useful method for turning crowns on octagons

Talk with other Shiloh Sharps shooters.

Moderators: Kirk, Lucinda

mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

Well, back to the point of the thread, a simple alternate method to make an accurate bearing to turn a good crown on a barrel in a lathe.
By the way it is my thread so I guess if I want to talk about set back too, how is that any skin off your nose as I'm doing both on this project?
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

This is the crown and chamber area that needs trimmed and set back on this 32-40 High wall.
I'll need to go back one turn on the set back and re-cut the chamber into fresh steel and about .250 or a bit more on the crown to get into tight lands from cleaning rod wear.
Then a good lap job and I bet she'll shoot as good as ever.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

This is the new crown and in checking the breech face square I found it was out by quite a bit so spent last night building a squaring tool. I use old barrel spuds as they are already threaded for the action being trued.
This rotary lap will make the breech face portion that supports the case head square to the bore plus is also got rid of most of the corrosion ring.
The case is deep on this breech face and a file check says it's still hard.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

The other two pictures. I'll finish up with a 320 grit disk once the face us true.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

When the face is square then the barrel breech will also be set back the one thread as the shoulder already has, and the chamber re-cut into fresh steel. This will give the bore a new throat as well as chamber. Finally the extractor cut will need to be made deeper and then the bore lapped and she should be done.
I use a flex shaft to turn the lap with a hand drill.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

One more important point that needs addressed when squaring breech faces and that is firing pin protrusion. Large rifle protrusion should be in the .062 +/- .002 range for safety and this one will need trimming as it was something like .080 before I got started on lapping it square.
Not sure yet if it will need bushing but hopefully not. If so I will make it the smaller size pin diameter.
These ole girls need lots of help in a bunch of areas most folks never consider.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

This is the block face lapped square to bore at 320 grit. The five degree angle the block rises at allows a smooth transition into the face lap area of the case head. Notice the corrosion ring is all but gone.
Took all evening to make the lap tool and perhaps five minutes to do the job but now I have the tool for all High and Low wall actions with this shank and thread.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

This is how the block face started out.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

Well the firing pin hole will be bushed to small diameter .078. I like to use a scope screw (8 x 40 tpi) which is very tough steel but still machinable. This mod has worked very well for me often, even on high pressure cartridges in bolt guns.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

Here are some shots of the firing pin alterations from about .140 down to .078 diameter and the corresponding bushing to match. The protrusion is .061 right in the length window it should be.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

I can only get three photos on the same reply. Here are the shots of the firing pin itself.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

Well the ole girl if finally done and back together. It took 1100 trips, 6-7 new poured lead laps and three grades of lapping compound to get the bore about as good as it can be made in such rough shape. It is without doubt the roughest bore I have ever tried to save although the lands look very strong and sharp but the grooves bottoms still look like the craters on the moon .
It will be interesting to see how accurate it is and if it leads up. My guess is it will do best with gas check lead bullets and a good bore anointing with a lubed patch before firing.
May have to reline it after all but I'm anxious to see what can be found out about rough bores and accuracy potential.
Also there is an interesting car-touch on the stock I'm wondering about.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

Some more shots of the 32-40 HW.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

In describing the barrel lap process the term 1100 trips means 2200 passes. Each trip is a pass up and back.
Here is the shot of the chamber area before set back and re-chambering.
The shank thread is 16 TPI so each revolution sets the shoulder back .0625. Cutting the chamber this much deeper did not take out all the deep pits in the chamber body but most of them. A piece of sand paper on a split stick to polish the chamber body after the reamer cut did clean it up fairly well.
I had to cut the crown back a bit farther so as to miss any pits in the clean up chamfer.
You do not have the required permissions to view the files attached to this post.
mdeland
Posts: 11708
Joined: Mon Nov 20, 2006 1:47 pm

Re: useful method for turning crowns on octagons

Post by mdeland »

One of the suggestions I got about the car-touch was perhaps the (CP) stands for Central Pacific Railroad ! I guess the thinking is that perhaps it's a railroad guards gun while carrying payroll or gold bullion.
Post Reply