Wild Extreme Spread

[pcso112]

I have 300 Whisper with a 21 inch Hart barrel, 1 in 8 twist on a Remington 700 action. I am using a YHM 762 Phantom suppressor. I have been trying to develop an accurate load using both 220 and 240 SMK’s with no luck. The 240’s would not stabilize so I moved on to the 220’s. My ES has well over 100 fps with some of the loads (1680) and as small as 60 with others (H110). I have had lots of stringing on the target as a result. Horizontally my groupings are 1/2 inch with most loads but my wildly inconsistent velocities are stringing two to three inches vertically at 100 yards.

I have tried Reloader 7, 1680, H110 and Trail Boss. I have tried four different types of primers. I have tried both 221 cases and 223 cases. I have tried it with and without annealing the brass. I am very close to putting the 223 barrel back on the gun and calling it quits.

I loaded some sonic 168 SMK’s with H110 to around 1960 and had an ES of 6 fps and one raged hole at 100 yards.

From my reading on this site and others I have gleaned that longer barrels may not be optimal for the Whisper. Will a slower powder help? Should I have the barrel cut shorter? Any help would be greatly appreciated.

[Gpz1100]

i've been told by reliable scources the round was designed for a 12" barrel. my longest is 18" and i'm fixing to have it cut down to 16". i'd go shorter but don't want to hassle with the batfe/nfa on a sbr. i have an 11-1/2" on a pistol that will out perform the rifle a little. sorry, that's all i got.

[dksd39]

Have no experience with a long barrel as both of mine are 16" My most consistant loads come from 220 SMK with 8.5gr LilGun-- much better than my Reloaded7 loads

[amafrank]

I've seen some drastic differences in consistancy when comparing my 16.25" barrel to the 9" barrel. 2400 works great in the short barrel with an average deviation of 9fps but the same powder in the longer barrel is up around 60fps spread if I recall correctly. On the other hand benchmark worked great in the longer barrel but was way out there in the short one. Sounds like you need something slower for the long barrel. Problem is that you will end up with a good powder for consistancy but probably supersonic....The powder that works well for one is not necessarily the best for the other. I'd think that the 21" barrel is a bit much for the round too unless you intend to do a lot of supersonic shooting. In that case you will need a much slower powder. If you are doing a lot of subs than a shorter barrel would make more sense. 16" should be great.
just my opinions of course.

Frank