300 whisper barrel

[m21black]

16.25" is the perfect barrel length for a 300 Whisper with or without a can and anything longer is a waste. With magnum rifles I understand a longer barrel but even a 308 is optimized around 18 inches. Long barrels are great with match rifles with open sites where you are extending your site radius.

Even if a 16" rifle looked fun why would you knock it if it worked better?Personally I like the look of a short rifle and even like the way it handles even better.

[320pf]

Last year I had the same question when I was researching the 300 whisper for my first wildcat project. I had Randall at AR15 Barrels.com run some QUICKLOAD calculations for me and my conclusions are mostly in agreement with m21black. You might get 25 to 35 fps more velocity for every in barrel added with the lighter bullets using the slower burning powders like Accurate 1680 going with a barrel length of 18 to 20 in. But you can pretty much match those velocities using the slightly faster powders like Win 296 or H110. The QUICKLOAD data indicate that Winchester 296 will generally give you the highest velocities for all bullet weights. I know H110 and Win 2965 are supposed to be the same but they are not. My reloading data also show that Win 296 yields higher velocities and lower pressure indicators (see discussion below).

I have also had pretty good results with Hodgdon Lil'Gun as far as high velocities and lower pressure indicators. But Win 296 produces better groups in my gun than Lil'Gun.

Randal ran these QUICKLOAD models using a 16 barrel for the following bullets and powders:

bullets
147 gr winchester FMJBT,
150 gr Sierra SBT GK,
155 gr Sierra HPBT PALMA MK,
165 gr Speer SPBT,

powders
Win 296
H110
Accurate XMR5744
Accurate 1680
Aliant Reloader-7

The run data indicate that all of these powders are 96-100% combusted in a 16 in barrel with the exception of Accurate 1680 with generally ran about 92-93% combusted. The p_muzzle for all the loads was down to about 5000-5500 psi. Win 296 consistently had the highest p_muzzle, indicating that the powder was giving the bullet the most push of the examined powders.

Randall also ran QUICKLOAD set for an 18 in barrel pushing 180 gr Norma Silverbl with the same powders and a few more. The results are pretty much the same. The QUICKLOAD indicate that the velocities from a 16 in. barrel are about 20-30 fps slower than from an 18 in. barrel. The calculated p_muzzle for the loads was down to about 3000-4000 psi in the 18 in barrel. This is a big drop (~2000 psi) compared to the p_muzzle data from the 16 in barrel. These results suggest that in a barrel length much longer than about 18-20 in. the bullet will start slowing down in the barrel because the gas pressure in dropping off and the friction of the bullet moving through the barrel is becoming greater than the push of the powder gases.



Note: the 180 gr loads results have been varified using 180 gr Sierra SBT GK.

See my loads listed on:

http://reloadersnest.com/frontpage.asp?CaliberID=135)

[m21black]

So it sounds like somewhere between 16-18" is the optinum barrel length for the 300 Whisper, I buy that. I still like the shorter barrel for suppressor use and the "ungainly" 24" barrel on a 300 Whisper is a "wasted effort".
My brother was actually speaking to Mike Rock about optinum barrel lengths for different cartridges, I'm a shooter with an engineering background not a ballistitian or barrelmakers but the physics that go on in a barrel are pretty amazing. Mr Rock confirms your statement about friction with to long of barrel and how it causes inaccuracy and a bunch of other negatives.

[kurtz]

I watched the debate on barrel length for the 300 whisper over the last several months before deciding on a platform, barrel length, and twist for my build ....I decided on a SSK 16" 1:8 CZ527 freebore chambered for 220gr matchkings....very happy with the performance of the rifle and the "quietness" of the SSK suppressor with sub-sonic loads......Also happy with the performance of super-sonic 125 TNT's, although the accuracy with the lighter faster 125's in the 1:8 was less than stunning.....

Well, the bug bit to build another rifle and I continued to watch the debate over shorter Vs. longer barrels, slower Vs. faster twist....I wanted to build a bench gun dedicated to super-sonic inexpensive to shoot 300 whisper loads so I put together, to play the "Devil's Advocate", a PacNor 24" 1:11 CZ527 freebore chambered for 125 TNT's just to see how it would work....

For super-sonic 125 use the PacNor 24" 1:11 will outshoot my other two SSK 16" 1:8 guns any day of the week....Once the 24" 1:11 settled in, unless I goof a pull, it will shoot an honest 1/2" at a 100yds.... I have shot several 10 round groups at 2300fps that can be covered with a penny ....

For a given load (18gr H110) the 24" 1:11 consistantly posts almost 200fps faster than the 16"1:8 bolt gun and right at 300fps faster than my 16" 1:8 AR....

Granted all of this is for super-sonic loads, the "stove pipe" does not have enough freebore to try 220 subs in, and from what I've found (somebody back me up here) the 1:8 is close to the edge of stabilization for the 220's so 1:11 is probably way out of reason, I have noticed several people building 1:7 and 1:6.5 for the 220 and 240 subs.....

Just wanting to share my $ .02

[skarke]

Great MJ crack :-)