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HNSB
10-20-2013, 06:06 PM
I just bought some new brass to put together some loads for a 45-70 (Marlin 1895).

I plan on putting a pretty good crimp on these, as they are loaded in a tube magazine.
I measured all the brass, and have a length variance of .0015. Is that enough to affect crimp / start pressure? How close is close enough?

+/- .0008 seems like tight enough tolerance, but should I take the time to trim them? If I do, I have to wonder if my Lyman case trimmer will be much more accurate than +/- .0008?

kevmc
10-20-2013, 06:33 PM
I wouldn't mess with it until I saw .005 or so diff.......

gray wolf
10-20-2013, 09:16 PM
Set you caliper for .0015 and look at the amount of light you see through it. I doubt you will detect that small amount when you load and shoot them. You should be fine, and the fact that you asked the question tells me you are trying to do the best job you can and that's a big plus.
Carry on.

cbrick
10-20-2013, 10:36 PM
Depends, if it was for a bench rest match I would say trim. For a typical hunting rifle at typical hunting distances and shooting it's pretty doubtful you could detect any difference in one and a half thousands. I know long range revolver match shooters that only trim to .0015" for uniform crimp.

Rick

HNSB
10-21-2013, 07:22 PM
Ok, I'll load 'em up as is.

Thanks for the replies!

bhn22
10-21-2013, 07:58 PM
.0015 as measured with calipers probably encompasses the minute slop in the calipers teeth. As above, don't sweat it...

HNSB
10-22-2013, 01:17 PM
My caliper is accurate and repeats within .001. If it didn't, I would get a different one.
I bought one of those cheap units once and it was no better than +/- .005.
It now resides in the landfill.

I used a mic for the brass, because I wanted to know within tenths what the length is.

Iron Mike Golf
10-23-2013, 11:56 AM
+/- .002 seems to work just fine for me using a Redding Profile Crimp die

Walstr
10-26-2013, 11:05 AM
[B]HSNB[B]: I've also wondered about the effect on COAL due to case length variances, using Roll Crimp to finish it. I just purchased 150 once fired cases of Winchester brass that are 1.115"!! That's .010" over SAAMI specs! I'm still trying to determine the 'how' & 'why' of this. IMHO .0015" ain't nuttin', .0150" could be trouble.

Since I'm in the process of 'designing' a 45-70-435gr boolit, my chamber slugging dimensions are critical. I find that my throat is a bit longer & the rifling is a bit larger in dia. than 'normal'. How & when the Ogive on my new boollit nose contacts the rifling, and how it will chamber during normal cycling, is still being considered. Thusly, I'll have to standardize on a given case length to prevent boolit from getting stuck in the rifling if I wish to eject a loaded round, & 'jumping' too far getting to it during ignition!

I'm really not hijacking your thread here, but sharing some similar concerns re: reloading dimensions for our cartridge. I too look forward to comments from the learned participants on this forum. Good luck in your new endeavor & keep us posted on the results.

HNSB
10-26-2013, 09:25 PM
I just loaded up my test loads. I'll be firing them tomorrow. I'll post here the variance on the chronograph.

My oal is .005 over what my manuals show. They load and chamber fine.

I'll let you know how it goes.

bbqncigars
10-27-2013, 10:11 AM
I only worry about precise case length for those loads that get a taper crimp over vs. the FCD that gets used for my Marlin. I spot check each batch with a case gauge while I'm prepping brass, and trim as needed.

MBTcustom
10-27-2013, 10:21 AM
Seriously, you gotta try the Lee collet crimper. No muss no fuss. +- .020? No problemo! Although I second cbrick's sentiments.