Need help - Problem with maintaining OAL while roll crimping

[cwbuff]

I'm hand loading Lyman 358156 boolits for my 357 Magnum Smith & Wesson 686-2. The OAL spec is 1.590". Following the Hornady seating die instructions, I backed off the crimp and seated two boolits at 1.590". Next I backed out the seater and then reset the die to apply a roll crimp. Then reset the seater to touch the bullet. When I'm done, the OAL is now about 1.566". What am I doing wrong?

[Dusty Bannister]

Is it possible that when you tighten the lock nut on the seating stem it pulls the seating stem deeper into the die due to loose thread fit? Probably just need to bring the seating stem to touch the nose of the bullet and then back off 1/8 turn and lock the nut and see if that takes care of it. Dusty

[cwbuff]

I "think" what is happening is that the roll crimp itself is pushing the boolit deeper into the case. Everything was at spec before the roll crimp. Then I backed out the seating stem and applied the roll crimp. After that is was seated too deep.

[Dusty Bannister]

So then you did not measure the OAL after crimping but before bringing the seating stem down on the nose of the bullet? To do that means you are really mashing a crimp into the case. Maybe an excessive amount of crimp that I had not given consideration to.

[cwbuff]

I seated the bullet with NO crimp to spec 1.590". The backed out the seating stem and then set the roll crimp. The OAL went from 1.590" to 1.566". So it was the crimp that moved the bullet. It does not look like a lot of crimp. But it moved the bullet because the seating stem was not engaged.

[Dusty Bannister]

If you repeat this with another prepared case and seat and crimp, does it do the same thing? Is this a single stage press?

[cwbuff]

Yes - did 2 cases - single stage press (RCBS Rockchucker II). I'm wondering if I seat the bullet 0.024" long and then crimp it if that will work?

[JonB_in_Glencoe]

What's the diameter of the driving band?
I suspect the crimp portion of the Die grabs the boolit's drive band, and pushes the boolit into the case.

[cwbuff]

What's the diameter of the driving band?
I suspect the crimp portion of the Die grabs the boolit's drive band, and pushes the boolit into the case.
Sized to 0.358"

[JonB_in_Glencoe]

Do you size with a Lyman sizer?
Just for the heck of it, measure the drive band.

[gwpercle]

I seated the bullet with NO crimp to spec 1.590". The backed out the seating stem and then set the roll crimp. The OAL went from 1.590" to 1.566". So it was the crimp that moved the bullet. It does not look like a lot of crimp. But it moved the bullet because the seating stem was not engaged.

If you stop and think about how a roll crimp "rolls " the mouth inward you can almost visualize how the motion will turn the case in and make it ever so shorter.
Allowing for this .024 difference is the solution . Honestly ...being .024 " shorter isn't going to make any difference at all. COL in revolver cartridges is not critical in the least. If the round slides in the chamber and the boolit doesn't protrude past the end of the cylinder...you good to go.
Gary

[cwbuff]

Thanks for the advise! Looks like some more experimentation is in order. I loaded a lot cast rifle bullets (.30-06, 8mm Mauser, .30-40 Krag), but this is my first try at cast bullets for a revolver where the roll crimp is important.

[mehavey]

If as-set you're getting too short an OAL, just leave the die locked where it is for
the crimp, and back the seating stem out a half turn -- and press on (pun intended)

[cwbuff]

If as-set you're getting too short an OAL, just leave the die locked where it is for
the crimp, and back the seating stem out a half turn -- and press on (pun intended)
I will give that a try. Thanks.

[mdi]

I "think" what is happening is that the roll crimp itself is pushing the boolit deeper into the case. Everything was at spec before the roll crimp. Then I backed out the seating stem and applied the roll crimp. After that is was seated too deep.
If this is the case, then the problem is too much crimp. I'd suggest you back the seating stem waaaaay up and ease up on the crimp. Also, is your seating die clean? Many times lube will build up in the die and cause shorter and shorter OALs...

[fredj338]

Many of us embrace seating & crimping in separate steps. If loading on a progressive, no reason to not do it that way. If not, small variations in seating depth mean nothing as to safety or accuracy.

[cwbuff]

Too much crimp?
214687

[WHITETAIL]

no, this looks good!
As long as the whole batch is the same.
You should be good.

[cwbuff]

no, this looks good!
As long as the whole batch is the same.
You should be good.
OK thanks a lot;