Need chrono'ed fps for.308 varget loads PLEASE

[Quarterbore]

Need chrono\'ed fps for.308 varget loads PLEASE

Shooting a savage 26" barrel 1-10 twist
need approximate fps(+/-30) for following Varget loads:
44.0 gr--168 amax.475bc= ? fps
44.5 gr--" "
45.0 gr--""
45.5 gr--""
46.0 gr--(hodgen says 2731fps for 24")
46.5 gr--
If you can get me close I'll appreciate it.
I loaded some 44.5 that shoot real good i figured they are traveling about 2650fps, just a guestimate.
Also tried some 155 gr.Amax w/ 46.5gr varget
very good results, guessing 2900 fps.
Thanks for any input.
assumming avg.temp. 45F

[ 02-19-2004: Message edited by: 308WIN ]

 

[Michael Eichele]

Re: Need chrono\'ed fps for.308 varget loads PLEASE

I have found that Hodgedon's cliam of around 2730 FPS at 46 grains is VERY close. Of course, that is subject to change with the cases you use, the primers, seating depth, barrel length, twist, barrel quality...That list is huge. The best thing to do is buy a crony. You will loose or gain about 60 FPS per grain or 6 FPS per tenth.

Guessing a velocity for you a within 30 FPS with out shooting your stuff over a chrony is near impossible.

[ 02-19-2004: Message edited by: meichele ]

 

[Jeff In TX]

Re: Need chrono\'ed fps for.308 varget loads PLEASE

I use 46 grs of VarGet with my 168 AMAX out of a 26" 1 in 11.27 twist Rock barrel. Figure on 2700 to 2730 fps.

By the way the published G1 drag BC on the bullet is .495, but the actual BC is .310 using a G5 drag model for boat tail bullets

That should have you very close.

Hope it helps

Jeff In TX ]

[ 02-20-2004: Message edited by: Jeff In TX ]

 

[Quarterbore]

Re: Need chrono\'ed fps for.308 varget loads PLEASE

I had know Idea of the difference of G1 & G5 drag. What does this all mean? False advertising?

When I use JBM ballistics to figure trajectory i always leave it at G1 and the published BC. Which has got me very close on steel out 800 yds and i'm guessing on my velocity (2740fps 45.5gr Varget) until i get a chronograph. How much difference could the G1 or G5 inputs really make? Probably less difference than not actually knowing you're velocity

[ 02-21-2004: Message edited by: 308WIN ]

[ 02-21-2004: Message edited by: 308WIN ]

 

[Michael Eichele]

Re: Need chrono\'ed fps for.308 varget loads PLEASE

Its not flase advertising, they dont figure BC's out to 1000 yards.

A given BC based on 0-600 yards and G1 are pretty precise. When you go to 1K, sometimes the G1 function works perfectly. Other times such as I have found with some of the AMAX bullets that the G5 function get you right on at 1k.

I have found with the 155 Scenar that a BC of .500 and G1 work perfect to 1K. The 155 AMAX and G1 worked perfect. The 178 AMAX only worked for me with G5 and a .318 BC.

Basically what I am saying is that the 178 out to 600 yards using G1 and a .515 BC followed the math perfectly. By the time it got to 1k it was 27" lower than calculated. When the figures were changed the the G5, it was still perfect to 600 and it was also perfect out to 1k!

Good shooting!

[ 02-21-2004: Message edited by: meichele ]

 

[Quarterbore]

Re: Need chrono\'ed fps for.308 varget loads PLEASE

Thanks, I see the light now.
So what is your most precise 300-1000yd bullet(s). The 155 & 168 Amaxs have been excellent for me haven't tried the 178's. I also tried Nosler J4's but not quite sure what to think about them yet.I'm Going to try sierra MK next.

 

[Jeff In TX]

Re: Need chrono\'ed fps for.308 varget loads PLEASE

Brad's program at JBM is using a modified calculation to better match the G1 drag model for longer ranges. Depending on the type of bullet sometimes it helps, sometimes it doesn't.