Subsonic question

[olywa]

I was looking at Contender barrels on Midway and noticed that they have the 300 Whisper and 30 Carbine both listed with a 10" twist. If the 300 Whisper will stabilize a 220-240gr bullet at subsonic velocities using a 10" twist rate, shouldn't the 30 Carbine do so as well? The Whisper holds a few more grains of powder but if you are loading subsonic would that matter?

It seems like the 30 Carbine would make a pretty viable alternative as a subsonic platform in 30 caliber, with no brass-forming issues to boot. Am I missing something or would this be worth exploring?

[Grumulkin]

I've thought the same thing & I think it would work.  I think it might be worth exploring but don't have much interest in the 30 Carbine or 300 Whisper so I haven't taken the time to experiment with this.

If you tried this, you would probably want the chamber of the 30 Carbine made so you could fire the longer bullets without having them jammed in the lands; otherwise, the bullet would be so far in the case you would have very little powder capacity.

[swampthing]

I don't like being the bearer of bad news. That won't work in either barrel. As both T/C barrels {all their 30cal. barrels} have a 1-10" twist rates. That is not fast enough to stabilize the heavy 240g bullets regardless if they are sub-sonic or not. SSK industries, where the 300 whisper was developed, uses a 1-8" twist barrel for that purpose.
 Why not a 45-70 "whisper" 350-500g @1050fps?

[olywa]

I was thinking that a 10" twist would be a tad slow as well. But one of the reviews on Midway was from a guy who said it worked for him. I wonder if you could get get a 170-190gr cast spire point to fly true with that 10" twist and retain most of its zip out to 200 yards or so?

I like the idea of a straight case paired up with a cast spire point. No fuss case prep and low cost bullets. Seems like it would be a fun formula. The 45-70 is intriguing but heavier than I want to go. The key for me would be in finding an existing barrel with a twist that would work. Or one that could be re-chambered to do so. I'm too cheap to spec a custom barrel that just "might" work out.

[oneshotonekill]

I think (hope) that is a misprint on Midway's site.  The Whisper barrels are supposed to be an 8 twist not 10.  Every whisper I've had was an 8 twist (bolt guns and encore).  Unless TC decided to cut cost by using standard 30 cal 10 twist barrels for all of their applications, just cut what ever chamber you need type of deal.  If that is the case the whisper barrels would probably be useless for subsonic loads.

[dmachine]

T/C barrels are 1:10 twist, (or at least used to be), SSK barrels are 1:8 You can use the 1:10 for subsonic loads up to about 180 gr. and they work OK for the most part. The 200, 220 & 240 gr. bullets need the 1:8 twist though, they "keyhole" alot in the 1:10 barrels. If your thinking about a Whisper barrel, 300 or 338, get it from SSK. They are the ones that invented it and they know what it need's. The T/C barrels are OK for hot loads and sub loads up to 180 gr. or so, but the 300 Whisper was made to run 220 - 240 gr. pill's at 1040 fps and to do so you need the 1:8 twist. The SSK barrels are also much more accurate and the chamber seems tighter. Stick with the real deal, get the SSK barrel.

[swampthing]

I don't think that the 300whisper is a "straight wall case." They are from 221 fireball case and have a short shoulder. The 30 carbine is a straight wall case, is cheap, a bit more plentiful, as it is available from most brass makers. The down side is that the earlier, if not all, 30carbine barrels where cut with, approximately, 1-14 twist. Lighter, sub 130g or so, bullets are needed, but, this set up will allow you to step up the velocity if you ever wanted use yourself as bait for coyotes or other predators.   

[PHATINJUN]

I had a 16" encore bbl that was 1-10 twist that I never did get  the 220gr bullets to shoot well out of. Every thing 180 and down shot well though. Kurt

[olywa]

Thanks for the replies guys. I knew that the 300 Whisper wasn't a straight-wall case but what I wanted was to find a viable straight-wall case to use as a subsonic platform. Based on the replies so far, it might be worth looking into the 30 Carbine with a 10" twist as long as I stay at or below 180gr. If I can find a 160-180gr hardcast spire point, maybe I'd have all the makings for a "poor man's" Whisper. Cheap components, very little case prep, might be a lot of fun in a 14-16" barrel. I'll have to see if I can work up the ballistics out to 200 yards or so.

[Sverre A.]

30 US with 150 gr. bullet/Vihtavouri N 340/5 gr. will give you a real good subsonic load.
And in my TC barrel - good accuracy (4 cm at 50 meters)

[Pine Point]

   I had a .30 Carbine barrel 20 yrs.ago that would shoot 311299 Lyman (206 gr.)cast of ACWW about 950fps.  That was a 10" twist. It would take chickens,pigs,and turkeys down no sweat.  I figured the drop at the rams was somewhere in the neighborhood of 8'.

[Steve P]

I have both barrels in the TC.  Both are 1-10" twist.  They both shoot the RCBS 165 cast bullet real well.  Pro's and Con's to both. 

30 carbine brass is easier to find and cheaper, but you have to be a bit more finicky on the trim length.  Get too short and the firing pin on the TC will just drive whole case fwd.  You could probably tailor a load with bullet into the lands to stop this, but you have to plan this ahead of time.
300 whispers are easy to make out of 221 fireball brass.  Some folks have a hard time finding the brass.  It's out there, just keep an eye out for next Remington run of small base brass. 
30 carbine does tend to have lots of noise and is dirtier, even with subsonic loads. 
300 whisper takes a little more powder to get same velocity as the 30 carbine.
30 carbine brass could have crimped in primer.  Make sure you check before you spend the $$ on the "great deal" brass.
If you want to go higher pressure and higher velocity, 300 whisper has greater capacity and options.  30 carbine can get same velocity, but noise and flames go with it.

Lots of things to think about before getting a barrel.  For all around plinking, I like the carbine as I can load up lots of ammo with the carbide dies.  I use the Whisper in IHMSA/NRA silhouettes because out to 200 meters, for me and my barrel, it is more accurate.

Good Luck!!

Steve 

[olywa]

Thanks guys, good info. As I dig into this deeper, it is evident that none of the barrels that I can pick up economically will have a twist rate that will support the heavier pills. Subsonic seems to be a custom barrel proposition. It's shame because I think a lot more of us would play around with this if it wasn't so cost prohibitive.

[EdK]

Not a surprise on the 1-10" twist really - many manufacturers do not use the ideal twist for a given chambering so that barrel inventory is minimized. For example Remington standardized on 1-16" for 35 cal many years ago and likely because it is ideal for a 35 Rem. Then Remington goes and makes a 35 Whelen with the same twist and they have a reputation for poor accuracy with a 250gr bullet even though that weight bullet is a great match for a heavy round in the Whelen.

T/C compromises twist rates all the time in many calibers. For example 1-16" is really too fast for 454 Casull and 460 S&W but they had already standardized on it for 45 Colt/45ACP.