Texan .308 FPE ?
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Texan .308 FPE ?
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Topic: Texan .308 FPE ? (Read 2733 times))
K.O.
Eternally Tinkering
GTA Senior Contributor
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Real Name: Kirby
Re: Texan .308 FPE ?
«
Reply #20 on:
July 21, 2017, 04:38:33 PM »
Dave honestly there is a building of a Knowledge Base that is happening because of this and a couple other forums... What bothers me most is the potential corruption of that...
The rest is pretty easy to drop with a little effort... I do see this thread as a effort to try and find if there is a chance for accurate info of what works and what does not and a search for the why...
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The Great Northwest, United States, Washington
ezman604
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Real Name: Dave - DEz
Re: Texan .308 FPE ?
«
Reply #21 on:
July 21, 2017, 04:41:43 PM »
You may be right Kirby. But I am seeing some of the responses differently. And not in a useful way.
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West Coast of TN -
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TPL
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Re: Texan .308 FPE ?
«
Reply #22 on:
July 21, 2017, 04:48:52 PM »
I still answer to Nick's question. With G1 BC 0.271, weight 154 gr, muzzle velocity @10 ft 986, at 8000 ft altitude, the velocity 796 is lost well under 600 yards for sure.
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Tampere
rsterne
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Bob and Lloyd
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Re: Texan .308 FPE ?
«
Reply #23 on:
July 21, 2017, 04:59:35 PM »
I think it is important to focus on the data presented (velocity at target and drop, because of BC), and not comment on the initial target claim.... People can make honest mistakes by using the wrong inputs, and that is quite a different thing from insinuating they are lying.... I think DEz is emphasizing that we need to distinguish between the two....
The difference in calculated trajectory between using the G1 and G7 model in the calculator is a lot, some 500 inches (~ 43 MOA at 1100 yds).... but on the other hand that is only about 20% of the total drop.... The important difference is the velocity at target, and hence the energy.... 653 fps instead of 796 fps means the impact energy is only 146 FPE instead of 217 FPE.... If the same shot was taken at sea level, the bullet would only hit at 577 fps (114 FPE) using the G1 model, compared to 739 fps (187 FPE) using the G7 model.... and an additional 340 in. or so of drop....
Bob
«
Last Edit: July 21, 2017, 05:03:16 PM by rsterne
»
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Coalmont, BC, Canada
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nielsenammo
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Real Name: Nick
Re: Texan .308 FPE ?
«
Reply #24 on:
July 21, 2017, 05:00:24 PM »
Quote from: ezman604 on July 21, 2017, 04:41:43 PM
You may be right Kirby. But I am seeing some of the responses differently. And not in a useful way.
I can see your point of view. However, from my perspective, I see a guy trying to sell his goods on here and other forums from what very much seems like false information. I think if someone is going to write the things he did there is going to be public backlash for it. I see this "world record" now posted on Facebook as a real post.
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La Verne, CA
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QVTom
GTA Senior Contributor
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Real Name: Tom
Re: Texan .308 FPE ?
«
Reply #25 on:
July 21, 2017, 05:47:31 PM »
Altitude and temp or atmospheric pressure to be more exact make a significant change in BC numbers. For instance, Nick and I tested a 99 gn 308 hp in the Slayer. We were a 4200 AGL and 85*f, the BC was .278 and I was ecstatic to say the least. BC was calculated using Strelok and 3 ranges, 75, 130 and 250 yards.
On the drive home, I realized the BC of .278 need to be adjusted for standard conditions. Using Strelok, which has provisions for temp and barometric pressure, the corrected or normalized BC was a mere .241.
One humorous note on that day was that I accidentally plugged in 20 instead of .20 as a guess to get my initial dope. Zeroed at 75 and clicking to 130 yards yielded hits on a 4" kill zone but after a few shots at 250 yards, I realized I was bouncing them off the ground into the steel. LOL. I can't imagine being that far off and trying to make a hit at 1000 yards!
Numbers Matter
Tom
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Acton, CA
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oldpro
GTA
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Real Name: Travis
Re: Texan .308 FPE ?
«
Reply #26 on:
July 21, 2017, 06:06:33 PM »
I have my own opinion on the matter but I think Till we see someone other than Dave test the bullet its a moot point. Heres a easy to follow write up explaining the association of bullet speed with altitude and also a lot of other useful information on the site to educate people (like Myself) who donot understand fully the principles involved in this topic. Hope this helps
http://www.accurateshooter.com/technical-articles/ballitics-altitude-and-air-pressure/
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Katy, Texas
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ezman604
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Re: Texan .308 FPE ?
«
Reply #27 on:
July 22, 2017, 02:47:03 AM »
No one will come here and advertise unless they are approved and complete the process to become a sanctioned GTA vendor. Personally, with no validation offered, I am very much a skeptic. The dialog in this thread is great, it offers up proof by example and through the math. Please do continue tossing the numbers and facts for all of us to absorb. But the personal attacks can be done elsewhere. We have rules against that and none of us would enjoy the type of atmosphere that such attacks will surely foster.
Good stuff Bob, Nick, Travis, Tom, Timo, Kirby and all. Please teach us more!!!
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West Coast of TN -
https://www.zeemaps.com/map?group=962067
Revelation 760 PumpMaster (Vintage 1967)
Powerline 1000S .177 (semi-tuned by me & innards by kiwi Pete)
Benjamin Super Streak .177/.22 (converted to NP & w/GRT-III)
Weihrauch HW97K .177
Benjamin Trail NP XL1100 (home tuned by muwah with Tuna trigger)
Stoeger X-20 RAMmed by Gene and Tuna trigger
AF Condor SS .25cal "Ruby"
Winchester 1000B RAMmed by Gene
Crosman 1377 "Goldfinger"
FX Crown .22, .25, .30 & arrow set
Ain't this a great place to be
TPL
Member 3000+Fpe Club
Marksman
Posts: 375
Real Name: Timo
Re: Texan .308 FPE ?
«
Reply #28 on:
July 22, 2017, 03:59:39 AM »
Ok, one more study with ballistic calculator. I put G1 BC 0.271 and tried to find so high altitude where velocity at 1100 yards would be claimed 796ft/s. Calculator limit is 15000ft and it is not high enough. Only by using G7 it is possible in 9850 altitude, that makes axactly 796. Then there is another strange thing. Flight time with that speed is only 3.4sec. If flight time is over 4 seconds, velocity must be much smaller.
There is no doubt, those numbers are simly impossible.
Edit: Sorry, I made a mistake, that was at 1000 yards only. At 1100 yards altitude must be 13100 ft and flight time is 3.765 seconds... and G7.
Edit 2: We can speculate with atmosferic conditions, temperature affects the most. Of course we don't know them, not one but these numbers comes possible with G1 in altitude of 10000 ft, temperature 140 F and humidity 50%. What do you think? Plus that we should take account on coriolis but then should know also exact latitude and direction of the shots.
«
Last Edit: July 22, 2017, 09:14:18 AM by TPL
»
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Tampere
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Texan .308 FPE ?