Trouble finding the lands…

[LVLAaron]

Working on my FTR rifle. It’s a .168 freebore chamber.

Before it had any rounds through it I measured w/ the Hornady Comparator and a Berger Juggernaut. I recall easily finding the lands @ 2.326

I put about 1500 rounds through it this season, and picked up some Berger 200 Hybrids and Berger 200.20x – so time to find the lands for these bullets.

200 Hybrid: 2.328
200.20x: 2.330
Juggs: 2.353 (27 thou over ~1500 rounds growth)


To get to my issue. When I’m running the bullet into the lands with the tool I run into a little resistance before I get to what I believe is the lands. It’s really slight and doesn’t take much effort at all to get past it. Once I’m past that bump the bullet moves freely a few tenths to the lands.


What could this be? Carbon ring? Funny lands? User error?


I ask for two reasons…

1, I just don’t know, and
2, w/ the 20x’s at the lands there’s very little bullet in the case neck. They are 3.1” OAL


I included all of the numbers here in case anyone has their CBTO’s handy for a .168 or .170 FB chamber to compare notes.

 

[Ggmac]

Is the slight resistance at the original land location ( or near it )

 

[LVLAaron]

Is the slight resistance at the original land location ( or near it )

Nah. If that's the original lands I've grown hundredths and the 200's would be shorter than mag length.

 

[Crosshair1]

I run similar, 170 freebore, with 185 juggs and has gained 4 thou in 900+ rounds.
Started 2.357 (after break-in) and now 2.361
I use a case gauge made from a fired case, i would imagine if using a hornady case there could be resistance before the lands as the bullet enters the bore off centre due to the undersized case.
Anyway it doesnt really make a difference once you have found the dead stop of the rifling.
Btw i've never measured prior to break in as Ive expected a large change as the leade has been smoothed out from machining.

 

[LVLAaron]

Good point. I don't have a bore scope but I could get a decent look with a light in the muzzle end. There's no obvious carbon ring or anything - If I were a betting man I'd say the bullet is just dragging across whatever this little lip is called.

 

[chkunz]

It may be that the leade is badly worn or gone at this point and the lands may be worn somewhat also. I once sectioned a 223 barrel that I removed, it still shot well after 6000 rounds but was down a few points at 600 yards. The leade was complete gone and just bright streaks where they had been and the start of the rifling. I just removed a barrel at 4000 rounds and am going to section it also and take a look. Some may have done this with a good borescope but I like to section the barrels to look and see.

 

[LVLAaron]

I've got one more match this season. I'm going to get another barrel screwed on over the winter season. I'll cut this one open. It'll be interesting, or a waste of a barrel.

 

[Immike]

Get somebody with a borescope to take a look inside for you. You may just have a carbon build up.

 

[LVLAaron]

Get somebody with a borescope to take a look inside for you. You may just have a carbon build up.

Time for me to get one.


Assuming it is a carbon ring, what should I be using to get it out? I have Bore Tech C4 and only use a jag and a nylon brush.

 

[Immike]

Time for me to get one.


Assuming it is a carbon ring, what should I be using to get it out? I have Bore Tech C4 and only use a jag and a nylon brush.

Some of other gentlemen on here that have more experience with hard carbon should help you. Keeping it clean is much easier and I have no choice with tight neck chambers.

 

[Toejoe12]

Time for me to get one.


Assuming it is a carbon ring, what should I be using to get it out? I have Bore Tech C4 and only use a jag and a nylon brush.

JB Bore paste, Iosso, Bore Tech Camilian gel. BT is the mildest abrasive of the 3

 

[Dusty Stevens]

I would just about bet you have a carbon ring if you only use a nylon brush. Iosso short stroked on a patch will get it out and butchs and bronze brushes will keep it out

 

[JohnKielly]

As a point of interest, did you keep the bullet you ran your original test with to use subsequently, or are you using another bullet?

 

[LVLAaron]

As a point of interest, did you keep the bullet you ran your original test with to use subsequently, or are you using another bullet?

I have some from the same lot number, but I'm going to start bagging and tagging them.

 

[KenOath]

Working on my FTR rifle. It’s a .168 freebore chamber.

Before it had any rounds through it I measured w/ the Hornady Comparator and a Berger Juggernaut. I recall easily finding the lands @ 2.326

I put about 1500 rounds through it this season, and picked up some Berger 200 Hybrids and Berger 200.20x – so time to find the lands for these bullets.

200 Hybrid: 2.328
200.20x: 2.330
Juggs: 2.353 (27 thou over ~1500 rounds growth)


To get to my issue. When I’m running the bullet into the lands with the tool I run into a little resistance before I get to what I believe is the lands. It’s really slight and doesn’t take much effort at all to get past it. Once I’m past that bump the bullet moves freely a few tenths to the lands.


What could this be? Carbon ring? Funny lands? User error?


I ask for two reasons…

1, I just don’t know, and
2, w/ the 20x’s at the lands there’s very little bullet in the case neck. They are 3.1” OAL


I included all of the numbers here in case anyone has their CBTO’s handy for a .168 or .170 FB chamber to compare notes.

I’m having a similar thing happen with a 5R Barrel at the moment, thought it may have something to do with the way the lands are with 5R rifling?? Once I push past the very light hang up I’m getting consistent measurements at what I believe to be the lands.. I’m happy with the way it shoots so I’ve just continued on