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Posted: 11/28/2007 10:46:08 AM EDT
[Last Edit: 12/1/2007 10:44:37 AM EDT by snapcap]
Hi!

Want to build an Upper in 300/221 (300 Whisper).
I am waiting for my paperwork to go through that allows me to own silencers.
Planning to run a silencer on this Upper.

Would like to make this a compact and handy setup.
Basicly I would like to have a SBR-Upper, am undecided about the barrel length.
Minimum 10 3/4" Maximum 14"
Have decided to go with a 11 1/2" barrel

Will be using a barrel with a 1-10 twist.
I am a little confused about the pros and cons of 1/8 vs. 1/10 twist.
Understand that 1/8 is best for heavy bullets at subsonic.
But will it also stabilze lighter bullets(180/150gr) at supersonic speeds?


Would really appreciate some input on barrel length vs. accuarcy.

If someone would like share some pics, please feel free to post.

Thanks for the info
Link Posted: 11/28/2007 11:45:35 AM EDT
From what I can gather, you will probably want at least a 1/8" twist to stabilize the heavier bullets at subsonic speeds.

Quarterbore
Link Posted: 11/28/2007 4:38:38 PM EDT
For the length barrel you are looking at and for use with a suppressor you definitely want at least as fast a twist as 1:8 or even 1:7 for subsonic use. Accuracy can be quite good but you will experience more bullet drop due to loss of velocity from shorter barrels. For that length you will also want it ported in the pistol position for reliable functioning.
Link Posted: 11/28/2007 6:57:50 PM EDT
[Last Edit: 11/28/2007 7:01:17 PM EDT by rrbgeb]
Couple of thoughts.

Your range of bbl lengths will burn most pistol powders completely. If going to the expense to SBR go short (and run the pistol port location). Might consider an SSK style adjustable port that you could turn off if desired. Would not think velocity difference would be a worry nor would accuracy. You have plenty of case capacity for most powders. Assumption is you will reload.

Your twist is the minimum. Like others have stated 1:8 or faster recommend especially with a can and heavy subsonic.

Enjoy. Its a great caliber.
Link Posted: 11/28/2007 7:16:50 PM EDT
[Last Edit: 11/28/2007 7:17:58 PM EDT by 320pf]
If you want to get any accuracy with the long heavy bullets (ie 200-240 gr BT) you will need to go with a 1:7 to 1:8 twist. With a 1:10 twist the maximum bullet weight that will work with subsonic loads is about 180 to 190 gr.

You will also want the gas port in the pistol position. I have two 16-inch AR in 300-221 fireball (a.k.a. 300 whisper). One is a Noveske 1:7.5 and the other is a Oympic 1:8. The gas ports are in the pistol position. I can shot both sub sonic and supper sonic with these barrels. I would recommend either of these barrel makers.

320pf
Link Posted: 11/28/2007 9:05:23 PM EDT
Just to make sure that I am understanding this correctly.

Went and read the information on Qaurterbores Site before I posted my thread.

- Carbine lenth barrel with the gasport at the pistol position
- 1-10 Twist max bullet weight subsonic 190 gr. (thought I could fudge here a little bit)
- 1-7.5 or 1-8 is better for subsonic use with heavier bullets

Or is it possible to use 1-10 with a heavier bullet at subsonic if I work out a good relaod? Will be using it mainly to hunt wild pigs. Heavier is better in these cases.

I am making the barrel myself and happen to have 1-10 barrel available. Am on a budget.

Thanks for the input, please keep the information coming.
Link Posted: 11/28/2007 9:13:27 PM EDT
You might get away with stabilizing a slightly heavier bullet if you load a protected point style bullet rather than a heavy BTHP.

David
Link Posted: 12/1/2007 10:54:50 AM EDT
Any issues with red dots or scopes due to recoil?
Will probaly go for an EO-Tech.
Link Posted: 12/1/2007 3:05:23 PM EDT

Originally Posted By snapcap:
Any issues with red dots or scopes due to recoil?
Will probaly go for an EO-Tech.


No. The recoil with the 300-221 fireball in not that bad

320pf
Link Posted: 12/1/2007 3:33:19 PM EDT
[Last Edit: 12/1/2007 3:35:35 PM EDT by rrbgeb]
Snapcap, if you have 1:10 bbl blank and you are making this bbl then just understand the potential limitations to effectively stabilize the over 190 gr. bullets which could result in a baffle strike. I would caution against trying to fudge with a subsonic reload in a short bbl.

Currently running a 1:6.5 and have had 1:8 that both stabilized 125 gr. on up just fine. Supersonic or subsonic.

Recoil is non-existent.
Link Posted: 12/2/2007 3:44:03 AM EDT
Ok, some times I am as thick as a brick, but I think I am coming to grips with the information.

Thanks.

Maybe going with a 9mm silencer would be a good idea, that way baffle strike might not be so likley.

Glad to hear that recoil is not an issue, because I am such a gentle flower!
Link Posted: 12/2/2007 4:15:05 PM EDT
[Last Edit: 12/2/2007 4:21:02 PM EDT by Manic]
I've stabilized bullets at 220 grains with a 16", 10 twist ,AR whisper, without issue. You will need an 8 twist to stabilize 240 SMK's and 250 Hawks in a barrel 12" or longer. A tighter twist than 8 will allow you to use a shorter barrel in the case of an SBR or pistol.
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