Thought provokng video on chamber to bore runout...reactions?

B

Boyd Allen

Active member
https://www.youtube.com/watch?v=JwGRUjg-yeI
After reading the posts in a thread relating to this subject, I did a search on Youtube for "chamber runout" There were a number of videos. This one was at the top of the results. I opened it thinking that I would see some proud smith showing how perfect the runout of one of his chambers was, but it was not as expected. Take a look and tell me what you think. Have done the same test? I do not think that it is commonly done. Maybe it should be.
 
Boyd Allen said:
https://www.youtube.com/watch?v=JwGRUjg-yeI
After reading the posts in a thread relating to this subject, I did a search on Youtube for "chamber runout" There were a number of videos. This one was at the top of the results. I opened it thinking that I would see some proud smith showing how perfect the runout of one of his chambers was, but it was not as expected. Take a look and tell me what you think. Have done the same test? I do not think that it is commonly done. Maybe it should be.
Click to expand...

Where he is making his mistake is that he is assuming the bore is straight. Look at the distance he runs that indicator in to ascertain that final runout. If he ran it in another two inches, it might run dead true, or even show runout in the opposite direction.

Also, when checking the lead in, which the reamer cuts, it is important to look at the difference between the lands and the grooves. This gives a good indication as to how true the chamber is with that original portion of the barrel. That is, after all, the first thing the bullet "sees" as it exits the case neck.

It all goes back to what I have said countless times. If you are dealing with a piece that is not truly straight with its own self, all you can hope to do is true two points. If you have to perform a machining operation on that piece so that what you machine runs true with the piece that is NOT truly straight with its self, you have to decide what two points are going to run true, and then establish your subsequent operations to run true with those two points.

The majority of what is discussed on this Forum is deciding what two points a craftsman chooses. Much of this is predicated on the type of machinery available.

My guess is, most people do not check their work. They assume that their set up is sound and does produce the desired results.

As I have written many times, when I check my work, I place the indicator stylus on on the back of the chamber, the front, the neck, the lead, and then the lands just forward of the leads, the first thing the bullet "sees" as it exits The section of the barrel, (the chamber), that you machined. What goes on further down I do not worry about, because there is nothing you can do about it.

The person in the video also makes a an absolute statement at the end. "This is why some guns just don't shoot"

Really? Prove it.
 
Last edited:
I agree with Jackie.
I have looked for a good indicator that is calibrated for a long contact and couldn't find one. That makes me think his reading is worse by a mutiple of about four. Maybe I shouldn't mention that but it also tell me he doesn't understand what he is measuring ether.
I think I would dial in the throat and the muzzle the check chamber then thread and shoulder. Then dial in throat and a little farther down then chamber to that. If both have issue then what
DWG
 
Last edited by a moderator:
Boyd,

I routinely look at the concentricity of the of throat, both visually and occasionally mechanically. When I check mechanically the barrel is still setup in the lathe and I check three points. The top of the lands which tells me if something moved after the initial setup, the freebore and the breech end. Sometimes the barrel moves a few tenths then I look at radial orientation and numeric value of the run out in the throat. The way I chamber I have yet to see a chamber where any small amount of run out did not match up both in radial orientation and pretty much the same numeric value as the barrel so concentricity is not a problem.
 
Help a rookie improve

Thank for starting the thread, Ive been meaning to ask your guys opinion on this subject, this is an opportunity.

This is sample of the AR barrels I do, please critique the outcome and give me pointers on how I can improve. I think the body run out looks good, the neck looks good, but the area past the neck and the area past it may be questionable, land and groove indications do not appear to be consistent around the bore.

Here are the videos I just uploaded into youtube. I made them short for ease of viewing.


https://www.youtube.com/watch?v=pZWSnhla8NM

https://www.youtube.com/watch?v=ZniqBVQ51IM

https://www.youtube.com/watch?v=LE-W22CgNds

https://www.youtube.com/watch?v=0uD_nz_qE9I


Thank you.


nez
 
Video #3 shows something odd. If that's in the throat, ahead of the neck you have one of or combination of theses issues. Groove diameter is excessively large and/or your reamers freebore diameter is under size, either made that way or from wear.

Tell us about the barrel and reamer.
 
Dave Tooley said:
Video #3 shows something odd. If that's in the throat, ahead of the neck you have one of or combination of theses issues. Groove diameter is excessively large and/or your reamers freebore diameter is under size, either made that way or from wear.

Tell us about the barrel and reamer.
Click to expand...

Barrel is Shilen and the reamer is PTG 223 Wylde

On video 3 is it possible when I went past the neck that I may be reading a portion of the leade angle, thus the shallow reading between the land and the groove?
 
Last edited:
I am the guy who made the video in question, and i would like to address a few comments made in this thread.

Firstly i do certainly understand barrels aren't straight. I like to get two points in the bore dialed and running true. They are a point right at the throat/lead, and the another point as far down in the bore as i can reach. This gets the chamber both radially and axially in line with the first 2"-3" of the barrel, and as Jackie says, the bullet "sees" a perfectly centered and axially aligned bore. When setup like this there is usually some runout at the muzzle, anywhere up to 0.040", but around 0.020" is more common. I index the barrel so that the high point of muzzle runout is aligned with the top of the action.
Secondly, as mentioned there is no commercially available indicator for doing this. The one in the video is a Mitutoyo 2 Um (0.002mm) unit with a long stylus attached. The standard stylus is 15mm long and i have replaced it with a stylus that is 75mm long (ie 5 times longer). This means the divisions on the indicator are now reading 0.01mm or roughly 0.0005" as mentioned in the video. of course care is needed when using an indicator like this as there is a considerable increase in stylus bounce and hysteresis.

The barrel in the above video was not one of mine, and had been done by someone else. It had the chamber set at around 0.0015" radial off set to the bore, and also around 0.0015" per inch axial runout. The "This is why some barrels don't shoot" comment was somewhat off the cuff i admit, and i agree there are a multitude of reasons why some barrels don't shoot well.

Lastly here is another video i made of one of my own chamber jobs. This video illustrates how i think the chamber and bore should run.

http://www.youtube.com/watch?v=lpP5WwC3oqo

Cheers
Lee
 
Last edited:
NezRongero said:
Barrel is Shilen and the reamer is PTG 223 Wylde

On video 3 is it possible when I went past the neck that I may be reading a portion of the leade angle, thus the shallow reading between the land and the groove?
Click to expand...

You're correct in that you could be on the lead angle.
 
Leeroy said:
I am the guy who made the video in question, and i would like to address a few comments made in this thread.

Firstly i do certainly understand barrels aren't straight. I like to get two points in the bore dialed and running true. They are a point right at the throat/lead, and the another point as far down in the bore as i can reach. This gets the chamber both radially and axially in line with the first 2"-3" of the barrel, and as Jackie says, the bullet "sees" a perfectly centered and axially aligned bore. When setup like this there is usually some runout at the muzzle, anywhere up to 0.040", but around 0.020" is more common. I index the barrel so that the high point of muzzle runout is aligned with the top of the action.
Secondly, as mentioned there is no commercially available indicator for doing this. The one in the video is a Mitutoyo 2 Um (0.002mm) unit with a long stylus attached. The standard stylus is 15mm long and i have replaced it with a stylus that is 75mm long (ie 5 times longer). This means the divisions on the indicator are now reading 0.01mm or roughly 0.0005" as mentioned in the video. of course care is needed when using an indicator like this as there is a considerable increase in stylus bounce and hysteresis.

The barrel in the above video was not one of mine, and had been done by someone else. It had the chamber set at around 0.0015" radial off set to the bore, and also around 0.0015" per inch axial runout. The "This is why some barrels don't shoot" comment was somewhat off the cuff i admit, and i agree there are a multitude of reasons why some barrels don't shoot well.

Lastly here is another video i made of one of my own chamber jobs. This video illustrates how i think the chamber and bore should run.

http://www.youtube.com/watch?v=lpP5WwC3oqo

Cheers
Lee
Click to expand...


Apologies Lee. I watched The first video in the shop and couldn't listen.
nice job on barrel indicating. The first barrel in question, have you dialed in the throat and the muzzle and then checked chamber? Maybe that barrel was dialed in different. And have you tested first barrel ?
 
Here's a little something to make you think about chamber to bore alignment.

The barrel I shot at Sunday's registered LV match at Oak Hills in Iowa was chambered by me. The chamber is noticeably off center. I don't know why I didn't see it when I did the chambering job(over 800 rounds ago), but there it is. That tiny ridge you normally see between the angled ends of the lands(throat or leade) and the end of the neck is not concentric with the surface of the grooves. Using a 4X magnifier I can usually see a nice even line or shoulder all the way around. It's probably only 0.001" or 0.002" tall. This one is off center to where one side is almost smooth and the opposite side is deeper than normal.

Anyway, it's not "right".

So I shot this "crooked chambered" barrel Sunday and shot a 100 yard group of 0.032" on my 3rd target and followed it up with a 0.085" group on the 4th target.

I don't know what that proves or disproves, but it makes me think that you can be a little off once in a while and, as long as everything else is spot on, maybe you can still get by.

Jerry

IMG_0029.JPG
 
Jerry W said:
Here's a little something to make you think about chamber to bore alignment.

The barrel I shot at Sunday's registered LV match at Oak Hills in Iowa was chambered by me. The chamber is noticeably off center. I don't know why I didn't see it when I did the chambering job(over 800 rounds ago), but there it is. That tiny ridge you normally see between the angled ends of the lands(throat or leade) and the end of the neck is not concentric with the surface of the grooves. Using a 4X magnifier I can usually see a nice even line or shoulder all the way around. It's probably only 0.001" or 0.002" tall. This one is off center to where one side is almost smooth and the opposite side is deeper than normal.

Anyway, it's not "right".

So I shot this "crooked chambered" barrel Sunday and shot a 100 yard group of 0.032" on my 3rd target and followed it up with a 0.085" group on the 4th target.

I don't know what that proves or disproves, but it makes me think that you can be a little off once in a while and, as long as everything else is spot on, maybe you can still get by.

Jerry

View attachment 18252
Click to expand...

Ya think;);)
 
With all of these chambering threads, I don't think I have ever seen one that anyone uses a roughing reamer to establish the chamber from the beginning without drilling or pre-boring and then finish ream with their finisher. Given that the pilot has a max .0002 clearance at the throat area, wouldn't that be a viable method to hold the concentricity and straightness that we all strive for? I realize that it may take some extra time and cost for the extra reamer, but shouldn't that take out more of the variables if the reamer is following the bore from the beginning?
 
Many of us have roughing reamers. Many of us have used them a time or two. But, a finish reamer will follow, exactly, the path taken by the rougher, period...

When a chamber area is drilled, most of the metal is taken out leaving much less material for the finish reamer to remove thus saving many more sharp edges to cut many more chambers.

The second common step in the chamber machining process is to lightly bore the first 1/2-3/4" of the chamber base. This assures the finish chamber will be in axial alignment with the chamber neck which is held true by the reamers pilot bushing.


.
 
So I guess the question is....won't a roughing reamer follow the bore exactly as well as the finish reamer will follow the rougher?
 
Rflshootr said:
So I guess the question is....won't a roughing reamer follow the bore exactly as well as the finish reamer will follow the rougher?
Click to expand...


IMO the pilot's not there to "follow the bore"...........

Both reamers will follow the bore if you just poke them in and push, that's the problem.

It's physically impossible to cut multiple chambers to the same dimensions using this method, bores wander wildly.
 
You must log in or register to reply here.
Back
Top