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Posted: 10/15/2012 6:17:55 PM EDT
[#1]
KevinB(KAC) says a 16" can do anything a 20". I have a 7.62mm 16" MATEN build and I'am happy with the results that I get.
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Posted: 10/15/2012 7:13:45 PM EDT
[#2]
I respect KevinB.
BUTT!!! when it comes to .308 in an AR platform: 1) 16" cannot do a 20" 2) 20" cannot do a 24" Modern powders say so. EDIT: Electronics and targets back that up. Show me a 16" that can break 2600fps with Varget... and that speed wins F-Class in bolt guns. just da-da-damn |
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Posted: 10/15/2012 7:25:47 PM EDT
[#3]
Article I found when Googling this subject.........Barrel Length and the Precision Rifle
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Posted: 10/16/2012 12:50:25 PM EDT
[#4]
Wow, the replies here are rich with data!
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Posted: 10/16/2012 1:14:54 PM EDT
[#5]
Quoted:
Wow, the replies here are rich with data! Yeah I was kind of just looking for anyone exact numbers. I am trying to see if the velocity loss is going to drop the bullet trajectories so much that my reticle isn't perfect with the factory ammo I typically run. |
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Posted: 10/16/2012 3:05:42 PM EDT
[#6]
I've jacked this from elsewhere on the same topic. take it for what it's worth.
150 gr HPBT Win 748 loaded to a chamber pressure of 56.4K PSI WARM load 45 gr NOT a starting load. I chose 748 as the powder as it is most like NATO powder. 26" = 2918 FPS MP= 6.6K PSI ––99.6 % powder burnt -2836 ft/lbs 24" = 2873 FPS MP= 7.4K PSI ––––––––––––––––––––––––––––2750 ft/lbs 22" = 2823 FPS MP= 8.2K PSI ––––––––––––––––––––––––––––2655 ft/lbs 20" = 2766 FPS MP= 9.2K PSI ––98.7 % powder burnt -2548 ft/lbs 18" = 2700 FPS MP= 10.5K PSI ––––––––––––––––––––––––––––2428 ft/lbs 16" = 2623 FPS MP= 12.0K PSI -97% powder burnt ––––2291 ft/lbs 14" = 2531 FPS MP= 14.0K PSI ––––––––––––––––––––––––––2133 ft/lbs 12" = 2417 FPS MP= 16.7K PSI -94% powder burnt ––1946 ft/lbs 10" = 2273 FPS MP= 20.5K PSI ––––––––––––––––––––––––––1721 ft/lbs 8.0"= 2080 FPS MP= 26.0K PSI -87% powder burnt. -1441 ft/lbs 6.0"= 1800 FPS MP= 34.1K PSI -79.4% powder burnt -1080 ft lbs |
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Posted: 10/16/2012 4:18:32 PM EDT
[#7]
Quoted:
I've jacked this from elsewhere on the same topic. take it for what it's worth. 150 gr HPBT Win 748 loaded to a chamber pressure of 56.4K PSI WARM load 45 gr NOT a starting load. I chose 748 as the powder as it is most like NATO powder. 26" = 2918 FPS MP= 6.6K PSI ––99.6 % powder burnt -2836 ft/lbs 24" = 2873 FPS MP= 7.4K PSI ––––––––––––––––––––––––––––2750 ft/lbs 22" = 2823 FPS MP= 8.2K PSI ––––––––––––––––––––––––––––2655 ft/lbs 20" = 2766 FPS MP= 9.2K PSI ––98.7 % powder burnt -2548 ft/lbs 18" = 2700 FPS MP= 10.5K PSI ––––––––––––––––––––––––––––2428 ft/lbs 16" = 2623 FPS MP= 12.0K PSI -97% powder burnt ––––2291 ft/lbs 14" = 2531 FPS MP= 14.0K PSI ––––––––––––––––––––––––––2133 ft/lbs 12" = 2417 FPS MP= 16.7K PSI -94% powder burnt ––1946 ft/lbs 10" = 2273 FPS MP= 20.5K PSI ––––––––––––––––––––––––––1721 ft/lbs 8.0"= 2080 FPS MP= 26.0K PSI -87% powder burnt. -1441 ft/lbs 6.0"= 1800 FPS MP= 34.1K PSI -79.4% powder burnt -1080 ft lbs Thanks man! That's what I was looking for. I figured it would be around 50 fps. I can easily drop to a 14.5" and still get done what I need. I think ill stick with a 16" though rather than the 20". |
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Posted: 10/17/2012 3:25:25 PM EDT
[#8]
Ft/lbs???
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Posted: 10/17/2012 4:16:07 PM EDT
[#9]
What are you planning on doing with it? Hunting, match, precision? Makes a difference. If its for a hunting, then the 16" is plenty. I've done well with mine. Otherwise, I think the 20" would be my goto length.
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Posted: 10/17/2012 4:34:59 PM EDT
[#10]
I shoot 3 gun on the 3 Gun Nation Pro Series. This rifle will be used for shooting Heavy Metal Division until Stag Arms puts out their .308. We shoot out to 600 max but at that distance it's a full size IPSC target. So speed and agility is as important as 1 hole accuracy. That's why I was considering a 14.5 or 16" over a 20".
Last season I won the Division title with an 18" frankengun but its reliability haunted me all year. Most of the longer shooting is only 200-350 at 10" circular steel. I am sponsored by Swarovski and run their Z6i 1-6x w/BRT reticle. |
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Posted: 10/18/2012 4:56:00 AM EDT
[#11]
I think gains, or losses, with factory loaded heavier bullets would be less.
IIRC, gains above 18 inches were marginal as per some snipers testing the same gun and chopping back the barrel 2 inches per each chrono event. Obviously, a hot loaded handload with a light bullet might need more tube. YMMV,and sorry don't have link... |
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Posted: 10/19/2012 4:28:14 AM EDT
[#12]
Great table and information!!!
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