5R runout demonstrated

[Ksracer]

One thing that hasn't been mentioned is reamer/pilot spindle SIZE. A 6mm reamer with a group 1 bushing spindle on it is far more likely to deflect than a .308 reamer with a group 3 spindle. If you don't believe me, put a reamer between centers with a tenths DTI on a flute and push it around a little.


Indicator sensitivity is something else we should be talking about. If you're using the Interepid, you might be able to divide the .0005 divisions where the needle stops moving, but how much does it take to make the needle START moving? Will the Mitutoyo with a short stylus pick up imperfections that the long stylus miss? Is it possible that that letting the long stylus ride over the lands and come back to "zero" will pick up run-out in the grooves that would otherwise be missed if the bore was more circular?

Do a test. Chuck up a smooth shaft and clamp a short tenths indicator rigidly to the tool post at the end. Put the long stem beside it mounted off your favorite mag base with the flexible arm. Start pushing on the shaft and see which needle moves first. Do they come back to where they started? I bet your going to find that the long stem has more hysteresis than the short stem.

 

[WSnyder]

The little "U" shapes at the end of the rifling don't seem to affect anything.

Reasons why some see this and some don't?

Chambering at a higher RPM often fixes the U. Different barrels types seem to cut differently. Not every one is super fussy about their chambering jobs.

I have seen abnormalities as well. It likely points to imperfect tooling used while manufacturing the barrel. Grooves and lands aren't always perfect and as long as everything indicates within your limits after chambering and the cuts are symmetrical all around I don't see a problem.

IMPORTANT
For any of you that get these loupes please don't freak out and start calling the barrel maker. Over time you will see many abnormalities in land configuration that DO NOT show up on the target.

 

[WSnyder]

I bet your going to find that the long stem has more hysteresis than the short stem.

They most definitely do and agree! It takes a bit of practice and a little finesse to use and read what the long stylus Interapid's are telling you. It can be done but definitely not as easily as the little Mit's.

 

[tobnpr]

If I ream slow I get a little "U" at the beginning of the rifling. If I increase the speed to 250+ I can usually get rid of the little U. That said, the little U doesn't hurt anything, but it is a sign of a six flute reamer in a five groove bore.

Look anything like this?


This is due to reamer geometry, barrel has smaller than nominal groove radius.

 

[INTJ]

Look anything like this?
View attachment 1365419

This is due to reamer geometry, barrel has smaller than nominal groove diameter.

I have seen it look a little like that, but not that deep of a U.

 

[Ksracer]

Look anything like this?
View attachment 1365419

This is due to reamer geometry, barrel has smaller than nominal groove diameter.

Can you elaborate?

If it was simply a "tight groove" barrel, i.e. one where the groove diameter is considerably smaller than the Free bore diameter, there should be a straight line between the ends of the leade. Looking lengthwise from the chamber end would show a step for 360deg, minus the land area. Much like what was shown in the other "concentricity" post

What I see there is would have to be from a groove that is tighter in the middle and a larger diameter next to the lands.

 

[xr650rRider]

Indicator sensitivity is something else we should be talking about. If you're using the Interepid, you might be able to divide the .0005 divisions where the needle stops moving, but how much does it take to make the needle START moving? Will the Mitutoyo with a short stylus pick up imperfections that the long stylus miss? Is it possible that that letting the long stylus ride over the lands and come back to "zero" will pick up run-out in the grooves that would otherwise be missed if the bore was more circular?

I've found the Interapid more responsive. I think Gordy Gritters in his book "Chambering Rifles for Accuracy" changes the tip out on the Mitutoyo to a 1.5" and 2.675" tip. With a 2.675" tip on the Mitutoyo it becomes .00038" per division but the springs in the DTI were never designed for the increased length and weight, so effects it's sensitivity negatively as well. Long Island indicator had a tech note on the issue.

Also in book referenced above Gordy talks about 5R reamer chatter from page 79-85. That's why Gordy graduates seem to have the most problems with it.

 

[LVLAaron]

I use the Mitu DTI - I'll agree the 2.6 tip is worthless. It's so long, if you're in a less than 30 cal barrel, You can't really get the tip of it running on the bore very well, the body of it rides all over the place. I do like the 1.5" tip - whatever that can't reach, I use a grizzly rod instead.

I'll have to see if I can find a deal on the Interapid. That extra length would be handy.

 

[INTJ]

I use the Interapid with the 2.75" tip for most things, and then I put on a 5.5" tip for the longer cartridges. There is a learning cure to using it, like with everything we do.

However, regardless of the tip, when the Interapid says there is no movement then there is no movement.

 

[xr650rRider]

I use the Mitu DTI - I'll agree the 2.6 tip is worthless. It's so long, if you're in a less than 30 cal barrel, You can't really get the tip of it running on the bore very well, the body of it rides all over the place. I do like the 1.5" tip - whatever that can't reach, I use a grizzly rod instead.

I'll have to see if I can find a deal on the Interapid. That extra length would be handy.

You might not have any extra length over the 1.5" tip. With the Mitutoyo, you can insert the body, with the Interapid you can't. So both are probably around same length. But there is more space between divisions on the Interapid 312B-15 and it just feels better all the way around. It was designed for the 2.675" tip where as the Mitutoyo wasn't, even though it's a .0001" DTI.

 

[LVLAaron]

Just looking a few posts up the Interapid looks like it has at least half an inch on the mitu with a longer tip.

The mity w/ 1.5 tip works fine for cases up to .308 in legth

 

[tobnpr]

Can you elaborate?

If it was simply a "tight groove" barrel, i.e. one where the groove diameter is considerably smaller than the Free bore diameter, there should be a straight line between the ends of the leade. Looking lengthwise from the chamber end would show a step for 360deg, minus the land area. Much like what was shown in the other "concentricity" post

What I see there is would have to be from a groove that is tighter in the middle and a larger diameter next to the lands.

I first saw this on a barrel I chambered a couple of years ago. Knew it wasn't the reamer because I'd used it on several barrels before with no issues. I was puzzled by it, posted it on the 'Hide- and the explanation made sense to me- here, see posts 2-9, same also by Fisher T&C post #14.

Gunsmithing - Chambering anomaly- yeah, another borescope question...

but this one is different from any others I've seen. Just chambered this barrel. There are perfect half-moons cut ever so lightly into the grooves at the beginning of the leade cut- full diameter of the barrel. All perfectly symmetrical, all aligned radially meaning the bore was correctly...

www.snipershide.com

 

[Ksracer]

I first saw this on a barrel I chambered a couple of years ago. Knew it wasn't the reamer because I'd used it on several barrels before with no issues. I was puzzled by it, posted it on the 'Hide- and the explanation made sense to me- here, see posts 2-9, same also by Fisher T&C post #14.

Gunsmithing - Chambering anomaly- yeah, another borescope question...

but this one is different from any others I've seen. Just chambered this barrel. There are perfect half-moons cut ever so lightly into the grooves at the beginning of the leade cut- full diameter of the barrel. All perfectly symmetrical, all aligned radially meaning the bore was correctly...

www.snipershide.com

That makes a lot of sense for a cut rifled barrel. It's a little harder to picture with a button rifled one, but I'm sure the bore on them can take on several unexpected shapes as tooling wears.

 

[INTJ]

I first saw this on a barrel I chambered a couple of years ago. Knew it wasn't the reamer because I'd used it on several barrels before with no issues. I was puzzled by it, posted it on the 'Hide- and the explanation made sense to me- here, see posts 2-9, same also by Fisher T&C post #14.

Gunsmithing - Chambering anomaly- yeah, another borescope question...

but this one is different from any others I've seen. Just chambered this barrel. There are perfect half-moons cut ever so lightly into the grooves at the beginning of the leade cut- full diameter of the barrel. All perfectly symmetrical, all aligned radially meaning the bore was correctly...

www.snipershide.com

I had the same issue as the guy in Post 14 did a couple weeks ago. It was a 300 Norma and a brand new JGS reamer. The barrel--a carbon wrapped light contour (sigh), was .3000 for the about first 1/2", .3002" for about the next 1/2", then 3.004".

At least those were the bushings that were needed to have the right fit. This one would have been a good candidate to prebore. I kept changing the bushings the deeper I cut.

With .500" left to go the rifling looked liked the video in Post 14. I kept increasing rpm, and finally went to the second JGS 300 Norma reamer we had (ordered a duplicate by mistake). I finally got it down to just the little "U" at the end of the rifling.

 

[Judd]

Bart 308 win 5r…I do start with a range rod before moving to the lands/grooves with the indicator on a 5r barrel. First video is case web area and you can see the longer indicator, the black mark is the second video and that is in the throat.

A guy that’s helped me mentioned videoing these measurements and I happened to cut this one today. You hit me at the right time, although not sure what this proves except this one is straight and not 5 sided.

I cut this one and increased speed as I went based upon y’all’s conversation here, thanks! I know some of the old timers hate these type of threads but I seem to learn a little something every time ones posted.

 

[DaveTooley]

That makes a lot of sense for a cut rifled barrel. It's a little harder to picture with a button rifled one, but I'm sure the bore on them can take on several unexpected shapes as tooling wears.

Steel is forced to flow in button barrels. That flow forms the lands. It doesn't always fully form the lands. Thus odd shapes on top of the lands are common. The carbide button doesn't wear in match grade barrels.
See the link below for more information about button rifled barrels.

Danjon

www.danjon.com

 

[Sniperhandle]

I have chambered a whole lot of 5C Barrels and a good number of 5R and haven't had any issues. I don't see why 5C would not be any different?

I wish Broughton still made barrels

 

[jelenko]

Steel is forced to flow in button barrels. That flow forms the lands. It doesn't always fully form the lands. Thus odd shapes on top of the lands are common. The carbide button doesn't wear in match grade barrels.
See the link below for more information about button rifled barrels.

Danjon

www.danjon.com

On their page it says a button goes through a barrel in 25 seconds. That must produce a lot of heat - yes?

 

[Dusty Stevens]

On their page it says a button goes through a barrel in 25 seconds. That must produce a lot of heat - yes?

You should see the amount of oil flooding in there

 

[DaveTooley]

You should see the amount of oil flooding in there

All the button people I know coat/plate the bore before pulling/pushing the button. Probably the secretive part of the trade is the lube. I know one manufacture had a copper infused lube.