Barrel Shroud / Sleeve for the Marksman 56-FTS Part 1

Started the full-length sleeve for the Marksman 56-FTS.   Didn't really get very far yet, but starting often begins long before any chips are made.  

When complete, it'll look like this, but 16" long to cover the entire barrel.  It's strictly cosmetic.  There might be some benefit, as the additional weight should slow down movement to some degree, but I really just want to have some simple, cleanly machined lines.

As I wanted the sleeve to look like a full length version of my modified Crow Magnum muzzle brake, I had to consider how to machine the 15"+ long flats on each side as well as the groove along the top.  The breech end will also need a taper, the muzzle end cut to length and beveled and finally some set screws for mounting.  And a swivel stud for a rifle sling and what else did I forget?  Oh yeah, where do I even start?

This is often just a mental checklist now:  Will this physically fit in the machine?  Do I have a way to hold it?  How accurate does it need to be?  What will (probably) be the most difficult step(s)? Do I need to make or buy any tooling for the project?  What options to I have for each machining step?  Pros and cons of each?  Is this really a good idea?  Am I out of my damn mind?

Purchased a two foot long piece of DOM (Drawn Over Mandrel) tubing last year from McMaster-Carr.  It's 7/8" (0.875") in OD and 0.635" ID.   The Marksman 56-FTS barrel is 16mm OD (0.629" ) leaving about 0.006" clearance to the tube.   For reference, a sheet of paper from the printer is a pretty consistent 0.004" thick.   

I opted to machine the taper at the breech end first then bring in the overall length.

Looks OK.  Some fine tool marks, but the sleeve will be bead blasted in the final steps.  Need to take this to length, finish the muzzle end, and polish out the OD before cutting the flats.  And that's where things stalled out.  I didn't want to cut and polish this thing at home.  And I really didn't want to cut those long flats on my small mill.

Took it to work and got the Ok to work on it after hours.

Metal cutting bandsaw.

XXX marks the off cut.   Coolant and auto feed.  Sure beats my hacksaw with those Harbor Freight blades.  

Cut it to 16-1/4" long. 

I've shown this machine before.  Its a Rand Bright cylinder polisher.  Has a roller than spins and draws the tube through where it's polished by a 4" wide sanding belt.  The belts are something like 90" long.

The white sheets of nylon are adjustable for tube width.  I knew that a co-worker had been running some hydraulic tubes that were the same diameter the day before, so that had also factored into my desire to do this at the shop.

Ran it right through.  Didn't even need to change the sanding belt.  After three passes, it looked great.  Probably equivalent to sanding it to 320 grit--and only took about 45 seconds for the entire job.  Since the Rand Bright was already set up for the 7 /8" width, it took me longer to uncover and recover the machine with a tarp than to do the polishing.   

That saw cut end needs some attention.

Over to the lathe and faced / deburred the muzzle end of the sleeve.   At this point, the sleeve is still about 1/4" longer than the barrel.  Again, just used the tools already in the QCTP.   

Now it was time to go home and finish the length.

 

As expected, just a bit long.

Out to the garage and faced, beveled, then polished the muzzle end to final length.

Decided it might be smarter to polish out and remove those small machining marks from the tapered end now rather than rely on media blasting later.

Final test fit for length.  Next, I'll machine the long flats on the sides.  My milling machine will make the length of cut, but I'd prefer to make these long cuts on a larger, more rigid machine.  And there's a face mill cutter at work that should give a better finish than the end mill I'd have to use at home.

More soon.  Thanks for checking in.