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HeymSR20
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Reged: 23/11/11
Posts: 245
Loc: Scotland
Can you convert a Martini International 22lr to 22 Hornet et
      #298453 - 05/04/17 09:29 AM

Here in the U.K. There are quite a few 22 or martini actioned target rifles still available for not much. Is it possible to rebarrel and redo the firing pin to work with a small centre fire - 22 or 17 Hornet or a rimmed 222.

I know a cadet might be an easier job but they are not often seen and go for silly money.

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MikeRowe
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Reged: 23/11/11
Posts: 478
Loc: Arkansas, USA
Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: HeymSR20]
      #298461 - 05/04/17 11:27 AM

I believe that by altering the length of the lever horns, the breech block face height can be made to suit centre fire. It's explained in the original armorers' manual. The extractor will need to be changed as well.

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CptCurlAdministrator
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Reged: 01/05/04
Posts: 5284
Loc: Fincastle, Botetourt County, V...
Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: MikeRowe]
      #298490 - 05/04/17 10:50 PM

Mike,

Won't such a change take the face of the breech block out of perpendicular with the bore?

I would think it better to re-work the breech block and striker to center fire configuration.

Curl

--------------------
RoscoeStephenson.com

YOUR DOUBLE RIFLE IS YOUR BEST FRIEND.



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DoubleD
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Reged: 23/11/03
Posts: 2437
Loc: Retired in Oklahoma
Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: CptCurl]
      #298495 - 05/04/17 11:28 PM

Yes the Francotte pattern BSA Martini can be adjusted for Center fire. There is no difference between a centerfire and rim fire in these guns beyond them being adjusted for different striker impact point and load position for the specific cartridge.

I have built a number of them over the years.

The way I was taught at school-American School is not the same as what is laid out in British military Armors manual nor apparently how BSA did it. Several years ago I got a good lecture from a gentleman who supposedly worked for BSA, about how us American's had messed this all up. After the lecture he showed me how to do it right. If he really did work for BSA he would have had to have been 14-15 years old.

He did say the breech block needed bushed for higher pressure cartridges like the .222 Rimmed.

I do not know about the Internationals. I think some have been converted to Hornet. I have just never worked with them.

--------------------
DD, Ret.

Edited by DoubleD (06/04/17 02:12 AM)

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DoubleD
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Reged: 23/11/03
Posts: 2437
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Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: DoubleD]
      #298498 - 06/04/17 02:05 AM

Quote:

Mike,

Won't such a change take the face of the breech block out of perpendicular with the bore?

I would think it better to re-work the breech block and striker to center fire configuration.

Curl



Mathematically there is a change in the angle.

Here is the drawing for the .22LR.



Here are the numbers for the math. To do the numbers you will need to use radii.

.22LR is .272” in diameter, .136” radius.

BSA.22 striker is .190” diameter, .095” radius

When properly adjusted the outer diameter of the striker should contact outer diameter of the cartridge, with the striker impact inside the rim diameter. That is the basic rule of thumb. There are other theories for this especially among target shooters, but this is the basic rule.

The center of the striker is .095” from the outside diameter of the rim, or .041” from the center. That means to change from rimfire to center fire the block must be moved .041”.

Now I long ago lost the capability to do these trigonometry functions in my head, so today I jumped to http://www.cleavebooks.co.uk/scol/calrtri.htm and plugged the numbers in.

The length of a BSA .22 breechblock from center of pivot pin to face of breech block is 2.3”. The amount the block must move to change from rimfire to center fore is .041 The angle of the breech face changes 1.02 degrees.

This breech face angle change is based on an assumption, that the breech face was perpendicular to start in the rimfire position. They often are not.

My first encounter with squaring of the breech face was from target shooters who wanted there rimfires squared. Of the number of these that I have “squared” back in my working days, the effect of squaring was never perceptible. But the target shooters were convinced it made a difference.

--------------------
DD, Ret.

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MikeRowe
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Reged: 23/11/11
Posts: 478
Loc: Arkansas, USA
Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: DoubleD]
      #298509 - 06/04/17 03:33 AM

Apparently the slight change in angle has not been a problem under field conditions.
I've not done a Martini conversion myself, just going off what's in the instruction book.
A lot of this stuff is not as critical as you'd think. Remember, we are not working with benchrest rifles.

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DarylS
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Reged: 10/08/05
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Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: MikeRowe]
      #298511 - 06/04/17 04:39 AM

I converted one (lifting horns built-up and filed for a better fit) for the Hornet case from rimfire and it works just fine. I also had to drill out and hard silver solder an insert to convert the rifle from the large round pin to small diameter round firing pin.

I do not use high pressure ammo in this rifle.

The original .220 (.22 LR) barrel was simply chambered for the Hornet case - really tight of course, but what many were subject to. Of course, there was a lot of trouble with pressure - piercing primers, now if I remember correctly.

I re-barreled it with a CZ Hornet barrel, then re-chambered that to .22 Ackley IMP hornet using my .17AH reamer, bushed to fit the bore.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V

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Marrakai
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Reged: 09/01/03
Posts: 3592
Loc: Darwin, Top End of Australia
Re: Can you convert a Martini International 22lr to 22 Hornet et [Re: DarylS]
      #298568 - 06/04/17 11:55 PM

Quote:

Remember, we are not working with benchrest rifles.


Mike:
A good many Martini International owners might be inclined to disagree with that statement!


--------------------
Marrakai
When the bull drops, the bullshit stops!
--------------------------------
www.marrakai-adventure.com.au

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