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Author Topic: Testing the .308 135gr BBT  (Read 5704 times)

rsterne

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Re: Testing the .308 135gr BBT
« Reply #15 on: July 31, 2016, 06:45:17 PM »
Ricky ran some downrange velocity tests today, so that I could calculate the Ballistics Coefficient.... He shot 10 shots, in two 5 shot strings, with the Chrony at 1 yard, refilling between strings, and then moved the Chrony to 51 yards and repeated (50 yard separation).... The 10 shot averages were 803.5 fps (2.6% ES) and 773.2 fps (1.7% ES).... The average temperature was 82*F, altitude 269 ft., barometric pressure 30.03", and humidity 89%.... I ran these numbers through my own Spreadsheet, the JBM BC Calculator, and ChairGun, and using the G1 Model got BCs of 0.163, 0.164, and 0.165, so the average BC (G1) at 50 yards, at an average velocity of 788 fps is 0.164, corrected to ICAO conditions....

Thanks for your help, Ricky, much appreciated....

Bob

AlvinYork

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Re: Testing the .308 135gr BBT
« Reply #16 on: August 01, 2016, 11:26:10 AM »
You moved the chrony to 51 yards? Hell, mine is five feet from me and I still manage to shoot the thing (in the shading connector rods)!

rsterne

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Re: Testing the .308 135gr BBT
« Reply #17 on: August 01, 2016, 03:37:44 PM »
You're not supposed to close your eyes before you pull the trigger, Alvin....  :P

J/K, of course.... :D

Bob

sixshootertexan

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Re: Testing the .308 135gr BBT
« Reply #18 on: August 01, 2016, 05:53:58 PM »
You moved the chrony to 51 yards? Hell, mine is five feet from me and I still manage to shoot the thing (in the shading connector rods)!
In the words of Alvin C. York. I don't see how I missed that great big ole target down there.

rsterne

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Re: Testing the .308 135gr BBT
« Reply #19 on: October 18, 2016, 04:17:56 PM »
Ricky recently shot a group at 200 yards that was just under 3" with these 135 gr. BBTs....

Bob
« Last Edit: October 19, 2016, 01:18:06 AM by rsterne »

sixshootertexan

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Re: Testing the .308 135gr BBT
« Reply #20 on: October 19, 2016, 03:52:53 AM »
I purchased a new set of Hawke rings for for my rifle and a set of inserts to go in them. The inserts give you 25 MOA of elevation. I sighted the rifle in at 75 yards and I now can click the scope to get on target at 200yards.

75 yard Target


200 yard target. Bottom hole was a sighter.




And this was hitting a gong at 200 yards before the new rings.
https://www.youtube.com/watch?v=9p0nX00bjpU


tnt76

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Re: Testing the .308 135gr BBT
« Reply #21 on: July 13, 2019, 12:37:11 AM »
I thought I'd add an unofficial report to the performance of these 135gr BBT also at 200yds.
This was the only group at 206yd I shot as I had spent all my air and time at 102yds dialling in the new parts on the rifle.
When I get out again I will shoot some again but into a GTA N.U.A.H. target.
Setup:
.308 Texan
1:17 Krieger #17 heavy varmit barrel
2600psi
870 - 875fps
Carbon bottle
Athlon Argos 8-32 X 56
2% tin lead mix
My 102 yard groups on the same settings were nothing to brag about, being 1.5 to 3in. I'm still playing with grips, fps and support. So  I foresee the 100yd and 200yd groups shrinking.
POI was low and right of aim.
This 206yd group measured 132mm (5.2in)
« Last Edit: July 13, 2019, 12:39:01 AM by tnt76 »

rsterne

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Re: Testing the .308 135gr BBT
« Reply #22 on: July 13, 2019, 01:58:53 AM »
Very cool.... Nice to see a plan come together....

Bob

 



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