Hi there,

What are reasonable accuracy expectations after a quality reboring job?

Thanks

depends on the original material and the guy doing the reboring. it can be good or frightful. it isn't really to hard to stress the steel especially if it was that way to start

Can't argue with any of the above. But assuming the reborer is competent, the rule of thumb is that a rebore is usually as good as the original barrel was at it's best.
Like butchloc said, that also assumes the barrel material is appropriate for reboring. Many hammer forged barrels don't ream well and some older barrel materials are so inconsistent that the hard and soft spots make it impossible to run a tool set up to cut both well.

It's like so many other things with barrels, new barrels included. That is, you won't really know what you've gotten until you try the finished product.

HOWEVER, when answering the same question, the NRA used to advise that one should not be surprised to find the accuracy of a rebored barrel to be even better than it was originally when new.

That has been my experience too, with the few I've had done (mainly by Ward Koozer and Al Petersen).

I have no idea if the reasons the NRA used to give are true or not, but basically they said the reasons for improved accuracy were:

1. The shooting and aging of the barrel before being rebored both tend to relax previously existing stresses, thus making it easier to bore straight holes, and

2. As most re-borers "cut" the new rifling instead of using some other method, there is usually little or no new stress induced.

(Unlike button rifling, cutting rifling does not create stresses, they said. Cutting rifling can release existing stresses, which can cause problems of its own, but if the barrel is already stress relieved by aging and use, then cutting of new rifling would not be releasing or creating stresses, either of which can cause accuracy problems.)

Like I said at first, I have no idea if they have it right or not, but my experience has been a generally better degree of accuracy after re-boring and re-rifling. So, I'll take their word for it.

quote:

Originally posted by Alberta Canuck:



1. The shooting and aging of the barrel before being rebored both tend to relax previously existing stresses, thus making it easier to bore straight holes, and

2. As most re-borers "cut" the new rifling instead of using some other method, there is usually little or no new stress induced.

(Unlike button rifling, cutting rifling does not create stresses, they said. Cutting rifling can release existing stresses, which can cause problems of its own, but if the barrel is already stress relieved by aging and use, then cutting of new rifling would not be releasing or creating stresses, either of which can cause accuracy problems.)

Like I said at first, I have no idea if they have it right or not, but my experience has been a generally better degree of accuracy after re-boring and re-rifling. So, I'll take their word for it.

This is in no way meant to be critical of this post, but all I can say is so much for the theory of re-contouring an existing barrel that has been (shudder) already shot releasing stresses that occured because of said shooting.

Shooting a barrel extensively:

A: Induces stress on the metal.

B: Relieves stress already in the metal.

I would tend to believe B.

Same as rebuilding an engine W/a "seasoned" block. The "seasoned" block is thought to be more stable due to all the heat/cool cycles & such stabilizing the metal.

quote:

Originally posted by wildcat junkie:

Same as rebuilding an engine W/a "seasoned" block. The "seasoned" block is thought to be more stable due to all the heat/cool cycles & such stabilizing the metal.

Exactly the same, but stated better.

The caveat may be that many hunters' barrels aren't fired enough to remove the stresses. So, those might well warp from stress-relief when re-contoured?

I suspect maybe barrels being rebored have seen a fair amount more shooting....and those are more likely to be stress-free

quote:

Originally posted by Alberta Canuck:

quote:

Originally posted by wildcat junkie:

Same as rebuilding an engine W/a "seasoned" block. The "seasoned" block is thought to be more stable due to all the heat/cool cycles & such stabilizing the metal.

Exactly the same, but stated better.

The caveat may be that many hunters' barrels aren't fired enough to remove the stresses. So, those might well warp from stress-relief when re-contoured?

I suspect maybe barrels being rebored have seen a fair amount more shooting....and those are more likely to be stress-free

True, but I was referring to all the gloom & doom that I have seen posted about re-contouring military barrels, the M98K in particular.

A cut rifled barrel that never saw a "button" or hammerforging process, shot perhaps many thousands of times, suddenly "releasing" built up stress when re-contored.

I did have a less than stellar experience W/a pencil thin re-contoured M98K barrel but my standards are perhaps a bit more stringent than most. Most would never have noticed a 3" shift in POI @ 100yds after firing 3 consecutive shots,. but I did.

That barrel was re-contoured in a straight taper to clean up the steps & that is not the best profile for stability as it removes a LOT of material & results in a muzzle OD in the neigbothood of .550" or less.

BTW:

I have heard the theory that "relined" barrels tend to be very accurate also due to their being "floated" so to speak in an epoxy bonding resin.

Wildcatjunkie -

My posts were in NO way intended to correct you or disagree with you. Rather, I thought they supported what you were saying (And which I felt you said clearly & well).

I am not surprised that you had good success with a significantly re-profiled military barrel that had been cut rifled originally and maybe shot a good deal of times.

That doesn't mean a person will always get that result, but it does mean the doomsayers are skating on thin ice when they suggest that re-profiling can ALWAYS be expected to give negative results.

In any barrel creating or re-creating process, there are always many variables in play.

Best wishes,

AC

quote:

Originally posted by wildcat junkie:
BTW:

I have heard the theory that "relined" barrels tend to be very accurate also due to their being "floated" so to speak in an epoxy bonding resin.

Or, maybe it could also be that the "outer" barrel and the epoxy provide some damping to the oscillations of the liner?

quote:

Originally posted by Alberta Canuck:
Wildcatjunkie -

My posts were in NO way intended to correct you or disagree with you. Rather, I thought they supported what you were saying (And which I felt you said clearly & well).

I am not surprised that you had good success with a significantly re-profiled military barrel that had been cut rifled originally and maybe shot a good deal of times.

That doesn't mean a person will always get that result, but it does mean the doomsayers are skating on thin ice when they suggest that re-profiling can ALWAYS be expected to give negative results.

In any barrel creating or re-creating process, there are always many variables in play.

Best wishes,

AC

No inferance of your "correcting" me @ all. Just pointing out that some seem to have have just the opposite opinions as we do.

As for the "good sucess" W/a "siggnificantly re-profiled" barrel, you did misread that post as I was not pleased & felt that the line had been crossed as far as the practcal limits of stock removal.

That is why I laid out a radiused sweep to leave as much material as possible on my current 98K barrel re-profile project.

I have a 98/22 as well as a 98/29 (29") barrel in hand now. 1 will be re-profiled W/a 0.647 diameter 12" long muzzle "cylindrical" section to W/a 9" long 6'10" radius sweep to acheive a medium/heavy 24" barrel for an 8mm/06 A/I..

The other I am contemplating doing a tapered muzzle section (the muzzle diameter @ the crown eill be 0.606") that will transition into a 9" long X'XX" radius sweep for a 26" light/medium profile 26" barrel for an 8X68S project.

quote:

Originally posted by Alberta Canuck:

quote:

Originally posted by wildcat junkie:
BTW:

I have heard the theory that "relined" barrels tend to be very accurate also due to their being "floated" so to speak in an epoxy bonding resin.

Or, maybe it could also be that the "outer" barrel and the epoxy provide some damping to the oscillations of the liner?

Yes, that is what the "floating" would accomplish I think.