5-Shot Conversion - Documented

[Lee Martin]

I started documenting a 5-shot conversion on my forum and thought the Ruger crowd may be interested too. Just like my OM .44 Special and Buffalo Seville, I'll cover each and every step in doing one.

As I've gotten older, I've fallen out of love with barrel bands on revolvers. Used to adore bands, but now my eyes don't take to them. Plus my preferred barrel length on Blackhawks is 6.0". The conversion will be the sister gun to this .500 Linebaugh:



The differences will be:

1) 6.0" straight taper barrel
2) Frame window opened 0.060"
3) Recessed cylinders (not a huge fan of them, but will do so here)
4) Jack Huntington Bisley mod with walnut panels

I'll discuss and photo document every step. From fitting an oversized bolt, milling the frame window, adding a stronger gate spring, making the cylinder, pawl and hammer/bolt timing, ratchet geometry, line indexing vs. line boring, heat treating, centering the barrel and cutting the cone, and making the front sight. It may take a week or two to get started, but it's coming. This first post is a placeholder....if it goes on the internet, I'm committing to the article. I hope folks find it informative.

 

[29aholic]

I can't wait

 

[Lee Martin]

First I fit the Bisley gripframe to the donor gun. I’d like to get this to Huntington to allow time for the reshape and wood carving. We’ll use a spare Bisley frame as a mock-up during the build.

I started with your basic stainless conversion kit:



I won’t inundate you with pictures on how to fit these. Many of you have done this yourself. As we all know, Ruger ships the frames oversized. Mating them to the frame entails bolting it up, marking the high spots, and a lot of filing and sanding. For those that haven’t done this, here are the main areas to focus on:



I went real slow, filing the overhang, assessing it against the frame, and then marking additional points to relieve.



Once filing was complete, I sanded with 100 grit to blend the two. This was followed by 220, 320, and 400 grit sanding. And here’s a quick tip – if you ever want to replicate Ruger’s brushed stainless, start with 320 and then lightly scuff with 400.





Throughout this thread, I’ll callout the time spent for each task. This should give you an idea of how long it takes for builders to complete these customs. In the case of the Bisley fitting, it took three hours.

 

[Lee Martin]

Quick update on how I’m progressing. I spoke with Jack and the gripframe is on its way to Nevada. He’ll reshape the Bisley and wrap it in high figure walnut. Then I had to dig up barrel. Searching the shop uncovered some from my .50 Alaskan BFR build. With Pac Nor backlogged six months, I’m glad I had a piece.

Stainless 0.510”, 1:18 twist, unturned @ 1.10” o.d. I only need six-inches. We’ll get another conversion out of this length.



Opening the frame requires a 3/16” carbide cutter. And it has to be a long endmill to clear the window. We'll perform this step over the weekend.



I also decided on a new .500 Linebaugh bullet; one I’ve wanted for some time. Using Mountain Molds software, I designed a 505 gr LFN on dual cavity blocks. I chose plain base because it’ll top out around 1,200 fps. The specs if anyone is interested in ordering the same:





I believe it’ll print better at 100 yards than the 525 WFN I’ve been shooting. I’ve spread the CoF and CoG more, lengthened the nose, upped the driving band height, and reduced the meplat. Casting a lighter 440 WFN from my LBT mold is another option for short range. But in multiple guns, it hasn’t done well past 50 yards.

 

[Lee Martin]

I milled the frame window this afternoon using the 3/16” carbide cutter shown above. First I clamped the frame in a Bridgeport mounted vice. A spacer block was inserted into the hammer slot.



A quarter-inch rod is then placed in the basepin hole and indicated. It ran out less than a half-thousandth end-to-end. Ruger drilled the cylinder hole dead perpendicular to the front and rear edges. I also leveled the frame on both flats.



The endmill is zeroed on one edge and using digital readout I noted the reading for the opposite side. Next I moved the table over 0.010” and I feed out the cross feed. Ten-thousandths made a nice cut and put little-to-no strain on the bit. Three passes were made per side.



Here’s a shot of our digital readout. You’ll notice the X-axis is at 0.0304”, which is the thirty-thou we removed. This was the final pass on the top edge.



Cutting the lower edge:





The roughed frame. I took a total of 0.060” top-to-bottom. Next time I’ll flat file the surfaces and sand to a mirror finish. The corners also will be dressed for less radius. I could’ve use a smaller diameter endmill to do this, thus making tighter corners. But the smaller the endmill, the more it’ll flex. Because the cylinder will be recessed and I’ll use minimal barrel protrusion, the corner radiuses can’t be too sweeping. However, some radius is recommended. Remember, a curved edge is stronger than a straight 90 degree. Ever wonder why airplane windows are oval and not square?



Total time for step 3 = 2 hours. BTW, I’m doing all the machining on this conversion. Dad says it’s time to pass the torch completely. Little stress though, because he’s always present.

 

[win1894s]

looks good thank you for sharing

 

[Mus408]

Great work and will be following!

 

[Hondo44]

Thx Lee,

Looking forward to your step-by-step build.

Might just be just the photo above, but seems like the main frame could come down just a bit where it meets the recoil shield for a more concentric curve with the top of the Bisley grip frame.

Not the case here, but that's one area especially needing attention when installing Bisleys on OMs.

 

[Ale-8(1)]

I love these threads, Lee. Hope my stupid questions aren't too big a bother.

You opened up the frame window 0.060" overall, 0.030" top and bottom. Before you cut, did you check to see that the opening was in fact "centered" on the base pin? I mean, one would assume so, but ya just never know. I suppose it wouldn't really matter if it were off a few thou so long as it clears your new cylinder, but I just wondered.

 

[Rumrunner]

Thanks for sharing great pictures and documenting. That 500 is a beauty.

 

[Kevin]

Thank you! This is great as I have a revolver being converted right now. It's very interesting to see the process.

 

[contender]

I've been following this build on Lee's site.
Folks,,, this is one heck of a project to follow. Lee is really putting his work out there.

 

[Arisin' Wind]

I love these threads by Lee. Beautiful work and to see it in progress is always a treat. Thank you Lee.

 

[Bear Paw Jack]

I appreciate your sharing the conversion and the work involved. Even the pictures are masterful. I'm surprised you don't do this for a living. It would be nice to have another custom builder out there, with folks aging.

 

[Lee Martin]

Small flat, round, and square files were used to dress the inner surfaces. I had to go slow throughout. The corners must be consistent and tight enough to clear the cylinder. When the entire window isn’t consumed and the cylinder isn’t fully recessed, it’s not as critical. I relied on eyeball and hand to do this. Remove too much steel and you’ll distort the edges. While that won’t obstruct function, it wrecks the look of the gun.







On our conversions, I also polish the inside of the frame. This removes the cast texture and machine marks left from milling. The top, bottom, and breech face are worked with 220, 320, and finally 400 grit sandpaper. If mirror finish is your thing, lightly hit it with 800 grit.









Recap of hours spent so far:

Backstrap fitting = 3.0
Frame milling = 2.0
Frame window dressing = 2.0
Total = 7.0

This weekend I’ll fit the oversized bolt to the frame.

 

[Kevin]

Awesome looking job!

Wonder what Ruger would say if we started to demand polished frame windows?

 

[Lee Martin]

Prior to the cylinder build and re-timing, there are parts to amass. I won't do a conversion until I have the final components. Below you'll find:

1) Power Custom oversized bolt - I'll have to custom fit this
2) Power Custom heavier gate spring - again, minor fitting required
3) Belt Mountain #5 basepin
4) Bowen Classic Arms target rear sight - doesn't play into fit and tolerances, but I still want it ahead of time.

 

[Ale-8(1)]

Awesome looking job!

Wonder what Ruger would say if we started to demand polished frame windows?

They'd say "Fine . . . koff up an additional $350 per gun, please!"

 

[Lee Martin]

Power Custom bolts ship wide at 0.100”. As noted, the frame slot mics 0.096”, the stock bolt is 0.092”. That 0.004” worth of clearance is more tolerance than I like.

The new bolt has to be precision ground on a homemade jig. The jig is just a piece of steel with both sides surface ground dead even. Two holes are drilled to affix the bolt so it doesn’t move while grinding. One hole holds the bolt peg, the other is for the cross pin.



The surface grinder I used is a Boyer-Schultz Six-Twelve Deluxe. These are high-end machines and hold to 0.0001”.



The jig is positioned on a magnetic chuck and the bolt is ground until it just fits the frame.



Final width mics 0.0952”, netting 0.0008” total clearance (0.0004” per side – very tight).

In the frame - it clears with no drag or side-play.



I also turned the cylinder from 2.0” round stock. This was done on our 15” Nordic lathe. Rough o.d. is 1.86”. This weekend I’ll cut it off, center drill, face, and final turn on a mandrel to 1.80”.

 

[Lee Martin]

I came home yesterday to find a box from Jack Huntington. He completed the gripframe much faster than expected.





I’ll spare you the obvious adjectives which describe his work. If you’ve ever considered his reshape, do it. He has done BFRs, XR3-REDs, and this Bisley for me. Nothing fits my hand better than his contouring and grips.

The 505 LFN mold also arrived from Mountain. From the time I placed the order to the time it hit my house was less than 2 weeks. You’re hard pressed to find better service.

 

[29aholic]

So, you only grind the one side of the bolt?

 

[Lee Martin]

So, you only grind the one side of the bolt?

Just one side.

 

[Lee Martin]

The rough turned stainless is cut 2.20” in length using an electric hacksaw.







Next I faced both ends in our Colchester lathe:







The basepin hole is drilled, first by spotting one end. This is followed by 1/8” and 15/64” drill bits.









A 0.248” reamer finishes the hole. After heat treating, I’ll hone it to 0.250”.







Using a mandrel, I put the cylinder between centers for outside turning. This ensures the outer diameter is concentric to the basepin hole. Final o.d. is 1.810”.

 

[TinkerDave]

Do you need someone to come sweep your floors? Man, you do great work. TD

 

[Lee Martin]

A Woodruff key cutter makes the bolt stops. Since I’m starting to do cylinders, I ordered a second. These come 1/8” wide and 1/2” in diameter. Clearly too thick for a 0.0960” notch. It has to be ground in a tool and cutter grinder.





Post-grinding:



Before milling the stops, I machined the ratchet boss 0.585” in diameter. Standard Ruger ratchet height is 0.150”. Mine will be shorter since I’m recessing the cylinder. 500 Linebaugh rims mic 0.060”, making the target height 0.090”.







I’ll now share some of the geometry involved in action timing. First, the cylinder is chucked in a horizontal indexing head and a mandrel is inserted. The key cutter is brought down to touch the top of the mandrel. The table is then raised 0.215”.



Math time. The stops on a Ruger are 0.704” in from the rear edge of the ratchet. My cutter measures 0.514” in diameter. That means the table is moved 0.961” from the back edge (0.704 + (0.514/2)). The cutter is cross fed until it touches the cylinder and our digital readout is zeroed on the Y-axis.



The cutter is slowly fed in to a depth of 0.060”. Dividing heads yield 9 degrees of rotation for one turn on the dial. The next notch, which is 72 degrees from the first, is positioned with 8 turns.



The next four stops are milled by repeating the above. Depth is monitored on our digital readout.









The bolt leads are done with a 3/8” endmill. Do not allow the endmill to reach the bottom edge of the notch. Otherwise, we’d lose our tight fit. Remember, the difference between my bolt and the stop is a miniscule 0.0008”. A depth stop is set to ensure we go no lower than the middle of the notch.

 

[Lee Martin]

A large wheel cutter is how we ‘gear’ the ratchet. But we can’t do a straight cut; the geometry dictates these be offset 20 degrees to the rear plane. The indexing head is canted 20 degrees out from the x-axis. The mandrel is reinserted in the basepin hole and the cutter is brought up to touch the bottom edge. Drop the table 0.090".





Now here’s the trick to timing the ratchet relative to the notches. Dividing heads have a 40:1 ratio between handle rotation and spindle rotation. Turn the handle 40 times and the spindle moves 360 degrees. Hence, one turn equals 9 degrees.

The ratchet's teeth have to be offset within a narrow range of degrees from the position of the bolt stop. Our indexing head is rotated 1 and 24/57 turns (~12.8). The cutter is zeroed on the back edge of the ratchet. IMPORTANT – the zeroing occurs on the outer most edge of the circumference. Once that’s done, the wheel is fed into a depth of 0.060”.





To cut the next cog, the indexing head is turned 8 rotations. This is one of the most precarious steps in making a cylinder. If the ratchet depth and position relative to the notches are off, we’re screwed. An error here sends it to the scrap pile.





We're not quite done with the ratchet. Next time, I’ll mill relief cuts in between the cogs.

 

[VernTMG]

This is some seriously cool work, I'm enjoying every part of it. So thanks and can you work faster so you can post more haha. Fun to watch the progress Thanks

 

[foxtrapper]

Amazing work!

 

[eric conrad]

Outstanding work. I could watch this all day.
Thank you. Eric

 

[Dave P.]

If it's ok I've got two questions.
What alloy is the cylinder out of?
And not knowing Ruger single actions I'm
guessing the bolt notches are offset .043
from the basepin centerline?
Thanks
Dave