Chamber Mouth Polishing?

[PS Paul]

Hi, folks. I did a search on the forum search tool, but did not get answers for what I want to accomplish.

I've loaded cast boolits in a RBH for almost 25 years. The last RBH I owned was .45 Colt and had oversized chamber mouths. Some were .454, one was .455 and one was .456. This caused some difficulties in obtaining accuracy (LOL!!) and casued errant flyers in groups. Took a bit of tinkering with moulds and powders/brass/hollow-based boolits to finally get her workin' up to snuff. A labor of love.....

Eventually ( and kind of regrettably) I sold that revolver off. Recently, I acquired a Lipsey's NMBH Flattop in .45 Colt AND .45 ACP on the smaller frame. I am sure some of you are aware of this neat little revolver which cannot be hot-loaded to 25,000 to 32,000 CUP like some suggest with the larger-frame BH's.

So the quest is as follows: I measured the chamber mouths on the .45 Colt cylinder with a pin gauge. They measure .451, BUT two of the chamber mouths are "just a cat's whisker tighter". I am talking just a touch tighter by a ten-thousandth of an inch or two. The .45 ACP chamber mouths are all completely consistent in diameter at EXACTLY .451.

So I don't want to appear "mental" over the ever-so-slight dimensional variations in the chamber mouths, but it seems to me there might be some method of basic chamber mouth "polishing" that a layman such as me could perform? I do have some mechanical abilities, but my hope would be there are a few of you who have used some type of dowel or rod with varying grits of polish or clover-compound or the like to barely polish out those chamber mouths by hand?

I do not want to go to a gunsmith because I can live with those very slight variations, but if it is something I could essentially do myself and make "near-perfect", I would likely feel a real sense of pride in accomplishment for doing so. Not to mention perhaps increased accuracy?

So I'm simply looking for a few suggestions from some of you fellow casters out there who have personal experience with something like this and perhaps who could point me in the right direction without doing irreversible DAMAGE to my revolver!!!

I will look forward to hearing back. Thanks!:-)
Paul

[PS Paul]

MODS, if this thread might belong in gunsmithing tips and tricks? Please feel free to change it to that area if so desired.

[L Ross]

PS Paul, I recently acquired an Old Model Blackhawk in 45 Colt and as soon as I got it im my sweaty hands I pin gauged the throats. Aaaaarrrggghhh! .450" for 5 of them and .449" for one, as you might quess it shot less than stellar groups and leaded slightly. I sent it to Cylinder Smith who had a prompt turn around, reamed the throats to EXACTLY .4525" and charged me only 42 bucks that included shipping! I wouldn't even begin to think about trying to lap my own for that kind of service.

Duke

[stubshaft]

Had the same problem with mine and Cylindersmith redid it for me.

[Wolfer]

If you go to the Beartooth bullets site and look in articles for ( Ruger America's best do it yourself kit ) he tell how to even up cylinders. Great article, I have it saved. If you can't find it PM me and I'll email it to you.

[PS Paul]

I found the article ion Beartooth. Thanks, Wolfer. That is EXACTLY the type of thing I'm looking for!

I am familiar with cylindersmith and his work/cost/turnaround. He does only .45 Colt cylinders any more, so I did consider that, but the cost is not the issue. Like many things I do and we casters enjoy, I want the satisfaction of doing it MYSELF, you know? Like I mentioned above, it is pretty close out of the box, but I feel it could be a bit better. I am getting groups under 2" with little load development, so I am not having the issues with inaccuracy the riter at Beartooth intially had with his 7 to 8" groups...... Appreciate the info!
Paul

[gray wolf]

Let me understand this,
.0001 is what your after and your not a first class machinist ?
The last time I looked a .0001 was quit small, as in shoot it first and after shooting it still leave it alone.
I say this cause IMHO if you miss the .0001 you will be chasing it the other way.
I would size for a snug thumb push through fit. Let the barrel see if it can find the .0001

[farmallcrew]

Not on a hand cannon, but on my Keltec P-11 and Pf9, some of my j words would get hung up feeding. couldnt figure out why. then someone told me that there might be ever so slight burs or grooves that wont let the next round feed correctly (this was happening with reloaded and factory loads). So i went to my gun medicine cabinet and got my metel polish, got my dremel and away i went. 15 mins later, feed ramp smooth, and havent had a problem since. So... i would say, a little polish on feed ramp or chamber mouth probably wont hurt.

[Multigunner]

Only time I've polished chambermouths was on an el cheapo foreign made .38 Special, not because the chamber mouths were tight but because they were roughly drilled out and not reamed. The walls of the chamber mouths were rough as a wood rasp.
I used a dowel rod and 1,000 grit silicon carbide paper then emery paper. Accuracy was unexpectedly good after that.

[9.3X62AL]

PS Paul--

What groove diameter are those .451" throats feeding into? THAT is the missing measurement. Once the groove dimension is known, the throats can be addressed IF NEEDED. I don't think .0001" of slop either way could be discerned downrange, but if your grooves are at .452" like those in my mid-90s BisHawk, then some surgery is indicated. If the grooves match the throats at .451", I would shoot it 400-500 rounds and see what develops. I usually invest in a box or 2 of factory ammo for each new firearm I buy, and run that through for a warrantee check. I figure if something catastrophic is going to happen or let go, I'd like that to happen with factory ammo on board. This makes for a much shorter cover letter to accompany the defective item.

That same BisHawk had throats that ran .448'-.449", so I got one of the piloted reamers developed for this task and opened the throats to .4525". I next polished them out with 400/600/1000 grit alum oxide sandpaper to .453". Now I fire .454" boolits through 453" throats that feed .452" grooves, and it shoots GREAT. Sometimes, ya gotta finish building a firearm. Still, I ran about 1200-1300 rounds through that mis-built Bishawk before taking tools to it. The thing actually shot jacketed bullets OK, but was a one-boolit-wonder with castings--Lyman #454490. Now, EVERYTHING shoots well--200 to 325 grain. It's quite a machine.

[PS Paul]

Gray Wolf, the two chamber mouths that differ from the opthers are just "ever-so-slightly" tighter. I do not have pin guages with that fine measuring ability. I know it sounds like just a "little" difference, but the idea is to simply polish them slightly so they are ALL the same-exactly. Not taking off a lot. The beartooth article actually describes just what I would like to accomplish.

9.3x62AL. I will be slugging the bore this Sunday. I am also going to slug just past the forcing cone where the frame and barrel thread together becasue i suspect a little "tight spot" there like many Ruger Single-actions. I've actually cast and shot over 2,000 boolits in the 3 months i have owned it (I know, not enough, but time constraints, you know?) with decent results, but i would like GREAT results and I BELIEVE I can ultimately achieve that goal with some "judicious" polishing? As mentioned in the OP, I do have "some" skills, but I do not think a first-clas machinist would be necessary UNLESS I wanted the mouths opened jup to .452. Then I would send it to cylindersmith. I am not a first-class machinist and the "snug thumb push fit" is what I hope to accomplish equally throughout all chamber mouths. The .0001 measurement is likely too fine, but I used that description of variation in measurement to simply illustrate that the mouths are close, but not quite 'perfect", if that makes sense?

So the message I am getting from several of you is that my hope to do minor polishing myself to get the desired results is possible. And I do appreciate all the feedback.

I am going to really think this whole thing over and chew on it for a bit. I may be desiring a solution to a problem that does not actually exist- but maybe not. After I determine the groove dimensions, I will take all the info and make a more informed decision at that time, thanks to the informing from all of you good fellas!

[gray wolf]

I am going to really think this whole thing over and chew on it for a bit. I may be desiring a solution to a problem that does not actually exist- but maybe not. After I determine the groove dimensions, I will take all the info and make a more informed decision at that time, thanks to the informing from all of you good fellas!
As always the information on this forum is great, We all had a little different approach to the problem. I quoted what you said cause it makes a lot of sense and I sure agree with you decision.

[Mal Paso]

I don't think the finish of the throat is as important as size and alignment. I bought the Manson Reamer Kit for $130 including all the bushings. It leaves slight tooling marks but the holes are true. The reamer manufacturing tolerance is stated size +0.0"-0.0005". http://www.brownells.com/.aspx/pid=7700/Product/REVOLVER-CYLINDER-THROATING-REAMER or buy direct: http://www.mansonreamers.com/index.html.

[PS Paul]

No sweat, Mr. gray Wolf. Reading it literally word by word, I see it might be a bit confusing. Picture this, doing the "thumb push-through" with a .451-sized boolit (I have .451 .452 and .453 sizing dies for my lubrisizer), two of the cylinders the .451 boolit kind of hang up and need more pressure to make it through- barely. I am really liking a lot of the information. Exactly the reason i posted this thread because there are many on this forum who I would consider "firearms genius", you know?

Now I am reading Mal Paso's post about "alignment" as opposed to sizing. I haven't actually considered this, so that is going to require MORE thought. LOL!!!

On top of ALL this, I have two other revolvers. One is a security six with only two chamber mouths that are sized evenly! Nowhere near as accurate as my NMBH, it can do 2.5" at 25 yds and sometimes just around 2" with three touching and the rest, presumably due to the chamber mouth variances, flying away. If the polishing thing works on my NMBH, it will be used on the others right away.

Funny the .45 ACP cylinder is just dead-on though. It is a touch more accurate, which I did not mention in the OP, so that too is a reason for me considering some slight "home improvement". I failed to mention this and it actually has a lot to do with my thoughts about polishing the .45 Colt cylinder in the first place.....

[9.3X62AL]

PS--

Your take on the matter seems sound to me--don't do more than is required to acheive the desired result. Your round-count to date is re-assuring, too--the OP made it almost sound like the involved revolver was nearly new and only slightly used.

A snugly-fit cloth patch on a correctly-sized patch jag can reveal whether frame constriction is present where the barrel threads into the receiver (or elsewhere, for that matter). One good quirk of that BisHawk of mine is the absence of such a constriction--it was and is a consistent .452" stem to stern.

Are you getting any leading in the bore? If so, where are the deposits showing up?

[PS Paul]

9.3, I have been shooting .453 and .454 boolits with almost ZERO leading. I got just a bit in the first 500 rds. at the range (all in ONE DAY!! Whew!), but it was all right at the end of the barrel, oddly enough, NONE anywhere near the forcing cone. NOT what I expected. I did run a brush/patch through very lightly twice during that marathon session....

Still doesn't necessarily mean I do not have that constriction, but I have just come to almost take that constriction for granted with most Ruger revolvers. I am going to go home tonight and try the patch-on-brush to see and i will post again. Thanks, man!
Paul

[swheeler]

9.3, I have been shooting .453 and .454 boolits with almost ZERO leading. I got just a bit in the first 500 rds. at the range (all in ONE DAY!! Whew!), but it was all right at the end of the barrel, oddly enough, NONE anywhere near the forcing cone. NOT what I expected. I did run a brush/patch through very lightly twice during that marathon session....

Still doesn't necessarily mean I do not have that constriction, but I have just come to almost take that constriction for granted with most Ruger revolvers. I am going to go home tonight and try the patch-on-brush to see and i will post again. Thanks, man!
Paul

Paul if your throats measure .451 why not shoot .451/.452 bullets, your bullets are getting sized to throat size anyhoo. I'm surprised you don't get lead in the throat or chamber shootin bullets this large. I would get the barrel slugged and go from there, that will tell you what the throats need to be sized to.

[PS Paul]

You know, Swheeler, I was thinking the same thing about .451 on my way home on the ferry. I have the sizer, but only used it to size a push-through boolit. Still won't fix the mouths perfect, but it might be a tad more accurate? Sluggin' barrel happens Sunday after some work on the deck before the WET winter sets in. [I]t's been starin' me in the face and like a light went off in my head. ha-ha! No matter what happens, I am still going to be thinking about those two "less than perfect" mouths though.... See, I've gone and worked myself up into a lather over this and now, after this thread and all the terrific suggestions, I just HAVE TO do some fixin' LOL!!!! Stay tuned..... Gonna check that barrel restriction tonight. It's my birthday today and I need to spend some time with the kids before I head to bed.