Narrow Groove Rifling in Persian Mauser

[Ricochet]

I've noticed that my new M98/29 Persian has very different rifling from any of my other Mausers. Its new-looking bore has four grooves that are much narrower than the lands, in about the same proportion that all the others have lands much narrower than the grooves. They look deep, too. I'm going to have to slug it and see what the dimensions are.

[Dutch4122]

Mine slugged at a perfect .323" and so far has shot very well for me with my group buy C326-175-FN sized to .325" and 17 grains of 2400. Playing with different lubes now and going to try 18 grains of 2400 soon also. But so far this "like new" bore definately likes air cooled wheel weight alloy gas checked at an average of 1725 fps.

Just gotta find the load she likes best!

[Ricochet]

A quick and dirty check with a micrometer about 1/2" down in the muzzle (which shows no visible cleaning wear) gives the interesting result of .322" across one pair of grooves, .327" across the other. I repeated the test several times with the same result. I'll have to slug it. This isn't the first time I've seen asymmetrical measurements in a Mauser or Mosin bore; it must pretty common. Probably mainly a phenomenon of cut rifling cutting in a single groove at a pass with variable tool wear and incremental shimming; I'd imagine buttons, broaches or hammering onto mandrels would have to be pretty even.

I saw somebody report recently, I think on Gunboards, that his Persian had .329" grooves.

[Char-Gar]

I may be all wet, but I would guess such a style of rifling would be very cast bulllet friendly. The narrow grooves won't displace as much metal as the wider ones and the wide lands should support the bullet nose very well.

I will find out as I have an unfired full miliatry 29/98 Persian and I bought another barreled action to make up into a Euro style sporter. It is off at the gunsmiths now having the barrel shortened and crowned to 24".

[StarMetal]

I believe my Yugo 48B has rifling like that, I'll take a look tomorrow. It was unissued and the groove came in dead on .323 also.

Joe

[Ricochet]

I believe the opposite is true about metal displacement, as we're shooting bullets sized close to groove diameter or slightly larger. The lands are what swage into the bullet and displace metal. So with a higher land-to-groove width ratio, we're sizing the bullet more.

I've heard good reports about the Persians' shooting, though, in any case. Haven't gotten to try mine yet.

[Buckshot]

.............Aren't the Persians made by Steyr, or BRNO? A real Mauser barrel should have a barrel form of narrow lands and wide grooves. The Turk "Mausers" have 4 equal width lands and grooves like the Swede "Mausers".

...........Buckshot

[Dutch4122]

.............Aren't the Persians made by Steyr, or BRNO?
...........Buckshot

Made by BRNO on contract for the Iranian Military in the late 20's. Some were made by the Iranians on Czech tooling under their supervision.

[Ricochet]

Yep. And all of the above mentioned are "Real Mausers."

[Ricochet]

Oh, but one correction. The Persian was an M98/29 model, but they were pretty much all built in the '30s. There was a batch built in the early '30s, and a batch in the late '30s. Mine was built in the year 1317, which corresponds to March 21 1938 to March 21, 1939. The Iranian built ones were all made in the 1940s, according to information posted over on Gunboards and milsurpshooter.net. They're marked accordingly, too. The Brno built ones are marked (in Farsi) on the left side of the receiver as built by the Arms Factory of Brno.

[StarMetal]

John,

Took a look at my Yugo today, it has very narrow lands and wider grooves, grooves look to be about twice as wide as a land.

Joe

[Ricochet]

Joe, that's how my M24/47 Yugo is rifled as well. And my M98/22, made by the Czechs about 16 years before the Persian. My Romanian contract Vz.24, built by the Czechs a year or so after the Persian, also has narrow lands and wide grooves. Makes me wonder if the narrow groove rifling was an option specified by Shah Reza or his representatives.

[Dutch4122]

Yep. And all of the above mentioned are "Real Mausers."

Excellent point!

[StarMetal]

Ricochet John,

I would think that type of rifling would be more conductive with a bore riding bullet. Something like the 314299 but in 8mm caliber. Not that it wouldn't shoot the other style bad, but there is alot of land area to support a bore rider.

Joe

[Ricochet]

I'm hoping that 8mm Max will work OK. It's a bore rider style, but rather fat nosed. I've just finished sizing and checking a batch. They were too hard to go through the sizer, so I stuck them back in the oven, quenched them, and sized them before they could harden up. They're at .323" now. Limited experimentation with some in unsized cases indicates that the boolits are just getting into the Persian's rifling with seating to the front of the front band, and the bolt of the Persian gives resistance to closing on those unsized cases. If that's a problem with the loaded rounds, I'll save them for the looser Turks and go to the Karabiner with the 0.1" shorter nose. I'm going to crimp these so the boolits will extract with the cartridges if they are slightly into the rifling.

[StarMetal]

John,

Now with my Yugo 48B I can load all those bullets you mentioned and none of their bases will be below the neck shoulder junction. They just touch the rifling and give a good snug bolt lockup. They all shot very well also.

Joe

[Ricochet]

You're right, Joe. My method of measurement was wrong. I've successfuly used this before in push feed rifles, but it doesn't work with CRF. I made the bullet a sliding fit in a case neck, closed the bolt, extracted it and saw to what length the bullet had been pushed in. Apparently the CRF Mauser, which has to be loaded from the magazine and sends the cartridge into the breech at an upward angle, was causing the bullet nose to encounter resistance on the side of the chamber and be pushed back in. I was also seeing scuffs on the side of the ogive that apparently weren't actually from the rifling, but that's what I thought they were from. When I measured by dropping the bullet straight in from the rear and putting a rod against it, I found it's actually stopping in the Persian at a depth that will make the Max's base just reach the bottom of the case shoulder. Won't quite make it into the neck. At the case mouth that translates into seating right at the top of the third driving band in front of the gas check with two lube grooves exposed, for contact with the rifling. That length will easily fit in the magazine, being almost 1/4" shorter than the Yugo rounds.

That also means there'd be room for 3.7 ml of powder. (About 46 grains, with 7383.) That'd be right at maximum.

3.7 ml fills it halfway up the neck, which is more than I want to compress it. 3.4 ml comes up to a hair below the bottom of the neck. The charges weigh right at 41 grains, sometimes .2-.3 less, when the dipper's struck off level with a credit card. Lee lists 41.3 grains of 4350 as the starting load with a 225 grain jacketed bullet, and I'm sure I'm in safe territory with that. (My 7383 gives nearly identical velocities to 4350 for equal charge weights in .30-06 and .22-250.)

[StarMetal]

John,

When testing cartridges for chamber fit a good idea (also from a safety aspect) is to run the bolt forward on an empty chamber/magazine and then put the safety in the halfway position, remove the bolt, and then unscrew and remove the firing pin, sear, shrouds, and safety unit. They put the bolt back in the rifle. Now you will have no firing pin spring resistance and get a good feel for what your cartridge is doing. There will only be a little extracter tension and of course that upward feed angle. I like that you can do that with a Mauser. Can on other rifle, but some are alot more difficult to dissamble that unit.

Joe

[Ricochet]

Good tip, thanks, Joe!

[Ricochet]

Last night I stayed up a little bit longer to function test the cartridges I'd loaded. Uh-oh! They won't feed from the magazine reliably in any of my Mausers. The big meplats hang up on the sharp edge of the barrel at the rear of the chamber. Some of them will feed the first two rounds from the magazine, then jam on the third. Most all of them will feed a single round loaded into the magazine, but the Persian won't even do that very reliably. And there's a bit of resistance closing the bolt of the Persian, not with any of the others. I measured the rifling origin as explained above and they're about .030" short, so I think the boolit noses are just tight in the throat of that one.

I'm going to take these out to the range with my 1903 Turk, single load and fire them, then experiment with dummy rounds to see if I can come up with a load that works out of the magazine by seating deeper. Since my earlier experiments with the sliding boolits ended up with them pushed in to about the front of the front band, I suspect that's where they're going to have to be seated to function.