Range Report Help calculating velocity

[ZLBubba]

I don't have a chrono yet and was wondering if anyone had a way to estimate the velocity I'm getting out of my 308 155gr Scenars. I'm shooting them out of an 18" barrel with 45.7gr of RL15. I have the dope in mils, but I can't find any ballistics calculators that will let me input bullet drop and approximate the muzzle velocity.

100 yards: 0
300 yards: .5mils
500 yards: 2.1mils
600 yards: 3.2mils

Yeah, I know, I should have asked for a chrono for Christmas. Any help would be greatly appreciated.

 

[BOLTRIPPER]

Re: Help calculating velocity

when is your birthday ?

 

[ZLBubba]

Re: Help calculating velocity

Haha, July. But I may just go out and buy a Chrono in March when I'll have more time for shooting.

 

[LR-WSM]

Re: Help calculating velocity

ZL, Have you checked the adjustments on tour turrets to make sure they are accurate. I ran your dope through my KAC program and the speeds I had to input in order to get close to your dope are unachievable with a 30" barrel let alone an 18" barrel.

3150 fps got me close on the 500 & 600 yard dope but was way off when I dropped to 300 yards.

Check your adjustments at 100 yards and shoot me a PM. I'll be happy to run some numbers for you.

 

[Brasscow]

Re: Help calculating velocity

Yeah... no need for me to run numbers. I know the 155 scenar and the 308 and can't imagine that everything is on the up and up considering your 18" barrel, the cold temps, and the 45.7gr RL-15 load. I'll second LR-WSM on checking things out thoroughly and posting back here.

 

[ZLBubba]

Re: Help calculating velocity

Ah, sorry about that. The temp was 95* when I shot those numbers. It was here in Maryland over at the Ft Meade range. Frankly, I think the imprecise dope comes from operator error, not the turrets. While the number don't match up perfectly, I think I'm around 2900fps in the summer. That seemed to be what my regression line would be at if I were averaging a bunch of groups.

Is 2900fps nuts with that load?

 

[Goldbeachman]

Re: Help calculating velocity

2900 fps isn't nuts with that load. But you can't recreate the mil elevation corrections at your stated distances at that speed (or even up to 3050 fps and have the 300 yard .5 mil correction work).

Those numbers are just kind of weird. On the other hand, if you properly zero'd your scope at 100 and those are accurate numbers for come ups at the actual distances you shot, I'd say you have a scope issue.

Having a chrono isn't going to help you with that kind of weird numbers. What kind of scope?

 

[winxp_man]

Re: Help calculating velocity

I pm'ed you some info for the 155 Scenar rounds that can maybe help you.

 

[ZLBubba]

Re: Help calculating velocity

Thanks for the PMs and assistance. I need to break down and get a chrono...

 

[LR-WSM]

Re: Help calculating velocity

ZL, what is the elevation above sea level at Meade range?

If you know the average Baro press, and humidity durring the hot parts of the summer that would be helpful as well.

 

[herr.baer]

Re: Help calculating velocity

I am in MD and have a chrono if you want to try and hook up to run some shots over it.

 

[ZLBubba]

Re: Help calculating velocity

I think the elevation is about 300 ft., but no idea what the baro was that day. I just remember laying on the 600yd line with sweat pouring down my face.

Thanks for offer, HB. Where do you usually shoot? I'm still looking for a good range that I can join.

 

[herr.baer]

Re: Help calculating velocity

PM sent