Shallow Headspace?

[bradley.moss72]

I bought a Rolling Block on Gunbroker. It has been rebarreled to 45-70. I suspect that it was not completely chambered. It has a .053 rim cut?

I have read where Paul Mathews had his chambered with a rim cut to accept brass with no more than a .066 rim thickness, which itself is less than the standard dimensions. Mathews talks of trimming brass to fit this.

I have found a few cartridges that would fire, but the hammer still binds up on the block.

My thoughts are to finish ream until it will chamber any cartridge.

What are your thoughts?

BW

Sent from my SM-G900V using Tapatalk

[roadie]

I would do a chamber cast before anything else, it'll give some solid dimensions to go from.

[country gent]

The Chamber cast may show its slightly short. Measure the rim cuts depth several places around the chamber to make sure its square and true. A couple thousandths diffrence around that diameter is a couple degrees out of square. Also check that the block is closing to square with the barrel face and the stub isnt to long or short. If the person machined the barrel stub short by .010 He may have left the rim cut shallow to compensate for it. Before cutting measure everything up and see what it is and How everything fits together.

[EDG]

This seems to be a common issue with rolling blocks.
I have bought (2) 40-65 dies on ebay that had the base of the FL die cut back a little to make sure the 40-65 would permit the rolling block to close.
The 3rd instance was a lot of .45-70 brass for a rolling block. The cases were R-P and the face of the head stamp had been skimmed about .004 to make them easier to chamber. The facing cut with a lathe left a shadow of the original head stamp on the brass.


I bought a Rolling Block on Gunbroker. It has been rebarreled to 45-70. I suspect that it was not completely chambered. It has a .053 rim cut?

I have read where Paul Mathews had his chambered with a rim cut to accept brass with no more than a .066 rim thickness, which itself is less than the standard dimensions. Mathews talks of trimming brass to fit this.

I have found a few cartridges that would fire, but the hammer still binds up on the block.

My thoughts are to finish ream until it will chamber any cartridge.

What are your thoughts?

BW

Sent from my SM-G900V using Tapatalk

[curator]

Many older rolling blocks have breech blocks with faces not exactly 90 degrees to the bore axis. This results in cases with off-perpendicular heads. Marking and orienting cases on each firing allows these bent-head cases to chamber.