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 August 14, 2012, 05:53 PM #1 jwrowland77 Senior Member   Join Date: March 23, 2012 Location: Conway, Arkansas Posts: 1,397 Variances with 9mm Rounds Does anyone ever get variances in their OAL when reloading 115 FMJ-RN 9mm rounds? I don't know if I'm doing something wrong or not but trying to find out. Let's say I set my dies for a OAL of 1.150. I've set my die by loading a round to this length. For some reason I am getting variances with it. Several rounds may be at the 1.150 that I have set, but then there may be a round that is 1.146 or 1.154. I could swear that I am using the same pressure, same motion, same everything. Does anyone else run into this while loading 9mm rounds? Thanks for any advice or help.
 August 14, 2012, 05:56 PM #2 Sparks1957 Senior Member   Join Date: September 4, 2011 Location: Vermont Posts: 1,552 I wouldn't call +/- 0.004 much of a variance. I wouldn't worry too much about one that size.
 August 14, 2012, 06:03 PM #3 jwrowland77 Senior Member   Join Date: March 23, 2012 Location: Conway, Arkansas Posts: 1,397 Oh ok. What size of a variance should I be in the lookout for? And what cause any variance considering you have set your dies at a certain length? This has always puzzled me.
 August 14, 2012, 06:10 PM #4 Brian Pfleuger Moderator Emeritus   Join Date: June 25, 2008 Location: Western Colorado, finally. Posts: 19,118 Once I get the die set for the length I want I don't even measure finished rounds. Unless there's something dramatically wrong, any variance you get is inconsequential. If they look the same by eyeball they're close enough. __________________ Still happily answering to the call-sign Peetza. --- The problem, as you so eloquently put it, is choice. -The Architect ----- He is no fool who gives what he can not keep to gain what he can not lose. -Jim Eliott, paraphrasing Philip Henry.
 August 14, 2012, 06:43 PM #5 serf 'rett Senior Member   Join Date: June 25, 2009 Location: Stuttgart, AR Posts: 1,568 Loading 9mm on single stage RCBS Rockchucker, seat and crimp separately I see +/- 0.001 but mostly less than even that. I suspect a progressive or turret wouldn't hold as tight of tolerances. __________________ A lack of planning on your part does not necessarily constitute an emergency on my part.
 August 14, 2012, 06:48 PM #6 jwrowland77 Senior Member   Join Date: March 23, 2012 Location: Conway, Arkansas Posts: 1,397 Hmmm, I'm using a single stage Hornady lnl.
 August 14, 2012, 06:53 PM #7 Misssissippi Dave Senior Member   Join Date: December 5, 2009 Posts: 1,411 I don't load to max level in 9 mm. I look for a + or - of 0.005". I wouldn't be too worried even at plus or minus 0.010" for any mid range load. At max. levels I return to plus or minus 0.005". A couple thousands of an inch can be caused just by the way you are using the calipers. Try measuring the same bullet 10 times. Rotate the bullet a little for each measurement. Is there any change? You probably will see a little bit and it will not be because the OAL changed just the way you are measuring.
 August 14, 2012, 07:33 PM #8 dunerjeff Senior Member   Join Date: March 31, 2011 Location: central Wisconsin Posts: 440 Unless your using a fixture that only hits the bullet on the ogive,any little tip damage,nick, ding, ect, will show variances in oal. __________________ sent via telegram
 August 14, 2012, 09:43 PM #9 jwrowland77 Senior Member   Join Date: March 23, 2012 Location: Conway, Arkansas Posts: 1,397 Question: my original work up for titegroup was an OAL of 1.164 using 4.0 grains as my most accurate. If I reduce this to 1.150 should I go ahead and do another workup or would the reduction of OAL to 1.150 be safe? I'm assuming it will do fine as far as cycling the gun since there will be a slight increase in pressure but wanted to make sure it wouldn't be too much pressure. By the books 4.0 is a mid-range load so I'm assuming it wouldn't hurt anything to simply reduce the OAL by just .01. Thoughts?
August 15, 2012, 03:25 PM   #10
serf 'rett
Senior Member

Join Date: June 25, 2009
Location: Stuttgart, AR
Posts: 1,568
Quote:
 By the books
What OAL was given in your reloading manual? Is that the length you used for your original loads? Is the proposed new length shown in your manual and if so, is your charge weight still mid range? If still mid range, then there's nothing left to do except load 10 or 20 test round and check them against your previous targets (and if they don't group as good, you can then start wondering if it's the new COAL, higher pressure or the blazing hot, dry weather we've been having here lately!)
__________________
A lack of planning on your part does not necessarily constitute an emergency on my part.

 August 15, 2012, 03:27 PM #11 jwrowland77 Senior Member   Join Date: March 23, 2012 Location: Conway, Arkansas Posts: 1,397 By the manual, OAL was 1.10. I was using 1.164. Going down to 1.15
 August 15, 2012, 07:42 PM #12 Misssissippi Dave Senior Member   Join Date: December 5, 2009 Posts: 1,411 You are not going to have any pressure problems since you still aren't near the OAL from your manual. The longer length will produce less pressure. This is assuming you are using the same bullet the manual called for. You might find it works well. I suggest trying only a few rounds to test it before trying entire box. If you are happy with the results then only load a box of 50 to give it another test. I have made the mistake before after doing a work up thinking I found what I wanted and then loaded 200 rounds. I found after shooting only 50 it was running on the dirty side too much. I added more powder on the next test loads and found it shot cleaner and was just as accurate as before. I did pull 150 bullets to fix things. Never again for me. Some powders seem to do better with the bullet closer to the powder and others don't seem to matter at all. I found AA5 is one of those powders. It is probably why they list their loads with short OAL.

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