Range Report Any DOPE on the .308 150 gr TTSX? True G1 BC?

[762libertarian]

Ladies and Gentlemen,

Yesterday I tried my new general purpose hunting load at 100,200 and 300 meters. It's the Barnes TTSX 150 gr launched at 2790 feet per second from a .308 Winchester case. Scope height is 2.2"

Zeroing at roughly 200 yards ( to get point blank range as far as possible with no more deviation from point of aim than 2") I got the following impact points on the varying ranges:

100 meters: +1.8 inches
200 meters: -1.3 inches
300 meters: -13.5 inches

The above is the mean deviation from the aiming point, measured with a ruler. I fired maybe 20 rounds at 100 and 200 each, but only a five round group at 300.

I tried to use this data to calculate the G1 BC of the bullet used. Barnes advertises 0.42 for this bullet. Litz did some testing on the barnes bullets and decided they exaggerated their BC's by 1-5%. I had hoped to get a BC of 0.40 (95% of advertised) or 0.39, but I cant get the numbers to fit without putting in a G1 BC of about 0.3. I do realize that G1 BC changes with the speed, but I wouldn't imagine that it's this dramatic in the first 300 yards.

Any of you guys have any data on this bullet?

Edit: Litz source http://www.dtic.mil/dtic/tr/fulltext/u2/a554683.pdf

 

[Dirty8404]

Just going to toss out there that for truing you need more distance.

Get a good 100y zero. Spot on. Go to 500y, tweak velocity to get on. Go to 800y, tweak BC to get on. There’s other distances people use (maybe 300/500 for that bullet would be good) but 300y is not enough, and I’ll bet velocity, a small zero offset or a combination of both is fucking up your numbers.

 

[dirthead1]

How did you determine your velocity is 2790? Adjust velocity inside 500 yards to get the predicted and actual curves to align. If you can shoot further, like 800 yards or so, you can then adjust bc in your calculator to match the actual drops. Bc has very little effect inside 500 yards.

 

[762libertarian]

I hear you. I'll go back to the range and shoot some more and see if the numbers match upp better.

 

[Deleted member 113831]

Ladies and Gentlemen,

Yesterday I tried my new general purpose hunting load at 100,200 and 300 meters. It's the Barnes TTSX 150 gr launched at 2790 feet per second from a .308 Winchester case. Scope height is 2.2"

Zeroing at roughly 200 yards ( to get point blank range as far as possible with no more deviation from point of aim than 2") I got the following impact points on the varying ranges:

100 meters: +1.8 inches
200 meters: -1.3 inches
300 meters: -13.5 inches

The above is the mean deviation from the aiming point, measured with a ruler. I fired maybe 20 rounds at 100 and 200 each, but only a five round group at 300.

I tried to use this data to calculate the G1 BC of the bullet used. Barnes advertises 0.42 for this bullet. Litz did some testing on the barnes bullets and decided they exaggerated their BC's by 1-5%. I had hoped to get a BC of 0.40 (95% of advertised) or 0.39, but I cant get the numbers to fit without putting in a G1 BC of about 0.3. I do realize that G1 BC changes with the speed, but I wouldn't imagine that it's this dramatic in the first 300 yards.

Any of you guys have any data on this bullet?

Edit: Litz source http://www.dtic.mil/dtic/tr/fulltext/u2/a554683.pdf

Is this a load you made, or factory? What is the load? It works at sea level with a .380 G1 at 2650 fps. Nothing works at 2790 fps. I suspect your velocity is off considerably.

 

[762libertarian]

I'll report back after next range visit. MV measurements have been consistent, I'd rather believe I messed up the 5 round group at 300.

 

[DIY Mtn Hunter]

Did you ever calculate a BC at the further yardages?

 

[762libertarian]

No, I think I messed up my shooting at the 300 yard range. At one time I had to send my scope back for repairs... maybe that was what caused my weird POI. (It's a Kahles, and they were great about it) Since I posted this thread I've had better results more consistent and with a predictable trajectory. Haven't done any calculations.