Going to be doing some roll crimping on 12 ga 1 3/4 rounds and want to know how much plastic to leave on the hull to make the roll crimp?

Would 2 inches be enough or would that be too much?

Cut one and try it, if you are using a clamping device to hold the shell then you can probably make the roll crimp turn down more. I do them by hand and the shell is very hard to hold and I get about 1/8” turning into shell.
I don’t do a lot of them or I would buy the tool.
You will also get better results with a drill press with a stop, than you will by hand. This was by hand and about all I could get to roll over. Attached File

I've had several batches of roll crimped shells pressure tested.  The last batch was a _really_ consistent 16ga load.   Unfortunately I'm not at home to measure for you exactly......but going from memory I'd say about 1/4" between the overshot card and the uncrimped case mouth will get you pretty close.  Possibly slightly less than that.

My experience indicates roll crimped shells are quite sensitive to getting the components just right.  By way of example I loaded up various batches with Unique and then Vectan A1, which are quite close in burn rate.  The Unique loaded shells never did produce anything more than marginally acceptable extreme spreads.  The A1 loads were darn nice once dialed in.

Order a precision reloading roll crimper.  IME its the best on the market.

Be prepared with multiple powders and wad combos if you really want to try this.

And no way I'd try this without a chronograph at least.

I'll try to remember to post pics of my home made shell cutter, and roll crimp shell holder.  They were reasonably easy to make, and the process goes WAY smoother with a couple of tools.

I’d like to see pics of that homemade shell holder!

I won’t be home til Tuesday but I’ll take some pictures. It was basically a piece of scrap oak trim with a clamp screw from the hardware drawer at an Ace Hardware. Didn’t take very long to make.

The shell trimmer took a fair bit more work but wasn’t difficult just finicky about razor blade angle.

The precision reloading is one of the worst roll crimper available.  Go over to "thereloadersnetwork" and get a 4 pin tool. I have the Lyman, both bp versions, and the pr one. The pr and BP ones leave a flat fat square crimp. The RN and Lyman both leave a nice thin rounded crimp. But the RN one is just better an all the others. It is more money but i would rather have something that works better.

I made one for 16 ga out of some pallet wood and a piece of steel flat bar.  I got the idea from pictures I saw here or somewhere.

The wood hangs over the flat bar a little so the vise gets a good squeeze on the wood and hull.  The wood was a solid piece I bored a hole through, beveled one side to clear the rim on the hull then sawed down the middle.  Hinge is Home Depot cheapy.  1/4" from the end of the hull to the OS card is a good starting point.

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I preheat the roll crimp tool with a heat gun.  Definitely takes a little bit of time to get a feel for the crimp time and movement.  My first three hulls usually look pretty scruffy.

1/4" above stack height is more then enough for roll crimping.

Have you ever used the Percision Reloading roll crimper? I ask because it doesn't leave a flat fat square crimp at all at least if you use it right.

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@tayous1

I measured and my best tested load the case mouth is .180” proud of the overshot card before roll crimping. The crimp does compress my column slightly.



It absolutely does not leave a square crimp, and is excellent if used properly IME.  I have both a 16 and a 12 by PR.  The both work excellent.  The proof is in the pudding.




Here are pictures of my shell holder. Note my 16ga holder is made with the grain going through wrong way. If you copy my style don’t do it that way.  These are scrap pieces of oak trim.  Cut to size.  Bore a hole through with the correct size wood bit for whatever gauge.  Cut a slot so the hole can crimp down.  Cut a channel for your clamp screw.  These are from a hardware store bin, don't remember what they are called.  Epoxy in ONLY THE INSIDE of the clamp screw.  Remember the hole can't clamp down on the shell if the threads can't move relative to the wood on the outside of the clamp.  My 16ga was thrown together in minutes as proof of concept, but it worked fine so I never re-made it.  My 12ga clamp I spent more time on to make it look nicer, but in practice they both work the same.  You can glue a small strip of fine grit sand paper into the hole to refine the fit and keep the shell from spinning when you crimp it.









Kingston_Fisher that is beautiful work!!  Very solid.  I made mine so that it holds the shell for both trimming to 2 1/2" in my trimmer, and for hand holding the shell in the drill press.  It still works, but I expect your style of shell holder is rather more solid.  Mine works fine, but I would guess the process is a little slower than yours. Well done.

Like I said, I have them all. The reloadernetwork 4 pin is the best one I have used. Works very well with hulls that were fold crimped. Way better than the others.

I looked back at my notes it is the BP crimper that leaves a sqaure fat crimp. The PR left more wrinkled rolls. I used to do a final crimp on my merc to put a slight taper on the crimp to help feed better. I don't do that anymore withe the RN crimper. Others are using the GAEP finisher crimp to do the same.

That's nice set up. Right now I'm looking to build something so I can cut the hulls to the perfect length.

Like to know how you built yours? I've been trying to use PVC pipe I have around.

@tayous1

Basically I took some scrap square oak trim boards, and bored a correct size hole (for whatever gauge you are trimming) through a few of them.  

Then I lined the holes up and clamped the boards together with wood glue.  You can see in the pictures it's several layers of oak board glued together.

Cut slices off all four sides just to clean them up and make the outside square using a chop saw.

Cut a slice off the top - you can see the parting line in the pictures.  Carved in a slot for a razor snap blade.  It needs to point down toward the hull mouth a few degrees so it bites in when you twist it - otherwise it will just skip across the surface.  The drill holes in this top slice for the wood screws that hold this slice back in place and tighten down on the razor blade to hold that in place firmly.

Last but not least start trimming off the bottom on the trimming block with a chop saw little by little until you are really close to the point it cuts your hulls to the right length - then finishing it off by sanding it off to the exact length.

When the shell is placed in the shell holder flush at the bottom, and the shell is inserted in the trimmer and twisted, it cuts the shell down until it bottoms between the two pieces.  And every shell comes out right at 2.58".

So found out 2 inches is what works well for me. My rounds might be a little longer then factory 1 3/4 yet I don't need to place that rubber device in my 590A1 or Shockwave to be able to load the ammo.

Can't wait to get a slug mold and try that out!