Chambering/Pilot question

[MikeMcCasland]

Hey Guys,

I recently had two barrels dropped off at my smith to get chambered. They were both identical barrels from the same (well known, cut rifled) barrel maker; ordered at the same time. I had them cut with my same JGS reamer that all my other barrels are cut on.

When I picked them up, I asked the smith if there was anything noteworthy during the chambering process, and he mentioned that one of the barrels required a .0002 larger pilot than the other; said he probably could have gone .0003 larger, but didn't have a pilot on that size.

When he was telling me about he, he acted like that was pretty significant occurrence, and thought maybe one would be faster than the other, but wasn't sure.

I borescoped the barrels when I got home, and the chambering job looks pristine to me, so not really sure what to do with this info.

It's my intent to just shoot the barrel as-is, and call the mfg if there are any issues. That said, I was curious if any of yall had run into that, and if so could you tell any difference on target?

Thanks,
Mike

 

[DaveTooley]

I've gotten inspection reports on hundreds of precision cut rifled barrels. They run from dead on to +.0003" over 99% of the time. If this a concern for you don't ever use button rifled barrels. The important dimension is groove diameter and uniformity.

 

[jackieschmidt]

I've gotten inspection reports on hundreds of precision cut rifled barrels. They run from dead on to +.0003" over 99% of the time. If this a concern for you don't ever use button rifled barrels. The important dimension is groove diameter and uniformity.

^^^^^
krieger guarantees their barrels to be on size in the grooves. If you get a .237 4 groove Krieger, it will be dead on in the grooves, but that bore diameter might be as tight as .2370 or as loose as .2375.
I think your barrels will be fine.

 

[MikeMcCasland]

Perfect. Thanks guys!

Didn't mean to come across as though I thought it was an issue; I just didn't know.

 

[STS]

You have a 50/50 chance that the barrel your gunsmith is concerned about will out shoot the other one. There's only one way to evaluate a barrel in the end, and that is to chamber it up and shoot it.

 

[gunsandgunsmithing]

I've tested a 30 cal that I spec'd the land diameter to be a full thou smaller than normal. Logic would have it, more pressure and speed. Reality was same load data and no measurable difference in speed nor accuracy. Both shot wonderfully. I agree that groove diameter and land to groove ratio is more significant.

 

[Alex Wheeler]

Like others said, theres not much in bore diameter. That does not effect the volume much. Groove diameter makes a very big difference. I have been experimenting here, and its been an eye opener. Actual results have been quite different than what I expected.

 

[liljoe]

The best barrel I have ever owned had the bore diameter a little bit big. I was quite concerned about it when I was clambering it. That barrel won almost every match it was in.
Don't let it get into your mind.
Joe