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Discussion Starter · #1 ·
I reloaded my first few rounds today.

I initially purchased a box of Black Hills Gold match with a 168 gr A-max on top. Here is what they measured out at:
OAL = 2.780
COAL 2.005
Neck =.331

I also have a box of Fiocchi Exacta match with a 168 gr SMK. They measured at:
OAL =2.779
COAL = 2.003
Neck = .332

I fired a few rounds of each and they did well.

I resized the cases and trimmed to the X die length of 1.995. I decided to use the Lyman #48 manual with these specs:
168 gr SMK
IMR 4064 @ a start load of 40.0 gr. Published vel is 2415 and press 35,500
OAL = 2.775

I verified the cases with a case gauge before seating the bullet and both brands looked good.
I set up a crimp for .331
The Fiocchi's came out perfect and measure well in the gauge.
The Black hills all bulged the case slightly lengthening the case out of limits.

I am guessing I need to back the taper crimp off some for the BH brand case.

What should I be using for a crimp setting? I have .331 as a good number in my notes but I don't remember where I got that info.

Thanks for any help.
 

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After bulging 400 rounds once as a newbie by using too much crimp, I have never crimped any bottleneck round in the last 30 years. Never had a problem. If the bullet has a cannelure, I just ignore it.

I should add that I do keep an eye on my neck tension by controlling the neck sizing.
 

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Just out of curiosity, why did you decide to crimp?
 

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Discussion Starter · #7 ·
Just out of curiosity, why did you decide to crimp?
I guess from different articles that I have read. I was under the impression that a crimp was required for a gas gun. No crimp will certainly simplify things. I hate ruining brass.

Do I just need to measure a round, chamber it from the magazine, carefully eject it and re-measure it to make sure the bullet isn't moving to far forward?
 

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There is no need to crimp a bottle neck rifle cartridge. If the neck tension is not sufficient to hold the bullet under recoil, a crimp won't help enough to make a difference in the long run.

- Ivan.
 

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I guess from different articles that I have read. I was under the impression that a crimp was required for a gas gun. No crimp will certainly simplify things. I hate ruining brass.

Do I just need to measure a round, chamber it from the magazine, carefully eject it and re-measure it to make sure the bullet isn't moving to far forward?
The reason crimping began was that the military found out that ammunition in machine guns had problems with the bullets moving. Also some magazine fed fully automatic weapons were moving the bullets when the weapon would recoil.

Some people feel that a crimp helps ensure consistent pressure/muzzle velocities because the bullet is restrained by the crimp until the crimp.

I have never crimped and have never seen the need for a crimp in my M1As. The friction of the case neck, as created by the resizing die, has always been enough in my opinion; but then I've never checked for bullet movement since I don't fire my rifle in full automatic and I'm satisfied with my pressures and velocities.

To test for bullet movement, I would load up a full magazine of my ammo and measure the length of the first cartridge that you put in the mag (that will be the last round that will be fired from the mag). Fire all the rounds except that last one. Don't fire the last one, let it chamber but don't fire it. Remove it from the chamber and measure it. If you get any shortening at all it isn't desirable but unless you are trying to get sub MOA groups you could probably tolerate a shortening of 0.010" without seeing much difference in bullet performance. Also remember that soft points (polymer, lead, etc) can be deformed and seem to be shortened without any real movement of the bullet within the case.
 

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I don't know that it's absolutely necessary, but I use a Lee Factory Crimp Die on all the loads I do for my semi-auto rifles, and my tubular magazine .30-30s.
While I've never seen a problem in my M1A, I have seen bullet movement in my Win model 94 .30-30. In a tubular magazine you have the weight of each cartridge adding to the compression forces within the tube during recoil. In addition to recoil forces that both magazine types experience, the tubular magazine, with each cartridge behind the other, causes the bullets to experience mass forces that are multiplied by the number of cartridges. The last couple of cartridges in that tube have been pounded with recoil and mass forces and if any of the rounds have bullet shift then those last one or two will definitely show a problem. It didn't take long for me to see with my eye that my bullets were shifting in the old .30-30 so I crimp those cartridges with a light crimp.

Crimping is a double edged sword. The problem that a shifting bullet causes is higher chamber pressures due to reducing the volume inside the case. On the other hand, crimping causes pressures to increase until the bullet overcomes the strength of the crimp; the deeper the crimp the higher the pressures will go. So the point is, if you don't need to crimp don't do it. And don't forget, the resizing die has a resizing button that is designed to expand the case's neck to a diameter that will apply the proper tension to the shank of the bullet. So if your bullets are shifting either the resizing button isn't doing it's job or your brass has a problem.

I have found that most people perform certain reloading procedures, not because they have found a need for them, but because they were told that it's always been done that way. I don't have a problem with the idea of crimping if you can prove that it is helpful in some way but I think that we need to encourage people to start verifying that it is necessary rather than just parroting what we hear.
 

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I suspect, without any real evidence other than a priori reasoning, that having a consistent crimp on the bullet may lead to more consistent ignition of the powder charge, and therefore less variation in shot-to-shot velocity. One of these days, now that prices on electronic chronographs have come down, I want to set up a chronograph with identical crimped vs. non-crimped loads and experiment.

Even if it works that way, it's unclear whether reducing variations in velocity by a few feet-per-second would have a noticeable effect on practical accuracy, but it's one more excuse to go out and shoot up a bunch of ammo. GI1
 

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I crimp my SMK's about .002-.003 just for better neck tension and to ensure no setback
 

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+1 For Lee Factory Crimp for a final "Kiss" to smooth the brass slightly at the bullet.
I do use SMK's, not cannelured, and I have had 100% feed and never a jam issue.
Not to say it's helping or not, just saying it's all working well with the rest of my Dillon 650 System
 

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I use the Lee factory crimp, about medium to heavy.

When I started reloading I read that its on "old wives tale" and not commonly used anymore.

However after I removed several live rounds that had been chambered in my M1A naturally and discovered them to be severely out of alignment. Concentricity gauge doesn't lie.

After that I started to crimp, and the issue was resolved.

This debate will go on as long as projectile weapons exist, along with the barrel break in discussion.

Up to you.
 

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I use the Lee factory crimp, about medium to heavy.

When I started reloading I read that its on "old wives tale" and not commonly used anymore.

However after I removed several live rounds that had been chambered in my M1A naturally and discovered them to be severely out of alignment. Concentricity gauge doesn't lie.

After that I started to crimp, and the issue was resolved.

This debate will go on as long as projectile weapons exist, along with the barrel break in discussion.

Up to you.
Interesting point, and one that I have never seen come up before. I might have to do a little testing to see what happens. I'm assuming you checked concentrically before after building the cartridge? How much change was there after chambering?

As of now I don't crimp and while your point about the concentrically would probably hold for all M1As, since they all feed the same, I have no problem with achieving sub MOA groups. So even if what you point out were true with my rifle I'm not sure if it would be of enough benefit to go through the bother of crimping.
 
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