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Old August 10, 2000, 09:09 AM   #1
Poodleshooter
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I'm stuck. My handloads through my AR-15HBAR w/ 1x7 twist are hovering in the 1.5-2" range. My usual handloads consist of Win 748 or Varget (98-100+% case capacity) under a 60gr. Vmax/55gr. Sierra SP or HP,etc. (I've stuck to the lightweight bullets since the only 75gr. I shot were some Black Hills loads that my reloads beat at 100yds.) I've determined that the next step I can take as far as accuracy is to find the optimum seating depth for some of my rifles. I understand that the critical dimensions are the case length, and the distance from the front of the bullets bearing surface to the beginning of the rifling. Can anyone recommend a step by step procedure for establishing how deep I should be seating bullets in a given rifle,including verifying accuracy with given seating depths? Up till now I have just miked all the cases to ensure they were below Max OAL, then trimmed any that were over length. I've found however that my bench mounted trimmer doesn't seem to trim very uniformly. Even when set to trim to the "trim to length" it still trims quite a bit below that. As far as seating, I just set the dies to seat to the middle of the cannelure. Not too scientific.
Any suggestions for additional accuracy would be appreciated.
Thanks
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Old August 10, 2000, 10:20 AM   #2
Banzai
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http://www.cctrap.com/~varmint/arelo.htm

Try there.

Also look here:
http://forums.ar15.com/cgi/Ultimate.cgi?action=intro

Tom


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Old August 10, 2000, 11:59 AM   #3
Monkeyleg
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How were your groups with factory ammo other than the 75gr Black Hills? With the 55 gr Black Hills and Federal Match I was getting "decent" groups. Then I switched to a Milazzo/Krieger trigger and the groups shrunk to around 1/2". That's using a 9X scope.

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Old August 10, 2000, 01:27 PM   #4
DaMan
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Poodleshooter, I take it your HBAR has the Colt chrome lined 1:7" twist. These have a very long throat.

You are going to have problems getting good accuracy with some of the pointier more ballistically efficient bullets and still keeping them magazine length.

Your choice is to single load longer cartridges or go to a bullet with a blunter design that brings the ogive closer to the riflings.

The Sierra 55gr. BTHP and the Sierra 52gr. Match King come to mind are the closest you can get the ogive to the rifling and maintain magazine length cartridges (2.260"). These might help you out.

I've also never had real good accuracy with W748 and these bullets. With the 55gr. you might try 4895 (H or IMR). And with the 52gr. MK you might try 4198 (H or IMR) or even H335.

Also I highly recommend the RCBS Precision Mic! This will allow you to set sizing die to bring headspace to only .004" under fired dimensions and you can also check where your rifle likes the bullet ogive to be located for best accuracy.

Regards! DaMan

[This message has been edited by DaMan (edited August 10, 2000).]
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Old August 10, 2000, 02:14 PM   #5
Poodleshooter
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Thanks for the links and info gentlemen!
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