.308 ballistics in 16" & 20" barrel


February 3, 2005, 12:51 AM
Anyone have any idea what the max lethality range difference would be in the two? What's in mind? Bushmaster .308 in 16 or 20 inch length

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February 3, 2005, 09:41 AM
Lethality range for what? A Texas whitetail, or an elephant? Seems to me they have different lethality ranges. I guess my question is...how are you defining lethality range?

February 3, 2005, 09:51 AM
so I guess I mean "Human size Zombies". So what's the max range I can expect to drop a zombie?

February 3, 2005, 10:08 AM
The rule of thumb is to reduce muzzle velocity by ~100fps/1" bbl length that you cut off (if I recall correctly). Assuming a 150gr. bullet with a BC of .314, fired from a 24"bbl...MV = ~ 2820fps for an average factory loading. Reducing that with the rule of thumb gives you roughly 2420fps and 2020fps for 20" and 16" respectively. Assuming you want around 450 ft-lbs of energy for your zombie (I don't know how much is actually appropriate), I would estimate around 800 yds for the 20" and 500yds for the 16". YMMV

February 3, 2005, 10:34 AM
Um, I believe the figure is 50fps/inch

February 3, 2005, 10:42 AM
Um, I believe the figure is 50fps/inch

OK, then adjust the numbers accordingly and figure you can punch a little further out. I couln't remember offhand the rule.

February 3, 2005, 10:53 AM
Appreciate it, this gives me a good idea about what I want.

February 3, 2005, 11:08 AM
I'm envious of the gun, regardless of bbl length!

February 3, 2005, 12:04 PM
My gunsmiths do some work on Remington 700 rifles and cut the barrels down to 16". They are a really sweet handling .308 and are apparently very popular with LE agencies and the military that operate in urban areas. Check around, its a great little gun.


Dave P
February 3, 2005, 12:26 PM
The remingotn LTR has a 20" bbl. I think my velocities are around 2500 fps. In my mind that makes it lethal for at least 600 yrds (but then I only punch paper!).


Southern Raider
February 3, 2005, 03:28 PM
My personal chrono test shows about 170fps drop in going from a 22" M1A to a 16" AR10. This same drop happens at about 75yds down range from the M1A. You really don't give up a lot in 308 with the short barrel.

However, muzzle blast and flash will be enhanced, and the burn will start to become erratic. This will manifest itself as a slightly larger muzzle velocity spread.

Dave R
February 3, 2005, 03:52 PM
I saw something similar to Southern Raider when I chonographed .308 surplus (Portugese FNM) from a 22" .308 Remington 700 vs. an 18"(?) CETME. I got about 2750 from the Rem700 and about 2550 from the CETME.

What does that mean in lethality? Someone with ballistics software may be able to quantify that for you. My gut feel is "not a whole lot". Maybe out a 500 yards+ it would make a difference.

February 3, 2005, 11:15 PM
16" vs 20" ? Not a whole lot.

Now, 16" vs 24", well, a little.

16" should be plenty good to around 5-600yds or so.

Close in, a .223 is actually MORE lethal than FMJ .308 :D

February 3, 2005, 11:37 PM
Every rifle and every load is different. I've seen 308s lose 75fps per inch and I've seen them lose 40fps per inch UNTIL you get below 18" and then the drop starts to be very dramatic. You simply can't get enough powder burnt to develop any decent velocity below 18".

I like bolt gun barrels at 24" you get the most out of velocity, it's not as hard on the ears and nowhere near the flash as a shorty. The only advantage of the short barrel rifle is in a very confined space.

20" out of an AR10 would be my minimum. else why bother? stay with the AR15... it's a much better weapon at short range/confined spaces anyway.

February 4, 2005, 03:34 PM
The rule of thumb for any gun and any cartridge is 50fps for each inch of barrel. When I looked into this last year for a .308 semi-auto, the number seems closer to 30fps. After some extensive number crunching, I realized that a 16" .308 COULD, with the right load, reach out to 800 yards (825 if I remember correctly) without going subsonic, which is important if you like accuracy.

A 24" barrel will get you to 1,000 yards.

I wound up with an 18" barrel due to the gas system on the AR-10 needing to be at a certain threshold to remain consistent.

February 4, 2005, 05:07 PM
Close in, a .223 is actually MORE lethal than FMJ .308

Not west german 7.62 NATO ball, same fragmentation as 5.56 ball, just more damage done. :cool:

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