throat?

[762willdo]

Is it possible to open the throat and a rifle you have already fired? if so what tools are required etc.
thanx

 

[fdshuster]

76willdo: If you mean to lengthen the throat, as if you wanted to seat the bullets further out in the case neck, yes, a gunsmith can use a throating reamer & give whatever freebore dimension is wanted. I did just that on a rifle I had with zero freebore. Could not get it to shoot, increased the throat to .060" of freebore and groups were smaller.

 

[watercam]

You can open up the diameter of the throat with a chambering reamer with the size you want. One needs to be careful that one only runs the reamer in until it just reaches the shoulder but does not cut the shoulder deeper.

 

[fdshuster]

I guess "willdo" should re-define what he wants to do, 2 completely different answers for the same question.

 

[762willdo]

i have a chamber with zero freebore and would like to open that up a little

 

[fdshuster]

Yes, easy for a qualified gunsmith to do, carefully, because I've been told it's easy to go longer than wanted. What caliber?

 

[RonAKA]

Before you jump in, it may be worthwhile questioning the gunsmith on how he will make sure the throat will be cut concentric with the cartridge and the barrel bore. I believe normal practice is to cut the chamber and throat with the same reamer, piloted in the bore to ensure concentricity.

 

[holstil]

This is one way to do it. I use the bullet I want to throat for seated in a case as a go gage. My throating reamers are piloted so I just let the bore guide it with the proper fitted bushing. A few twists of the wrist (or fingers) is all it takes. It is amazing how very little effort it takes to remove material with a throating reamer.
You can set the bullet in the case plus or minus for jam or jump. Having a depth fixture, like the top of a micrometer bullet seating die without the stem and opened up to the reamer OD helps.
I use min. spec throats on my chamber reamers so I can throat for different bullets.

Jim

 

[fdshuster]

jim: "It is amazing how very little effort it takes to remove material with a throating reamer". Exactly what I was referring to when I said it must be done "carefully". I actually wanted .045" to .050" of freebore, from the original reamer zero freebore dimension, but it turned out to be .060" to .065". It all worked out though since the groups did improve when I was able to jump the bullets. After the work was completed I checked out the throat with my Hawkeye, and all was concentric.

 

[Rustystud]

There are several ways to judge your throat reaming depth. Remember you are cutting a cylinder with a specified taper not a linear hole. I would suggest you use a PTG piloted throating reamer, Uni-throater driver and make three bushings to fit over the uni-throater two with set screws. The first bushing is turned to fit the bolt race. It has a square back that is longer than the action tang. This bushing is held into place by and rear scope base screw. The following two bushings will have squared ends and have set screws. Select the correct pilot bushing for the bore. Insert the throating reamer into the bolt race followed by the guide bushing. Lock the guide bushing into place. Slide the throating reamer into the barrel gently until it bottoms out. Then slide the second bushing down against the first until it bottoms out. Lock the first bushing by tightening the set screw. Slide the third bushing down and insert a fealer gauge for the amount of throat you wish to remove. Lock the third bushing with the set screw. Then loosen up the set screw on the second bushing. Then ream until the third bushing bottoms out. Don't forget to use a good cutting oil infront of the reamer. before inserting the reamer. Use a sized case with your bullet seated to dept as your gauge.

This can also be accomplished with a Lambeth/Kiff Micrometer Adjustable Reamer Stop.
Nat Lambeth

 

[holstil]

fdshuster, I understand. Glad to here it worked out for you.

Rusty, as always, thank you.

Jim