OAL question

Chambers · Mar 21, 2011

I'm having an annoying variation in my overall length that I can't figure out. This is for my .40S&W 2011. I'm using a EGW U-die, a RCBS seating die, and a Lee factory crimp die.

I set my seating die for 1.1375" with only one cartridge on the press...the one I'm using to set the die. Everything looks good, so I crank a few out. The first one is 1.1375", the rest are 1.140" - 1.144". I can't figure out why they are longer. When I run a single cartridge through it comes out exactly 1.1375" every time.

I understand there can be some variation but .065 seems excessive to me. Any ideas?

steak · Mar 21, 2011

Are you possibly short stoking it with the added friction from the extra rounds on the press?

Chambers · Mar 21, 2011

Definitely not.

steak · Mar 21, 2011

Is there any wobble to the die plate?

HiredHand · Mar 21, 2011

What type of press are you using?

steak · Mar 21, 2011

Wow, I just did the math. thats over a 1/16 and inch! My guess is as you add rounds and are having more friciton that the press is "giving" a little bit somewhere. Maybe you should set it just a tick deeper and recheck with about 10-15 dummy rounds and see where it averages out when you have a full plate shell going

Chambers · Mar 21, 2011

It's a Dillon 550.

HiredHand · Mar 22, 2011

You might need to check this product out. http://www.uniquetek.com/site/696296/product/T1230

Edit: You could probably find all the parts needed locally and much cheaper to do this conversion yourself.

ChrisC · Mar 22, 2011

Think in hundredths not thousandths....even as good as a dillon 550 is its not a match grade machine.

ChrisC · Mar 22, 2011

And unless you using a micrometer your measuring equipment can be off a touch on each measurement.

Wall · Mar 22, 2011

Mike,
You need to make all die adjustments with a fully stocked shellplate. This will minimize any variations due to wobble.

technetium-99m · Mar 22, 2011

Just accept it at face value and set up your dies with a full shellplate. My powder measure even changes a bit with a full shellplate.

Chambers · Mar 22, 2011

Thanks guys. Makes sense. I think I finally got it all figured out.

Scott Hearn · Mar 22, 2011

Mike, not to be a smartass or anything but those numbers are only .0065" different.

And that's pretty typical for what I get on my 650 and the LNL AP when I had it. And since I was a machinist back in the day, that's about exactly what I would expect to see. Go ahead and tweak it to where you want it with a full shell plate and it will probably stay around a .003" range when you your shell plate is full. There is really nothing to worry about. The variance you are seeing is coming from shell plate flex, the tolerances in the press linkage, and there are variances in the ogive of all bullets (it takes some pretty harry trig to see these numbers). If the press didn't have any slop at all, and was rock solid we couldn't move the handle and the shell plate wouldn't index. And even single stage presses will give you some OAL variance, this is where the ogive thing comes in.

You are doing just fine, just fine tune it with a full shell plate.