Is my barrel FUBAR?

[Bolivar]

Hello all. I am running into a new to me problem with a Finnish M39

Here are the pertinent details:

Mosin Nagant Model 39
Bore Slugs to 0.313
Bullets: Hornady 174 GN RN Diameter 0.312
Brass: Graf and Sons
Powder, Reloader 15 46.6 Gn (Box max per Hornaday)
Book Velocity 2600 fps
Measured Velocity 2200-2300 fps average

All cartridges come out of chamber with powder residue and there is powder residue on bolt.

Also there is a bad smell after firing (like sulphur)

It seems to be that pressures must be low and eratic (hence low and variable velocity). Since the brass is coming out dirty and I have that smell issue, it seems like the cases are not expanding to the case walls in firing to properly seal the breech.

I think the throat (at least) is toast.

Any different ideas or confirmation of my theory?

Thanks

Information

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[Claven2]

I think you need to consider trying a different powder and get the velocity closer to book. Sooty cases usually means your pressure is too low, hence the case mouth may not be forming an adequate seal at the chamber end.

Also, you may wish to consider trying to locate some .313 bullets to try.

[irishsteve]

Sounds like its not sealing alright.Looked in my Lymans book.47 grains of reloader 15 is a max load so at 46.6 you arent shooting to light thats for sure.You might try annealing some brass to see if making it softer will allow the neck to open more,and seal.Also try a different brand case,and see if it seals.As long as your head space is good the worst case is short case life like shooting .303 in a SMLE with a large chamber.How does it shoot? Still grouping well?

[Bolivar]

No. Shoots like hell

Testing yesterday, 10 rounds ended up in 4.5 inches, neglecting one flier. Formed two distinct groups of 2 inches or under.

Groups were pretty much divided between rounds going out around 2200 fps and 2400 fps.

[Patrick Chadwick]

If you have the feeling there is nothing to lose, consider the following:

a) if you seat the bullets further in, the case will expand a bit more in those few microseconds before the bullet is clear of the neck. BUT this will also raise the pressure, so do it in steps and check for signs of excessive pressure.

b) Try deliberately bell-mouthing the case up to the point where the mouth scrapes on the chamber - just the mouth, not the whole neck. This is a trick used in BPCR shooting for ancient rifles with worn chambers where the bore will not permit oversize bullets.

c) If b) produces cleaner cases, then measure cses from different manufacturers and pick those with the thickest necks.

Patrick

[Patrick Chadwick]

PS: The bell-mouthing trick also helps to center the neck ( and thus the bullet) in an oversized chamber. If you know your bullets are a bit loose in the transition before they are properly engraved, this may really help to improve the grouping by reducing the skew of the bullets when they hit the leade.

But this is a BPCR trade secret! Don't tell anybody or they'll all want to do it!

Seriously, it is also described in a very respectable book by Haendler & Natermann on the correct use of their copper-plated bullets. I tried them out in my M1917 last week, and was positively surpised to get 5 shots in 35 mm at 100 meters, with 4 of the 5 well inside 1 MOA.

If you can get this type of bullet where you live, they are worth trying. They are copper-plated (NOT jacketed) and also have a fine plastic (?) coating that means absolutely no other lubrication of any sort is required, and there is no leading or coppering. The thin copper layer means that the bullet upsets a bit in the throat and bore sealing is good.

This makes them a good choice for oversize bores where you can't quite get the correct diameter bullet - or daren't use one, because of a tight chamber neck. So my next test will be with a Carcano, where the Hornady bullet is better than most, but still not quite right

Patrick

[Bolivar]

Patrick

Thanks for the tip. I'll ask around at my favorite gun store and see if the guys there can move me along in the direction you are pointing. The bell mouth die bit might be just the trick. Besides, I may have to resort to cast bullets. I've always wanted to but have not had a reason.

Great another way to spend time and money on milsurps

Bolivar

[Patrick Chadwick]

... is fine if you are looking for the work. But with my BPCR rifles where I HAVE to cast my own, I don't need any more of that kind of work. And if you use cast bullets in smokeless loads you are going to get involved with lubrication and gas checks. Plenty to keep you busy!

Since the plated bullets only cost 12 apiece in hundreds, I personally would not bother if you can get what you want. I have seen this type of bullet offered by a US Company, but they don't seem to have the range of Haendler & Natermann, who have a 180 gn flat-base round nose 312 bullet and published load data for the Nagant. E-mail them at HN.SPORT@natermann.de and ask if they have a US or Canadian distributor. And in case you are wondering, I have NO connection with the company, other than as a satsified user.

In the meantime, I suggest you try the bell-mouthing trick with the long flat-base round-nose .312 Hornadays.

Patrick

[Bolivar]

Patrick

Thanks again for the info. I have sent them an email to see if it possible to get their products in Canada.

I will try the bell mouth trick first anyway, after I reverify the gun with some commercial loaded ammo.

It will probably be some time before I get back to this rifle but I will try to let you know how my trials and tribulations work out.

Bolivar