Too much crimp on this 308?

J

jamesf553

New member
Hey guys, thanks for all the advice on my .338 lapua reloading!

So, I also have an m1a scout rifle and I wanted to start reloading for that as well. Not so much for practicality, more just for fun. I ordered a lee full die set which comes with a factory crimp die which got really good reviews. Creates it's own cannelure as it crimps allegedly (which is great for these because if you seat them at the 30-06 cannelure the COL is too long)

Anyway, I tried it for the first time and I just didn't see any noticeable difference afterwards so I fully crimped it and want to make sure it's not too much where the bullet gets stuck or something. Can you take a look at the pics?

They're .30 cal surplus black tip bullets pulled from 30-06, 163 grain. I believe steel core. I just used a lower end load of n550 for 165gn since there's not any data for 163 projectiles. Does the crimp look safe to shoot? Thanks guys!

https://drive.google.com/file/d/1TPw-AfFxXzNzvBDhySSQeqikqd1JxhtN/view?usp=drivesdk

https://drive.google.com/file/d/1uYGND0ygOmwwI3pZu9TsWYLMpMlwhWKD/view?usp=drivesdk

https://drive.google.com/file/d/13X--NuJIItHaVZkmVCTLFewXBGcOiRaw/view?usp=drivesdk
 
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I doubt crimping will affect the accuracy of any military bullet, FMJ or AP. However, for good bullets, such as hunting or match bullets, don't crimp. Crimping will crush the soft lead core of the bullet, altering the center of gravity. You move the center of gravity out of the axis of rotation your bullet will wobble like one of those "wounded ducks" that you see occasionally thrown in a football game. The inaccuracy will increase with distance.

Let neck tension hold the bullet in place. I earned my Distinguished Rifleman Badge, and a Regional Gold, with the M1a, and I never crimped my match bullets, and I never met a single competitor who did.

Crimping is only needed in tube loaded guns, like lever actions, or machine cannon, where the feed rate is so high the bullet might pop out of the case. You might need to crimp elephant gun ammunition, I have had bullet set back in a 375 H&H, as I recall.
 
Hmmmm, I have only been reloading since 1957 and I have never crimped jacketed rifle bullets. Try it without a crimp.
 
Yes. There's no safety issue here. One of our members who used to be a Test Director at Aberdeen Proving Grounds said he'd found aged ammunition with cold bonded bullets with pull up to 600 lbs (ten times normal) but that they still fired fine. Most high power rifle bullets don't start moving measurably before the pressure reaches around 10,000 psi, according to H.P. White laboratories. That would be 745 lbf (pounds force) on the base of a .30 cal bullet. The bottom line here is that your crimp will be pretty weak compared to all that. If there is any ballistic advantage to crimps that cannot be achieved by choice of powder and primer, match shooters haven't discovered it yet.

If you need the crimp for other reasons, such as those previously mentioned, pull the bullets and sandwich them sideways between two caliper jaws and hold them up to the light to see if you've created a crack of light at the crimp site. If so, you have distorted them a little and will probably have some slight asymmetry to them which will open groups up a bit. The wobble in flight isn't really the problem at shorter ranges, as the disturbance force applies equally all around with every rotation of the bullet, tending to correct path error. The problem is due to the eccentric rotation of center of mass around the bore axis. This causes the bullet to be lobbed sideways as it exits the bore, in the direction of spin, tangent to the side of the bore the center of gravity was closest to at the moment it cleared the grip of the rifling. It's the same thing that happens if you tie a string to a weight and spin it around your head and let go of it. It takes off tangent to circle it was making around your head and in the direction of spin. This motion introduces drift in that direction that stays with the bullet to the target, as it is too slow for drag to reduce it significantly during the bullet's TOF. So it just keeps moving the bullet away from the intended POI, making the group bigger.

Where:

MV = muzzle velocity in ft/s
T = rifling pitch in inches
r = the radius of the center of gravity off the bore axis in inches
Vd = drift velocity in ft/s to the side of the aimed-for trajectory

Vd = pi × MV × r / T

Example:

MV = 2640 fps
T = 10 inches
r = 0.0005"

Vd = 0.415 ft/s = 4.97 inches per second.

If the bullet TOF to a 100 yard target is 0.12 seconds, then it will drift 0.6" away from the group center by the time it gets there. The same bullet at 1000 yards will have about 9 inches of drift off POA by the time it gets there. I ran this for the 165.7-3.0 grain .30-06 AP bullet with G1 BC of approximately 0.4 at the muzzle. That said, the wobble will eat up some energy by adding to drag, so the bullet won't actually get to the longer distances quite on time and drift introduced will be a little worse than that.

The AP bullets do have steel penetrators. The original .30-06 penetrator design had tungsten steel in the penetrator with took the weight up about 3 grains, but it was cost prohibitive during the war, so regular steel replaced it, lightening the bullet. Snipers reported the flat base design to be more accurate than the M1 ball boattail projectile and to prefer them. I would be spinning or otherwise checking them if you are looking for an accurate load.

VV N550 is on the slow side for the .308 with this bullet in the M1A. Its gas system was made to run with powder more in the IMR4895/BL-(C)2/748/CFE223 burn rate range, and you won't need to compress these. Though it isn't as sensitive to differences as the Garand is, you'll probably find you can find your brass more easily when it hasn't been tossed quite so hard by these other powders. Varget and 4064 are often reported as giving best accuracy, but they lose 50 fps off top velocities.
 
Unclenick said:
Yes. There's no safety issue here. One of our members who used to be a Test Director at Aberdeen Proving Grounds said he'd found aged ammunition with cold bonded bullets with pull up to 600 lbs (ten times normal) but that they still fired fine. Most high power rifle bullets don't start moving measurably before the pressure reaches around 10,000 psi, according to H.P. White laboratories. That would be 745 lbf (pounds force) on the base of a .30 cal bullet. The bottom line here is that your crimp will be pretty weak compared to all that. If there is any ballistic advantage to crimps that cannot be achieved by choice of powder and primer, match shooters haven't discovered it yet.

If you need the crimp for other reasons, such as those previously mentioned, pull the bullets and sandwich them sideways between two caliper jaws and hold them up to the light to see if you've created a crack of light at the crimp site. If so, you have distorted them a little and will probably have some slight asymmetry to them which will open groups up a bit. The wobble in flight isn't really the problem at shorter ranges, as the disturbance force applies equally all around with every rotation of the bullet, tending to correct path error. The problem is due to the eccentric rotation of center of mass around the bore axis. This causes the bullet to be lobbed sideways as it exits the bore, in the direction of spin, tangent to the side of the bore the center of gravity was closest to at the moment it cleared the grip of the rifling. It's the same thing that happens if you tie a string to a weight and spin it around your head and let go of it. It takes off tangent to circle it was making around your head and in the direction of spin. This motion introduces drift in that direction that stays with the bullet to the target, as it is too slow for drag to reduce it significantly during the bullet's TOF. So it just keeps moving the bullet away from the intended POI, making the group bigger.

Where:

MV = muzzle velocity in ft/s
T = rifling pitch in inches
r = the radius of the center of gravity off the bore axis in inches
Vd = drift velocity in ft/s to the side of the aimed-for trajectory

Vd = pi × MV × r / T

Example:

MV = 2640 fps
T = 10 inches
r = 0.0005"

Vd = 0.415 ft/s = 4.97 inches per second.

If the bullet TOF to a 100 yard target is 0.12 seconds, then it will drift 0.6" away from the group center by the time it gets there. The same bullet at 1000 yards will have about 9 inches of drift off POA by the time it gets there. I ran this for the 165.7-3.0 grain .30-06 AP bullet with G1 BC of approximately 0.4 at the muzzle. That said, the wobble will eat up some energy by adding to drag, so the bullet won't actually get to the longer distances quite on time and drift introduced will be a little worse than that.

The AP bullets do have steel penetrators. The original .30-06 penetrator design had tungsten steel in the penetrator with took the weight up about 3 grains, but it was cost prohibitive during the war, so regular steel replaced it, lightening the bullet. Snipers reported the flat base design to be more accurate than the M1 ball boattail projectile and to prefer them. I would be spinning or otherwise checking them if you are looking for an accurate load.

VV N550 is on the slow side for the .308 with this bullet in the M1A. Its gas system was made to run with powder more in the IMR4895/BL-(C)2/748/CFE223 burn rate range, and you won't need to compress these. Though it isn't as sensitive to differences as the Garand is, you'll probably find you can find your brass more easily when it hasn't been tossed quite so hard by these other powders. Varget and 4064 are often reported as giving best accuracy, but they lose 50 fps off top velocities.
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Thanks for the detailed info, I will try some different powders.

The main reason I got so set on crimping is because I saw a thread and follow up pictures on what happened to a guys hand when he didn't crimp his lever action rounds. Gun exploded and his hand is barely able to be stitched up. Definitely made me paranoid.
 
I crimp my autoloading firearms but dont bother in bolt actions. I also just barely crimp in the auto a little goes a long way.
 
When I crimp I want all the crimp I can get, I do not get cute and or fancy and I want my bullets to have that jump, in my opinion nothing beats the running start. When it comes to crimp there is no such thing as 'too much crimp'.

I never got into the tension thing because I started with tension gages, one more time all of my tension gages measure in pounds, two of them measure tension in pounds but are converted to thousandths when measuring deviation.

I have pulled thousands of bullets, I do not know how some reloaders can have all the luck; I have never gone into a 9 line bind when pulling bullets, I have had necks come off with the bullet: But on those I believe reloaders got real creative in cleaning cases with a liquid that had an acid base.

Acid base liquid, I do not get fancy with having my own formula' I use vinegar for the worst of cases and I rinse in boiling water 'twice'.

And loading: I do not get into mortal combat with loading, I do not load ammo for years into the future. I tumble cleaned and prepped cases to know off the dull look and load then head for the range.

Pull down cases: I have pulled thousands of cases with head stamps going beck to 1938. I have pulled down loaded ammo by reloaders and smiths, about 80% of the ammo I have pulled down would have fired, that leaves the reloads that had bad case prep including cases that appeared to have a big problem with what looked like electrolysis.

F. Guffey
 
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