300 blackout subsonic pistol upper

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Richbirdhunter
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300 blackout subsonic pistol upper

#1

Post by Richbirdhunter » Wed Dec 25, 2019 5:53 pm

I’m looking for a good twist rate for a 300 blackout. I’ll probably be loading a 220 grain bullet at about 1050 FPS. I’m looking for a 100 yard gun or less. I’ve read conflicting reports about 1:8 twists, bullet won’t stabilize and target keyholing
Disclaimer: Anything I state can not be applied to 100% of all situations. Sometimes it's ok to speak in general terms.

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The Annoyed Man
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Re: 300 blackout subsonic pistol upper

#2

Post by The Annoyed Man » Wed Dec 25, 2019 6:26 pm

I haven’t heard if this issue, myself. My own 10.5" barrel has a 1:8.5 twist, and it stabilizes 208 grain subsonics quite well, as it also does lighter bullets. I haven't shot any 220s yet. Other .308 diameter barrel bores I have are either 1:10, 1:11, or 1:12. But those barrel twists are for stabilizing .308 Winchester/7.62 NATO bullets at MUCH higher velocities, in longer barrels. I had originally just assumed that the typical 1:8 or thereabouts twist was aimed at stabilizing the lighter 110-125 grain bullets; but now I wonder, since .300 Blackout/Whisper was originally conceived as a suppressed cartridge of intermediate power from short barrels, if a 1:8 or 1:9 twist wasn’t chosen for stabilizing bullets in short barrels. Since .300 Blk barrels were originally pretty short (8" to 9"), maybe the twist was chosen to try and get at least 1 full turn in the barrel before the bullet exits—thereby better stabilizing the bullet.

I wonder what others have heard or experienced.
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Jago668
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Re: 300 blackout subsonic pistol upper

#3

Post by Jago668 » Wed Dec 25, 2019 7:59 pm

I've got a 10.5" that is 1/8 and it works fine for me so I don't know. Actually been thinking about selling it but because I don't shoot it, not because it doesn't work.
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Richbirdhunter
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Re: 300 blackout subsonic pistol upper

#4

Post by Richbirdhunter » Wed Dec 25, 2019 8:06 pm

Jago668 wrote:
Wed Dec 25, 2019 7:59 pm
I've got a 10.5" that is 1/8 and it works fine for me so I don't know. Actually been thinking about selling it but because I don't shoot it, not because it doesn't work.
What kind of groups are getting at 100 yards?
Disclaimer: Anything I state can not be applied to 100% of all situations. Sometimes it's ok to speak in general terms.

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Jago668
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Re: 300 blackout subsonic pistol upper

#5

Post by Jago668 » Wed Dec 25, 2019 8:21 pm

Richbirdhunter wrote:
Wed Dec 25, 2019 8:06 pm
Jago668 wrote:
Wed Dec 25, 2019 7:59 pm
I've got a 10.5" that is 1/8 and it works fine for me so I don't know. Actually been thinking about selling it but because I don't shoot it, not because it doesn't work.
What kind of groups are getting at 100 yards?
I don't know, haven't gone to a 100 yard range. But at 50 it's more accurate than I am.
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Re: 300 blackout subsonic pistol upper

#6

Post by troglodyte » Thu Dec 26, 2019 10:54 am

Over at the 300blktalk forum they seem to like the 1/7 or 1/8 for the heavier subsonics. My 7.5" is a 1/7 and works well with supers. Haven't tried subs yet since I don't have my suppressor.
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