Direct Read Dial-In, Lands or Grooves?

[INTJ]

I use an Interapid (all the cool kids do ) and usually read off the lands when dialing in a barrel. After all, the lands are the original drilled part of the barrel, and the rifling is cut into that. Most of what I chamber is cut 5R, with an occasional cut 4 groove.

Yesterday and again today I had barrels for which I couldn't get a stable reading off the lands. So I switched to the grooves and was able to dial in. These were just hunting barrels so not a big deal. However, that is the first time I have had to read off the lands.

How do you other direct dial guys do it, lands or grooves?

 

[B Nettesheim]

I’ve had the same trouble before, I mount the indicator stand on the crosslide and in this situation all it needed was a small adjustment to the crosslide. I think it was side loading the stem.

 

[WayneShaw]

Not trying to start an argument, but the grooves make up a much greater surface area for the bullet to engage and follow, where the lands only induce the spin. The bullet will fill the grooves, not ride on top of the lands.

 

[boltfluter]

Not trying to start an argument, but the grooves make up a much greater surface area for the bullet to engage and follow, where the lands only induce the spin. The bullet will fill the grooves, not ride on top of the lands.

Very true. But the lands and the grooves had better be very concentric or there are bigger problems than how the barrel is dialed in. Just my personal experience.
Paul

 

[LVLAaron]

Mitutoyo 513-504 on the bore/grooves.

You couldn't get a stable, or consistent reading?

 

[DaveTooley]

Tell us about the barrel. Cut or buttoned? Not all lands form a perfect radius in most button rifled barrels. I've seen some funny shapes over the years. One button rifled barrel had a .001" lip sticking up on one side of the land. Others were sunken in the middle. Also how are you setting up your indicator? I use the 3 o'clock position with the ball slightly above the centerline. I find just a bit of a side load stabilizes the readings.

 

[jackieschmidt]

If you are using a properly fit live pilot reamer, the pilot bushing is going to follow the lands, regardless of what you indicate.

One thing you can learn from using a independent stylus indicator rather than a range rod is exactly what the lands and grooves look like. I have seen some pretty strange shapes on either the tops of the lands, or the bottom of the grooves.

A number of years ago, we started noticing that the grooves on a certain very popular brand of cut rifled barrels were not a true round arc. As the indicator stylus would drop into the grooves, you could pick up as much as .00o3 out of true arc.
That meant the bullet was in fact not round after It traveled down the barrel.

A very well known shooter was setting the world on fire with one of these, and the manufacturer actually coined a name for it.

However, what was finally revealed was in order to prolong the life of the hook tool used in the cut rifled process, , they were sharpening the face of the tool to regain a sharp cutting edge. However, due to the back clearance of the cutting edge, this change ever so slightly the profile of the cutting edge.

Or at least that was the rumor.

Soon after, they ceased this. The grooves started being a perfect arc on bullet diameter again.

In all honesty, those barrels shot shot quite well.

 

[hoz53]

I use an Interapid (all the cool kids do ) and usually read off the lands when dialing in a barrel. After all, the lands are the original drilled part of the barrel, and the rifling is cut into that. Most of what I chamber is cut 5R, with an occasional cut 4 groove.

Yesterday and again today I had barrels for which I couldn't get a stable reading off the lands. So I switched to the grooves and was able to dial in. These were just hunting barrels so not a big deal. However, that is the first time I have had to read off the lands.

How do you other direct dial guys do it, lands or grooves?

I use an Interapid (all the cool kids do ) and usually read off the lands when dialing in a barrel. After all, the lands are the original drilled part of the barrel, and the rifling is cut into that. Most of what I chamber is cut 5R, with an occasional cut 4 groove.

Yesterday and again today I had barrels for which I couldn't get a stable reading off the lands. So I switched to the grooves and was able to dial in. These were just hunting barrels so not a big deal. However, that is the first time I have had to read off the lands.

How do you other direct dial guys do it, lands or grooves?

do you find the little ball on the end of the stem may be to big to fit down in the grooves? have you ever had to change it to a smaller one?

 

[INTJ]

Tell us about the barrel. Cut or buttoned? Not all lands form a perfect radius in most button rifled barrels. I've seen some funny shapes over the years. One button rifled barrel had a .001" lip sticking up on one side of the land. Others were sunken in the middle. Also how are you setting up your indicator? I use the 3 o'clock position with the ball slightly above the centerline. I find just a bit of a side load stabilizes the readings.

Correction. 5R button carbon wrapped barrel. Both of them actually looked like seconds and I had to clean gunk out of the breech on both barrels. They were new from the manufacturer.

It's like the lands were rounded across the whole top vs just radiused on the edges.

 

[INTJ]

do you find the little ball on the end of the stem may be to big to fit down in the grooves? have you ever had to change it to a smaller one?

Indicator tip seems to fit fine

 

[INTJ]

Mitutoyo 513-504 on the bore/grooves.

You couldn't get a stable, or consistent reading?

Correct. Not on the lands. First time I have seen that