck tension, this impact of the magwell hitting the bullet tip, it can drive the bullet deeper in the case. This can cause feeding problems as the overall length is affected. But MUCH more importantly is the fact that the decreased internal space in the case can cause an over-pressure spike with potential catastrophic damage to your gun and you. So for tube mag guns and heavy recoil guns, I crimp. I also crimp for revolvers because the round can LENGTHEN under recoil, and lockup the cylinder by being too long for clear rotation.
 
My 44 mag, and the 45-70 I was loading for my brother get crimps. They come with the bullet seater/ crimp die. This is also because before loading you expand the case end so it accepts the bullet easier with less bullet shaving.

I also use a crimp on my 303 british. I found that it helped with the groups to tighten them up. The FMJ and SP both have crimp groves. They get the seated bullet, then all run thru the crimp die to finish them off.

I also tried on my 6.5 prc. I was using the hammer hunter bullet, and read about guys tightening groups using these because of the groves. Seemed to settle the bullets into a better group as well. I have not tried other bullets in the 6.5 PRC with crimping, as I was getting tinny groups already with the bergers, and they don't have the crimp groves.
 
I crimp lever gun cartridges, handgun cartridges (unless it's a single shot), and some rifle cartridges. I have found that using a collet crimping die on certain cartridges led to more consistent velocity and slightly better accuracy. This also varied from rifle to rifle. I did my initial testing with 4 rifles, all 308's that were designed for accuracy (a Rem 40X, a PH1200TX, a custom built 700 with a 40x barrel (I have two of these). It helped a lot with one of them, a little with another, and no measurable affect in the other two. The other cartridges I have tried this on where there was an improvement were a 260 and one of my 222's. I haven't figured out why it works on some, and not on others as of yet. FWIW - dan
 
dan belisle said:
I crimp lever gun cartridges, handgun cartridges (unless it's a single shot), and some rifle cartridges. I have found that using a collet crimping die on certain cartridges led to more consistent velocity and slightly better accuracy. This also varied from rifle to rifle. I did my initial testing with 4 rifles, all 308's that were designed for accuracy (a Rem 40X, a PH1200TX, a custom built 700 with a 40x barrel (I have two of these). It helped a lot with one of them, a little with another, and no measurable affect in the other two. The other cartridges I have tried this on where there was an improvement were a 260 and one of my 222's. I haven't figured out why it works on some, and not on others as of yet. FWIW - dan
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Good info Dan. You're talking about a Lee factory crimp die...correct?
 
My experience with it has been that if the neck tension is too low, crimping helps tighten up velocity spread by increasing the amount of pressure required to initially move the bullet.
That may also be the effect if your burn rate is slightly too slow, although that's pure speculation on my part.

In effect, it increases neck tension. Most noticeable in my 223 and 32 Special.
It isn't always the best thing for accuracy, unfortunately.

Lee recommends 1/2 turn from contact with their factory crimp die. I find that 1/4 turn had the desired effect on velocity in my case. If I use it for its primary purpose to keep the bullet from moving, then 1/2 turn is more secure, but somewhat harder on the brass.
 
Yes, in my experience the crimp makes more pressure. Some of the reloading programs will calculate the pressure increase for you.

Having that said, not all crimps are equal but you should observe the pressure calculation whether a full crimp or a slight crimp. You case trimming length also has to be very critical to get a uniform crimp equally on all the cases.

Its also important to know that the brass is clean or brushed well on the inside of the neck. A loose neck because of debris during the neck sizing gives a poor crimp and loose bullet.

I personally like to crimp for any medium to heavy hitting loads to ensure my OAL with bullet stays consistent. Although some loads even with more pressure from the crimp don't really respond any different in group size.
 
I bought a factory crimp die for my 308, not for my precision loads, I use an expander manderal to gain consistent neck tension there, but for the 500 or so tracer bullets I have that I was having ignition problems with, would only get 1/5 to light, they all seem in good shape and ignite easily with a propane torch, so trying a factory crimp to see if it will improve success
 
Craig0ry said:
I bought a factory crimp die for my 308, not for my precision loads, I use an expander manderal to gain consistent neck tension there, but for the 500 or so tracer bullets I have that I was having ignition problems with, would only get 1/5 to light, they all seem in good shape and ignite easily with a propane torch, so trying a factory crimp to see if it will improve success
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We shot many thousands of tracers in the infantry, sometimes they don't begin to light up until they are down range by a few hundred yards. But you didn't say what distances you were shooting nor when they were lighting up? I had a buddy who had an old batch from somewhere in the middle east, they didn't work well at all but I think age and poor storage and dirty cartridges was the problem. but not suggesting that is your case.
 
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