300 whisper barrel length

[300whisper_newbie]

gt3499a Wrote :

does anyone know what the optimum barrel length would be for the 300 whisper cartridge? I have read that ssk has done versions as short as 10". this seems good to me, but I dont know if it would be long enough to stabilize the heavy bullets?

I would like to hear from anyone who has a sbr in this caliber or 308. would 12 or 14 inches make it that much better?

Dan

[300whisper_newbie]

QuarterBore Wrote :

From what I have read the 10-inch barrels with the 1:8 twist will be fine with the heavy subsonic loads. If I ever get a pistol scope on my AR-15 pistol I could advise how well she works as my 300/221 AR-15 pistol has a 10.5-inch 1:8 Douglass barrel

http://quarterbore.com/ar15m16/postbanar15pistol.htm

I am curious why you want oppinions from guys with 308s as you can not compare the 300 Whisper to the 308.

[300whisper_newbie]

gt3499a Wrote :

thank you for your response, quarterbore. the reason that I would like to hear from someone with a 308 is that I have not ruled out buying a rifle in 308 and shooting subsonic ammo which is almost identical to 300 whisper, right?

preferable if it was a semi 308, I would have an adjustable gas valve to turn off while shooting the subsonic.....have you seen an adjustable gas system that could be turned by hand? looked like the one in the picture from ssk would have to have a wrench?

Dan

[300whisper_newbie]

QuarterBore Wrote :

I am not familiar with subsonic ammo for the 308 although I have heard that it exists. For what it is worth, I doubt you will ever get 308 Subsonic ammo that will function in any semiauto and I am very sure that subsonic loads will be very expensive. Reloading a larger case line a 308 to subsonic velocity is EXTREMELY DANGEROUS and should not be attempted unless you don't like having an intact head! Remember that gunpowder burns at a consistant rate when packed but a little powder in a large case can and will EXPLODE.

JD Jones and SSK really got things right with the 300 Whisper and I would strongly suggest that you look at the 300 Whisper over any other subsonic 30-cal cartridge. If you want to shoot a subsonic load out of an AR-10. you may do very well to look at the 308-based 338 Whisper which SSK sells. This is an upper I may consider for my own AR-10 in the future but right now I have all the projects I can afford to consider.

Read this page from the website here for an example of what can happen if you mess with that which should not be messed with... and this was an accident!!!

http://quarterbore.com/ar15m16/ar15kaboom.html

[300whisper_newbie]

PassGas55 Wrote :

One problem you will run into is that the 220 or 240 grain bullet at subsonic may tumble because of the typical twist out the 308. In fact I think that the suppresor manufactors do not recomend subsonic loads out the 308. They will not warrenty baffel strikes.

[300whisper_newbie]

JF Wrote :

I have a .308 TC Encore barrel in a 1:8 twist. It shoots very good and accurate full power loads with 165 and 180gr bullets. As far as subsonic loads in it, it easily shoots one inch (and sometimes less) 100 yard groups with 200 and 220gr bullets.

It takes some patience to figure out bullet drop when you switch back and forth between subsonic and supersonic but once you know, it is very easy to hit the bullseye. I sight it in for supesonic loads and then make scope adjustments for one subsonic load. I cheat sheet taped to the stock helps me remember.

There are several powders that are suitable for subsonics loads in a 308. I prefer XMP5744 since it is designed for low charges in rifle cartridges. It gives me very consistant velocities. Police departments use 2400 for their subsonic loads. I believe that Black Hills ammo also sells sub 308 loads.

[300whisper_newbie]

Dasher Wrote :

7.62x39 is another option for accurate subsonic shooting.

The case is closer to the 300 Whisper in capacity, as compared to the .308. It will run 240gn Sierra's and the 8" twist barrels are common. Plus the chamber is very common so reamers are easy to find.

Accuracy wise .... we will see, A friend of mine has just picked one up, so we are planning to compare it to the 300 Whisper.

7.62x39 based on Rem788 action with 16" MAB 8" twist barrel, Reflex suppressor.

vs

300 Whisper, Built on CZ527 Kevlar Varmint, 18" Shilen Barrel, Full length PES Suppressor. This is as it was, currently has extended Picatinny rail fitted with IOR 2.5-10x41 Ill 1st FP scopy and IOR Tactical QD rings.



I havent had much chance to test and play with the 300 Whisper, but initial indications are very good. The barrel is long, but the expectation is to test and chart the performance then shorten the barrel in stages down to the theoretical ideal for Supersonic and subsonic of 14"

Note: the suppressor is designed to fit all the way back to the receiver.

[300whisper_newbie]

JF Wrote :

I love the 300 Whisper. But you may want to decide what you intend to use it for before you buy. I was after a dual purpose carbine. I got a 16 inch Contender barrel (I love single shots) in 300W. I believe it to be the king of subsonic 30 caliber cartridges when you get it in a 1:8 twist. It also is pretty decent at its supersonic loadings.

If you are wanting more top end speed in addition to the sub loads, the 7.62x39 (as mentioned in the previous post), the 30BR or even the 308 is a possibility. All of them have their + and -. It just depends on what you want to use it for most of the time. I reload all of my ammo and cronograph the different loads to the speeds I want.

I won't be getting rid of my 300Whisper Contender or my 308 fast twist Encore barrel ever. I'm heading down to Texas next week to see what kind of exotic game I can take with my 1:8 twist TC Encore 308. There are some feral goats on the ranch I will be hunting that I plan to help cull with my subsonic 308 loads if the goats do their part. But I'll keep it loaded with 165gr supersonic loads most of the time.

[300whisper_newbie]

Dasher Wrote :

Hi JF

How have you found the 30BR in comparison to the 300 Whisper? Have you seen or tried the 338BR?

I am looking to build up a 338Whisper, a JDJ 338 Whisper Shilen Barrel and dies, brass came up at a good price when the local JDJ agent had to sell up. So that is the next project, previously I'd been looking at a 30BR or 338BR, but I can find very little on these as subsonic configs.
The 338 Whis is a leap of faith also, as I havent seen a lot of data on them, but assuming it performs as well as the 300 Whisper subsonicly then it should be good.

[300whisper_newbie]

JF Wrote :

The 30BR is similar to the 308x1.5. It is a 7mmBR necked up to 30 caliber. They use them often at bench rest matches with great results.

I almost bought a 30BR 1:8 twist barrel for my Encore. But before doing that, I decided I would take out my 308 bolt gun (1:10 twist) and see how it liked subsonic bullets. I was able to get subsonic load to about the 200gr bullets before they started to flop around on the way to the target. However, I was able to get pretty consistant velocities and thus passed on the 30BR barrel in favor of the 1:8 twist 308 barrel.

My 1:8 twist 308 holds its own against my 300Whisper barrel with heavy 220gr subsonic loads. They both shoot one inch groups at 100 yards. But my 308 allows me to shoot 165gr bullets to 2700fps. This dual purpose functionality is what I was after and was very pleased.

If I was brand new to reloading, didn't have a chronograph or only wanted to shoot heavy sub bullets, I would stick with the 300Whisper. It is a great cartridge and I do not intend to put it down.