.30-06 from 20" Barrel and .308 from 18" Barrel

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Wool Jacket

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Well, my quest for the ultimate truck and saddle bolt gun has brought me to two Rugers, the .308 Ruger Scout (18.7" model) and the Ruger Guide gun in .30-06.
There are things I like about both rifles. For instance, the Scout already has a peep sight and it's somewhat shorter and lighter; but, I prefer the Guide Gun's hinged floorplate and it doesn't have a ridiculous rail on the barrel that will leave empty screw holes when I take it off.
But one thing I don't know is how either of these cartridges perform from these barrels lengths. So, can anyone tell me how the muzzle blast of a .30-06 from a 20" barrel compares to a .308 from an 18" barrel?
Also, and I know I'm splitting hairs here, but does anyone have an idea about the velocity differences these two setups would show using factory ammunition?
 
I just looked at the weights and you know you're comparing 7.3 pounds to 8.12. And one inch of length depending on if you use a recoil pad or not.
 
As a rule you will lose around 30fps for each inch of barrel you shorten. Most factory loads are clocked from 24" barrels. Remove 4" and you lose around 120fps. Remove 6" and you lose around 180fps. As for the muzzle blast there is only one way to check that out. Go shoot them.

From what I have read a 30-30 loses about 17fps for each inch of barrel removed. The only way to know for a certainty is to shoot over a chronograph.
 
I've found that 15-25fps/inch of barrel to be pretty accurate with 308. With 30-06 around 20-30fps/inch is more accurate. The 30-06 will lose more speed as it is shortened, but since it starts with more it'll still end up faster than a 308 if both have equal length barrels.

But this only applies when you start with a long barrel and shorten the same barrel. When you compare 2 different barrels all bets are off. Even from the same manufacturer two different barrels of equal length will rarely shoot ammo to the same speed. Somewhere around 25-50 fps is pretty normal and in a few rare cases I've seen as much as 130 fps.

I've seen 20" 30-06 and 308 rifles shoot faster than another 22" gun, and I've seen some shoot 150 fps slower than a 22" gun.

I have owned 20" 30-06's in the past and currently own an 18" 308. The muzzle blast from the 308 isn't noticeably different than my 22" guns. I would notice a difference with the 30-06, but didn't think it objectionable.
 
As near as I can tell after a bunch of years of messing with the '06 and a few with the .308, when you get down to short barrels, the .308 is at least equal to the '06. That's with the common 150-grain factory loadings.

As I understand it, the .308 was among the first of the computer-aided designs, specifically for barrels around 18" to 20". The '06 is well known to do best for muzzle velocity at around 24" to 26".

When the .308 first came out, I read that the factory load was to 55,000 psi. At that time, factory loadings for the '06 were around 50,000 psi. I guess that's part of the 'why" of the equality.
 
Muzzle flash from a .30-06 from a 20" barrel compared to a .308 from an 18" barrel will be about the same. Gigantic ball of flame.
With like bullet weights and barrel lengths, the '06 runs about 100FPS faster.
"...15-25 fps/inch of barrel..." Depending on who you ask. There was a gun rag article long ago the proved it was 100 FPS per inch. Forget who wrote it or which gun rag.
"...308 was among the first of the computer-aided designs..." Not a chance. Mainframes(nothing else existed) in 1952 didn't have that capability. The .308 is just a modified .300 Savage anyway. And it was designed for a 22" barrel.
 
Wool Jacket, l shoot a 21" brl. on my 308 , powder burning rates will change muzzle flash & velocity. From 20 - 26" barrels a 20" barrel will do the same if not better out to 600 yards. Shorter barrels are more ridget less wipe, more accurate then the 26" with the right powder & bullet , that's just my O.
 
Muzzle Blast

As mentioned, the '06 runs at 50k and the latest 308 runs at 52k. My '06 uses 52gr of 4064 and my 308 uses 43gr of Varget. The '06 muzzle blast, in a 24" barrel, is stout. The 308 muzzle blast, in an 18" barrel is not bad at all. When I first started loading the 308 in my 788, I was using 50gr of W748. The blast would light up the night. Remember, the '06 was designed around a 24" barrel in the Springfield and Garand. The 308 was designed around the 22" barrel of the M14. I would get the Scout because it will be handier and more efficient, particularly if you reload.
 
T.O.Heir
Muzzle flash from a .30-06 from a 20" barrel compared to a .308 from an 18" barrel will be about the same. Gigantic ball of flame
Click to expand...

I was going to mention this also. I have a 30-06 with a 22" barrel. Through my scope, I see lots of orange and little else when I pull the trigger. If flash and boom isn't something you adore, a 30-06 with a 20" barrel might just be a non-starter for that reason alone.
 
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