Throat reaming

[rasp65]

I need to lengthen the throat on my 6.5x55 AI by about .010. Dave Kiff said that his Unithroater could do the job. How involved is this kind of a job? He said it could be done with the barrel in place. Has any one used this throating reamer before?

 

[Fred Bohl]

I use Dave Kiff's Unithroater in 6mm and have done a total of 11 barrels,7 PPC and 4 6BR) so far. Only two were done thru the action,not difficult) the other 9 were done with the barrel off the action,easier and frankly my preferred way - I'm more confident but both ways work well).

All 11 were competition barrels that were starting to open their groups. The borescope showed uneven burn back on the lead ramps with most loss on the lead ramps nearest the bottom of the barrel when mounted. I just removed enough to restore an even straight lead. The least was 0.003 and the most was 0.009 depth. After correcting for the longer seating length and small powder charge adjustment, all the barrel owners report the grouping capabilities to have returned to prior levels.

 

[Rustystud]

Rasp65:

It is very easy to over cut a throat, you are removing very little metal.

I throat one of three different ways:

1. With the barrel chucked up in the lathe. I use a PT&G piloted throating reamer. I either ues the tail wheel and its dial or a block on the ram with an indicator. I leave the tail stock loose and slowly run the ram in until the reamer engages the rifling. I then lock the tailstock. I set the indicator and back the reamer out. Then start the lathe and ream the desired amount.

2. With the barrel in a chuck or vice I use a PT&G throating reamer with a Lambeth/Kiff Micrometer Adjustable Reamer Stop and a hand driver. I insert the throating reamer until it bottoms out. I slide the Lambeth/Kiff Micrometer Adjustable Reamer stop on to the reamer and slide it's collar up against the tenon face. I set the set screw. I then attach the hand driver and back the Micrometer adjustable reamer Stop back the desired number of .001 and set it. I them ream the throat.

3. With the barreled action in a vice. I have/make a bushing that is turned to fit the bolt race and lock in place with either the rear scope base screw or action screw. This bushing has a ID of .4375 and sticks out beyond the tang. The back is faced off square. I use a PT&G throating reamer, PT&G Unit T handle,.4375 OD)driver, inserted inside the aformentioned bushing with a Lambeth/Kiff Micrometer Adjustable Reamer Stop. Insert the T handle through the Micrometer Adjustable reamer Stop body,.4375 ID),then through the Bushing, and attach the piloted PT&G Throating Reamer. Slide the whole thing into the bolt race, lock the bushing in place. Slide the throating reamer in until it bottoms out. Then set the MARS and dial it back the number of .001 you want to cut. Cut your throat in alignment with the bolt race. The Pilot and bushing will guide your throating reamer.
Rustystud

 

[rasp65]

Thanks for the info. The rifle is a Ruger No.1 so there is no raceway to use as a guide. Does cutting by hand require a coolant flush of some kind?

 

[Fred Bohl]

Your last question should be more knowledgeably addressed by Nat (Rustystud) but since he has not as yet I'll tell you what works for me.

Work with the barrel pointed straight down. Apply a little light cutting oil to cutting edges of the reamer and make your cut,you are removing very little metal to go a few thousandths deeper) then flush the chips out the barrel,I just use "Tap Free" because I have a lot and it is cheap locally). Finally do a very good cleaning of the barrel.

 

[Rustystud]

If you can expose the face of tenon then you can use a MARS and a hand driver. I would put the barrel level in a vice and use a good high sulfer cutting oil. I would use an air hose to blow the chips back into the chamber and not down the barrel. Then wipe the chips out with a rag. The whole job would take less than 5 minutes to do.
Just my .02 cents worth.
Rustystud

 

[rasp65]

Thanks Rustystud & Fred The info you provided has been most helpful. Bob