who does this method? Chasing Lands

[Outdoor]

I just watched Eric Cortina explain why chasing your lands means nothing. Must admit ,

In short, he suggested to Jam your lands back off .020. Then load 5 shots groups ( could be 3) and keep backing off by .003

You will get large group, large group, a better group then maybe 2 or 3 groups that are tight. That is your best seating depth and it means nothing with respect to the lands? He claims you need multiple tight groups that are .003 apart before you settle. Then take the longest AOL and subtract .001. Has anyone done this type of testing?


Sorry, I am new to this method and looking for input

 

[60723]

I have done this several times. After a hundred rounds test .003 longer. If good that is new seating depth. If not go back where you were

 

[Murray Brook]

I've listened to Erick's video and if I'm not mistaken he states that every so often he lengthes his CBOT by several .000. This IMO is chasing the lands. JMO

 

[Chilly807]

^^^^^ exactly right

 

[Ccrider]

Great question. I have not seen .006 seating depth windows for top accuracy, so I just took that part of it as his personal experience.

 

[LVLAaron]

I've listened to Erick's video and if I'm not mistaken he states that every so often he lengthes his CBOT by several .000. This IMO is chasing the lands. JMO

True. His method is a lot less "trouble" though. Sometimes people go through so much effort to always be some exact number off the lands, they end up chasing their tail. His method of "test one that's seated a little longer every now and then" is a much simpler way to do it, imo.

 

[Murray Brook]

True. His method is a lot less "trouble" though. Sometimes people go through so much effort to always be some exact number off the lands, they end up chasing their tail. His method of "test one that's seated a little longer every now and then" is a much simpler way to do it, imo.

Yes. But why would you change your CBTO unless the accuracy dropped off. I take it that the load worked at a certain CBTO because it was a certain distance from a fixed point. In the case of a rifle the easiest fixed point is the rifling. You lengthen the CBTO this to get back to that certain distance from a fixed point ( lands) that worked good because of land erosion .

 

[TTE]

Great question. I have not seen .006 seating depth windows for top accuracy, so I just took that part of it as his personal experience.

Depends on what top accuracy means to the shooter and the distance they are shooting.

 

[DShortt]

I've tried it. Can't say that I have experienced identical results.

But, I don't have 'wood' hanging on the wall.

Who cares what I think?

 

[LVLAaron]

Yes. But why would you change your CBTO unless the accuracy dropped off. I take it that the load worked at a certain CBTO because it was a certain distance from a fixed point. In the case of a rifle the easiest fixed point is the rifling. You lengthen the CBTO this to get back to that certain distance from a fixed point ( lands) that worked good because of land erosion .

You're not changing it... you're testing it. If it's better; that's your new number.

 

[Murray Brook]

You're not changing it... you're testing it. If it's better; that's your new number.

If your developing a target load should you have not already tried that CBTO. I know in my testing I would have. I always test both side of a CBTO.

 

[DLT]

I've listened to Erick's video and if I'm not mistaken he states that every so often he lengthes his CBOT by several .000. This IMO is chasing the lands. JMO

What I think about it too

 

[Ccrider]

Depends on what top accuracy means to the shooter and the distance they are shooting.

I accepted this as part of the situation also. I wonder how many benchrest shooters would agree or use this method without dialing in to the most accurate depth.

 

[LVLAaron]

If your developing a target load should you have not already tried that CBTO. I know in my testing I would have. I always test both side of a CBTO.

Yes... but then you shoot and wear out the barrel... you need to adjust... maybe... or do you? Try a load 3 thou longer and find out.

 

[dgeesaman]

I just watched Eric Cortina explain why chasing your lands means nothing. Must admit ,

In short, he suggested to Jam your lands back off .020. Then load 5 shots groups ( could be 3) and keep backing off by .003

You will get large group, large group, a better group then maybe 2 or 3 groups that are tight. That is your best seating depth and it means nothing with respect to the lands? He claims you need multiple tight groups that are .003 apart before you settle. Then take the longest AOL and subtract .001. Has anyone done this type of testing?


Sorry, I am new to this method and looking for input

Erik is having fun with semantics. There is a relationship between the optimal seating depth and the engagement to the lands and you have to compensate for that as the barrel wears. His point is that it’s more complicated than to develop a load and expect the optimal tune to always be the same exact distance from the lands as the barrel wears and the lands “move” forward.

His method makes sense: once you have a good seating depth you don’t know exactly when to change it and by how much but it generally works to have the seating depth grow longer as the barrel wears. So his method is to regularly shoot a few rounds at a slightly longer length as your current tune and if those rounds also shoot like your tune, use that longer length going forward. That way you continuously test a little bit to stay on the optimal seating depth. I think of it as chasing the lands with your eyes closed.

 

[Murray Brook]

Yes... but then you shoot and wear out the barrel... you need to adjust... maybe... or do you? Try a load 3 thou longer and find out.

I guess what I'm trying to say that I would have already tried a CBTO .003 longer and fell no need to try anything more till the accuracy changes. I have had barrels that I have had to chase the lands and others that remain with the same CBTO through out the life of the barrel. I can't speak for all shooters but know of many that change nothing as long as their accuracy is good

 

[LVLAaron]

@dgeesaman summarized it perfectly.

I'll add. If you're not testing, you're guessing.

 

[G Liles]

This^^^^^^

 

[fisherman987]

I accepted this as part of the situation also. I wonder how many benchrest shooters would agree or use this method without dialing in to the most accurate depth.

Probably none.

 

[BoydAllen]

Accuracy requirements vary by the kind of shooting being done, as do the number of rounds between cleanings, based on match format. Erik is an accomplished F Class shooter, were he as serious about short range group, I predict that his methods would change. Each shooting sport has its own reality that influences what woks best for that sport.