Custom Martini rimmed blackout

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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adamwalsh0693
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Joined: Wed May 10, 2023 5:26 am

Custom Martini rimmed blackout

Post by adamwalsh0693 »

Hi all I am getting a Henry Martini made up into a rimmed 300 blackout. I have got hold of a 1/10 twist barrel that the gunsmith thinks we will be able to get work with subs. It's a 26 inch barrel also. Mainly want the rifle to work on subs not fussed about substituting for a lower grain projectile as long as it will work. As I want it to work at about 50/75m subsonic and possibly use supersonic at about 100/150m for deer. I know 1/10 isn't ideal but more looking for anyone that has run subsonic from a 1/10 twist barrel and their own personal experiences.
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dellet
Silent But Deadly
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Joined: Fri Nov 30, 2012 1:25 pm

Re: Custom Martini rimmed blackout

Post by dellet »

That should be a nice set up.

Nothing special about a 1/10 twist, it will limit you bullet choice to around 200 grains, just depends on the actual bullet length. Plenty of stability calculators out there.

The barrel length will cause more “problems” than the twist rate. There is a good chance that you will need to ADD powder to Published data. With a heavy, slow moving bullet, they can actually start losing velocity in the barrel. Just depends on the powder. Not a big deal, just be aware of possible low velocities. Use a chronograph until you get some data.

It would be good to start your charges a bit on the high side, instead of low like many do with subs, a long barrel and low velocity can lead to a stuck bullet.

I have a 24” 1/10 and favorite bullets are 208 AMax and 175 SMK. With N120 for a powder.

What are you using for brass?
357 Max or 222 rimmed?
Or standard 357 with a short neck

Good luck and keep us posted.
300 Blackout, not just for sub-sonics.
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