Excessive Runout on New Barrel When Chambering

[DaveTooley]

Great info, thanks for sharing!

We need to create an anonymous poll to see how many folks indicate all at one end versus both ends, it would be interesting to see those numbers.

I know some who do both and I know at least one who it’ll depend on how much time he has, the both ends method is faster because you don’t need to “time” the action to the barrel high/low.

No need for a poll. Those of us on this forum that do it for a living have never been secretive about how we setup barrels. We each develop processes that work. And work every time.

 

[Judd]

Why? It will only show what some folks here are doing. It will not show what the majority of the winning smiths are doing.

I just thought it would be interesting...evidently not

Just want to say thanks for everyone sharing and also would probably be good to remember that everyone was a rookie once.

 

[butchlambert]

I just thought it would be interesting...evidently not

Just want to say thanks for everyone sharing and also would probably be good to remember that everyone was a rookie once.

Not trying to demean you or your thread. If you are in fact really interested in the methods go to my pinned thread on the Advanced Gunsmithing forum. Several ideas there. Also, do a search on this forum. Seems there is a thread like this every week or two. Another way is to join the NBRSA and get the monthly magazine. It shows the results from around the country and what the winners are using.

 

[okie]

butch or tooley---How do they indicate a pre-fit barrel at the volume type barrel makers shop? (if they even do)--simply just run reamer in it???

 

[butchlambert]

butch or tooley---How do they indicate a pre-fit barrel at the volume type barrel makers shop? (if they even do)--simply just run reamer in it???

Okie, I don't do pre-fit barrels. Some of the barrel mfg. do them in centers and steady. Volume or not, they indicate in their own way as we do.

 

[okie]

Okie, I don't do pre-fit barrels.

yeah--I was just wondering.... thanks mr. butch

 

[Coyotefurharvester]

If the chamber and threads are concentric with the bore how does the muzzle run out matter(other than how much windage and vertical adjustment is required to calibrate the optics)?

 

[Judd]

Not trying to demean you or your thread. If you are in fact really interested in the methods go to my pinned thread on the Advanced Gunsmithing forum. Several ideas there. Also, do a search on this forum. Seems there is a thread like this every week or two. Another way is to join the NBRSA and get the monthly magazine. It shows the results from around the country and what the winners are using.

Didn’t take it that way at all. I do watch here quite a bit and chime in when I feel like I can provide valid content or opinions. I actually printed that entire thread out and have read it all, a TON of great information in that thread...thank you for putting it together, I know that was time consuming.

I’m definitely still soaking everything up with a sponge that I can and appreciate how helpful and open so many folks have been to me...both here and otherwise.

 

[DaveTooley]

butch or tooley---How do they indicate a pre-fit barrel at the volume type barrel makers shop? (if they even do)--simply just run reamer in it???

I guess you could call me a volume shop. Things have slowed down some but at one time it wasn't unusual for me to get 125 barrels in at a time. As you would expect I don't do them on a manual machine. I chamber on a Haas TL-1. I chamber exactly the same way on the Haas as I did on a manual machine. The setup is the same. I run the finish reamer the same way. It's everything in between where the machine saves time. I indicate the throat and the muzzle then go to work.

Large shops as in firearms manufactures don't go to the pains I/we do setting a barrel up. Most put the barrel in a collet, close the door and push a button. A few minutes latter they have a chambered barrel. They use reamers I can't use. They require high horsepower machines with aggressive feeds to get a chamber plowed out.

 

[okie]

I guess you could call me a volume shop. Things have slowed down some but at one time it wasn't unusual for me to get 125 barrels in at a time. As you would expect I don't do them on a manual machine. I chamber on a Haas TL-1. I chamber exactly the same way on the Haas as I did on a manual machine. The setup is the same. I run the finish reamer the same way. It's everything in between where the machine saves time. I indicate the throat and the muzzle then go to work.

Large shops as in firearms manufactures don't go to the pains I/we do setting a barrel up. Most put the barrel in a collet, close the door and push a button. A few minutes latter they have a chambered barrel. They use reamers I can't use. They require high horsepower machines with aggressive feeds to get a chamber plowed out.

thanks for your response--I assumed you were quite tedious in indicating, I am starting to understand a little more as time goes on. thanks again, marc

 

[tobnpr]

If the chamber and threads are concentric with the bore how does the muzzle run out matter(other than how much windage and vertical adjustment is required to calibrate the optics)?

There's a difference between using the muzzle as one of the two points used for dialing in the bore, and "clocking" the muzzle runout to be oriented "up" which is done via the shoulder like you would on a brake.

"If the chamber and threads are concentric with the bore..."
You're not understanding the process.
It's WHICH two points are used, that establish HOW one establishes the bore centerline used as the reference. Bores aren't perfectly straight. Top tier barrels are damn near so, but can still wander.
You can pick any two points as your reference. Some pick the muzzle and throat. Some pick breech and throat ala "Grizzly" rods and/or direct indicating with a long stem.

Hope that helps.

 

[AccelR8]

Large shops as in firearms manufactures don't go to the pains I/we do setting a barrel up. Most put the barrel in a collet, close the door and push a button. A few minutes latter they have a chambered barrel. They use reamers I can't use. They require high horsepower machines with aggressive feeds to get a chamber plowed out.

And, based my admittedly limited personal experience...that is rifles and replacement barrels I've bought over the years (for AR15s used in target shooting)...said manufacturers and also big volume barrel suppliers to the industry, get a fair number of poorly chambered barrels. I say this because I've had some that would only shoot mediocre and inspection, by chamber casting before the mighty Teslong bore scope came along, and later using that bore scope, I see what I can only interpret as crooked chambers, chambers not properly aligned with the bore.

I'm not a gunsmith but I've got a lathe and I'm not afraid to use it. I've decided that, while I may still buy the lesser expensive barrels, I'm done buying finished AR15 barrels or pre-fit rifle barrels. Chambering my own, I know it's done to my satisfaction.

 

[butchlambert]

And, based my admittedly limited personal experience...that is rifles and replacement barrels I've bought over the years (for AR15s used in target shooting)...said manufacturers and also big volume barrel suppliers to the industry, get a fair number of poorly chambered barrels. I say this because I've had some that would only shoot mediocre and inspection, by chamber casting before the mighty Teslong bore scope came along, and later using that bore scope, I see what I can only interpret as crooked chambers, chambers not properly aligned with the bore.

I'm not a gunsmith but I've got a lathe and I'm not afraid to use it. I've decided that, while I may still buy the lesser expensive barrels, I'm done buying finished AR15 barrels or pre-fit rifle barrels. Chambering my own, I know it's done to my satisfaction.

I understand a chamber not being coaxial with the bore, but what is a crooked chamber?

 

[AccelR8]

I understand a chamber not being coaxial with the bore, but what is a crooked chamber?

I guess not coaxial is what I mean, just didn't think of how to say it.

 

[AccelR8]

I understand a chamber not being coaxial with the bore, but what is a crooked chamber?

Here's what I see often. This not the worst example I've had but this is what I found on my hard drive on short notice. How should this be interpreted? Same barrel, images about 180 degrees apart.

I don't want to derail this thread so I'll bow out here. When I first replied I actually thought I was in a different thread. Sorry.

 

[clowdis]

Here's what I see often. This not the worst example I've had but this is what I found on my hard drive on short notice. How should this be interpreted? Same barrel, images about 180 degrees apart.

Not trying to derail the thread. I would encourage the OP to go for it...!

Looks like the bore bushing was too small allowing the reamer to drift off center. Either that or no bore bushing was used at all.

 

[DaveTooley]

In the early years I bought into the idea that bushing fit was critical. It's not about the bushing size. Reamers go to the center of the barrel or at least try to. A properly setup barrel, a properly roughed in chamber doesn't require a bushing on the reamer.

 

[clowdis]

In the early years I bought into the idea that bushing fit was critical. It's not about the bushing size. Reamers go to the center of the barrel or at least try to. A properly setup barrel, a properly roughed in chamber doesn't require a bushing on the reamer.

Agree but I have to wonder if the chamber wasn't prebored and the barrel wasn't properly indicated this could happen. Come to think of it, it's pretty darn amazing that even after all the things people do to chambers, the many different chambering setups, a top class modern barrel will still shoot "lights out".

 

[markwalker]

Had a chance to finish the given barrel today; what a surprise !!!

Prepared to finish the muzzle end (crown, thread for tuner), same process was used just like the breach end; wanted to stay consistent

Rough indicate the bore at the muzzle using range rod and test indicators. Next, the .0001” test indicator with a long stylus was used for final dialing in using two points at the muzzle end.

Again the two test points were about .0001-.0002” out (just want minimal needle movement on the test indicator.

What a surprise, the outboard end (now the breach end) now measured .005” of runout...

So here is a summary;

Setup breach end to machine the chamber, barrel was dialed in using two points (one in the throat area the other at the chamber end).

Measured runout at muzzle was .030” or more.

Next the barrel was flipped to machine the crown, process used shown above.

Measured runout at the outboard end (chamber) was .005”...

So I believe their is/was something wrong in the breach end of this barrel blank to begin with. I even cut another 1” off.. same measurements. Not sure what.. but it’s there

The next step is to shoot the barrel and see what the target looks like.

From what I have learned from the responses above is to select a test point to be dialed in just foreword the chamber (in the throat area). The second point can be the muzzle end or at the back end of the chamber.. you only get two points

In my case their is something going on in the breach end.. by selecting the test point just ahead of the chamber. the next thing was to bore undersize, and then final ream.

Anyway, should be able to get to the range in a few weeks.

 

[Shooter71]

It’s extremely easy to flex a barrel into submission leading to exaggerated muzzle runout during chambering. It’s also possible to have the angle of the bore (during crowning) cancel out any expected runout that was experienced during chambering.