doublegunshop.com - home Forums General Discussion Classic & Custom Single Barreled Sporting Rifles @ doublegunshop.com Martini a la Hoffman

The project is proceeding nicely. Here is a synopsis of problems solved.

Centerfire breach block
The striker nut retaining screw on the rimfire block had been broken off and had to be removed. I drilled the screw stub with a twist drill very near the minor diameter of the screw and then attempted to tap it with a 2-56 tap with the broken screw remnants in place. I broke the tap off in the hole and Morris had to burn the tap out using EDM. The threads were then carefully chased with a bottom 2-56 tap.

The first step in converting the rimfire block to centerfire was to thread the firing pin hole in the breach face with a 4-40 tap. A screw was turned in until it reached the bottom of the firing pin hole channel. The protruding part of the screw was then TIG welded around its juncture with the breach face. A surface grinder brought the weld level with the face.


The rimfire pin was ground from the striker.

The centerfire pin center was located on the breach face and drilled with a 1/16" twist drill through the face with the striker in place. This provided a secure location to solder a new firing pin in place in the striker.

Morris turned the four barrel blanks round, established a precise common OAL for the barrel set, threaded and chambered each and then crowned them.





Each barrel was test fired to ensure primer detonation. Using a common rimfire block without making adjustment for the slight size difference in the .17 HMR and the .22LR didn't matter.



Martini lever movement has two positions. The first "nearly opened" position is maintained by striker spring tension. If the lever is pressed forward from this position the block under striker tension then allows the insertion or removal of a case from the chamber. The modified rimfire block would not lower sufficiently to allow the insertion and removal of the 5.6x50R or the .25-20 WCF rounds. The bottom of the block had to have metal removed to allow the block to drop further.
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The next step will be to manufacture a common takedown taper pin that will work with all four barrels. Morris plans to create the taper cut on the thread bottom for each of the barrels with EDM. He has the fixtures designed, built and hardened that will hold each barrel while it is profiled on the HAAS CNC.
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Here are the last two images that don't appear to be visible in the original post.

Morris completed the final preparation on the barrels with the setup to cut the groove for the takedown cross pin. Each barrel had to be screwed into the action with equal force, then moved to the EDM and indexed. With the 4� tapered electrode mounted the action was removed and the cut was made to proper depth. For those interested in the minutiae the full story is at: http://blog.alaskaarmsllc.com/ovate-barrels-part-4/

For those just interested in the results here is what the EDM cut looks like on the first barrel. The barrel work is simply top notch with precise facing and threading evident in this image. The chambers too, are top notch.


A lengthy description of the action and barrel preparation briefly posted here previously is found at:
http://blog.alaskaarmsllc.com/ovate-barrels-part-3-installing-chambering-barrels/

Morris has finished production of the CNC fixtures, they are ground, and the first profiling run should occur in the next several weeks.

Morris has completed the CNC run of all four barrels for this project. The last step for the barrels is the final polishing. Here is what the MasterCam solid looks like and some images of the actual barrels follow that.






These four barrels were intended to proof the fixtures that Morris has designed and created as well as test the feasibility of doing complex barrel contours using CNC. Morris' extraordinary machining skills and barrel artistry have not disappointed. This is simply top notch work that can be extended to the gun making trade.

Each of the barrels has a different sight configuration. The 5.6x50R will have a Fecker 10x scope as the primary sight. A longitudinal front sight dovetail is planned to support a pop-up front blade. Between the scope bases is a flat for cutting a cross dovetail for a standing rear blade.

The .17 HMR only has scope bases and a 6x Unertl Small Game scope will be affixed.

Although the .25-20 WCF and the .22 LR have scope bases they will use sights as the primary system. The .25-20 will have a Beech type front sight and a standing rear blade. The .22 LR will have a BSA #8 peep sight mounted on the rear of the action with a quick detach system and will have a Parker Hale #2 globe front.

I plan to build a cabinet for the rifle and its components and have a rough drawing that will get refined.

Within a week I hope to have a detailed description of the fixtures, the CNC setup and staged images of mill progress on the barrels posted to Morris' blog for anyone that is interested in more details of this project.
Dennis

Dennis,
This is very impressive(even astounding) work.Please pass this to Morris.
Mike

Not only are the barrels fantastic, but the stock blank is, too!

Mike,
Morris appreciates the feedback on the barrels. Something like this would look good on a reproduction miniature Henry chambered for a rook and rabbit cartridge.
Dennis

Gee Dennis, now all you need is a pattern gun

Terry,
Glad you like the barrels and the wood.

I took the comb of the blank down to about a half inch of its final height last week and was surprised to see what is emerging. The top of the bases on the barrels are .575" above bore so the open sights will have to be positioned high enough to see over these. As every, the stock configuration has some level of compromise when both a scope and iron sights need to be accommodated.

Working with four cartridges with quite different ballistics and the same butt stock might be trickier than I'd imagined. I have one specific load for each of the cartridges in mind and hope to test fire each of the barrels with sights soon.
Dennis

I have always enjoyed seeing orate barrels on Rook Rifles and commercial Martinis. So many rook rifles I have found have been bored out to .410. Lining an ovate barrel, especially if it was reamed off center, is challenging. What you and Morris offer is an incredible opportunity for custom rifles and restoration.

With machinists like Steve Earle producing Daniel Fraser rifle actions, and I hope someone comes up with a modern Farquharson action, this style of barrel would be perfect.

Nice work Dennis !

... Joe