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9/19/2017 7:27:10 PM
Posted: 12/25/2005 9:13:25 AM EDT
Will be buying a Fulton Armory varmint upper. Question is, should I go with the 20" or the 24". Will be used for target shooting only off the bench so weight is not an issue. Other than weight, is there a disadvantage to the 24"? Plan on mounting a Super Sniper 10X with Larue SPR.

Comments on scope and mount choice also appreciated.
Link Posted: 12/25/2005 10:35:36 AM EDT
[Last Edit: 12/25/2005 10:36:31 AM EDT by Sig685]
The same load in my 24 inch 1:8 twist barrel is usually about 200FPS faster than in my 20 inch 1:8 twist barrel.
Link Posted: 12/25/2005 4:48:46 PM EDT
Link Posted: 12/25/2005 6:19:09 PM EDT
Randall, I am not going to argue with you; you are probably more correct than I am and I have a small set of data points. For instance, the Black Hills 77 gr SMK MC comes out of my 20 inch at a measured average velocity of 2522. The exact same comes out of my 24 inch at and average of 2725, or 203FPS faster.

The BHA 77 SMK-MC is the only "factory" ammo I use. Everything else are my own reloads. Here the velocity differential runs between 105-195 FPS with a heavy cluster around to 140 mark.

All the bullets are moly-coated, BHA and reloads.

My pet 600 yard load is a 75 gr AMAX MC, of course and comes out of my 20 incher at an average of 2760. It's close to 3000 in my 24 incher.
Link Posted: 12/25/2005 6:33:05 PM EDT
Link Posted: 12/26/2005 7:14:11 PM EDT
It's 25.5 grains of Varget. Again, please remember the bullets are moly-coated.
Link Posted: 12/26/2005 7:29:49 PM EDT
[Last Edit: 12/26/2005 8:57:05 PM EDT by Randall_Rausch]
Link Posted: 12/26/2005 8:06:23 PM EDT
The COAL is 2.455. I measured my cases just above the extraction grove and I have found very little expansion, it was certainly well within acceptable parameters. I had a couple of other people check my fired cases and they also found not pressures signs. The primers are definitely not flattened and there is no extractor mark on the bottom of the case.

I know this is a warm load, and if it weren't for the moly-coating, I would not be using it.
Link Posted: 12/26/2005 8:56:29 PM EDT
[Last Edit: 12/26/2005 9:03:07 PM EDT by Randall_Rausch]
Link Posted: 12/27/2005 8:25:48 AM EDT
Randall, thanks a lot I really appreciate the information and the confirmation of my load. I cannot stuff any more powder in the case and even at 25.5 grains, I can hear the powder getting slightly compacted when I seat the bullet. BTW, the ogive is about .010 from the lands and this load is VERY accurate.

It would seem then that my load is chronographing about 80FPS slower than prediction in my 20 inch barrel. The average MV was 2760, the standard deviation was 23 and the extreme spread was 60. This was a 10 shot string and I tried to highball the Chrony about 14 feet from the muzzle.

My goal was to reach 2700 FPS with the AMAX, and I am pleased with the results; no pressure signs, predictable and useful external ballistics and very accurate, what's not to like.

Thanks again for you information. I have already bookemarked your web site and I now know where to go to spend some money on my toys.
Link Posted: 12/28/2005 8:39:19 PM EDT
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