The Firing Line Forums - View Single Post - M1903a4---It's finished

HiBC · April 22, 2013, 09:48 AM

The major work is done on my bolt.Started with a new Browne and Sharpe bolt.Locking lug surface to bolt face was off .0002 from the bolt I chambered with.

I turned a mandrel for inside the bolt,.421 under the threads,.463 for the ID at the cocking cam.Snug slip fit.

I drilled a 3/16 hole up the middle of the outside shank end of this mandrel,then I side drilled a port in it to feed water to the root of the bolt handle.I also cut a shallow groove in the od of the mandrel through the port.

So,the mandrel did two things,it supported the id of the bolt,and it fed cooling water to the id at the root of the bolt handle so the cocking cam would stay cool.I hung an old Camelback hydration bladder and hose to provide an "IV" bag to supply the water

First step was to straighten the bolt handle out pretty much like an old mauser,not perfect,but mostly.

Then,took an abrasive wheel,and about at the edge of the receiver rail,I cut from the top down about 3/4 the way through the bolt handle,leaving about a .100 web on the underside of the bolt handle.

It was easy to heat that thin section with the torch,and use it as a hinge to bend the bolt down.We used that water feed through all this,worked great

Now there was an open vee to weld up.Used a flux core wire welder a second or two at a weld,then dunked it in water after each weld

It looks just like an original A4 so far,and the cocking cam stayed cool.No pit/porosity problems.

I bought the New Zealand repro Redfield 7/8 rings/Redfield JR mt.Cant recommend them,Should have waited for some originals to E-bay.

Had to re-machine bases to fit receiver properly.

Worse,the rear ring windage screws are undersize to the pockets in the base so the heads are unsupported when you tighten them.

The screw cups fit the rings poorly.

I found some original base windage screws ,color case hardened.They are a larger OD,the base will support the heads.I have to re-cut that crescent shaped cut in the rings to accept them.Next project!

April 22, 2013, 09:48 AM	#17
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,286	The major work is done on my bolt.Started with a new Browne and Sharpe bolt.Locking lug surface to bolt face was off .0002 from the bolt I chambered with. I turned a mandrel for inside the bolt,.421 under the threads,.463 for the ID at the cocking cam.Snug slip fit. I drilled a 3/16 hole up the middle of the outside shank end of this mandrel,then I side drilled a port in it to feed water to the root of the bolt handle.I also cut a shallow groove in the od of the mandrel through the port. So,the mandrel did two things,it supported the id of the bolt,and it fed cooling water to the id at the root of the bolt handle so the cocking cam would stay cool.I hung an old Camelback hydration bladder and hose to provide an "IV" bag to supply the water First step was to straighten the bolt handle out pretty much like an old mauser,not perfect,but mostly. Then,took an abrasive wheel,and about at the edge of the receiver rail,I cut from the top down about 3/4 the way through the bolt handle,leaving about a .100 web on the underside of the bolt handle. It was easy to heat that thin section with the torch,and use it as a hinge to bend the bolt down.We used that water feed through all this,worked great Now there was an open vee to weld up.Used a flux core wire welder a second or two at a weld,then dunked it in water after each weld It looks just like an original A4 so far,and the cocking cam stayed cool.No pit/porosity problems. I bought the New Zealand repro Redfield 7/8 rings/Redfield JR mt.Cant recommend them,Should have waited for some originals to E-bay. Had to re-machine bases to fit receiver properly. Worse,the rear ring windage screws are undersize to the pockets in the base so the heads are unsupported when you tighten them. The screw cups fit the rings poorly. I found some original base windage screws ,color case hardened.They are a larger OD,the base will support the heads.I have to re-cut that crescent shaped cut in the rings to accept them.Next project!