Gene Beggs
Active member
Maybe this thread should be on the 'Gunsmith' forum, but I thought others might also be interested so here goes.
When about ninety percent finished with a barrel installation, stop about .060 short of the final chamber depth and remove the barrel from the lathe, screw it into the action and tighten to full torque. Scribe or punch a twelve o'clock reference mark on the OD of the barrel, near the receiver. This mark will be used to reindex once the curve is located.
Make a faux receiver from two inch aluminum barstock, bore true and single point the threads to match those in the receiver and take a light truing cut across the face.
Screw the barrel into the faux receiver and tighten lightly. Don't get carried away; hand tight is usually enough.
For the next operation, you can use a Deltronic pin inserted into the bore at the muzzle or do as I do and use a small portion of the muzzle which has been turned true with the bore. Place a dial indicator on the muzzle and rotate the spindle slowly by hand. You will quickly locate the point to be placed at six o'clock. Mark this on the OD of the barrel with a scribed line or punch mark. The angular difference between the two marks is used to calculate the amount that must be removed from the tenon shoulder. Clear? (It's harder to explain than do.)
Let's say we determine that the barrel must be rotated 135 degrees in order to line up properly. So, how much is that in thousandths? I'm sure you pros know a better way to compute this but here is how a redneck, eyeball engineer does it.
If the tenon is threaded 18 tpi, the barrel advances .0555 per revolution. 135 is .375 percent of 360. .375 percent of .0555 is .0208. That is the amount that must be removed from the tenon shoulder.
Hope this helps.
Later,
Gene Beggs
When about ninety percent finished with a barrel installation, stop about .060 short of the final chamber depth and remove the barrel from the lathe, screw it into the action and tighten to full torque. Scribe or punch a twelve o'clock reference mark on the OD of the barrel, near the receiver. This mark will be used to reindex once the curve is located.
Make a faux receiver from two inch aluminum barstock, bore true and single point the threads to match those in the receiver and take a light truing cut across the face.
Screw the barrel into the faux receiver and tighten lightly. Don't get carried away; hand tight is usually enough.
For the next operation, you can use a Deltronic pin inserted into the bore at the muzzle or do as I do and use a small portion of the muzzle which has been turned true with the bore. Place a dial indicator on the muzzle and rotate the spindle slowly by hand. You will quickly locate the point to be placed at six o'clock. Mark this on the OD of the barrel with a scribed line or punch mark. The angular difference between the two marks is used to calculate the amount that must be removed from the tenon shoulder. Clear? (It's harder to explain than do.)
Let's say we determine that the barrel must be rotated 135 degrees in order to line up properly. So, how much is that in thousandths? I'm sure you pros know a better way to compute this but here is how a redneck, eyeball engineer does it.
If the tenon is threaded 18 tpi, the barrel advances .0555 per revolution. 135 is .375 percent of 360. .375 percent of .0555 is .0208. That is the amount that must be removed from the tenon shoulder.
Hope this helps.
Later,
Gene Beggs