Throat reaming techniques?

[Mram10us]

I had a short chambered 7mm a while back and wanted to lengthen the throat. I cut out .050" too much because it cut so fast and it was my first and only time. What techniques do you guys use to throat ream?
1. How do you find the exact start of the lands with those sharp little suckers?
2. How do you go about measuring where you want to end up if doing by hand?
3. If a chamber is already done and out of the lathe, would you rechuck or do by hand?
Thanks in advance

 

[J E Custom]

I had a short chambered 7mm a while back and wanted to lengthen the throat. I cut out .050" too much because it cut so fast and it was my first and only time. What techniques do you guys use to throat ream?
1. How do you find the exact start of the lands with those sharp little suckers?
2. How do you go about measuring where you want to end up if doing by hand?
3. If a chamber is already done and out of the lathe, would you rechuck or do by hand?
Thanks in advance

When I can, I like to order a reamer with the exact throat i want, this way the throat alignment is true to the chamber. When I can't go this way, I use a system for throating that has bushings that not only align the throater it can also set the depth I want. This is a handmade throating tool, but its works very well and I always set it short on the first cut and make a final cut to the exact depth I want. normally I can come within .001 of what I wanted. (This is a hand done process).

The bullet shape and magazine length has a lot to do with the throat depth I want.

J E CUSTOM

 

[Mram10us]

When I can, I like to order a reamer with the exact throat i want, this way the throat alignment is true to the chamber. When I can't go this way, I use a system for throating that has bushings that not only align the throater it can also set the depth I want. This is a handmade throating tool, but its works very well and I always set it short on the first cut and make a final cut to the exact depth I want. normally I can come within .001 of what I wanted. (This is a hand done process).

The bullet shape and magazine length has a lot to do with the throat depth I want.

J E CUSTOM

Thanks. Reamer is just a hair shorter than what I want. I made up a tool that slides in bushing in the action to get it close, but as you know, it isn't as good as dialing in the lathe. I'll try hand reaming and aim really short like you suggested.

The part that got me last time was trying to find the start of the throat. It was very hard to find the zero with the throat reamer in the tailstock. Hopefully it's easier with the hand reamer

 

[Mram10us]

Here's the tool I made up. Just a simple aluminum bushing that fits in the rear of the action action and an aluminum rod with 1/4" hole for the throat reamers. Nothing cosmic, but since it's for slow speeds, I decided on aluminum.

 

[Mram10us]

Worked great! Cleaned in between cuts with a patch and rechecked the coal. Took 4 passes. That little jig worked great. Checked with borescope after and it looks right