autogun

Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons, particularly in larger calibres (12.7+mm).

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USN and 6mm ARC   Ammunition <20mm

Started 30-Oct by autogun; 1771 views.
autogun

From: autogun

30-Oct

This one seems to have slipped by me. We haven't said much about the 6mm ARC (or at least, that the forum search function can locate - just a couple of brief mentions). So I was surprised to read that the USN has purchased Barrett REC 7 rifles in this calibre, along with Hornady ammunition for them.

Does anyone know more? Is it the USN as in SOCOM who bought them? For what purpose - testing or service? And does anyone know the ballistics of the loading chosen at whatever barrel length the REC 7 has?

autogun

From: autogun

30-Oct

Thanks for these, but when I click on imgur in the hope of getting a bigger version I get a screen full of pictures and video clips about anything but ammunition...

QuintusO

From: QuintusO

30-Oct

Right-click on the image itself, open image in new tab.

I don't know why it won't embed properly all the time, it's a delphi thing.

taschoene

From: taschoene

30-Oct

autogun said:

Does anyone know more? Is it the USN as in SOCOM who bought them? For what purpose - testing or service? And does anyone know the ballistics of the loading chosen at whatever barrel length the REC 7 has?

IIRC, isn't the Navy the acquisition authority for all SOCOM small arms buys?  If so, these could be for anyone.  

EmericD

From: EmericD

30-Oct

Don't take it for 100% sure, but the bullet may be a 95 gr SOST.

MV probably around 2800 fps from a 18" barrel.

stancrist

From: stancrist

30-Oct

EmericD said:

...the bullet may be a 95 gr SOST.

Basis for that statement?

EmericD

From: EmericD

30-Oct

Really indirect bits of information...

1- One initial Hornady report on the 6 mm ARC said that an "undisclosed MoD" was waiting for rifles and 95 gr load not available to the public.

2- During 2015-2016, I was in touch with a foreign MoD that wanted to try a 6.5 mm Grendel AR-15 with a 123 gr SOST bullet, but preliminary design shown that muzzle velocity was too low for delivering the required ballistics. I recommended to reduce the bullet diameter to 6 mm, and (.243/.264)^3*123 = 95.9.

QuintusO

From: QuintusO

30-Oct

EmericD said:

Don't take it for 100% sure, but the bullet may be a 95 gr SOST. MV probably around 2800 fps from a 18" barrel.

Oh, gross. If it's untipped then that ruins a lot of the characteristics of the 6mm ARC. One of the big problems with SOST bullets when I've tried designing them is the large meplat that's required. I think the best i7 I've ever gotten with a SOST was something like 0.98. Not good.

QuintusO

From: QuintusO

30-Oct

EmericD said:

Really indirect bits of information... 1- One initial Hornady report on the 6 mm ARC said that an "undisclosed MoD" was waiting for rifles and 95 gr load not available to the public.

Really? They said "undisclosed MoD"? That implies a commonwealth or european user. The US doesn't have MoDs.

EmericD said:

2- During 2015-2016, I was in touch with a foreign MoD that wanted to try a 6.5 mm Grendel AR-15 with a 123 gr SOST bullet, but preliminary design shown that muzzle velocity was too low for delivering the required ballistics. I recommended to reduce the bullet diameter to 6 mm, and (.243/.264)^3*123 = 95.9.

I've been telling Grendel fans that it doesn't have enough muzzle velocity for years. The 6mm AR (which is very close to the ARC) has much better overall characteristics.

And like I said in the previous posts, SOSTs have serious problems with drag if they're not tipped. If you tip them, they seem to be fine so long as you get creative with the relief bands.
 

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