Interesting point Joe brought up about thread wear. Got me thinking and doing a little math. Assuming .001 wear, a square thread responds in a ratio depending on the thread pitch. A 60° V thread responds in a 1/.866 ratio, which results in a 20% increase in linear movement to take up the slack.

Without typing all the math, a 16 TPI square thread would need 5.76° of rotation to take up .001 wear, while a 16 TPI V thread would require 6.912° of rotation.

However, the square threads I've seen on barrels are typically a 10 TPI thread, and the same .001 wear would result in 3.6° of rotation (4.32° for a 10 TPI V thread).

That's a 20% increase for the V thread over a square thread, but a 60% increase for the 16 TPI thread over the 10 TPI. It's not so much the V thread that causes the apparent wear as the finer pitch they use.

As for a takedown on a Ruger, the easy way out is to use the original main spring and hammer strut.  Doesn't require anything more than a pin to remove once the hammer is cocked. Doing it with a flat spring requires, most likely, a screwdriver (which you already needed to remove the forearm anyway), or you could possibly swing it aside if the hammer had a tail extending forward of the receiver face. An internal torsion spring might be a challenge.

The hanger came off mine sunday. I left 1/4" for the extractor pin. I'm planning on replacing it with a lug attached to the barrel, which will anchor the original main spring system for now. I haven't decided whether I'll try to implement the ejector spring or not.

Wesg, a question. When you calculated the takeup with the different thread systems, did you apply the vee-thread formula to both parts of the thread? 'Cause I think both sides (bbl & frame) would be subject to the same reaction since they're both slanted 60 degrees.
Just a thought, Joe

Hello Folks

Lots of good thinking going on here, its wonderful.

Wesg - how are you planning to attach the mainspring anchor to the barrel - I'm thinking a dovetail slot same as a sight mount, or will you solder/weld something on ??

Interesting point about the wear, the reason I was thinking about the locking nut was to remove the "slack" without rotating the barrel (and sights and fittings . . . ) and I thought headspace might be compensated by adjusting the reloading dies.  If the wear is minimal as per Wes's estimate then headspace won't be signifgantly affected.

Cheers - Foster

Joe,

The finer pitch sounds like a good idea. I'll go with the V thread on mine, and just open it up whatever it takes to straighten it out. I haven't laid a cutting tool on it yet. Just ground the sides flat for reference, and cut the hanger on the wire EDM so I had a narrow gap in case I decided to weld it back on at some point. Am I in for a surprise? The Ruger bolt action I did wasn't any problem to rework.

Foster,

I'm thinking of an oval block held on with a couple screws. Probably set it in a shallow pocket to take the shear load off the screws. Depending on how that looks I may go with a dovetail instead.

Hello

I have just been reading the De Haas "Gunsmithing Ideas" book and found a gem of an idea that had not previously registered on me.

He is suggesting that a hanger be attached to the underside of the barrel via screws into the reinforce of the barrel.  On the Ruger this would enable a switch barrel/takedown to be adopted, whilst retaining the current mainspring arrangement, albeit with a little modification.  He allows in the book that  this was his preferred forend attachment method.

Has anyone tried it or know of other folk who have  - results??

Cheers - Foster