Proper method for throating reamer use???

S

Silverfox

Guest
I have a .17 Tactical that has 0" of free bore and want my gunsmith to use a throating reamer to increase the free bore to .040". My gunsmith is somewhat reluctant to try this procedure. Please enlighten me on the steps you would use so you are sure you are only cutting .040" of free bore and not more than that. After the barrel is set up in the lathe, would you recommend doing the increase in free bore by hand? Thank you for any assistance you can give to me.
 
There are two ways I approach jobs like this. One I can do it with the barrel on the rifle or set up in the lathe.
Barrel on; Make a rod guide for the action. This entails drilling and reaming a 3/8 hole through a rod. after drilling and reamer turn the outside diameter to fit the action. Next take a piece of 3/8" drill rod and make a t-handle long enough to reach through the rod to the chamber. Do what ever is needed to hold the throating reamer on the end. Now you have a way of holding the reamer, guiding it and turning it at the same time. How to control the depth? Take a short piece of round stock the same size or smaller than the rod guide, drill and ream a 3/8" hole through it. Add a set screw from the side, slide it on the the T-hande before inserting the reamer into the action. Push the rod guide forward until it touches the rear of the barrel, run your reamer in until you just feel it begin to cut, slide the stop you have on the rear of the T-hande up until the gap between it and the rod equal the amount you want to lengthen the throat. Lock it down then crank away until the stop hits the rod guide.

barrel off and indicated in the lathe: Hold the throating reamer with a very short handle on it. Run it in until you feel it start to cut. I zero my travel indicator, start up lathe and cut to my number.

It's easy to over shoot your stopping point.

Dave
 
Dave Tooley--Thank you very much for the information.
 
You can also use a uni-throater that Dave Kiff makes. It has a long bushing that goes around the body that goes to the shoulder. Behind the bushing it is threaded for two rings, one a stop ring and the other a lock ring. It has a graduated dial that allows you to go in however many thousandths you want once you determine where the chamber reamer cut the original throat. You can either use it in the lathe or use a long t-handle wrench that screws into the back of the uni-throater. It's very easy to go too far when using a throating reamer. The uni-throater helps keep you from going to deep, but the key to using any throating reamer is to determine your starting point where the throater just starts cutting. If he has a bore scope, I'd check the progress as the reamer is deepening the throat. Go slow and check it often.
 
Mike, I suppose I've been fortunate so far.. Once I determine a starting point I believe my tailstock numbers and cut the entire throat in one pass.. One not so fine day I may go in too deep but it hasn't happened yet !! I'm just using the standard throaters in various calibers and they've done a wonderful job.
 
Pat, as long as you can determine where your throater starts cutting it's no big deal to advance the throat in the lathe. Run it in however much you want to go in and you're done. The uni-throater will work for those who don't have a lathe, but at more expense than a regular throater.
 
Throating

First, let me say a sharp throating reamer can cut the rifling out of a barrel so quick you don't know it has been cut. Think both Dave and Mike covered this but I have learned the hard way a couple of times and don't wish a set back or barrel replacement on anyone.

You certainly don't have to do it this way but it works very well.

For Remiingtons or clones Make a bushing (.701 OD and .4375 ID) to fit the bolt raceway that is long enough to extend past the tang.

Make a stop with a set screw or buy a Lambeth/KIFF Micrometer Adjustable Reamer Stop. Slide the stop or MARS onto the PT&G Uni throater driver. Now slide on the bushing. Now screw on the throating reamer with the propper pilot bushing. Leave evrything loose except the reamer. Insert the reamer, and bushing into the bore and bolt race respectively. Use a scope base screw or action screw to secure the bushing inside the bolt race. Slide the reamer and unit throater in until the reamer bottoms out. Don't push it too hard as you will damage it. The reamer is now at it's cutting starting point. Slide the stop up until it bottoms out. Insert a selected fealer gauge between the stop and the bushing. Then lock the set screw in the bushing. If you are using a MARS bottom it out then dial it back the desired depth. Now you can ream the throat a specified amount.

Nat Lambeth
 
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