MCA chamber adapter...308 to 7.62x39


November 23, 2008, 12:12 PM
I'm thinking about getting one of these for my .308 1916 Mauser..anyone used them. Seems like a good way to tame a short handy mil-surp and consolidate calibers at the same time.
If it works I may get one for my Mosin 7.62x54 as well.

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November 23, 2008, 12:21 PM
I wonder about the difference in rim size and extracting the cases. Do you have to knock out the cases with a wood dowel or cleaning rod? Just wondering.


General Geoff
November 23, 2008, 02:59 PM
7.62x39 uses slightly larger bullets (.311 inch) compared to .308 (.308 inch). Not sure if this would impact usability or not.

November 23, 2008, 04:42 PM
You notice that they sell broken shell adapetrs in a prominant place. For a reason. Not only is the rim size of the x39 smaller, as stated, the bullet is .003" larger, and this is not a good thing to shoot through your -06 bore. I don't even think that you can shoot 308 in a 30-06 with a adapter, because the .308 has less body taper, it may not go all the way in. About that i don't know.

November 23, 2008, 11:53 PM
Well, I do have experience with using chamber adapters – I really like them, and I do have a Spanish 1916 Mauser chambered in 7.62x51 that I also considered converting to 7.62x39 – BUT I passed because 7.62x39 wouldn't feed from the magazine correctly. For that rifle I load my own x51mm that are less powerful – and since the Mauser barrel slugs out at .315 – I use large Mosin-Nagant sized cast bullets.

If you don't mind loading each cartridge one by one in the Mauser – go ahead and try the adapter. They are super cheap, and your Mauser will easily handle the extra couple thousandths in bullet diameter. Have you slugged the barrel yet? If it slugs large like mine, it might be much more accurate with the larger bullets.

Adapters that are properly sized and seated, stay in place, and can save you a ton of money.

My grandson and I were shooting two rifles today with adapters. He was shooting a Czech VZ52, originally chambered in 7.62x45 and converted with adapter to 7.62x39. That rifle has had an adapter now for at least 10 years and 5K rds. Because of the low recoil, ability to rapid fire with significant power, it has been a favorite of my grandkids for years.

I was shooting an 1895 Brescia, originally chambered in 6.5 Carcano and converted with adapter to 6.5x39mm. The Brescia slugs tight – so std 6.5 mm (0.264) bullets suit it, and given the old girl is well over 100 years old, 1.5 cc of powder is more than enough stress on the old iron – and using the smaller cases saves me money on cases, and saves me the hassle of topping each load with filler.

I've also converted my Garand to 7.62x51. Worked fine. I shot it that way for about a year before converting it back to 30-06. 30-06 just seems 'right' for a Garand for me.

November 24, 2008, 07:03 AM
Thanks Jaime. Nice to hear from someone who has actualy used it. I havent sluged the barrel yet, but I'm going to. I'm gonna cast some bullets in whatever size it turns out to be. Loading one at a time isnt a big deal...I plan on buying a single shot magazine adarter for it anyway.

November 24, 2008, 10:29 AM
I picked up one of their .32 acp to .308 adaptors and am looking forward to trying it.

FWIW, from their website...

"Simply coat the the outside of the adapter with non permanent Locktite™, place a fired 7.62x39 case inside the chamber and close the bolt. After 10-12 hours, eject the 7.62x39 case and you are ready to start shooting. Inexpensive Russian ammo costs 25-50% less than any regular 308 or 30-06. A broken shell extractor will remove the adapter and return the gun to it's original caliber. If you are careful, the adapter is reusable!"

So it appears their .308 to 7.62x39 is a little different then their typical adaptor

November 24, 2008, 01:59 PM
DO be careful with those chamber adapters.

IIRC, the US Navy experimented with .30-06 to .308 adapters for some M1 Garands. Worked OK untill the adapter got pulled out with a fired shell, shooter didn't notice, and then touched off a .308 round in a now .30-06 chamber...

November 24, 2008, 06:07 PM
So it appears their .308 to 7.62x39 is a little different then their typical adaptor
how so?

.32 in a in a .308....that should be fun!

November 24, 2008, 11:43 PM
I've heard the adapter eject story many times here on THR - I think I have a better explanation of why the US Navy discontinued the experiment with adapters.

I commute about 90 miles each way to work, and I don't make much money so I use used tires. Because of the cost of having a tire guy un-mount and mount a set of tires, it doesn't make any economic sense for me to mount a set of tires that has only a couple thousand miles left on their lives. Even if the tires were free, if the labor to mount and balance a tire was $15, the tire would cost me a couple bucks per thousand miles; and I'd be scrounging up another set almost immediately.

Same way with an adapter. Putting an adapter in a Garand barrel that is 90% worn out would take as much time (actually more) for an armorer as putting a new barrel on. So if using up 10 almost worn out Garand barrels would cost 10 times the labor as putting on one new barrel, if the labor costs anything that more than justifies putting on new barrels,

Properly set, an adapter will stick like anything to a rifle chamber, but if you look at the work involved in cleaning, inspection, and checking erosion, head space, etc. It didn't make any sense for the Navy to keep cycling almost worn out barrels through the system.

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