Martini International centerfire conversion

31 August 2003, 14:50

Does anyone know if the Martini International action is suitable for conversion to centerfire? I have a Mark I that I want to rechamber to .22 hornet.

If so, anyone have any recommendations on a gunsmith experienced with Martini's?

01 September 2003, 06:51

browningguy

I'm not a gunsmith but would think they would be fine. A lot or the half-action size Martini's have been converted to 22 Hornet, 32-20, 357 Maximum etc. and seem to hold up well. I've got three of the small size actions originally chambered in .300 Sherwood and .380 Long and they work fine.

02 September 2003, 06:16

<kailua custom>

Dear Markb- The action can be made into a C/F but it`ll require doing a conversion on the bolt itself. I did the same thing and bushed the bolt and redid the firing pin. Changed to 25 Hornet. Lot of work but the little rifle shoots good. Aloha, Mark[in Or]

02 September 2003, 09:26

tincan

quote:
Originally posted by kailua custom:
Dear Markb- The action can be made into a C/F but it`ll require doing a conversion on the bolt itself. I did the same thing and bushed the bolt and redid the firing pin. Changed to 25 Hornet. Lot of work but the little rifle shoots good. Aloha, Mark[in Or]

is this action strong enough for a 17MachIV?

-tincan

02 September 2003, 11:41

markb

{{The action can be made into a C/F but it`ll require doing a conversion on the bolt itself}}

I want to make sure I understand this. I know that the firing pin will need to be moved (obviously) and bushed. Is there something else that has to be done?

Mark

[ 09-02-2003, 03:27: Message edited by: markb ]

07 September 2003, 15:39

rupert

I've just measured a cadet-type BSA Martini (about 2 inches) and a MkII International-type BSA Martini (about 1 and half inches) and there is a considerable difference in the amount of room available to slide a cartidge into the chamber when the breech block is down. I've read a report in Australian Shooters Journal that the cadet-type can take up to the 5.6 x 50rimmed with a squeeze. But I'm not sure what length cartridge can be accomodated in the International. I'd be really interested in a report from you about the options that you find out about when you come to rechamber your International. Of course, the International would be a better action if the cartridge of choice would go into the chamber. The trigger on an International is so sweet and usually not damaged. And the triggers on cadet-type BSAs can be nice but are so often damaged by the backyard tinkerer.

07 September 2003, 15:45

rupert

Oh, and in reply to your question re what else to be done. I believe the ejector may or may not need to be modified to eject the case. If the cartridge of choice is rimmed then the modifications are minor but if the cartridge of choice is not rimmed then the modifications are larger in scale. I would not contemplate a non-rimmed cartridge at all. If a particular cartridge is the choice then make a rimmed version of it, e.g., instead of 221Rem, use 357max brass which is the same base and has a rim.

01 November 2005, 22:51

belaw

Rather than start a new thread I thought I'd hijack this old thread which I found.

I'm considering the same thing markb was- a Martini International in .22 Hornet. What I'm curious about is whether (in addition to the action work) I can just rechamber or whether a new barrel would be mandatory.

02 November 2005, 16:20

max(hm2)

there is a real size difference in the bore diameter of 22 rimfire and 22 centerfire. at one time, they may still, the bullet makers made undersize bullets for this type of conversion.

02 November 2005, 19:16

belaw

Hmmm. I guess I need to figure out what more bore size really is.

How do you slug a bore? Is this a do-it-yourself project, or does it require special equipment/skills?

16 November 2005, 05:34

trepur

Interesting to see that old post come back. I did a bit more checking about the original question and the answer from a very skilled gunsmith was 'no'. The breech block ramp angle in the international is too steep and the groove for the cartridge to slide in on the top of the breech block is too narrow. Secondly, and of more importance, the extractor does not have enough metal in it to be made larger to extract the Hornet case. Thirdly, the extractor is too brittle to made larger successfully. Fourthly, the extractors are like hens teeth to find and very expensive when you do find them so modifying an extractor and finding it breaks or doesn't work is not an option that a responsible gunsmith will contemplate. As far as the bore diameter is concerned: that is of no consequence. There have been many 22rf barrels screwed into Cadet actions, rechambered for 222Rem and shot for years with standard size centre fire 224 bullets. I have a 22 Hornet on its second 22rf barrel and its shoots the 224 bullets very successfully. On the other hand, if you have a very tight 22rf barrel (say 218 in the bore) you might need to keep the pressures of your reloads down. You can check the bore diameter by slugging it with a 22rf lead bullet, upset (squashed) in the bore between two brass rods, and then pushed. Don't drop it on the floor and measure it with your trusty micrometer.

16 November 2005, 08:09

belaw

I posted this same question on a benchrest forum, mainly because the rimfire guys are probably going to be more familiar with the Martini International than anyone else. The final consensus was that the a centerfire conversion is, at best, impractical. Their suggestion was to simply rechamber to .22 Mag.

I finally decided just to keep the original LR chambering. .22 mag ammo is a little pricey in comparison and I understand it has a reputation for so=so accuracy.