Author Topic: Crimping Question -- OAL change before / after crimping (Read 470 times)

Racer X · « **on:** May 12, 2007, 03:44:50 AM »

I am loading for my 45 Colt with 270 SAA bullets and seating / crimping in 2 separate steps. I use a Redding Proflie Crimp die.

My question: Is is normal for the OAL to shrink a few thousandths after crimping? Before I crimp, my OAL is ~ 1.655". After crimping, the OAL shrinks .003" to .005". Is this normal, or am I applying too much crimp?

coyotejoe · « **Reply #1 on:** May 12, 2007, 05:00:10 AM »

I often use the Lee "factory crimp die" to crimp in a separate operation as you are doing but can't say I've ever measured OAL before and after. I guess it stands to reason that there would be some shortening but so what. The OAL is generally determined by the location of the crimp groove in the bullet and with revolvers it hardly matters. If the case is not damaged then your crimp is not excessive.

Larry Gibson · « **Reply #2 on:** May 12, 2007, 08:04:43 AM »

Racer X

As you are applying the roll crimp (?) the inside of the case mouth is pushing down on the bottom edge of the crimp groove on the shoulder. You are essentially further seating the bullet. Is this "shrinkage" causing any problems?

Larry Gibson

stuffit · « **Reply #3 on:** May 12, 2007, 09:44:20 AM »

Isn't the Redding Profile Crimp Die referenced in the first post just a contour fit taper cfimp die? I could be mistaken but didn't think it had the roll crimp feature incorporated into it.

stuffit

quickdtoo · « **Reply #4 on:** May 12, 2007, 09:55:29 AM »

Redding's description says it makes a roll crimp.

Quote

Profile Crimp Dies
These handgun cartridge crimp dies were designed for those who want the best possible crimp. Profile crimp dies provide a tighter, more uniform roll type crimp requires the bullet to be seated to the correct depth in a previous operation. These dies are not for cartridges that headspace on the case mouth.

http://www.redding-reloading.com/pages/crimpdies.html

stuffit · « **Reply #5 on:** May 12, 2007, 10:01:02 AM »

Thanks, Quick. That kinda explains why mine for my 45 Auto Rim hasn't acted exactly like I'd expected it to. Must read the description and directions better in the future

stuffit

Racer X · « **Reply #6 on:** May 12, 2007, 04:00:45 PM »

Quote from: Larry Gibson on May 12, 2007, 08:04:43 AM

Racer X

Is this "shrinkage" causing any problems?

Larry Gibson

I have not shot the ammo yet so I can't tell.

Glanceblamm · « **Reply #7 on:** May 14, 2007, 04:03:09 AM »

Racer X

Larry Gibson took the words right out of my mouth on the inside of the case mouth pushing down on the bottom edge of the crimp groove.
If you get much tighter than you are right now, you will start to see small shavings of the brass up at the case mouth and you may have seen this on a few already. To push it even further, you get into the bulging, wrinkling, and finally a crushed case.

Putting a roll crimp on the shallow, rectangular cannolure of the jacketed bullet often makes you wander if you have enough and it can be easy to over do it…It is not like that longer, beveled crimp groove of a cast bullet that makes it easy to see a good crimp.
The dial caliper can be the best tool you have as you can measure oal between each downward increment of the die so as to stay out of the negative numbers. After some practice you will be able to feel by hand when the brass is crimp firmly into the groove or if you are putting too much pressure on it.

I don’t think that you hurt your ammo one bit but rather are at a point of realization that makes one get into Case Preparation rather than Reloading.
Before you know it, you have not only trimmed all the cases to the same length but also uniformed the primer pockets and flash holes and more but that’s another story.