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Good Evening, 

Thinking about having a 300 Blackout built , 

not sure what barrel twist I need 1-7 or 1-8 , I what to shot it subsonic so maybe going to use heavy 200 grn Bullets ,

any advice from members using this calibre very welcomed.

thanks in advance.

steve.

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Thanks Andrew,

that’s the barrel twist I was considering after doing a bit more 

research into calibre it seems the way to go, just wanted someone that uses a blackout to confirm that for me thanks for you help.

 

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I have a suppressed (a Wildcat Evolution) Remington Model 700 SPS Tactical AAC-SD in 300 AAC Blackout, its 5R barrel has a twist rate of 1:7".

I normally use 165 grain H&N round nose copper-plated, plastic coated bullets loaded to subsonic velocity for plinking, but they are hard to get now.

When fired from the suppressed rifle they make 'very' little noise. The firing report is more akin to an air-rifle than a firearm. The main noise heard is the bullet's impact with the target.

I have a few other bullets to develop loads for, these can be seen in the attached image.

Left is an NOE '311-232-FN PB AZ1' 235 grain plain-based cast lead bullet. The middle is a custom 220 grain ball-tip subsonic expander produced by Pete Watson of MME for me. The right an NOE '311-232-FN GC AZ1' 236 grain gas-checked cast lead bullet. The two lead bullets were cast and sized (to 0.309") by me.

When they finally arrive, I've also got a job lot of 240 grain Sierra Match Kings to develop a load for too.

20220117_105050.jpg

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1 hour ago, banus02 said:

sorry if off topic but could the mme bullet be used subsonic in a 308 win rifle?

 As far as I know it's 308 cartridge agnostic, though I'd imagine some smaller cartridges (30 Carbine, etc.) would have a problem using it 😄 I guess it's all down to if your rifle has a fast enough twist rate?

The MME 220 gr BT bullet is about 1.414" (35.92 mm) long. So at subsonic speeds (lets say 1,070 fps), to be gyroscopically stable it will need a twist rate of about 1:11". Obviously that's a very crude estimation, but probably not too far off.

When I enquired about heavy-weight 308 BT bullets, Pete Watson stated in an email that he could make any weight up to 250'ish grains.

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5 minutes ago, banus02 said:

good evening blueboy 69, i have a ruger precision rifle with a 1 in 10 twist .so this should be ok ?

It would seem likely that it would be stable. The specs for the MME 220 gr BT bullets are:

Overall Length: ≈1.414 inches (≈35.92 mm)
Plastic Tip Length: 0.057 inches (≈1.44 mm)
Weight: ≈220 grains (14.26 grams)

You can use those details to plug into the various online stability calculators to do your own calculations.

I don't have any ballistic drag data for it, but when I test some loads, I'll use the Labradar to get this information.

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On 1/15/2022 at 12:08 AM, 1sakonut said:

Thanks Andrew,

that’s the barrel twist I was considering after doing a bit more 

research into calibre it seems the way to go, just wanted someone that uses a blackout to confirm that for me thanks for you help.

 

 I wasn't 100% certain but I checked. That CZ is a 1:7 as well. You can't go too far wrong with that twist. ~Andrew

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