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Ooops, sorry oomans, we may have got that arse about tit.

Having just acquired a Kuo Mosin (Nagant) M28/76, we're interested in finding out what the true bore diameter and chamber size are. We think it is .310 and 7.62x54R but various interweb sites suggest otherwise: it could be .308 and 7.62x53.5R. If we slug the bore, surely we drive the soft lead ball from the breech to the muzzle rather than vice versa? How do we check the chamber size?

7.62x54r vs 7.62x53r, Russian 54r milsurp is .311"

Round length: 77.00 mm (54R: 77.16)
Case length: 53.50 mm (54R: 53.72)
Rim diameter: 14.40 mm (54R: 14.48)
Bullet diameter: 7.85 mm (54R: 7.92)

We'd like to blat 7.62x54R surplus through our new bangstick (the canned bangs are cheap) but we want to be sure they'll fit and be released into the wild safely...

Don't know if this helps


The Finnish commercial ammunition manufacturer Lapua does not make a difference between the 53R and 54R, but produces cartridges that will function in weapons chambered for either one.

The Russian ammunition maker Barnaul states that Russian cartridges marked 7.62×53 are the same as 7.62×54. From their web site: "Some hunters have been confused because there have been varying marking on the package, case bottom and stamps: 7.62×53: 7.62×53R: 7.62×54: 7.52×54R. This happened because the 53.72 mm case length was rounded off differently in various countries. After Russia became a member of the European Permanent Coordinated Commission, the final name - "7.62×54R" - of the cartridge was accepted.

To slug the bore drive it from muzzle to chamber.

Make sure the barrel and slug are thinly lubed, preferably with badger fat.

For an impact impression of the freebore/lead/groove/bore see this article in the library.

http://www.full-bore.co.uk/viewtopic.php?f=36&t=855

Is the Mosin choked at the muzzle? Mine appears to be right at the muzzle end.

Just a thought that if pushed all the way through you will just get the size of the choked part???!!
Or does that not really matter?

Mark

We don't know... but an expert will doubtless be along soon to enlighten us.

I don't believe they are choked at the muzzle, mine certainly aren't.

Regardless of which end of the barrel you push the slug through from it will only ever give you the smallest barrel size, however when pushing the slug through you can feel tight spots, rough areas etc. and mark where the are on the barrel.

Starting from the muzzle is just easier than pushing it into the freebore and then the lands, you get more of an exact start when you seat the slug in the muzzle whereas the freebore are is more progressive usually.

Best I can offer so you will have to settle with that 'till one of our experts comes along.

meles meles wrote:Ooops, sorry oomans, we may have got that arse about tit.

Having just acquired a Kuo Mosin (Nagant) M28/76, we're interested in finding out what the true bore diameter and chamber size are. We think it is .310 and 7.62x54R but various interweb sites suggest otherwise: it could be .308 and 7.62x53.5R. If we slug the bore, surely we drive the soft lead ball from the breech to the muzzle rather than vice versa? How do we check the chamber size?

Use candle wax to slug the bore AND get a chamber cast, make sure the bore is clean and free of oil etc.

Push a paper plug down the bore as far as you wish, pour molten wax, allow to cool and tap out from the muzzle end.

Two things to be careful of, don't get wax into the locking lug recesses etc, as it is a PITA to get out and it will prevent you tapping the slug out. and be GENTLE when you measure the slug, remember it is wax.

ukrifleman.