questions about measurement tolerance

jnestle · June 23, 2010, 03:52 PM

I have reloaded pistol cartridges and am now about to reload rifle - 243 specifically. My questions:
how close to the published measurements do you need to be in terms of "trim to" length and overall length do you need to be?
In trimming my cartridges I find that my Lee zip trim system cuts slightly more than suggested - which makes the case about 0.05 shorter than suggested on average. considering I am only loading for deer hunting rounds I only need decent accuracy for 100 - 150 yds. Will this slight difference in case length make a significant difference in terms of hunting accuracy and or safety?

Thanks in advance,

JN

wncchester · June 23, 2010, 04:32 PM

" which makes the case about 0.05 shorter than suggested on average. "

You are correct, it's a suggestion. Nothing will blow up or fall off if a case is a tad short nor will it have much, if any, effect on accuracy.

(I'm assuming you mean the cases are 5 thou short, not 50 thou.)

.284 · June 23, 2010, 08:43 PM

Have you trimmed all your brass? If not, then stop. There has to be an adjustment that will leave your brass .005 longer. If you have trimmed it all, you're still okay. My buddy just bought a RCBS X die which calls for the user to start .005 shorter than the load trim to length measurement. I would say as long as you have the right neck tension when seating and you are getting close to a full caliber seating depth you should be okay.

Sport45 · June 23, 2010, 10:02 PM

The Lee trimmer is a fine tool but it is not adjustable. Well, I suppose you could grind the end to shorten it. Anyway, the ones I have are pretty reliable for trimming consistently to minimum case length. I believe what you want are consistent lengths more than anything else.

reloader28 · June 23, 2010, 10:11 PM

Dont worry about it. You'll be perfectly fine.
I've shot some that a friend loaded that were trimmed 1/16" shorter than minimum and they shot OK.
They say the best accuracy is when your casing is out close to the end of the chamber, which well past maximum in most guns that I've measured, but not all.
If you want that kind of accuracy, you should measure your chamber and go from there, but for a hunting rifle it is not nessicary.

I agree with the consistant lengths.

June 23, 2010, 03:52 PM	#1
jnestle Member Join Date: March 15, 2010 Posts: 15	questions about measurement tolerance I have reloaded pistol cartridges and am now about to reload rifle - 243 specifically. My questions: how close to the published measurements do you need to be in terms of "trim to" length and overall length do you need to be? In trimming my cartridges I find that my Lee zip trim system cuts slightly more than suggested - which makes the case about 0.05 shorter than suggested on average. considering I am only loading for deer hunting rounds I only need decent accuracy for 100 - 150 yds. Will this slight difference in case length make a significant difference in terms of hunting accuracy and or safety? Thanks in advance, JN

June 23, 2010, 08:43 PM	#3
.284 Senior Member Join Date: July 8, 2009 Location: davison, michigan Posts: 665	Have you trimmed all your brass? If not, then stop. There has to be an adjustment that will leave your brass .005 longer. If you have trimmed it all, you're still okay. My buddy just bought a RCBS X die which calls for the user to start .005 shorter than the load trim to length measurement. I would say as long as you have the right neck tension when seating and you are getting close to a full caliber seating depth you should be okay. __________________ Guns have only two enemies, rust and politicians! Deer are amazing creatures....so please don't burn the sauteed onions and I'll pass on the steak sauce, thank you.

June 23, 2010, 10:02 PM	#4
Sport45 Senior Member Join Date: May 25, 1999 Location: Too close to Houston Posts: 4,196	The Lee trimmer is a fine tool but it is not adjustable. Well, I suppose you could grind the end to shorten it. Anyway, the ones I have are pretty reliable for trimming consistently to minimum case length. I believe what you want are consistent lengths more than anything else. __________________ Proud member of the NRA and Texas State Rifle Association. Registered and active voter.

June 23, 2010, 04:32 PM	#2
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	" which makes the case about 0.05 shorter than suggested on average. " You are correct, it's a suggestion. Nothing will blow up or fall off if a case is a tad short nor will it have much, if any, effect on accuracy. (I'm assuming you mean the cases are 5 thou short, not 50 thou.)

June 23, 2010, 10:11 PM	#5
reloader28 Senior Member Join Date: October 13, 2009 Location: nw wyoming Posts: 1,061	Dont worry about it. You'll be perfectly fine. I've shot some that a friend loaded that were trimmed 1/16" shorter than minimum and they shot OK. They say the best accuracy is when your casing is out close to the end of the chamber, which well past maximum in most guns that I've measured, but not all. If you want that kind of accuracy, you should measure your chamber and go from there, but for a hunting rifle it is not nessicary. I agree with the consistant lengths.