No crimp needed after expanding???

[bcr]

So yesterday I had something happen I've never experienced before. First time loading 10mm, although I've loaded a lot of .40 S&W.

As always, I very gently expanded the case mouth just enough to get the boolit started. After I seated the boolit, I checked the case mouth diameter to see how much of a taper crimp I would need. The case mouth was 0.423", which is nominal. So apparently it doesn't need a crimp, and I confirmed that they chamber in my gun. I've never had this happen though where I didn't need ANY crimp, and I'm hoping there aren't any issues with the boolits moving in the cases. Running 7.5 grains of Power Pistol under a 170 gr. MP WFN solid, PCd.

[mehavey]

The seating die body was seated low enough that tapering started at the end of the stroke.
Works best when case length is controlled so the taper action is uniform when it happens.
;-)

[bcr]

I'll check this but I don't think so, I always seat and crimp in two steps and back the die body way out so it's not applying any crimp.

[charlie b]

I had that happen a lot with .45acp. Then one day I had a round strike the feed ramp. Pushed the bullet all the way in the case. I decided to do a 'push test' on some of the others. It was surprising how easy it was to move some of the bullets (conventional lube). Started crimping after that. Just enough to keep the bullet from moving.

[Der Gebirgsjager]

You won't know for sure until you try a few! :grin: I think mehavey's observations are good-- but only you can check the die for it's adjustment. He brings up an interesting subject though-- seating and crimping at the same time. You'll get two basic opinions on that one...it's the worst thing you can do, or it's a real time saver. I've done it, and it worked for me. The uniform length of the brass is important, and some individual guns' chambers won't allow it. In a semi-auto, especially a powerful one like 10mm the cartridges waiting in line in the magzine do receive a certain amount of pounding as preceding rounds are fired, and a firm crimp whether done intentionally or not is advisable.

DG

[BLAHUT]

I always seat and taper crimp in one step, need brass all same length for that to work.

[Kenstone]

Well, did it pass the plunk test?
Did it pass the "push against the bench" test?
That would be the ultimate test...

Plus fill a mag and fire all but the last 2 rounds, leaving one in the chamber and one still in the mag.
Check/measure the OAL of the round left in the mag for bullet setback.
If the OAL hasn't shortened, you are good to go with your no crimp process.
jmo,
.
Edit: added the push against the bench test reference.

[El Bibliotecario]

I had that happen a lot with .45acp. Then one day I had a round strike the feed ramp. Pushed the bullet all the way in the case. I decided to do a 'push test' on some of the others. It was surprising how easy it was to move some of the bullets (conventional lube). Started crimping after that. Just enough to keep the bullet from moving.

This is a valid concern. I have had .45 ACP factory rounds lose their neck tension and the bullet pushed back after repeated unloadings and rechamberings in a Govt model Colt.

[mdi]

I do not crimp any semi-auto handloads. I flare as necessary and deflare with my deflaring dies (aka taper crimp dies) ...

[Sasquatch-1]

I will usually do a twist test. I grab the bullet and the case in opposite hands and try twisting the bullet as hard as I can. If the bullet moves it needs to be crimped.

[fredj338]

Taper crimp is crimping by definition. I flare enough to make sure I get no scraping of the bullet base when seating. That much flare wont chamber in any of my pistols any caliber, so they all get gentle taper crimp.

[Rapier]

Taper crimp as a separate station on the Dillon. Seat no crimp at all, then taper crimp, with no seater plug.

[Mk42gunner]

Well, did it pass the plunk test?
That would be the ultimate test...

Plus fill a mag and fire all but the last 2 rounds, leaving one in the chamber and one still in the mag.
Check/measure the OAL of the round left in the mag for bullet setback.
If the OAL hasn't shortened, you are good to go with your no crimp process.
jmo,
.
While this would be a good step, you should also measure the length of the round that got chambered. Hitting the feed ramp can do nasty things to lightly crimped rounds.

And you should fully clear your weapon anyway, accidents happen.

Robert

[GregLaROCHE]

Sometimes a heavy crimp is needed especially if you are not using the gun in a controlled environment. Crimping if not only sizing to fit the chamber.

[Hanzy4200]

I always taper crimp a tad. Only exception for me is .380 acp. For some reason I have issues if I don't factory crimp that round.

[bcr]

I figured out what's going on . . . the sized (new, Starline) brass is 0.417-0.418" at the case mouth. So I'm opening it up to 0.423" to start the boolit, but that's the nominal size it should be. So I'm putting a gentle taper crimp on them back to 0.418" and I'll see how they do. Hopefully they still headspace OK.