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Chambering reamer piloting

Froneck

Titanium
Joined
Dec 4, 2010
Location
McClure, PA 17059
I have been using a set (rougher/finisher) of .22lr from Clymer for quite a while. Not sure what style. decided to try Bentz style from Manson. Also thought replaceable bushing pilot would be good to have, at the time I needed .217" pilot. (ordered and received) I then got a tightbore barrel blank form Lilja, pin gauge indicates I need .215" pilot (.216" pin will not fit) Just a note I only do Target Pistols! Bushings were ordered and received from Manson.
One day a thought came to mind, what good is the pilot on the finished if a roughing reamer was used? Pilot will do nothing until the very end. I know a reamer will tend to follow a hole and amount of material removed from .22 barrel for chamber is very little. But would it be better to short stroke the reamers so finisher pilot will be guided?
 
A few years ago the top rimfire bench rest smith's were boring the chamber on cnc lathes.

The best method I found was to bore 3/4 of the chamber depth then ream with a (solid adjustable) reamer holder.

I found it critical that the inch or so of the barrel after the chamber be absolutely dead on dialed in like .00005 stuff.
 
What's to bore on .22LR? Pilot diameter .217" another reamer ,218". If chamber is .226" on the small side, Cutting .004"/side cut easily can start oversize!
I understand so little needs to be cut rougher is not necessary but is supposedly increases the life of the finisher. And making target pistols for someone like my son who is one of the best in the country I want as much accuracy from the barrel as possible.
 
IMHO the purpose of boring is to remove ANY runout that exists in the chamber area when compared to the transition area from chamber to barrel.

I fit my pilot bushing after the boring so no false readings.

Also bushings are available in .0002 steps.

Are you slugging the barrel to make certain that the small end is at the muzzle?
 
IMHO the purpose of boring is to remove ANY runout that exists in the chamber area when compared to the transition area from chamber to barrel.

I fit my pilot bushing after the boring so no false readings.

Also bushings are available in .0002 steps.

Are you slugging the barrel to make certain that the small end is at the muzzle?
this
 
Barrel I get from Lilja have chamber side marked. In the Past I had no problem getting .22LR to group 1/2" or less at 50 yards in semi-auto pistol barrels. Being NRA Precision pistol competition longest range is 50 yards there is no sense to try longer distance.
 
Reamers... like so much else ...

'Consumable tooling' ...

I'm with the dial and bore crowd... but my primary is just a .225 2' throater. Bolt guns ...

Fine with a Bentz too, 1 or 2 thou under the mouth.

More ... most ... important is keeping the leade from chip welding. Rather infuriating to 'set back' a barrel before you've even finished chambering it. My fingernail is usually enough. Otherwise, I've got a stick of copper that comes in handy on occasion. Mostly CF with real shoulders.
 
Reamers... like so much else ...

'Consumable tooling' ...

I'm with the dial and bore crowd... but my primary is just a .225 2' throater. Bolt guns ...

Separate throater and body reamer could almost produce what I'm guessing is the current state of the art in rfbr chamber design.

This is close except there is a slight relief cut in just before the 15° throat angle that allows the case crimp area to expand beyond the body diameter...

The theory is it releases the bullet more consistently...I think it's all very ambiguous
 

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Maybe doable with modern cnc tool grinders.

I'd probably just get 2 reamers made. A 225 2deg throater like I'm using, and another for the body. Saves trying to make that teeny 15deg transition from the 226 body dia.

It also saves the throat portion from transiting the full depth. Adds wear and the risk of scoring where you don't want it.

One other thing, I scrub the chamber good with a patch with JB worked into it. Seems to knock off whatever tiny burrs the reamer leaves on the leade.

My HP barrels ... the whole waste a day cleaning after 1 shot over and over ... I'll shoot a whole match on a new one, and find little or no copper in it when I clean.

I've had a couple from 'Pro's' that required mining ...

I kinda suspect the pressure flush with water soluble coolant is a factor. And of course they just don't check for chip welding.

A Krieger from one vendor, the change in seating depth from new to when it finally quit copper fouling was obscene. And I could track the progress with my borescope. The copper fouling stopped when the last of the tool marks burned away.

You don't have that 'advantage' with a rimfire.

Bolt guns, I chamber a bit deep and then face and thread to headspace. Just in case.
 
I do a similar chamber polish with jb except I turn a piece of uhmw to the groove diameter and just long enough to reach the end of the leade.

This is my idea on how to do it but this finishing step is probably the single most guarded secret in
Rfbr.
 

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Had to pour another shot of Ardbeg ...

'Nutation' ... like a football not properly thrown, where the 'points' move in a circular pattern around the path of trajectory, rather than track it in a proper spiral.

I rotate it between my fingers ... probably does nothing ... while slowly rotating it between my fingers in that motion. Forward and reverse on the spindle, until it's just touching the edge of the grooves.

I think it's a 10-24 slotted round head, bare steel, I found in a junk box. The head radius looks good for 22 to 30 cal. I might have done a 338 with it as well.

Comments from the 'experts' * ... don't touch it with anything but copper or brass ...

Pffff, it ain't the material, it's the pressure.

* I ain't, nor ever will be ... or consider myself... an 'expert'. But my xxxx seems to work just fine ...
 








 
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