Downrange Chrono vs Computer generated velocities

Ian M · #1 10-14-2002, 06:03 PM

Here is an interesting list comparing my recent downrange Oehler velocities with the info from the latest Barnes reloading manual.
.308 Win. 45.5/Varget 26" Mike Rock Barrel
Yds Barnes Chrono'd
Mzl 2600 2608
100 2412 2428
200 2233 2209
300 2063 2050
400 1901 1919
500 1748 1763

The Barnes book provides a pretty good indication of downrange velocity if you don't have a chronograph and go to the bother of shooting through it downrange.

Len Backus · #2 10-14-2002, 07:27 PM

Ian

I think somewhere I got the idea that BC's actually vary depending on the stability of the bullet as it leaves the tip of the barrel. Therefor, a certain bullet design may exhibit different BC's in different rifles or with different load parameters in the same rifle. Have you any thoughts on this?

Ian M · #3 10-14-2002, 09:22 PM

Len,
Velly intelesting... but I must admit to being a trigger-puller first and foremost and haven't got a clue about the theoretical stuff. That is why I hang out at your site, hopin' to learn some of that magic, eh! (a little Canadian content there)

Will leave the Ballistic Co-efficient stuff to the folks who enjoy or need it. I just want to make first shot hits, clang lots of steel and enjoy a bunch of shooting and hunting while we still can.

For some dumb reason I distrust the tables and computer generated figures. I prefer to shoot actual drops and get actual velocities. Sure like to have actual drop figures and charts for my hunting rifles.

Len Backus · #4 10-14-2002, 10:13 PM

I agree. I always rely on my own field-generated drop tables. I do however, rely on the "official" BC for guessing at wind drift.

Jon A · #5 10-14-2002, 11:35 PM

Great info, Ian!

What elevation are you at? What was the temp that day? We "BC freaks" need to know the details....

[img]images/icons/grin.gif[/img]

Ian M · #6 10-15-2002, 09:00 AM

We are at 1890 feet above sea level and the temp was in the mid 40's.

Load was .308 Win., 168 Barnes XLC, BC is .476 according to Barnes manual, 45.5 Varget in a BHA match case, Win. primer, O.L. was 2.83", 26" Mike Rock barrel.

CAM · #7 10-15-2002, 09:40 AM

Very Very Interesting. I understand most of the BC stuff with the standard being. Sea level, temp 59 deg, BP 29.53, RH 78%. My question is this. The listed muzzle velocity will be the same at sea level as at 10,000 ft.? I do not have a chono at this time (on the wish list) so do I use the listed muzzle velocity and correct everything with the MAGIC B.C.
Keep up the good info and good luck to every one hunting. [img]images/icons/smile.gif[/img]