Does anyone know of a gunsmith that currently offers Taylor Throating on an a la carte basis? I have a stainless Ruger flattop .45 convertible that has some serious thread constriction. It seems that nobody makes the remaers for this any longer - at least nobody that I contacted.
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A compression ring of several thousandths inch----presumably at juncture of frame & barrel shoulder---indicates over-advanced THREAD TIMING on barrel tenon.
Thread timing is the coordination of barrel threads to threads in the frame. The BARREL SHOULDER determines where the barrel stops when screwed into the frame. If the barrel stops too soon before the rib or front sight reaches Top Dead Center, and the barrel is over-tightened to reach TDC, compression at that point pushes steel into the bore. I don’t want that pressure there. I want the barrel to hand-tighten
10-12 degrees BTDC (Before Top Dead Center).
A “coarse” thread Ruger) requires more precise thread timing than a fine thread. (S&W).
A fine thread advances the barrel into the frame more slowly per degree of turn.
Deformation: elastic or plastic?If a compression ring or thread choke rebounds when the barrel is loosened, it’s called ELASTIC DEFORMATION.
If a compression ring remains when the barrel is loosened, it’s called PLASTIC DEFORMATION.
Aside from the misalignment potential of reaming
freebore with the barrel tenon in the frame, is there a chance elastic deformation will cause a hollow ring when the barrel is removed? I don’t know.
When a Ruger barrel hand-tightens 30-35 degrees BTDC, wrenching the barrel to Top Dead Center will form a compression ring. Push a tight patch through the bore and feel the resistance. It can take a lot of fire lapping to remove the compression ring. You can ream
your revolver by hand; not my revolver. Providing the bore is straight----without tight or loose spots----and groove diameter is not excessive to hold the bearing surface of the bullet straight, I would take specific steps to eliminate compressing ring.
FREEBORE1) Indicate barrel in lathe.
* Ream FREEBORE----.0005” to .001” over groove diameter x about .775” to .800” deep (enough to slightly exceed barrel face-to-frame measurement.
* Reamer must have a gentle slope to top of lands. Abrupt lands will tear the bullet.
2) Turn barrel shoulder enough to hand-tighten 10-12 degrees BTDC. Use TPI (Threads Per Inch) and degrees of over-advance to calculate shoulder removal in thousandth inch.
* Trim barrel face for desired cylinder/barrel gap. Presence of cylinder endshake limits how close you may set cylinder/barrel gap.
3) Check forcing cone: a) concentric to bore, b) smooth, not too deep.
* If forcing cane is tilted or rough, recut in lathe. My preference----11 degree included angle.
* Note: don’t recut a 5 or 8 degree cone to 11 degrees, as the root diameter will be excessive.
*To repair an overly-deep forcing cone, set the barrel back an additional thread or two.
4) Trim ejector assembly as necessary.
David Bradshaw