Rebore Accuracy?

[bradshaw]

The question, whether a “custom” revolver barrel is more accurate than a factory barrel does not submit to a Yes or No answer.

The subject of revolver barrel accuracy raises another question: Has any documented an accuracy comparison between, let’s get specific, a Smith & Wesson .41 barrel----before & after rebore to .45? Or, the before-and-after of a .38/.357 barrel to a larger bore?

I do not know and would like to know before-and-after accuracy comparisons. Perhaps no one cares. Had custom revolvers been permitted in IHMSA silhouette, we might have first-hand evidence of success or failure of reboring. For sure, a custom revolver could be entered in the IHMSA Unlimited category... and was. However, no one intent on winning tried it more than a few times. I suspect a rebored S&W .357 or .41 Mag would not record accuracy equal the original chambering. 100 yards should be sufficient distance.

Perhaps a member of Singleactions will shed light on this mystery.
David Bradshaw

[willicd]

I'm much more a student of the rifle but it's been shown many times that an improvement in accuracy when reboring a rifle barrel is not uncommon. Barrel manufacturers even rebore their own products if they don't meet specs the first time.

[leadhound]

Since barrel is removed, rebored, recrowned and rechambered, how many variables are at play? Sometimes just recrowning a barrel can suffice a bad shooter. Have heard of barrels that shot better when cut shorter, and pitted ones that shot cloverleafs? These last two are far from the majority however and stories to say the least.

[bradshaw]

"Since barrel is removed, rebored, recrowned and rechambered, how many variables are at play? Sometimes recrossing a barrel can suffice a bad shooter.”
----leadhound

Phrased as though variables are few and inconsequential.
* Does the rebore follow a crooked hole, or straighten it?
* Or, correct variations in barrel-wall thickness? Revolver barrels are not chambered.
* And the old crown.... the crown relegates to the bottom of the list in revolver accuracy. A bore swaged by the crowning operation may have a raised, minuscule “thread choke.” A crown which is burred or out-of-square may tip the bullet. A muzzle is plugged with snow or dirt is apt to flare, unless cleared before shooting. A clean, square, undistorted crown saves itself, but the crown cannot correct a bullet thrown off balance between chamber and bore. For all that, the crown continues to have a placebo effect.

Obviously, some rebores are successful. If folks weren’t happy with the result, the practice would end. Some of it sounds a bit casual.,,, send out a cylinder to be rebored----without the guns. Was chamber-to-bore alignment dead-ours before the custom work? And, whether or not chamber-to-bore alignment was dead nuts before custom work, is chamber-to-bore alignment dead nuts after customizing?

Surgery is a serious subject. The better the shape a person is in pre-surgery, the better he or she is likely to emerge. With a gun, if the frame is junk we can look for another. Metal or Man, the gathering of information should precede work.
David Bradshaw

[willicd]

ALL barrels are "crooked", and that's a fact.

[bradshaw]

May 8, 2020 16:26:07 GMT -5 willicd said:

ALL barrels are "crooked", and that's a fact.

*****

willed.... not sure your declarative statement, “ALL barrels...” etc., is to argue or inform. If your purpose is to inform, please explain.
David Bradshaw

[willicd]

I've built a couple hundred rifles using every custom blank under the sun and I've never seen one with a bore that doesn't have run-out from one end to the other. A pistol barrel is no different. If you dial in the chamber end of a barrel paying no attention to what the other end is doing, several thousandths and sometimes up to .050 run-out will be seen. That means the bore is not straight. I've never seen one that was and I really doubt anyone else has either.

[flyingzebra]

We use all makes/brands of barrel.
Even the super-gooch high end cut rifled barrel blanks will show run-out.

Every revolver barrel starts out it's tour through the shop between centers in the lathe.

This is the way.

Also, it's rare that there's problems with re-bored barrels. Re-bore jobs tend to yield very accurate guns and great satisfaction for the clients.

[bradshaw]

willed, flyingzebra..... spoke with Lee Martin awhile earlier, Lee had just returned from shooting with his father an XP-100 his father built in .358 Winchester. And Lee squeezing 300 rounds through his Blackhawk .41 Magnum. (My first experience shooting an Unlimited pistol involved a double pistol-grip XP-100 with 11-inch barrel in .358 Winchester, loaded with Rocks & Dynamite at----where else----the first IHMSA International Championship, Los Angeles 1977. So I caught Lee headed for the Hoppe's after squeezing 300 rounds through his Blackhawk .41 Mag. Must say, the boy likes to shoot. With this shooter headed to blast water jugs, we kept conversation short (some might say otherwise).

Lee’s take
* Barrels are not perfectly straight. Even the best barrel.
* A drill follows a hole.
* Measurement does not replace results on the Firing Line.
* When setting up to turn a barrel, Lee indicates off respective grooves at both ends.
* Bench Rest shooters start a barrel fresh, do not rebore a barrel. Prefer to vertically CLOCK a “bend”----orient NODE vertically.
* Bench Rest shooters----100, 200, 300 yards----generally prefer orient “bend” to 6 o’clock.
* 1000 yards shooters prefer to orient ”bend” to 12 o’clock.
* A vertical node is easier to shoot consistently than a horizontal node.
* A rebored revolver barrel may be fine, just don’t expect great work to be a given. Prove on firing line.
* “And the Bradshaw term, Revolver accuracy is an orchestra of dimensions.”

Lee emphasizes there is nothing casual about good gun work. Occasionally, we are treated on Singleactions, to photos of inferior gunsmithing. The way we see it, good shooting informs, and information is your friend.
David Bradshaw

[flyingzebra]

Thanks for the notes there Mr Bradshaw.
Keep it coming.
Every day brings a new lesson, some days bring many new lessons!

[bradshaw]

Without direct experience shooting rebored revolvers I understand the caliber change but not a known accuracy differential. Perhaps someone here knows the process to re-rifle, which must begin with perfect bore alignment, and barrel clamped to resist movement.

For me to take the attitude revolver ACCURACY is a given, I’d have to deny experience with revolvers which just didn’t have it. (Talking factory barrels, not rebore.) Accuracy combines three essential ingredients----1) revolver, 2) bullet, 3) shooter. The revolver can’t do it without the bullet and the two can’t do it without the shooter.

1) Revolver
The instrument. Music is played with the instrument.

2) Bullet
Touch without touching. The best bullet requires a good revolver to fly straight. Of course, the bullet can’t do it without a compatible load.

3) Shooter
Us, our most variable ingredient. Which is why I say there is no such thing as a easy shot. Each shot is work, an exertion. There is no shortcut. What in retrospect appear an "easy shot” can such the concentration right out of you. Revolver & bullet exist in the present. Neither revolver nor bullet has a brain to indulge distraction. The shooter owns sixgun & bullet from HAMMER FALL to IMPACT, and all the way through the target.

To pronounce a shot “easy” before making it invites distraction. The slightest distraction takes the shooter out of the present. Sharpshooting lives in the present, cannot abide distraction.

A revolver more accurate than the shooter serves the shooter.
David Bradshaw

[magpouch]

As a machinist that has never ever (ever) made a gun barrel, I am quite familiar with gun-drilling. The gun drill is the roughing tool that makes the hole in the barrel and they can cut incredibly straight, but the term "straight" is relative of course. A gun drill can also wander. There are many factors on the drill itself and the process used to create the bore to start the drill in. All the other tools that follow the gun drill will follow the same trail.

I read somewhere several years ago that because bores wander inside the barrel, Savage actually had an operation where a very experienced person actually bent the outside of the barrel in order to straighten out the bore. That takes talent I bet.

To me the manufacture of rifled barrels is fascinating and I bet from the outside it must seem reasonably simple, and to the folks that do it to make a fine barrel it must give fits. Then again in this age of CNC machines it may be much easier than I think. I'd love to spend some time where they are made and find out.

[Fowler]

Heck barrel bending is an art and nothing new. The old British masters of double shotgun and rifle barrels have to bend barrels back and forth to make sure the pattern or hits are exactly to the sights. It’s part of why good double rifles are so bloody expensive and moody to find loads that shoot to the sights.

I work in the machining world, we know when dealing with pipe and tube there are only a few constants: there is no such thing as a straight tube, there is no such thing as a round tube, and there is no such thing as a square tube. You May have to get to a bunch of zeros and tiny fractions but I can guarantee every bore is out of round and crooked.

So we accept this and minimize all the variables possible and it produces what we hope to me the most accurate product in the end. It is why there is built in tolerance for everything machined, the less tolerance allowed the more expensive it is going to be. The reason a factory Ruger costs X and a full custom reworked rifle is someone basically took the tolerance levels closed to zero than the factory could since they have more budget and time to work with.

In the end the target still is the proof of success or not of course.

[bushog]

The smaller the variance the larger the sample size has to be in order to show a significant difference.

[ddixie884]

I believe Mr. Bowen was of the opinion that a good rebore was as good or better than a typical factory barrel. One pretty knowledgable guy over on the S&W forum had a Factory S&W .44spl barrel and cylinder for a conversion and Hamilton told him to sell them and He would alter his .357 parts for a better custom. I was surprised but bought his parts..............