Hey guys does anyone know a accurate way to indicate a tapered barrel in a milling machine? I will just use an indicator for back and forth, however, up and down has me stumped. I know I read somewhere before how to do it but I can't recall where. I wanted to replace a fixed from sight by milling off the existing post then cutting a slot through the leftover existing base. I need to get the front sight level so I can get this done.
Indicating a barrel on a milling machine
- Thread starter Shooting in the wind...
- Start date
WSnyder
Silver $$ Contributor
Pick two points on the barrel. For example let’s use the breech and the muzzle. Divide breech diameter by 2. Divide muzzle diameter by 2. Subtract the muzzle number from breech number and that will give you the indicator drop from breech to muzzle. Raise/lower muzzle accordingly. That would work for indicating horizontally as well as vertically.
Ex:
Breech dia 1.25/2=.625
Muzzle dia .800/2=.400
.625-.400=.225
.225” indicator drop from breech to muzzle.
Zero indicator at breech, move to muzzle and raise/lower to indicate .225”.
Ex:
Breech dia 1.25/2=.625
Muzzle dia .800/2=.400
.625-.400=.225
.225” indicator drop from breech to muzzle.
Zero indicator at breech, move to muzzle and raise/lower to indicate .225”.
For that job, it needs to be close but not perfect. I looked for it to take a pic and it's missing at the moment but a few years back, I made a tall post for a 3/8 dovetail with a set screw that I could indicate off of to level up the front sight on both planes for just such work. Never a problem and it was easy to use.
Wow thanks, man does that help. I looked for hours trying to find the answer. I really appreciate you taking the time to help a fellow.
Many of you will discredit this, but having installed over 100 big bore barrels with irons, I came up with this simple and time saving jig.
Old way:
New Way:
Barrel bands are both screwed and silver soldered.
Same for rear sight base, screwed and silver soldered.
Top of ramp must be parallel to bottom of receiver. Same for rear sight island, top must be parallel to bottom of receiver.
The goal of iron sights and scope rings is to have the base of the receiver as the reference plane. Barrel must be torqued properly into the receiver prior to aligning the sights or rings.
All required surfaces of the jig parts are machined true, including the bottom of the long plate, so when it is clamped to the milling machine table everything is true.
I drill and tap on the vertical mill, along with any dovetail milling if required. Mill has a 10x54 inch table so I can work the full length of the barreled action.
Rifle in the jig is a very nice Columbian 98 Mauser. Barrel is a No. 4 LW chambered in 9.3x62. Will become a dark timber Elk rifle. No scope, irons only.
I machined an accessory for round bottom receivers, in this case the bolt lug raceway is the reference plane.
The V blocks that hold the barrel are adjustable vertically.
If milling dovetails, just omit the sight bases.
I align the jig to the mill table using a length of ground round stock clamped in the V blocks to indicate on.
Old way:
New Way:
Barrel bands are both screwed and silver soldered.
Same for rear sight base, screwed and silver soldered.
Top of ramp must be parallel to bottom of receiver. Same for rear sight island, top must be parallel to bottom of receiver.
The goal of iron sights and scope rings is to have the base of the receiver as the reference plane. Barrel must be torqued properly into the receiver prior to aligning the sights or rings.
All required surfaces of the jig parts are machined true, including the bottom of the long plate, so when it is clamped to the milling machine table everything is true.
I drill and tap on the vertical mill, along with any dovetail milling if required. Mill has a 10x54 inch table so I can work the full length of the barreled action.
Rifle in the jig is a very nice Columbian 98 Mauser. Barrel is a No. 4 LW chambered in 9.3x62. Will become a dark timber Elk rifle. No scope, irons only.
I machined an accessory for round bottom receivers, in this case the bolt lug raceway is the reference plane.
The V blocks that hold the barrel are adjustable vertically.
If milling dovetails, just omit the sight bases.
I align the jig to the mill table using a length of ground round stock clamped in the V blocks to indicate on.
Last edited:
Machining some parts. Green stuff is coolant.
If you do a lot of sight work, a similar jig is well worth the time invested to make.
I have a Forster Jig, but it is way too small.
If you do a lot of sight work, a similar jig is well worth the time invested to make.
I have a Forster Jig, but it is way too small.
I suggest to young guys to always draw a good picture of what you’re doing and label all the measurements you know, and often it helps make more sense out of the situation, AND helps reduce simple errors for even experienced guys. Every calculation is done twice to prevent simple calculator errors.
Anytime someone had a goof up and asked for help resolving it, the first question I ask is did they draw a good picture - almost always the answer is no.
Yep I do this already.
Infrequent Shooter
Gold $$ Contributor
I think M John knows his way around S.A. Mausers.Many of you will discredit this, but having installed over 100 big bore barrels with irons, I came up with this simple and time saving jig.
Old way:
New Way:
Barrel bands are both screwed and silver soldered.
Same for rear sight base, screwed and silver soldered.
Top of ramp must be parallel to bottom of receiver. Same for rear sight island, top must be parallel to bottom of receiver.
The goal of iron sights and scope rings is to have the base of the receiver as the reference plane. Barrel must be torqued properly into the receiver prior to aligning the sights or rings.
All required surfaces of the jig parts are machined true, including the bottom of the long plate, so when it is clamped to the milling machine table everything is true.
I drill and tap on the vertical mill, along with any dovetail milling if required. Mill has a 10x54 inch table so I can work the full length of the barreled action.
Rifle in the jig is a very nice Columbian 98 Mauser. Barrel is a No. 4 LW chambered in 9.3x62. Will become a dark timber Elk rifle. No scope, irons only.
I machined an accessory for round bottom receivers, in this case the bolt lug raceway is the reference plane.
The V blocks that hold the barrel are adjustable vertically.
If milling dovetails, just omit the sight bases.
I align the jig to the mill table using a length of ground round stock clamped in the V blocks to indicate on.
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