Lapping Compound for chamber

[Steamin]

Could a guy use valve lapping compound for the chamber as long as he doesn't get carried away with.
A co-worker and I were repacking valves last night and got on the discussion of this and we didn't know.
So what's the general consensus.

Steamin

[STUMPJMPR]

0000 steel wool on a cleaning rod with a drill works good for polishing shotgun barrels.....How abrasive is lapping compound...I used Isso bore cleaner which is a mild abrasive on the steel wool.....I imagine the same thing would work good for a chamber...

[Smokin Joe]

Flitz on a bore mop, chucked in an electric drill.

[Steamin]

Clover compound, 320 grit - fine.
We use it for polishing the mating surfaces of the valve.

[MTGlass]

I'd bet you'd be fine with Clover 320.  I've not used it for chamber polishing, but it's what I would use.  I have Clover 320 and 400 at home.  In their Technical Manual, Beartooth Bullets recommends Clover 320 silicon carbide grease mix for fire lapping with cast bullets.

This the stuff? http://www.use-enco.com/CGI/INSRIT?PMAKA=391-5872&PMPXNO=947034&PARTPG=INLMK32

[NFG]

A roll of 1" wide 320 wet/dry loose fit in chamber rolled on a piece of brass, some cutting oil and medium fast drill speed.  The object is to scratch up the chamber slightly...NOT to polish it.  A polished chamber will not hold a case as well as a scratched one so you get more thrust on the bolt head.  A highly polished chamber is great for case forming tho' for the same reasons because a slightly oiled case in a highly polished chamber will slip easier and fill the chamber better.

I always scratch up a well cut chamber...just a bit...you don't need much...just knock off the shine...and do it just about like you would do the walls on an engine...45° cross hatch pattern.  Stay away from the shoulder...just the chamber side walls.

'Njoy

[LaOtto222]

NFG is correct - you do not want to polish your chamber to a high shine. It will give you more problems than you can imagine.

[trotterlg]

After I cut a new chamber in a barrel I use a piece of Scochbright pad about a 1/4 inch wide and 3 inches long folded over an old bore brush.  Put lots of oil on the pad and run it in the chamber with an electric drill.  Seems to put just the right finish on it.  Larry

[NoBull60]

  Call me on this. I'm a little duh on this. What is the purpose of the bolt lug/face? And why is the base of the bullet so much stronger that the side walls? Doesn't an unpolished chamber cause stuck cases? Could scarring on the case become a problem for reloading inside of the dies (stuck cases)? Now, these are all legit questions. I'm not trying to stir the pot here so don't go and ream me new chamber. Ok?  Please enlighten me before I mess up my new handi chamber. I ask these because I've "read" other opinions/ideas on different sites regarding this matter. I'm just asking for the facts, "Jack". in addition to opinions.


                                                                              NoBull60 

[STUMPJMPR]

If its a brand new factory cut chamber and its not giving you any problems why mess with it?

[trotterlg]

"Mirrror" finished surfaces tend to stick together, try picking up one piece of glass stacked on top of another, they will stick together because there is not enough room between them for air to flow into.  Polished metal blocks do the same.  Some slight distortions of the surface are good in some cases and a rifle chamber is one of them.  The distortions need to be rounded soothe ones, not the sharp rings that are left by reaming.  Larry

[Smokin Joe]

There is a good article about this over at Varmint Al's page:

http://www.varmintal.com/a243z.htm

If you read the whole thing it will cause your brain to itch, so here's the gist of it:

"DISCUSSION.... There have been many statements about the necessity of having a rough or "not too smooth" rifle chamber and for sure, not polished rifle chamber. Many of the statements go on to say that the friction between the cartridge brass and the rifle chamber prevent the load on the bolt face from being excessive. This series of calculations show, at least to me, that the bolt face load is not appreciably higher with a smooth or polished rifle chamber. What a rough or high friction rifle chamber does do is to stretch the brass on each firing if full length resizing is used. If only neck sizing is used, and the bolt closes with mild resistance, then only the deflections in the bolt lugs and the action stretching will, with a rough chamber, contribute to more brass case stretching but will be kept to a minimum.

POLISHED CHAMBER NOT ZERO FRICTION.... One of the misconceptions, I believe, is that many people perceive that polishing the rifle chamber leads to a friction coefficient of zero. That is not the case. Even when polished, the surfaces under high magnification look like raspy files and the imperfections of the mating surfaces lock up with each other and still exhibit friction forces. A polished rifle chamber does not lead to excessive bolt load forces.

THE BRASS STRETCHES.... At modern rifle gas pressures, the brass case stretches to let the case head rest on the bolt face. The tri-axial state of stress in the case wall will allow for but a few hundred pounds of axial force before the cast will undergo plastic flow and only support a couple hundred pounds of axial force. If you experience case thinning near the case head on your brass, it can probably be reduced by polishing your rifle chamber."

[dpe.ahoy]

Wow, That's alot of info!   I thought I was reasonably smart, but most of that is over my head.   Thanks for breaking it down.  Does this mean I have wasted days cleaning case lube off cases?    Just a thought.  Now, How do I scratch the itch in my head?   DP.

[NoBull60]

            Wow!! So a little smoothness is o.k. so long as it's not too polished. Maybe to some extent the same that the rifling would get smoothed after using J-B paste for 50 strokes (more or less). I hope I'm understanding this correctly. VarmintAl seams to HIGHLY educated regarding this matter. That's heavy duty reading. Way above my understanding. I'll just try a few strokes with J-B.

                                                                      NoBull60

[Smokin Joe]

Now, How do I scratch the itch in my head?

My Doc says when your brain itches, "go home and think real hard about 50 grit sandpaper:

 

[Cat Whisperer]

EXCELLENT REFERENCE!!!!!!

[ib_crawlin]

A mini automotive brake hone chucked in a drill motor run at low speed with plenty of WD-40 for lube. Followed by a round cloth polishing wheel and compound spun by a Dremel tool.   Works great for shotgun chambers.

RON

[NFG]

Well actually........unless an empirical study has been done, which I'll bet has never happened before nor will never happen...most of the information re-guarding the ins and outs of chamber "mirror smooth vs all scratched up" is mostly by guess and by golly.  It seems to work...don't ask my how or why...don't bother me with expert opinion...I don't care if Johnny says nyet...get out of my way, it's beerthirty!!!

Varmint Al is an excellent engineer and has many accomplishments behind him if you bothered to read his resume...I would certainly not argue with him, but I'm still from Missouri...I have to get my hands dirty and mathamatical constructs are just the beginning of a study and even then doing a scientifically accurate experiment takes a reason, money and equipment...all of which I don't have in abundance.

All I can say for sure is the way I do it was passed down from previous experienced 'smiths, it seemed  to work for them and me...and I WOULDN'T us a brake hone in a rifle chamber although they do work well for shotgun chambers AND bores...I've done that several times before and will do again if I mess up and rust the **** out of a bore again.

AND...I would be very interested if someone would do an actual scientific test on...say a 1000 chambers...using all the extant required equipment and publish the results in a reputable publication.  That way the correct application and use will be established and we can use all the 'net BS in our gardens or to grow hair or find some other moneymaking application....  I could use a large infusion of capitol.

'Njoy