Choke bore - or something to be concerned about?

[hockeyref]

Some background: I was cleaning out the GPR last night and decided to wrap a patch around an old brush for a bit tighter fit. Wasn't sure if I was seeing rust or crud that was "still" coming out from when I used some bore butter last year (I thought that I got it clean, but you guys have documented the tenacity of that stuff). My Procedure always starts with two patches wet with a whitches brew of 1:1:1 Alcoholeroxide:Murphys to quickly cut the crud and then immediately follow up with water plunging\flushing. On the initial patches I got what looked like coffee stained patches.... So, I used the brush and patch combo and really scrubbed her out. After a little while I started to just get streaks from the rifling... Sometimes really dark, but usually just light enough to see the outline. Kept at it until it got to a minimum.Then I swished her out with a couple oz of alcohol and patched with the brush again. Final step was the brush\patch with oil on it.
Now here's where I noticed it.... Guess the slick oily patch and the tighter patch & brush combo made it easier to feel. The first 12" of bore from breech on out is looser than the rest to the point that there is a specific location that it widens\tightens up (right at the end of underlug that has the ramrod guides on it). Pulling back out I can feel the taper.... first 12" is loose and consistent, then a choke point (almost like a shotgun forcing cone) then a gradually tighter bore out to the muzzle.

Now, I know a choke bore can be desirable on a modern cartridge gun, but what are the implications here? Almost makes me want to try an over-powder wad just for giggles. Gun loads easy enough.... shoots well.... Patches seem to be in good shape, not burned or shredded, occasionally a few frays or cuts. I still need to smooth out the rifling where it meets the crown just a tad bit but I'm probably just gonna shoot it in rather than mess with it too much.

 

[CoyoteJoe]

Inconsistent bore diameters are pretty common in modern rifles as well as muzzleloaders. I've had many barrels where I could feel tight and loose spots as I ran a very tight patch through a clean bore. As little as .001" may be very noticeable when pushing a tight patch and jag combination. Yours at least sounds like it is "choked" the right way, tighter at the muzzle than breech. I've been stuck with barrels which were much tighter at the breech or which had alternate tight and loose spots. Unless you want to get into a major project of lapping the bore I'd just not worry about it.

 

[BrownBear]

My most accurate by a large margin is a Green River Rifle Works 58 cal Hawken. And it has a seriously choked bore. I have to use .562 balls to shoot it- they're really tight at the muzzle. A bare .575 ball just sits on top of the muzzle, and a bare .570 will hang if it has the slightest irregularity. Yet when the patched .562 ball gets about half way down the bore, the load will virtually fall to the breech with the weight of the rod alone. We're talking serious choking here.

I talked with the GRRW gunsmith that built the rifle, and he gave me some background on GRRW barrels. Somehow the way they bored them ended up with a progressive choke from one end to the other. They never bothered to try to beat it, because all the shooter reports bragged about the increased accuracy.

I'm no smith and certainly no expert on barrels, but this one is so good it has me looking for another. Caliber won't matter. I'll just be proud to own another GRRW, choked bore and all.

 

[Sperit de bois]

FWIW I was told and shown by an old time gunsmith the bad side of Peroxide,,,It bubbles cause it creates "oxygen",,so when it is mixed with Water it creates rust,,,,,Water and alcohol will combine then add the peroxide and you have created the near ideal rust environment.
As for doing anything else to the barrel,you wrote it "shoots well" ,,,you want to take the chance?????????????????? clean it,shoot it,leave it alone, IMHO!!.
I figure there is more"damage" near the breech cause there is more powder burning,higher temps and more crud,as the projectile is going down the barrel there is less heat,less powder buring???
The way a barrel is cleaned to,next time you see anyone cleaning a barrel see how they "scrub" more closer to the breech than up the barrel to the muzzle,could be their concerned about the rod coming out of the barrel,their arm is tired???I catch myself doing it,so the muzzle area gets the least cleaning,when ever you put in/remove a cleaning patch it has to come past that point in the barrel,,,,,,,
My last step in the cleaning process is a patch with Silicon spray down the barrel,then follow that with a monthly swabbing,,,keeps away the rust ,,and you can day dream about the woods!!! not a bad thing.

 

[Zonie]

I'm kinda disappointed.
I watched for 5 minutes after putting some Pyrodex into a bowl of water and not one single bubble of oxygen or anything else rose to the surface.

Even stirring it didn't make any gas. (Which is more than I can say for Stumpkillers chili.)

Yes, there is no doubt that there is a source of oxygen in Pyrodex. That's why it can burn in a barrel.
For that matter, there is also a source of oxygen in real black powder and I know without testing it that the oxygen will not be released by pouring water on it.

Another old time gunsmith story bites the dust.

 

[armymedic.2]

Peroxide zonie. Not fake powder :grin:

 

[ohio ramrod]

Having read a long time back that the old time gunsmiths alwas reamed their barrels from the breech end to give a slight "tapering" as their reamers dulled, I started lapping any barrels I reworked to give a slight taper ( I am talking about approximately .0001 of an inch). And find it makes loading easier . And the accuracy is as good or better than new barrels. As to over powder wads I started using them years ago and find they improve accuracy for me.:idunno:

 

[Zonie]

Ah yes.
My vision was getting fuzzy when I first read your comment.

I agree that Peroxide will readily release oxygen. After all, the extra oxygen is the only difference between Hydrogen Peroxide and plain tap water.

Sorry for my mistake (but for anyone who wants to know if Pyrodex gives off some mysterious vapor when it gets wet, the answer is, it doesn't seem to do anything except to pi$$ off my wife for "putting that toxic waste in another one of my bowls." :rotf:

 

[Stumpkiller]

Even stirring it didn't make any gas. (Which is more than I can say for Stumpkillers chili.)

I warned ye about stirrin the chili. Just makes it madder.