Advice on Mosin caliber conversion

[bbguns44]

I am thinking of making a chamber insert for a Mosin to allow
firing 7.62 x 25 ammo. Single shot mode only. I know the x25
bullet is .308 & the Mosin barrel is .311.

I want to be able to just load one 7.62 x25 cartridge at a time
into my Mosin & shoot it.

Anything I need to watch out for or think about ?

[JeffM]

If you build one and it works, make one for me!

[AJAX22]

I've been thinking about doing the same thing.

I've saved up some pieces of .30 cal barrel to use as a blank to turn into the shape of 7.62x54R cartridges.

I haven't come across a proper 7.62x25 chamber ream yet though (I haven't been looking very hard)

I think a 91/30 barrel would really be quite efficient.

[M. Sage]

Anything I need to watch out for or think about ?

Seems like you'd need more than a chamber insert. A 7.62x25 base is a lot smaller than X54R... Or am I missing something there?

[AJAX22]

The chamber insert is not a permenant fixture in the gun M. Sage


It ejects like a spent 7.62x54 casing when you work the bolt

[gunrun45]

I thought the 7.62x25 was a rimless design?

[762cavalier]

It is. See Ajax post just above yours. make a chamber insert in the shape of a x54 cartridge with a smaller chamber at the base of the insert that will hold x25 cases. insert ejects when you work the bolt. You would need several inserts to load a magazine, but it would be a great way to use the little x25 cartridges in Mosin.

[M. Sage]

The chamber insert is not a permenant fixture in the gun M. Sage


It ejects like a spent 7.62x54 casing when you work the bolt

Ah, I gotcha. I was thinking along the lines of the chamber inserts that the Navy rifle team used to convert Garands to .308 years ago.

[bbguns44]

It has also been suggested that a quick experiment with putting the
powder + bullet from a x25 into a 54R case will allow quick checking
of the performance without going to the trouble of making an insert.
Sounds like a good idea to me. If the x25 shoots well at 100 yds in
my Mosin, then it'd be worth making the insert. I was actually thinking
of a non-ejecting insert. Need to modify the ejector a little & maybe a
bolt head insert to reduce the diameter.

[762cavalier]

I'm not sure if just transferring the powder and bullet into a 7.62x54 case would work all that well nor would it give you the same performance,as there is a lot more volume in the x54 case, which would translate into much lower pressure. It may even end up sticking a bullet in the barrel, especially a 91/30

[sloguy]

i have a 30-06 to 7.62x39 adapter. but my 30-06 is just too much fun and so accurate that i havent bothered installing it. its a semi-permanent adapter tho.

i also have a 30-06 to 30 carbine adapter. that one is meant to be removed after each shot and is not semi permanent like the other adapter. it just ejects like a regular empty brass.

the 30 carbine adapter seems to be accurate enough. and far quieter than 30-06. the longer barrel makes a huge difference in sound.

anyway, if the case heads are different enough then it might be easy to make a adapter that ejects.

[sloguy]

I'm not sure if just transferring the powder and bullet into a 7.62x54 case would work all that well nor would it give you the same performance,as there is a lot more volume in the x54 case, which would translate into much lower pressure. It may even end up sticking a bullet in the barrel, especially a 91/30

or........ ignite it all at once and cause a pressure spike?

[762cavalier]

yup, forgot about that possibility.

[bbguns44]

"translate into much lower pressure"
It was also suggested that some fluff be stuffed into the case to insure
the powder is close to the primer. There are a number of unknowns in
this experiment. But cheap ammo in cheap gun would be very appealing
if it shoots like a 9mm rifle.

[sloguy]

how hard would it be to make a chamber ream?

could i use empty brass and coat them with an abrasive and lap out a chamber that way?