Turning the outside of the muzzle end for the tuner, effect on inside diameter ?

[High Noon]

Question for the rimfire team. I have a top quality build by one of the top quality gunsmiths using a new 2500X and Shilen barrel. I asked the accuracy rimfire gunsmith to build it just like he would for himself. I always do that when building a new match rifle as I feel they are a lot smarter than me…lol…I do ask for specific components and even that I’ve learned may not be too wise. So over the decades I’ve become a lot better listener to these talented machine artists ! When I received the rifle he had also installed a Harrell tuner but I noticed he had turned a little off the muzzle end of the barrel right under the tuner area. My concern and question would this make the inside of the bore slightly larger in this critical area which we know would be be the worst place to be larger. The rifle does seems to really shoot well, I’ve had it at the Lapua test center and it was doing very well with CenterX and at my range and club it shoots quite well if I do my part. Thanks everyone! High Noon

[tonykharper]

Question for the rimfire team. I have a top quality build by one of the top quality gunsmiths using a new 2500X and Shilen barrel. I asked the accuracy rimfire gunsmith to build it just like he would for himself. I always do that when building a new match rifle as I feel they are a lot smarter than me…lol…I do ask for specific components and even that I’ve learned may not be too wise. So over the decades I’ve become a lot better listener to these talented machine artists ! When I received the rifle he had also installed a Harrell tuner but I noticed he had turned a little off the muzzle end of the barrel right under the tuner area. My concern and question would this make the inside of the bore slightly larger in this critical area which we know would be be the worst place to be larger. The rifle does seems to really shoot well, I’ve had it at the Lapua test center and it was doing very well with CenterX and at my range and club it shoots quite well if I do my part. Thanks everyone! High Noon

High Noon,

Let us start with the facts.

It is a fact that if you reduce the outside diameter of a barrel the inside diameter will become larger.

How much larger depends on how much is removed and the quality of the steel. Any metallurgy book will verify this.

Question: Will this hurt the accuracy potential of the barrel? Not knowing the rest of the build and what may be wrong with it there is no way to know. You could have far worse problems.

Another question is why did the smith not just bore the tuner to fit?

Last fact. If you are happy with the rifle, it really doesn't matter.

TKH (4628)

[tim]

Todd, Tony is absolutely right but also, why ?
CF tuners are usually threaded because of serious muzzle blast and pressure. No such issue in RF.

[wk4036]

I have slugged every barrel that my smith has done for me that has been cleaned up for a tuner and they have been just as they should be, the average he has taken off is around .005 so i wouldn't lose any sleep over it.

[tonykharper]

I have slugged every barrel that my smith has done for me that has been cleaned up for a tuner and they have been just as they should be, the average he has taken off is around .005 so i wouldn't lose any sleep over it.

wk4036,

Many people come to this site to get information about RFBR and high precision rimfire shooting.

With that in mind could you please clarify your statement about .005 being something not to lose sleep over.

Everyone appreciates a good night's sleep but .005 can ruin your entire weekend at a big match.

Then could you explain why it is better to take .005 off the barrel than it is to take .005 out of the tuner?

Not trying to argue, just want to put out the best advice to those that visit this site.

My point being cutting .005 out of a tuner causes no potential harm but taking .005 off the end of a barrel will open it up.

That is not to say there aren't other things wrong with the rifle that hurt its potential far greater than opening up the barrel. There very well maybe.

But the question is why do it?

TKH (4628)

[High Noon]

When I had the rifle built I actually had the rimfire accuracy gunsmith fit two match barrels and both have a slight area turned off under the tuner. I have only fired the Shilen and like I said shows very good potential. But ….I’ve been in the precision shooting game (centerfire) long enough and understand how and what can effect a barrel so this turned ares has always been in my head. I’m currently not where I can measure the barrel but will in a few weeks and report. With that said in Bill Calfee’s excellent book on “The Art of Rimfire Accuracy” pages 203 & 204 he actually turns a slight area under the tuner and shows pictures of the process. He explains these turned “target” areas allow a gunsmith to easily center the barrel if adjustments are ever necessary if I’m understanding it correctly. However, he does write in several other places that you should never alter the outside of the barrel especially in the muzzle area. So let me ask, would the only sure way to know would be to carefully slug the barrel? If so who can supply slugs? Thanks everyone…

[George Atkins]

wk4036,

Many people come to this site to get information about RFBR and high precision rimfire shooting.

With that in mind could you please clarify your statement about .005 being something not to lose sleep over.

Everyone appreciates a good night's sleep but .005 can ruin your entire weekend at a big match.

Then could you explain why it is better to take .005 off the barrel than it is to take .005 out of the tuner?

Not trying to argue, just want to put out the best advice to those that visit this site.

My point being cutting .005 out of a tuner causes no potential harm but taking .005 off the end of a barrel will open it up.

That is not to say there aren't other things wrong with the rifle that hurt its potential far greater than opening up the barrel. There very well maybe.

But the question is why do it?

TKH (4628)

Maybe it is to offset the torque of tightening the tuner. Maybe it was to insure the tuner sets in the particular spot, if it were ever taken off and reinstalled. .005 is a very small cut. I will agree that taking material off the outside, will cause the inside diameter to expand, but at .005 on the outside, I would only guess the inside would expand .00005 if that. Cannot see that making any difference.

[stiller]

wk4036,

Many people come to this site to get information about RFBR and high precision rimfire shooting.

With that in mind could you please clarify your statement about .005 being something not to lose sleep over.

Everyone appreciates a good night's sleep but .005 can ruin your entire weekend at a big match.

Then could you explain why it is better to take .005 off the barrel than it is to take .005 out of the tuner?

Not trying to argue, just want to put out the best advice to those that visit this site.

My point being cutting .005 out of a tuner causes no potential harm but taking .005 off the end of a barrel will open it up.

That is not to say there aren't other things wrong with the rifle that hurt its potential far greater than opening up the barrel. There very well maybe.

But the question is why do it?

TKH (4628)

I agree with you that it is better to open up the tuner. I would also. All that being said, HOW MUCH causes an affect? 0.0005, 0.0050, 0.0500, etc. If you sand the barrel to polish it and accidentally sand more on the end is it degraded. I have had a tuner fit a little too snug to my liking, and just hit the muzzle end a bit more with the belt sander when I polished it and it was fine. Did I open up the end of the barrel?

Moral of this story is everything is about degrees of change. I will bet a good chunk of cash that 0.005 removal of the od at 0.900 versus the bore on a 22 will not affect the bore enough to measure it for sure. I would also bet with normal taper in a barrel, you cannot feel it either. 0.0050 may be another story, but that is about what comes off the chamber end and I have measured that and it is not really very measurable.

After all of this can you explain why the ID grows when the OD is cut down? What is the mechanism inside the steel that causes it, why does it happen, can it be stopped etc. Just curious what the real cause and effect are, and not just the button barrels do it and others don't. A true understanding of why things happen is paramount when trying to deal with it.

[tim]

Would it not be somewhat barrel dependent? I have been told by a button bbl mfg. that if that particular blank had some stress in the blank toward muzzle, even after stress heat treating it “may” result in dimensional change.
Never really did it but sounded like it made sense.
Point is still,don’t need to so why ?

[Tad.E]

Simple concept, true OD to ID at a new established point.....The crown.


Kind of hard to stomach putting the time and energy of finding the best place to crown, dialing it in, and executing the best crown possible all to stick a tuner on the end of that in a crooked or offset way by not cleaning off the out of concentric OD at that point. Some barrels takes very little, such as 0.002" cleanup. Some take more such as 0.010". Just depends.... I believe Calfee has said 0.025" or less makes no noticeable difference on the typical barrel.

Anyone ever check the ID of the tuner ahead of the clamping area against the ID of the tuner in the clamping area? Some tuners wont make it past a visual inspection here out of the box. Just part of how they are machined and another hurdle to cross.

Tad

[kevinnevius]

I agree with you that it is better to open up the tuner. I would also. All that being said, HOW MUCH causes an affect? 0.0005, 0.0050, 0.0500, etc. If you sand the barrel to polish it and accidentally sand more on the end is it degraded. I have had a tuner fit a little too snug to my liking, and just hit the muzzle end a bit more with the belt sander when I polished it and it was fine. Did I open up the end of the barrel?

Moral of this story is everything is about degrees of change. I will bet a good chunk of cash that 0.005 removal of the od at 0.900 versus the bore on a 22 will not affect the bore enough to measure it for sure. I would also bet with normal taper in a barrel, you cannot feel it either. 0.0050 may be another story, but that is about what comes off the chamber end and I have measured that and it is not really very measurable.

After all of this can you explain why the ID grows when the OD is cut down? What is the mechanism inside the steel that causes it, why does it happen, can it be stopped etc. Just curious what the real cause and effect are, and not just the button barrels do it and others don't. A true understanding of why things happen is paramount when trying to deal with it.

Jerry:

I hope you are well!

I will try to give an explanation a shot (after trying to unsuccessfully model it on several occasions) - just my opinion here:

As an oversize button swages or cold forms the rifling impression, it induces localized hoop stress into the steel (as is plasticly deflects the bore as it passes). This hoop stress is in compression - the plasticly displaced material tries to rebound but cannot completely. This stress is contained by the remaining barrel steel in the cross section. This compressive radial stress dissipates gradually as you move away from the bore through the cross section. As we remove material from the OD, we weaken the barrels ability to resist the localized hoop stress at the bore, and the ID moves dimensionally outwardly (larger) to equalize the internal stresses in the new (smaller OD) barrel profile. Sorry if that didn't make sense.

Cut rifled barrels do not induce residual hoop stresses in the manufacturing process.

In my humble opinion, it is very important to remove a small amount of material to ensure bore / OD concentricity at the muzzle. It's important as the tool engages the material when machining the crown, and it's important that the tuner be centered and concentric with the bore as the bullet passes through it.

I don't believe .005" give or take has any effect on bore ID at all - at lease none that I can measure. And it has never affected overall accuracy - again, in my experience.

All the best to you,

kev (OU812)

[tonykharper]

When I had the rifle built I actually had the rimfire accuracy gunsmith fit two match barrels and both have a slight area turned off under the tuner. I have only fired the Shilen and like I said shows very good potential. But ….I’ve been in the precision shooting game (centerfire) long enough and understand how and what can effect a barrel so this turned ares has always been in my head. I’m currently not where I can measure the barrel but will in a few weeks and report. With that said in Bill Calfee’s excellent book on “The Art of Rimfire Accuracy” pages 203 & 204 he actually turns a slight area under the tuner and shows pictures of the process. He explains these turned “target” areas allow a gunsmith to easily center the barrel if adjustments are ever necessary if I’m understanding it correctly. However, he does write in several other places that you should never alter the outside of the barrel especially in the muzzle area. So let me ask, would the only sure way to know would be to carefully slug the barrel? If so who can supply slugs? Thanks everyone…

High Noon,

There is or at least was a pellet company that sell or sold slugs that many used to slug rimfire bores. I can't remember the company name.

But most people just pull bullets out of rimfire rounds and use them.

It can be dangerous so I'm not recommending anyone do this. If one uses the plastic piece that separates the rounds in an ammo box you can get them out without deforming them very much.

Slugging a barrel and developing a feel for it is an art. Being able to tell a tight spot from a rough spot is nearly impossible. It is equally difficult to measure the slugs you push part way or through a bore.

TKH (4628)

[doghunter]

This is an interesting discussion as I am contemplating making a tuner for my Annie.

The barrel has a slight bulge at the end, 'supposedly' to provide a choke when the remainder of the barrel is contoured.

There have been a few tales of woe when such a barrel has been shortened.

Here is a linky to one typical discussion about this http://benchrest.com/showthread.php?...540#post534540.

I also fail to understand why a tuner requires to be flush with the barrel contour along it's length (apart from keeping crap out from a gap) as I assumed that the tuner acted through it's attachment point.

Go easy, I still have a lot to learn.

* doggie *

[PedroS]

Anschutz barrels, including the match ones are profiled before laping, so I think the choke is achieved by a correct laping and not because they have a bulge at the end.
In fact both Anschutz and Feinwerkbau ones are lapped. We are talking here match grade only.
The match Anschutz are very good, I have no experience with Feinwerkbau, but as any barrel you have to get lucky to find the "one".
Also, the bulge serve more to correctly support the front sight for ISSF and open sights categories, than a slim barrel can. Having a bulge puts more weight on the front, so, it also contracts the upper recoil, which is the worst enemy to ISSF shooters. They have long barrels and front heavy. To counteract the down recoil they use a hook on theirs back plate system.

[linekin]

I agree with Tad & Kevin here in that it was probably done to get the O.D. concentric with the bore in hopes that when the tuner was mounted the I.D. would also be concentric with the bore.
I re-crowned a barrel that didn't shoot to my expectations. Mounted a tuner & indicated on the i.d of the inner tube of the tuner. I don't recall the amount of the runout but seems like somewhere in the neighborhood of .010 or so. So I bored it concentric to the bore. The exercise didn't turn this into a "killer" barrel but I did at least have a consistent shooting rifle without some of the unexplained chit I was seeing.
Was it the recrowning or the boring the id of the tuner concentric I can't say. I will say its an excercise I've done with the few barrels I'd done since. Just figure every little thing helps. Peace of mind kinda thing....

Keith