Put a new spin on Needle guns?

Joe been thinking about how I would open a tapered case chamber .oo3 about a quarter inch in front of the rim recess. Not being a machinist may well be something I am missing, help me understand.

Best way is run the reamer a bit deeper. It was ground to the cases taper. No reamer, it’s back in America, Rifle is in Australia.

That leaves boring bars. Not a problem to open up a hole .003. But it only needs to be opened for a quarter inch . What happens after the bit gets in .25. can’t leave a shoulder . Do you taper the chamber so it runs out to case size at neck ?  That’s not much taper in a couple inches run  and needs to be precise.  I have turned sharp outside tapers with the compound,  slight tapers outside offsetting the tailstock. Pretty sure I would mess up a chamber trying to open it up that small amount on the lathe .

Boats

Boats a bit of Crocus cloth on a split stick spun with a drill is more than enough to remove a few thousands while only being worked in just that short area where the web is sticking and it does not require the barrel to removed or re-chambered. We are only talking about a thou. or a thou. and half being cleaned up per side. But unfortunately it does away with an excuse to by a lathe to take the same amount off the cases in the same area. I have seen this approach being done by some of the top Smith's and have even done it myself with no fear of having any ill effects or having incurred any when properly done with care. I have also seen it done with a bit of lapping compound on a nice fitting fire formed case being spun or just turned by hand and then polished up a bit after.

JLouis

I have done some Chamber lapping, have a couple of laps in my tool box now. Ones a flap wheel style in 12 g, cleans up old SXS shotgun dirty chambers. Another is the lap I made for the .25 Kraig when I first started having extraction problems. It’s a 25 Kraig case with a mandrel installed through the primer pocket . Chucked in a variable speed drill,charged with compound. I found it ineffective solving the extraction problems, did not remove enough material in the right place. Then realized I had two different brass sizes. One worked one would not.  That’s when I turned a couple thou off the thick base cases and solved the problem. 

Recently polished a Marlin 1894 25/20 with extraction problems. Rough rifle, polished chamber and a stoned and re sprung extractor fixed that one

Real difficult extraction problem I had was a brand new Anshutz 1712 small bore Silhouette rifle. Returning it to Anschutz they wanted to blame the ammunition. Proved to them the rifle was only used with RWS R 50 also German & it,ought to work. Then they wanted to fix by polishing the chamber. It was nice and smooth, just too small. I did not like the solution but  in the end they polished and it worked fine. 

Lapping or polishing is certainly appropriate in some situations.  

Boats

Just an update on my case sizing problem, I have been using a bore brush wrapped with 0000 steel wool to polish the inside necks of my cases for some time now.
Today I decided to turn down some of the .303 brass that was sticking in the chamber and found that if I put the case over the brush in the drill it held it securely enough to let me file it with a fine flat file and finish it off with the emery paper.
Nowhere near as good as having a lathe but a lot cheaper.
Mike.