Throat -leade finishing question

J

jGEE

Guest
Probably been asked a lot but- Would anyone care to comment on throat/leade finishing for a newbie?

Seems this might be a "black art" not many want to discuss. How is it done or maybe a few hints would really be nice. If anyone has some links to the subject that would be nice also.

I'm guessing some sort of honing/polishing. Maybe with a patch coated with fine compd, seems you would want to do some very fine polishing without knocking down the leading edge of the riflings. Is this the correct idea? thanks joe
 
No Patch

Joe:
You have the concept, but not the method. My best smith, pored a lead lap and with a special compound he formulated, would lap the leade so the bullet would have a smooth transition into the bore, but maintaining the sharp configuration of the interior of the barrel. Patches, will have a tendency to round off the corners of the rifling. Sadly he passed away can't help us any more. There are some other quality smiths, that can do a pretty good job finishing a chamber to get them that same smooth transition.
 
If you are talking about a new chamber,yes, there will be a slight roughness. This is simply the tool marks left by the chambering reamer. Looking at that area with a borescope it will look like a very fine toothed file.

The break-in process burnishes these surfaces to where the remaining roughness is not an issue. I have used 1000 grit AlOx on a patch which shines some of the roughness off. Never have determined if this helped, other than shortening the number of green patches when breaking in.

So far I have broken in about 25 Krieger barrels. Only one even had a green patch, and that was just that one barrel. I have broken in some other brands that took up to 20 patches to get rid of the break-in greening.
 
???If ????

If there is a need to lap or polish the throat after chambering, (beyond what the first few firings removes), then you probably need to trouble shoot your chambering procedure........jackie
 
I think the chance of damaging the barrel by 'polishing' the throat is far greater than any problem the surface left by the reamer may be.
 
Thank you guys, seems maybe i am worrying about something that would be for "later on" to worry about, lol. I have a lot to learn and am trying to find the things i can attempt to correct.

I have ran across several threads that mention throat lapping or polishing- just wanted to know if there was something there. I appreciate you guys letting me post here at BC. joe :)
 
Joe

I seem to remember that Lothar Walthar has a procedure to lap the throat of their L-50 Barrels due to many Gunsmith's inability to achieve a decent finsh in that area.........jackie
 
From my limited experience the leade on a rimfire must be polished/lapped/burnished/whatever. Not so on the centerfires I have chambered. I only found this out after I bought a borescope.

The rimfires I chambered still had the 'file teeth' after several hundred firings. The centerfires were smooth after just a few firings.
 
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