Roll crimp

I do the press the round into the top of the bench method I press the tip of the loaded round into the bench, if it doesn't move, I'm good.

If your roll crimp is too great, frequently you will get a bulge of the case at the mouth. This can make chambering difficult.

It is about the only need for trimming straight walled hand gun cases. If the cases are a uniform length, the roll crimp will be more uniform. This is helpful particularly if loading at or near maximum loads.

A uniform roll crimp will help with uniform ignition from case to case.

Generally, trimming is a one time thing for the life of the case as straight walled hand gun cases do not change length much. But, don’t assume they won’t change lengths, check the lengths periodically.

The short answer is yes, it is possible to do too much of a roll crimp. A roll crimp that is too heavy can cause the case to buckle. This can happen fairly easily with jacketed bullets with a canaluere if you crimp too hard, too much of the soft brass case is rolled into the hard jacketed bullet, and has no place to go, so the case buckles. So with those the goal is to crimp to the depth of the canaluere and no more. On the other hand it is hard to overcrimp the roll crimp on a soft swaged lead bullet, that’s what I use In 38spl. But with hardcast lead, the harder alloy might cause a buckled case if overdoing the roll crimp. I think crimping to the depth of the crimp groove and no more will prevent problems. Hope this helps.

These are about as crimped as I’ll go, the crimp groove in these bullets allows a nice roll without creating the “overcrimp bulge” that will keep your rounds from chambering.

Most rounds I make I crimp a bit less than these. These are low-end rounds I loaded for a plate match and I wanted to ensure consistent ignition with the lighter charges.



Stay safe.

For revolver insufficient retention of the case on the bullet will result in the lengthening of the COL of the unfired rounds in the cylinder, and a possible shortening of COL in auto feeders and lever actions.
A revolver acts like a inertia puller, with the last round in the cylinder being effected the most.
When testing my reloads I have calipers with me and check to see if retention is adequate.

These particular cartridges have a very heavy roll crimp...



...but you will note you can still see the outline of the bullet, which tells me the cases still have good neck tension on the bullet. It is possible to over crimp a bullet... and actually push the case down, bulging it. Usually it shows up as less neck tension on the bullet, but I have seen cases form a ring about half way down the case...



Properly sized and crimped rounds will chamber easily (in a clean cylinder.) If you have to stuff cartridges in a cylinder, it can indicate a number of things... starting with a bulged case.

Telcontar89 said:

Should I see a detent on the case after the crimp has been done? Like the case is biting into the crimp groove on the bullet.

Click to expand...

Yes, and how much of a "roll" into the cannelure you see depends on things like powder charge and powder type. As has been said, too much of a crimp can bulge the case and actually deform the bullet or/and lessen the hold of the crimp by reducing neck tension. Rule of thumb is, the heavier the recoil the heavier the crimp. It is more of an experience thing. Most folks try to crimp as little as possible in order to lengthen case life as it is working the brass that weakens and hardens it. When doing really heavy roll crimps, it is generally better to do the seat and crimp in two steps instead of one, this way the bullet is not moving as the crimp is applied.