Help: Berger bullet seating depth, distance to lands???

[kskevin]

Guys, my distance to lands is driving me nuts. I'm an engineer so the details and precision are something I can't let go off and I'm off deep into the rabbit hole. Would appreciate some perspective.

Have a GAP 280AI and had been measuring distance to lands every couple hundred rounds or so. The distance was decreasing with increasing round count (impossible). My measurement approach was a very loosely seated bullet in the same once-fired case (in my chamber), cycle the bolt closed, measure CBTO (hornady comparator guage/calipers), repeat several times to ensure consistency, log the info. The decreasing distance and some significant variation really had me questioning everything. Thus, I switched to the Wheeler method of measuring and this has led to at least very consistent results on 'kissing' the lands BUT.... this distance to kissing the lands is significantly shorter than what I was getting with the loose bullet seating/cycle bolt method especially on Berger VLD bullets. Here's the comparison data

Round Ct	Berger 168g VLD	Nosler 160g AB	Hornady 162g Amax	Comments
45	2.790"	2.861"		Loosely seated bullet, measure CBTO
111	2.800"	2.869"	2.805"	"​
311	2.790		2.778	"​
400		2.869"	2.774"	"​
550	2.653	2.821	2.697	WHEELER Method
DELTA Wheeler vs Previous	-0.137"	-0.048"	-0.077"

Note the change in CBTO for each bullet to just 'kiss' the lands via WHEELER method vs previous results is significantly shorter.

So Here is my dilemma....
Up until now (prior to WHEELER measurements) I've been thinking i've testing various 'jump' distances during load development by seating the bullet deeper at increments of 'at the lands', -0.040", -0.070", -0.110" but in reality according to CBTO via WHEELER method I was actually, in the case of the Berger bullet, starting off jammed as much as +0.137" and never even seated the bullet deep enough to ever test any jump (what I thought was -0.110" / 2.680" was really still jammed +0.027" according to WHEELER measurements).

Notice with the Nosler 160g AB the difference in CBTO for WHEELER method vs base method was much less of a delta. Given this, I'm wondering when measuring CBTO via chambering a loose fitting bullet if the much more slender nose of the Bergers and Hornady AMAX results in more easily jamming the bullet very deep without even realizing it and in much higher measurement error/variation. Just seems crazy I was really jamming the bullet this much via previous method. Seems WHEELER method is a more precise/true measurement of just 'kissing' the lands.

Therefore, I think I need to re-test seating depth for all my loads using the WHEELER method as my chamber leade distance for each bullet and then test deeper seating depths vs that as my reference point. Does this sound right? Other Thoughts?

Appreciate any enlightenment you have to offer.... #frustrated

Kevin

 

[918v]

I use a slit case. The bullet stays put. I measure coal to the tip, not bto. I get the bto dimension separately off the bullet when it’s not in the case.

 

[Steel head]

You doing this on a perfectly clean barrel with the same exact bullet?

 

[kskevin]

You doing this on a perfectly clean barrel with the same exact bullet?

Not the same exact bullet but I do measure the ogive length of the bullet and have it recorded and all the bergers I have used to measure the CBTO have all been within 0.001". However, the last set of measurements I did between the 'loose bullet' method and WHEELER method were done using same bullet and at same time on the gun so barrel condition would have been identical.

 

[918v]

You can’t get an accurate measurement on a loose bullet

 

[Rocketmandb]

Honestly, all the measurements are within what I'd consider the margin of error of most measurement devices (excluding when you changed - where you would expect different measurements). The first measurement should be used only as a baseline off which you do your tuning - within some realm of reason, the accuracy of that measurement is essentially immaterial. Tune against that baseline. As you send more rounds down the barrel, to keep up with it you can:

1) Use the same method Cortina uses which is to find your best depth, then every time you shoot, load a few rounds like 5 thousandths longer. If those rounds group as well or better than the others, use that as your new depth.

2) Load up Berger hybrids, tune to depth, then literally forget about seating depth for many hundreds of rounds until groups marginally open up, then remeasure and reset.

On my 6 BRA with 105 hybrids, I'm barely over 1000 rounds on my barrel and just did my first reset. And I didn't need to, but I messed around with the seating die and lost my baseline.

 

[jmw]

^^^^^^

 

[Johnny00K]

The only method that is truly accurate is the Wheeler method. You are removing the ejector/plunger when doing this right? If done in a clean rifle it is an exact measurement, as in 100% precise. This is the only accurate way to measure a chamber for ideal seating depth. All other methods are junk numbers that do you more harm than good. Jamming a bullet that far will wreck your load work, that causes a massive pressure spike.

 

[rustyinbend]

I've actually had good luck with a Hornady modified case, the Hornady OAL gauge, good calipers, and a light touch. Distance to lands is usually pretty getable and seems to not change much. I take 10 measurements, throw out the two longest and two shortest, and use the average of the remaining six. So far, it's worked well. Done this with 6.5-CM, 300-WM, 300-PRC, and 338-LM. It's really important that the bullet move very freely in the modified case. I usually wrap fine-grain sandpaper around a punch, and ream out the neck of the modified case to ensure the bullet moves with a very light touch. That makes it easier to "feel" contact with the lands when plunging the bullet forward. Interestingly enough ... more often than not I'm constrained by the magazine length, not the distance to the lands. I know that often I could go longer, but I'm just not into feeding one bullet at a time.

 

[Steel head]

I've actually had good luck with a Hornady modified case, the Hornady OAL gauge, good calipers, and a light touch. Distance to lands is usually pretty getable and seems to not change much. I take 10 measurements, throw out the two longest and two shortest, and use the average of the remaining six. So far, it's worked well. Done this with 6.5-CM, 300-WM, 300-PRC, and 338-LM. It's really important that the bullet move very freely in the modified case. I usually wrap fine-grain sandpaper around a punch, and ream out the neck of the modified case to ensure the bullet moves with a very light touch. That makes it easier to "feel" contact with the lands when plunging the bullet forward. Interestingly enough ... more often than not I'm constrained by the magazine length, not the distance to the lands. I know that often I could go longer, but I'm just not into feeding one bullet at a time.

I also use the Hornandy.
I clean the barrel up good then push the bullet in till it stops, if I get three consistent measurements I’m good.

 

[kskevin]

You can’t get an accurate measurement on a loose bullet

Not completely "loose" but with very little neck tension. Enough to allow the bullet to push further into the case when it touches the lands but not so much tension that it jams it. Likely not the most precise/repeatable approach as you can see from the variation I was seeing in all the previous measurements at various round counts. This is why I did the Wheeler method approach but was shocked at how different the CBTO distances were with the 'kiss' vs loose/lightly seated bullet method.

 

[kskevin]

Honestly, all the measurements are within what I'd consider the margin of error of most measurement devices (excluding when you changed - where you would expect different measurements). The first measurement should be used only as a baseline off which you do your tuning - within some realm of reason, the accuracy of that measurement is essentially immaterial. Tune against that baseline. As you send more rounds down the barrel, to keep up with it you can:

1) Use the same method Cortina uses which is to find your best depth, then every time you shoot, load a few rounds like 5 thousandths longer. If those rounds group as well or better than the others, use that as your new depth.

2) Load up Berger hybrids, tune to depth, then literally forget about seating depth for many hundreds of rounds until groups marginally open up, then remeasure and reset.

On my 6 BRA with 105 hybrids, I'm barely over 1000 rounds on my barrel and just did my first reset. And I didn't need to, but I messed around with the seating die and lost my baseline.

After all the input from this forum and LRH forum, I did the Eric Cortina approach with a hard jam. Found those measurements to be very close to my original measurements (just a bit longer as you would expect from a hard jam). Will back this off about -0.015" as a starting point for max CBTO and do all my seating depth step testing from there.

Eric Corina method CBTO

• Berger 168g VLD 2.793"
• Nosler 160g AB 2.874"
• Hornady 162g Amax 2.798"

Quite a few insights from all of this with just a couple being

1. Massive difference in 'kiss' vs hard jam (Wheeler vs Cortina methods)
2. Seems the high BC / more slender profile ogives can push much deeper into lands past the kiss vs other less slender profile bullets (ie... CBTO deltas for different measurement approaches 0.140" Berge VLDs, 0.053" Nosler ABs

 

[47guy]

i do the same thing as @Steel head but i do it one time and done...i then seat my bullets at .070 deeper than that measurement and im done.

 

[rady]

You sound like me as I would dwell on getting this thing exactly right. New MRAD 6.5C barrel use to drive me nuts as the OAL would greatly vary. After a few firings of commercial ammo, things seemed to level out. I found that if I just dropped a bullet from the chamber on a vertically oriented barrel, I was within 0.001" of my hornady oal readings. I would just take the oal and allow the bullet to slide inside the case, then measure with the piano wire.
Only down side to this method is you have to hand tap the barrel to release the bullet. I also confirm the measurements using the oal in the conventional method with the same bullet.

Just my opinion, but I think sometimes we over analyze this stuff. My distance to the lands and bullet seating seems to work well with these methods. Sub moa's for a relatively new shooter and center fire reloading.

 

[Dthomas3523]

As long as your measurement keeps you from sticking a bullet, it doesn’t matter how perfectly you measured your touch or jam.

Just make a measurement a starting point. Then do seating depth testing from there.

Then when you want to test again, you use your current loaded round measurement and test up and down from there.

It literally doesn’t matter if you know exactly where your lands are. You’ll find a seating depth that will work for your barrel in the current condition it’s in.

 

[918v]

Not completely "loose" but with very little neck tension. Enough to allow the bullet to push further into the case when it touches the lands but not so much tension that it jams it. Likely not the most precise/repeatable approach as you can see from the variation I was seeing in all the previous measurements at various round counts. This is why I did the Wheeler method approach but was shocked at how different the CBTO distances were with the 'kiss' vs loose/lightly seated bullet method.

Still can’t get an accurate measurement using this method. The bullet has to be supported fully by the neck. A slit case is far better and consistent. Secondly, if the bullet is able to move in the neck then you can’t take accurate readings off the ogjive because that requires pressure and pressure will move the bullet.

 

[John Glidewell]

I use the Hornady tool and a cleaning rod down the muzzle. You can push the cleaning rod against the bullet and feel it hit the lands. It takes some practice as you have to hold the tool all the way in and use a finger on the back of the tool plunger at the same time. But if you practice you can feel the bullet move back and forth as it is pinched between the tool and the cleaning rod and you will feel the bullet tap the lands. I get very consistent measurements this way. I can not be 100% certain but this method probably puts the bullet a few thousandths into the lands, but I always back off .025 or .030 as a starting point.

 

[Johnny00K]

I use the Hornady tool and a cleaning rod down the muzzle. You can push the cleaning rod against the bullet and feel it hit the lands. It takes some practice as you have to hold the tool all the way in and use a finger on the back of the tool plunger at the same time. But if you practice you can feel the bullet move back and forth as it is pinched between the tool and the cleaning rod and you will feel the bullet tap the lands. I get very consistent measurements this way. I can not be 100% certain but this method probably puts the bullet a few thousandths into the lands, but I always back off .025 or .030 as a starting point.

I used to use the Hornady OAL method. It is pretty accurate, we were within 5-10 thous, but it definitely can have user error. If you buy a tap you can make your own modified case instead of spending $10 on one. Do the Hornady Method a few times, now you know where to start the Wheeler test at. Sounds like alot but I find this to be the quickest and most accurate. No guess work involved. BTW, do not try to drill the base on a piece of brass with a hand drill, you will bleed everywhere. Drill press works great.

 

[Expert684]

All of the Bergers I shoot seem to shoot the best with a .014"-.018" Jump. 6.5 and 30 cal, hybrids and Juggernauts. Just my two cents.
Oh and I've seen Bergers and other brands have a variance as much as .060" from batch to batch. it sure messes you up when you have a .004" window to work in.

 

[Tokay444]

The only method that is truly accurate is the Wheeler method. You are removing the ejector/plunger when doing this right? If done in a clean rifle it is an exact measurement, as in 100% precise. This is the only accurate way to measure a chamber for ideal seating depth. All other methods are junk numbers that do you more harm than good. Jamming a bullet that far will wreck your load work, that causes a massive pressure spike.

That isn’t exactly true. It still relies on human feel, and it’s a comparative measurement, as well as bunch of other manufacturing variables in the bullet you use, the comparators, etc. etc. etc.
An actual precise and 100% repeatable method is a sphere and depth mic. Not too many people are going to go to that length, except maybe an engineer like OP, so the Wheeler method gets us enough of what we need to get started. Know how I know he’s an engineer? He told us in the first sentence. It’s what they do.

 

[Dthomas3523]

The only method that is truly accurate is the Wheeler method. You are removing the ejector/plunger when doing this right? If done in a clean rifle it is an exact measurement, as in 100% precise. This is the only accurate way to measure a chamber for ideal seating depth. All other methods are junk numbers that do you more harm than good. Jamming a bullet that far will wreck your load work, that causes a massive pressure spike.

Ya, no. As outlined in the post above.

None of what we do is all that precise and it doesn’t need to be.

 

[Johnny00K]

That isn’t exactly true. It still relies on human feel, and it’s a comparative measurement, as well as bunch of other manufacturing variables in the bullet you use, the comparators, etc. etc. etc.
An actual precise and 100% repeatable method is a sphere and depth mic. Not too many people are going to go to that length, except maybe an engineer like OP, so the Wheeler method gets us enough of what we need to get started. Know how I know he’s an engineer? He told us in the first sentence. It’s what they do.

It's the only precise method with tools that are easily available to us. After his first post you're really going to add a sphere and depth mic to the confusion?

 

[Tokay444]

Ball bearings and depth mics are readily available to everyone the same as calipers and comparators are.
He’s, “an engineer”.

 

[Dthomas3523]

It's the only precise method with tools that are easily available to us. After his first post you're really going to add a sphere and depth mic to the confusion?

It’s not that precise.

Also, it literally doesn’t matter if you start .005 or .020 off the lands when you start seating depth testing. The only important part is that you don’t stick a bullet.

It also doesn’t matter where your lands are at 200, 300, 500, 1000 rnds. You just do a seating depth test up and down from your current seating depth.

The only number that matters is the rough number that you come up with when the barrel is new. That’s your do not pass this point or you may stick a bullet.

This is another subject that gets over analyzed to death.

 

[db2000]

As long as your measurement keeps you from sticking a bullet, it doesn’t matter how perfectly you measured your touch or jam.

Just make a measurement a starting point. Then do seating depth testing from there.

Then when you want to test again, you use your current loaded round measurement and test up and down from there.

It literally doesn’t matter if you know exactly where your lands are. You’ll find a seating depth that will work for your barrel in the current condition it’s in.

^^^Exactly
It’s all relative. You’ll go nuts trying to follow everyone’s advice on how to best measure to your lands. Not that it’s bad advice necessarily just unnecessary to obsess over it. I wish someone would’ve just told me this from the start

 

[Rocketmandb]

This is another subject that gets over analyzed to death.

Wait, what? That's just crazy talk.

 

[Newbie2020]

As Erik Cortina says “STOP CHASING YOUR LANDS!!!”

 

[MakeSawdust]

I agree with everyone that this is way over analyzed. The one thing that hasn't been brought up is the speed at which the throat erodes. To learn, I used a borescope to make sure the throat was clean and checked my distance to the lands every 200 rounds with the Wheeler method and the Mark Gordon method (both measurements were within .002 of each other every time). With a .243 Ackley shooting 115s over H1000 is was getting .008 to .012" of throat erosion every 200 rounds.

I chased my tail chasing the lands for the entire life of the barrel. After that I realized that I never had an issue when I didn't know any better. I did a jump test starting at .040 off and going deeper into the case. The load will usually hold for at least 800 rounds. Sometimes it will hold for the entire life of the barrel.

When guys are posting that they need to be within a .004 window from the lands, that condition is lasting between 100 and 200 rounds. I would have a hard time believing that is true. Often times, I stop doing load development when the gun will shoot sub half minute for 5 shots and the sd is under 10 for 10 shots. I rarely need to do seating depth testing to achieve that.

Someone who is a better shooter/reloaded will have to chime in with how to go from 1/2 to 1/4 minute. I know I have been able to seating depth tune loads to be very tight, but I assume when things go from .25 to .5 moa it is my day to day variation as a shooter more than throat erosion etc. I am definitely not a consistent 1/4 moa shooter.

 

[Dthomas3523]

I agree with everyone that this is way over analyzed. The one thing that hasn't been brought up is the speed at which the throat erodes. To learn, I used a borescope to make sure the throat was clean and checked my distance to the lands every 200 rounds with the Wheeler method and the Mark Gordon method (both measurements were within .002 of each other every time). With a .243 Ackley shooting 115s over H1000 is was getting .008 to .012" of throat erosion every 200 rounds.

I chased my tail chasing the lands for the entire life of the barrel. After that I realized that I never had an issue when I didn't know any better. I did a jump test starting at .040 off and going deeper into the case. The load will usually hold for at least 800 rounds. Sometimes it will hold for the entire life of the barrel.

When guys are posting that they need to be within a .004 window from the lands, that condition is lasting between 100 and 200 rounds. I would have a hard time believing that is true. Often times, I stop doing load development when the gun will shoot sub half minute for 5 shots and the sd is under 10 for 10 shots. I rarely need to do seating depth testing to achieve that.

Someone who is a better shooter/reloaded will have to chime in with how to go from 1/2 to 1/4 minute. I know I have been able to seating depth tune loads to be very tight, but I assume when things go from .25 to .5 moa it is my day to day variation as a shooter more than throat erosion etc. I am definitely not a consistent 1/4 moa shooter.

Most guys getting consistent .25 or less (like day in and day out consistent), are running a front rest snd 20-40lb rear bag with ears.

They are also testing seating depth before every match.

 

[kskevin]

latest load development. I think I found the sweet spots.

• 1st pic is 168g Berger VLD, 58.7g RL23, 2969fps. 5shot, 100yd, 0.435"
• 2nd pic is 180g Berger VLD, 56.8g RL23, 2842fps. 5 shot, 100yd, 0.598"