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Old August 14, 2012, 05:53 PM   #1
jwrowland77
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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.
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Old August 14, 2012, 05:56 PM   #2
Sparks1957
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I wouldn't call +/- 0.004 much of a variance. I wouldn't worry too much about one that size.
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Old August 14, 2012, 06:03 PM   #3
jwrowland77
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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.
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Old August 14, 2012, 06:10 PM   #4
Brian Pfleuger
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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.
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Old August 14, 2012, 06:43 PM   #5
serf 'rett
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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.
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Old August 14, 2012, 06:48 PM   #6
jwrowland77
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Hmmm, I'm using a single stage Hornady lnl.
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Old August 14, 2012, 06:53 PM   #7
Misssissippi Dave
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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.
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Old August 14, 2012, 07:33 PM   #8
dunerjeff
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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.
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Old August 14, 2012, 09:43 PM   #9
jwrowland77
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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?
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Old August 15, 2012, 03:25 PM   #10
serf 'rett
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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!)
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Old August 15, 2012, 03:27 PM   #11
jwrowland77
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By the manual, OAL was 1.10. I was using 1.164. Going down to 1.15
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Old August 15, 2012, 07:42 PM   #12
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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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