OzFclass

Just curious if anyone out there who is an experienced machinist (like me)and can explain how to line up the bolt head with new barrel adaptor whilst keeping it tight!
Cheers!

I'm inquisitive also. I suggest you buy from Brownells the following book. It doesn't cover Omarks but I think it will answer your questions regarding general information on headspacing etc.
Cheers,
Richard.

THE COMPLETE ILLUSTRATED GUIDE TO PRECISION RIFLE BARREL FITTING by JOHN HINNANT

John L. Hinnant. 8½" x 11". Revised third edition 304 pages. Self-covered. Not fancy but a very well illustrated, well written, in-depth analysis that provides both the advanced and beginning student a complete and informative shop manual. Covers literally every aspect of turning, chambering and fitting barrels on bolt action rifles including correct machine lathe setup, tool making and sharpening, threading, chambering, crowning, bolt-facing, plus the proper use and care of reamers. New section devotes 39 pages to action blueprinting.

Thanx heaps mate!!!

If the adaptor does not have a built in recoil lug then the front of the receiver has to be machined OR shimed to atain the correct phasing of the thread.
Final finishing of this surface need patience to achieve the correct fit.

If the adaptor uses the original Omark seperate recoil lug, then there are a number of different thickness lugs that are interchanged to achieve the corrrect fit. In this case if you dont have the range of lugs available, then either laping the lug with wet and dry paper on a flat surface or using shims to get the correct result is necessary.

Tip
DO NOT OVER TIGHTEN THE ADAPTOR JUST TO GET THAT LAST FLYSH OF ROTATION. The junction between the adaptor and receiver will pressure weld togeather over time and removal will damage either or both.


Tip
It may also be necessary to build up the front edge of the bolt handle to achieve the correct operation of the primary extraction cam surface of the action.

Tip
Check that the bolt head retaining pin is of the later design having a 7/32" diameter at the small end. If it is smaller then it should be upgraded for safety.

Legal note
In some states it is necessary to have a Firearms Dealers license to carry out this work

Ken L wrote:If the adaptor does not have a built in recoil lug then the front of the receiver has to be machined OR shimed to atain the correct phasing of the thread.
Final finishing of this surface need patience to achieve the correct fit.

If the adaptor uses the original Omark seperate recoil lug, then there are a number of different thickness lugs that are interchanged to achieve the corrrect fit. In this case if you dont have the range of lugs available, then either laping the lug with wet and dry paper on a flat surface or using shims to get the correct result is necessary.

Tip
DO NOT OVER TIGHTEN THE ADAPTOR JUST TO GET THAT LAST FLYSH OF ROTATION. The junction between the adaptor and receiver will pressure weld togeather over time and removal will damage either or both.


Tip
It may also be necessary to build up the front edge of the bolt handle to achieve the correct operation of the primary extraction cam surface of the action.

Tip
Check that the bolt head retaining pin is of the later design having a 7/32" diameter at the small end. If it is smaller then it should be upgraded for safety.

Legal note
In some states it is necessary to have a Firearms Dealers license to carry out this work

Ken L wrote:If the adaptor does not have a built in recoil lug then the front of the receiver has to be machined OR shimed to atain the correct phasing of the thread.
Final finishing of this surface need patience to achieve the correct fit.

If the adaptor uses the original Omark seperate recoil lug, then there are a number of different thickness lugs that are interchanged to achieve the corrrect fit. In this case if you dont have the range of lugs available, then either laping the lug with wet and dry paper on a flat surface or using shims to get the correct result is necessary.

Tip
DO NOT OVER TIGHTEN THE ADAPTOR JUST TO GET THAT LAST FLYSH OF ROTATION. The junction between the adaptor and receiver will pressure weld togeather over time and removal will damage either or both.


Tip
It may also be necessary to build up the front edge of the bolt handle to achieve the correct operation of the primary extraction cam surface of the action.

Tip
Check that the bolt head retaining pin is of the later design having a 7/32" diameter at the small end. If it is smaller then it should be upgraded for safety.

Legal note
In some states it is necessary to have a Firearms Dealers license to carry out this work

Thanks for the tips Ken!!!

HI all, haven't been here for ages so I thought I'd drop in and hijack somebody's thread...anyway I have a couple of Omark actions (1 is advertised for sale at the mo..) and I'd like to know what size thread the various makers use for the barrel to screw into the adapter ? Does anybody know ?
cheers
Sam
PS did a search but only found a post where I had asked this question in 2006 !

All Omark adaptors I have seen use 14 tpi and the diameter is very close to 1 inch. There is a 1 inch 14 UN Special thread of this size and I wonder if the adaptors were cut with one of these taps (before CNC machining days).

In my opinion it is a pity the thread diameter is not a little larger or they had used a finer thread.

Peter Smith.