Chasing the lands is stupid... What do you think?

[Erik Cortina]

if measuring to the lands is not important then why do you do it when you first performed a seating test? why would you care ?

the logic doesn’t hold up for me. This is just my uneducated opinion.

I did it only to make sure I don’t jam a bullet in the barrel and have it potentially get stuck.
If you are limited by mag length, then treat mag length as jam and proceed the same was as described.

 

[Erik Cortina]

Using your described "jamming" method, can totally understand why you have no consistency in actual "touch" measurements, or why you have no clue to where your lands contact really is (or how much your throat is actually eroding).

When experienced with the fallowing method, repeatable and exact measurements are easily obtained:

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You missed the point. What angle is the throat you are measuring after 1,200 rounds? What about after 1,800? You aren’t measuring the same surface, so how is your measurement “accurate”?

 

[Erik Cortina]

Like as mentioned earlier he finds the lands and works back but he is simply doing this by trial and error and not recording the actual number although he has to record the number to begin with I think he’s just looking for some attention

you totally missed the point. That’s ok.

 

[Erik Cortina]

Good video, but he still "chases the lands" for best accuracy when required (his definition of "chasing the lands" differs from others). Very practical explanation IMO.

How do I chase something that I don’t measure? The point is, that lands and seating depth do not move in 1:1 relationship, so that’s why I don’t chase the lands. I simply make sure I stay in my node and don’t care where the lands are.

 

[gunsandgunsmithing]

For what it's worth, I dont chase lands either, with a tuner. We can debate about minute details but ultimately, changing seating depth does the same thing as moving the tuner....changing the timing of bullet exit and muzzle position.

 

[Dusty Stevens]

However if you're not very good at sizing , your case headspace ( base to datum ) measurement can very as much as .005+ which means your distance to lands can very that same amount from cartridge to cartridge when fired .

my seating die sits on the ojive of the bullet and holds the case at the base. So if i bump a case .001 or even .015 the relationship of the bullet to the lands (jump or jam measurement) is the same no matter what i do. I could use 3 different sizers and my jump/jam would be the same every time.

 

[DJSBRS]

you totally missed the point. That’s ok.

So with your theory, you would never support setting a barrel back to get a fresh throat?

DJ

 

[NA Woody]

Thanks for posting the video Erik. Good information!
I'm pretty sure Erik has forgotten more about this sort of thing than many of us know....

 

[bugman]

.....that loud sound is thousand of "critters" being thrown into trash cans.

.....you know, "critter" as in the barrel stub chambered with your reamer to be used as a headspace gauge and initial chamber OAL reference.

....I guess you could always face off the chamber part, and just use it as a HS gauge.

 

[jelenko]

What angle is the throat you are measuring after 1,200 rounds? What about after 1,800? You aren’t measuring the same surface, so how is your measurement “accurate”?

Erik - I think I get the idea, but wouldn't the bullet still engage the lands at the same point? I'm thinking that the bullet always engages the lands at the same point on the bullet ogive. While the approach angle of the throat might change with erosion, wouldn't the bullet not engage until it reaches the point where the lands are unworn? As the lands erode, they have to be wider - so the bullet slips in until the ogive contacts the lands - yes?

 

[BoydAllen]

That was a thought provoking presentation. I had to smile because using jam as your reference is so old school short range benchrest. I will add a couple of things. IMO this truth, the part about .020 shorter than jam still being in the lands is probably true for any bullet that a long range shooter would choose, BUT not necessarily for bullets with smaller ogive numbers where they contact the rifling. Not that I use touch for a reference for short range, but I do like to know the distance from touch to jam. For touch I like Alex Wheeler's method. I work with seating depths that are longer than touch pretty much all the time, but I know friends who have found their best node jumping, and in some cases quite a distance. For those situations I would refer you to an article that is in the front of the Berger manual, and on their web site. While it references VLD bullets, I called and spoke with one of the technicians at Berger and he told me that the method works for other styles of bullets as well. Here is a link.
https://bergerbullets.com/vld-making-shoot/
Based on this information, I have been approaching investigations of jumping bullets all wrong, primarily because I have used the same small moves for initial testing that I would when seating into the lands. Do a little reading. I think that you may be surprised. Getting back to this presentation, I will save it, and review it from time to time because it is based on a lot of experience. Thanks for sharing.

 

[OmegaRed]

I typically start at what I call full jam. That being, as far into the lands as my neck will allow. That leaves only one direction to work. That said, I can make small adjustments or, depending on application, I may just back it out enough to find the point where the bullet wont stick and dump powder, and work from there.

We were just having this conversation this yesterday. How do you determine what that measurement is (jam vs. when the bullet force overtakes neck tension)? How do you remove the bullet while maintaining an accurate measurement (cleaning rod gentle tapping, just pulling the bolt back, etc.)?

 

[Lucky Shooter]

I've been through this touch/jam exercise and have been able find the touch and jam points with some degree of consistency------and fully understand these conditions are reference points to work from.

I've never found the best accuracy to be at jam and usually it occurs closer to touch than to jam. Other very good shooters seem to prefer working from jam----and I don't question their results.

I've quit even finding jam----just find touch and go
longer from that point.

Am I leaving something on the table by ignoring jam ? BTW., this is without a tuner.

A. Weldy

 

[Kimber.204]

How did we get to the bottom of the second page and no one commented about @Erik Cortina shirt??? Hahaha.

It seems like a lot of folks are taking offense to what Erik is proposing or they are discounting what he's saying based on semantics. I think Erik's comment on the relationship to throat wear and seating depth is very important. Just because the touch point is further out doesn't mean that the geometry between the bullet ogive and the throat/leade/lands is the same as it was 1000 rounds ago.

I think the article(s) about bullet jump on precision rifle blog bring up some good info as well. Here's one of them: https://precisionrifleblog.com/2020/04/28/bullet-jump-research-and-load-development-tips/

Thanks for the videos Erik.
Regards,
Ross

 

[dcali]

I work with seating depths that are longer than touch pretty much all the time, but I know friends who have found their best node jumping, and in some cases quite a distance. For those situations I would refer you to an article that is in the front of the Berger manual, and on their web site. While it references VLD bullets, I called and spoke with one of the technicians at Berger and he told me that the method works for other styles of bullets as well. Here is a link.
https://bergerbullets.com/vld-making-shoot/

I've also found that Berger's method has nothing to do with VLDs, and works with anything. More generally, I think the best way to find a good seating depth is to test in huge increments and then to refine the best one.

Side note: I've always been confused with the old school definition of jam (the depth at which the bullet starts getting seated by the lands. Surely this is an inconsistent number? Less consistent than touch, for example? Or is it? Touch would vary with teh bullet ogive, while jam would vary with the ogive and neck tension. I've never tried to measure a sample to find out which is more consistent, and I'm not even sure I could accurately, but I don't see the value in the jam number over the much easier to nail down touch.

I just use the "as-new" touch as a datum for the life of the barrel. It's easy to find accurately and doesn't change. The rest is sorted out on the target.

 

[gunsandgunsmithing]

I think whatever method you use to find the lands is mostly inconsequential, as long as your method produces good results on target.
The value of everyone using the same method is for forums and load sharing.
Even then, each barrel/ bullet/load may well be different for us all. I dont get caught up in what method anyone uses, as long as the results on paper are good.

 

[Metal God]

my seating die sits on the ojive of the bullet and holds the case at the base. So if i bump a case .001 or even .015 the relationship of the bullet to the lands (jump or jam measurement) is the same no matter what i do. I could use 3 different sizers and my jump/jam would be the same every time.

No it's not , If your case headspace is 5 to 7 thou shorter then your chambers headspace . The cartridge is moving in the chamber that much . So if some of your shoulders are bumped .002 while others are bumped .005 to .007 . That is a .005 variance of where your ogive will be in relation to the shoulder because you are seating from the head of the case . Thats a big deal because the case headspaces off the shoulder not the head of the case . So when the firing pin pushes the case forward and the case shoulder stops on the chamber shoulder . That case shoulder to bullet ogive is what sets your jump , touch or jam length not your case head to ogive measurement .

Put another way , Lets say you only neck size and the case is a semi tight fit to the chamber . When the firing pin hits the primer the case has no room/extra space to move forward in the chamber so your bullet when fired is at the same place in relation to the lands as when you originally seated the bullet or recorded your lands measurement . Now take that same case and bump the shoulder back .005 then seat the bullet to the same COAL as before . Now when the firing pin hits the primer is pushes the case that extra .005 forward you bumped the shoulder resulting in the bullet moving forward that same .005 actually changing your jump , touch or jam measurement that same amount .

It's VERY important if you are only adjusting your seating depth by just a few thou that your head to should datum distance is very consistent from case to case . If not adjusting just 2 or 3 thou is a waste of time because your case can move that same amount in the chamber . Meaning cases with a .002 bump will move that much while cases with a .005 bump will move that much more negating or doubling your .003 adjustment .

 

[gunsandgunsmithing]

We were just having this conversation this yesterday. How do you determine what that measurement is (jam vs. when the bullet force overtakes neck tension)? How do you remove the bullet while maintaining an accurate measurement (cleaning rod gentle tapping, just pulling the bolt back, etc.)?

The sure way is to use a case that falls out and remove the extractor, tapping bullet and case out with a cleaning rod.

 

[Alex Wheeler]

The root of the question is, does a bullet's relationship to it's first point of contact at the lands correlate to the the tune? I think Erik is making the point that in his experience it does not. In that case, maintaining that relationship of bullet to first point of touch is undesirable.

 

[jackieschmidt]

.....that loud sound is thousand of "critters" being thrown into trash cans.

.....you know, "critter" as in the barrel stub chambered with your reamer to be used as a headspace gauge and initial chamber OAL reference.

....I guess you could always face off the chamber part, and just use it as a HS gauge.

I think I will keep all of mine.

The video is a good exercise in common sense. As a Short Range Benchrest Shooter, I know how important seating depth is in obtaining optimum agging capability.

I think the single biggest detriment to shooters getting the optimum performance for the Discipline they are shooting is not loading at the range. I see shooters at my Club show up with a box full of loaded rounds, all segregated with various differences in the hope that one just might produce acceptable results.

Think of all of the time that can be saved and informatIon garnered by being able to make changes on the spot in a timely manner.

For short range, we focus very little ES and SD. As long as one bullet stacks on another, that is all that counts.

For the long range guys, the ability to shoot extremely small groups can be secondary to getting the Extreme Spread and Standard Deviation as optimized as possible. It does no good to have a 600+ yard rifle that shoots .400 groups at 200 yards but has a ES of 30 FPS, or a SD of 15. But then, it does little good to have the same rifle shooting at a extreme spread of less Han 10 and a Standard Deviation of three if the darned thing is shooting one inch plus groups at 200 yards.

If you load at the range, you can find the best performance in both categories.

It takes a little effort, but one that pays off.