Why would the OAL shrink when crimping?

[Jal5]

Reloading 45 ACP using Lee dies. Lee TL452230-2R slug. I set up the bullet seater die for 1.250 OAL and they varied slightly to 1.249-1.250. Using the same die set I wanted to put a slight crimp on them in the last step so that the mouth was .470 but the round changed OAL at the crimp step to 1.234 to 1.241 I don' have a taper crimp die so I was just trying to get a crimp using the roll crimper.
The seater stem was backed almost all the way out so that wasn't the cause of the OAL shrinkage.

All ideas would be appreciated. Joe

[Love Life]

Adjust your seating die so that even after the final crimp stage the OAL is where you want it.

[Garyshome]

The crimp die is pulling the boolit out? I was/still am having that problem, I think I had too much LLA on the boolits and it was gumming the crimp die.

[Love Life]

I believe the crimp die is pushing the boolits down in this case. As the case rolls in (OP is using a roll crimp die), however slightly, it pushes the boolit down a smidge. Same happens with taper crimp, just not as pronounced.

[Jal5]

Its definitely not pulling the boolit out, it is pushing it down. I think Love Life has it right. I will readjust the seater die with the next bunch to allow for that .016 that the crimp operation is pulling the boolit down inside the case. The tricky part will be that the amount of "pulling down" is variable in this situation from .009 to .016. But I guess if I cannot get it where i want it to be this way I can always buy a taper crimp die.

[Love Life]

You'll experience the same with a taper crimp die. I just live with it as. I seat my 45 acp to 1.250. Most come out at that, but some do come out shorter. However, they are not short enough to cause concern.

[John Boy]

HAve you checked the die to see if there is an 'gunk' inside, especially in the cavity of the plug?

[Jal5]

I will check the die later tonite but it is a brand new set and these were the first 20 rounds thru it.

ADDITION-
No build up lube in the die as I expected.

[Tom Myers]

Just a thought, but try this.

Leave the die adjusted for crimping, just as you had it and then back out the seating stem, place a bullet in the case ready for seating and run the case and bullet up into the crimping die to see if perhaps the bullet may be too large to pass up into the seating stem well. If this is happening, the bullet would be pushed deeper into the case but it wouldn't happen until the die was adjusted down for the final crimping operation.

[Jal5]

Good idea Tom I will try it

[country gent]

Measure a case several times and then crimp and remeasure its length It will be slightly shorter due to the roll over. when you are crimping the case mouth may be bring the bullet down with it.

[prs]

Jal5, this new set of Lee dies for 45 ACP should have come with the combination seat/crimp die as a taper crimp. 45 Colt would come with roll crimp. That is the way my three dies Lee sets are.

I recently began seating and crimping some rounds in one step with my 45ACP dies due to adding a bullet feed die to station 4 for powder coated boolits. Anyway, by setting the crimp to read .470" at the case mouth I seem to have found the sweet spot where the crimp does not plow the sides of the boolt. But since the crimp is placed with downward force, the round will shorten a little. But the decrease should be consistent.

Is this a progressive press? The instructions in the Lee die sets are written for single stage and turret where the shell plate is singular. On a progressive with multiple shell holders on a large plate, the plate will rock if you turn a die (i.e. the deprime/size die) in that extra half or quarter turn as instructed, it will tilt the plate and that tilt will vary some depending upon if other stations are occupied by a round or not. In this case install dies with the press fully closed upon its limit of travel and turn the contact
die(s) in to make just firm contact, no more.

prs

[Jal5]

There isn't anywhere on the die set the box or the manual that states it's a taper crimp die. I need to do more research on that point.

It's a single stage press a Lyman. It does make sense that the crimp can pull the boolit down but it's inconsistently doing that. Maybe the case lengths are that inconsistent- I never measured them and don't trim pistol cases. I reloaded some of this Same batch of cases with FMJ projectiles and didn't have this same problem.

[44man]

Inside of die is too small for boolit fit. I see it all the time. Extra crimp dies are worse. I have boolits that will not go through some crimp dies and even had to lap a Hornady seater. Boolit would not pass through.
Remove the seating stem and see if a boolit will go through the die.

[Jal5]

44man- that boolit is .452 after sizing and I just tried your suggestion- that boolit won't go through the seater/crimper die by itself. Now what??

[fouronesix]

Just a suggestion to simplify life. Get a taper crimp die for the 45 ACP. Back the seater die out enough so it only seats the bullet. Then run the round up into the taper crimp die to finish. Adjust the taper crimp die to just barely massage the case mouth into contact with the bullet wall.

Trying to use some kind of seater die/roll crimp die combination for cartridges like the 45 ACP is asking for trouble. Even the Lee FCD for the 45 ACP (the one with the carbide ring) is not as forgiving as a dedicated taper crimp die.

[JWFilips]

In your case I'm not sure but I do know if doing a roll crimp with ...let's say a 38 special and you didn't seat to the crimp grove ..."just enough"..... the roll crimp will sometimes bring your (COL) your boolit down a tiny bit as the crimp & brass follow the crimp groove in the boolit. I know it may not be your case but it may help others reading this thread. Just my 2 cents

[fouronesix]

Not to mention that for rimless cartridges like the 9mm, 40 S&W, 45 ACP, etc., when loaded for semi-autos, a roll crimp is NOT the type crimp to use. Those actions/cartridges rely on headpacing on the mouth… any kind of roll crimping can cause all kinds of problems.

[44man]

44man- that boolit is .452 after sizing and I just tried your suggestion- that boolit won't go through the seater/crimper die by itself. Now what??

You can lap the die until the boolit slides through with little pressure. Just do the portion above the crimping edge. Split rod with abrasive.
This is a common problem since dies are made for jacketed bullets. You will not hurt anything and will be well satisfied.
Hornady dies are much easier to work with and only one caliber needed fixed. Floating seat die that pops out into your hand. Separate crimp dies are also easy to fix.
Normal dies are harder to get the rod and abrasive up where needed.
Good idea to get a crimp die and lap it, use the regular seat die to get the boolit in and then crimp with the other die. Redding and Hornady have good crimp dies. Adjust your seat die to only seat without the boolit going past the crimp shoulder.
Don't fool with a Lee FCD, it can ruin and size your boolit.

[Jal5]

Thx I did decide to go with a separate taper crimp die. And will lap it as needed. Should make the whole process that much easier too. Joe