I have a 30-06 remington 742 carbine. The remington ballistics calculator says the 150gr core lokt should be at 2910fps. My chrony reads 2700. Does the carbine barrel make it lose 210 fps? The speeds of my reloads are all under the numbers in any of my reloading books also. So basically does my 06' with a carbine barrel turn into a .308?

You'll lose some velocity with a shorter barrel, but I'd chrono the same load in a real rifle and compare with your carbine before I worried too much about it. Ammunition companies have been known to be overly optimistic about their ammo's velocity in their advertising.

At normal hunting ranges the deer will probably never notice the difference.

quote:

Originally posted by richyb:
I have a 30-06 remington 742 carbine. The remington ballistics calculator says the 150gr core lokt should be at 2910fps. My chrony reads 2700. Does the carbine barrel make it lose 210 fps? The speeds of my reloads are all under the numbers in any of my reloading books also. So basically does my 06' with a carbine barrel turn into a .308?

Since when does factory advertised velocities coincide with reality. Dunno what your barrel length is but my 18.5" Ruger RSI in .308 pushs a hot 165 gr. handload to 2550 FPS. That same load in a 22" barreled Winchester M70 does 2610 FPS.
FWIW, the last time I chronographed factory ammo, the 175 gr. Federal brand 7x57 ammo did 2210 FPS,almost 200 FPS slower than the advertised speed. Some 180 gr. Winchester power point 30-06 ammo chronographed at 2600 FPS average, 100 FPS slower than advertised. This was from a Ruger #1 with 26" barrel. From a 22" barreled commercial FN Mauser they did 2560 FPS.
Makes me wonder if the factories are quietly downloading ammo, especially for cartridges used incaliber that were used in rifles of questionable strength? (7x57, 30-06 just to name two)
Paul B.

OK I'm not sure what barrel length Rem is using for the 2910. But taking a load ot 4350 that gave me 2925 in a 22" in QL dropping the barrel to 18.5 lowered the velocity by 130fps. I've very seldom had a factory load give the posted velocity. Plus you are bleeding of some gas to function the action.

Your 2700 is totally realistic. I might even consider it good.

Most of the time, factory advertised velocity is from a 26" pressure test barrel, under optimal conditions, and their number is right at the muzzle, not 10-15 away like it is when you measure it with a chronograph.

I don't think they flat out lie about their numbers, it's just a bit difficult to duplicate the conditions they use to get them in the real world with a real rifle.

To be honest, I wouldn't sweat it. A 150 grain .30 cal bullet at 2700 fps is pretty darn good for medium sized game animals.

thanks. I figured it was speed loss from the carbine but wasnt sure if that was too much loss or not. Guess its like the fps with compound bows. They give you the max speeds that realisticly you wont have.

my working rule of thumb
-2-3% for it being an autoloader
-25fps per inch

if 2900 is real
-2.5%
2827
-100 fps for 4 inches of barrel
2727

and that aint bad

I have done a lot of game killing with 18 to 20" 308's and some with 19 to 20" 375 H&H's.

Never noticed that they killed any less effectively, nor were they less accurate.

Ammuntion companys used to use a 30 inch test barrel.
That was decades ago but I dont know if they ever changed.

Cheers, John