dirty barrels

[dully1963]

Hi
Just a quickie anybody know why some barrels seem to be more accurate when they are dirty
cheers

 

[bouddha]

I doubt seriously that they are "more accurate" when dirty (fouled) than when cleaned. They may very well shoot to a different point of aim, possibly due to pressure variance between clean and fouled causing velocity change. If you were to clean the barrel exactly in the same manner and to the same degree, every shot through a clean barrel should be as accurate as the gun will ever produce. One round through a clean barrel and five through a fouled barrel are likely going to shoot to different points of aim and give the appearance of differing accuracy.

 

[gotcha]

I think this phenomenon is generally associated w/ bbl's of lesser quality. IE: Inconsistency of either bore or groove diam. & width, straightness of tube or chatter marks from machine tools. As the imperfections of bore are filled in with gilding material & powder fouling the dimensions actually become more uniform. (key to a quality bbl.) Vibrations may actually diminish & enhance accuracy. Before I could afford match bbl's I had factory bbl's that after thorough cleaning would start grouping again after 4 or 5 rounds. Some MUCH longer. There may be other reasons but, this is what my experience has taught me.

 

[necchi]

If you were to clean the barrel exactly in the same manner and to the same degree, every shot through a clean barrel should be as accurate as the gun will ever produce.

Not with my rifles.
I know mine shoot better dirty, but I'll be darned if I can explain it as simply as dully asked ???

And each seems to like it's own level of "fouled" barrel to produce the best accuracy, some want at least one, some like 3-5 shot's and one notable 223 needs at least 8-10 shot's before it settles in,,

I'm sure it's what you touched on there bouddha,, the fouling creates a different pressure,, but it's the pressure dynamics as it applies to all of the other harmonics of the barrel.

 

[fredhorace77]

I think this phenomenon is generally associated w/ bbl's of lesser quality. IE: Inconsistency of either bore or groove diam. & width, straightness of tube or chatter marks from machine tools. As the imperfections of bore are filled in with gilding material & powder fouling the dimensions actually become more uniform. (key to a quality bbl.) Vibrations may actually diminish & enhance accuracy. Before I could afford match bbl's I had factory bbl's that after thorough cleaning would start grouping again after 4 or 5 rounds. Some MUCH longer. There may be other reasons but, this is what my experience has taught me.

+1

 

[BoydAllen]

This is a characteristic of barrels that, for one reason or another, are not as smooth inside as most lapped match grade barrels. When they are shot after cleaning, it takes a number of shots for the bore surface to become consistent, down its entire length, so that bullets "see" the same condition. Years back, when factory barrels were all that I had, it was usual that a barrel would take 5-6 rounds or more to settle down, and then, because roughness accelerates the rate of fouling, after 25 or so rounds I would see the accuracy start to gradually fall off. This situation eventually caused me to invest in my first lapped barrel, a Hart, from which I have never looked back.

 

[dully1963]

Thanks for all the replies,Its' was one of those things that just niggle away at you ;D