Sunday, December 23, 2012

Muzzle Brake for a Crosman 600 -- Part 1

Been telling myself that I'd finish this Crosman 600 for way too long now.  I fit a longer barrel to the gun several years ago then later switched from 12 gram CO2 cartridges to bulk-fill with an extended gas tube from Bryan and Associates.  So, now, the problem here is rather obvious--the barrel is too short.  Could've made a new barrel, but I've already been down that road.  A muzzle brake that extends to the end of the gas tube seems like a reasonable solution.

A piece of 5/8" aluminum rod.

Suppose I'm technically making a "shroud" since it's going to cover the entire exposed length of barrel.

Faced off one end and spotted with a center drill.

Progressively drilled about three-quarters of the way through until I had a 7/16" hole to fit over the barrel.

A slight chamfer to remove the sharp edges.

Flipped the piece, faced and center drilled.

Drilled 17/64" to ensure the .22 cal pellet will clear with room to spare.

Countersunk the muzzle.

A couple of edge finders.

Want to find the center of the workpiece.  Set the work on parallels in the milling vise and found the edge. The contact tip is 0.200" diameter, so the edge is 0.100" from the center of the indicator.  As I want to center on a 5/8" diameter piece, I need to move the milling table half of 5/8" PLUS the 0.100" the center of the indicator is from the edge.  (5/8)/2 + .100

Cranked in 0.4125" of travel and I was on center.

Used a 7/8" ball mill to radius the bottom of the muzzle brake shroud to match the gas tube.

Wasn't sure how much metal to leave in the web, so I checked the gap between the barrel and gas tube with a feeler gauge.  Want to free float the shroud, so the web needs to be slightly thinner than the feeler gauge stack.

A couple more passes and...

it'll clear with several thou to spare.

Test fit.

Looks promising.

Need to make a small relief cut in the shroud to clear the flange at the rear of the bulk tube. I should be further along soon.  Check back in a couple days.

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