I have to disagree with you, Benchrest guys absolutely do care where the lands are. The vast majority of benchrest shooters that I've met jam their bullets and chase their lands. The most significant impact on harmonics comes from the change in the pressure pulse. Increased freebore: as the lands erode, the "jump" (the distance the bullet travels before engaging the rifling) increases. Pressure drop: the longer jump typically allows more gas to bypass the bullet before it seals (obturation) and gives the bullet more "runway" before it hits resistance. This often results in a lower peak pressure and a slightly different pressure curve. Harmonic timing: Since the bullet is now entering the rifling at a different velocity and the pressure is peaking at a different microsecond, the bullet may no longer be exiting the muzzle at the "quiet" point of the harmonic swing (the node). Benchrest guys like Speedy or Bruce Teal are on a different level, however, but still it doesn't hurt to take advice from guys who know what the hell they're doing.
Finding the lands without any tools.
- Thread starter Paddyd
- Start date
jds holler
Gold $$ Contributor
Mike, has this scenario been verified with scientific pressure test equipment, and harmonic ummm photography, or is it mainly theoretical?
I'm not disagreeing with it or trying to be a wise-ass, just interested to see how these values were obtained. jd
Multiracer
Gold $$ Contributor
My apologies to Speedy. The video I saw is entitled "chasing the lands is stupid" by Eric Cortina. It's about 5 years old but if you listen carefully to what he's saying and how he explains it a whole lot of it makes good sense.
PMA Tool sells a touch point tool, you use is like Speedy shows but it can reach inside of an action so you don't need to pull the barrel. There are four of them for different case heads, 223, PPC, 308 and WSM. I keep one in my loading box.
www.pmatool.com
PMA Tool
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The stuff I post is from articles and books I've read about internal ballistics and barrel harmonics. I don't do any of the very specific testing, as I don't have access to a temperature-controlled shooting tunnel or the equipment that a lot of the guys doing the testing have access to. But when a world-class guy like Jack Neary or Speedy says something i tend to listen to their wisdom on the matter and take it for what they say it is. You also have to remember that there is a stark jump in pressure between Jump/Jam; in some instances, upwards of 10k psi gain can be seen in jammed loads. This would tell me that taking a load that's jammed, say + .010 in a virgin barrel and shooting 500 rounds through it, the throat is going to wear on average .002-.005 per 100 shots, depending on the cartridge being used and how hard you're pushing it. Well, if the throat erodes .020 after 500 rounds and you're still shooting the same exact CBTO, your pressure is going to drop because you're not jamming the load anymore, and your load could change a little or a lot. I have seen this in a few cases as my SD went to shit because the pressure of the load dropped, allowing some of the gas to escape around the bullet before it obturates and seals the barrel. Sub 10 FPS ES load went to 40 FPS ES very quickly. If you want a good read look up the houston warehouse experiment.
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Ummm...bottom line is that the target doesn't lie. I wouldn't lump harmonics into the effects of bullet jump or jam per se, but they are related. Changing jump doesn't change the bbl's frequency so much but it can affect amplitude a bit. That's not really the issue though. I look at it mostly that jump/jam affects how the pressure builds and to a lesser degree, peak pressures. Weatherby made a living from higher velocities in part from long free bores, just as an example. They still made more speeds at the same max pressures. But yes, this isn't really hard to verify with a Pressure Trace system. You can actually see the bullet jumping to the lands on the screen, as there is a jump in pressure when it comes into contact with the lands. Pretty neat tool and as far as I know, they are no longer in business, but yes, it made these types of things quantifiable. I had one but it died from an apparent lightening strike. The electronics must have been very sensitive because the storm didn't hurt anything else other than the PT itself due to being left hooked up when the storm happened.
Reading is great but testing is how we know stuff. Tuning is best described as timing bullet exit with optimal muzzle position, by one means or another. In a nutshell, we speed or slow the bullet exit time with load changes. We speed or slow the bbl with tuner adjustments. Either way, we're timing bullet exit with optimal muzzle position. Not trying to make this a tuner thread but just pointing out how they both essentially are doing the same thing in regard to timing. IME, best accuracy happens at anti nodes, not nodes...but we all know what we're referring to when we refer to "nodes" in the context of rifle accuracy. To keep this from going into the weeds with tuners, I'll leave it at that unless someone wants to start one of those threads.
The target doesn't lie though. You can see what I'm talking about yourself with a sine wave test.
Reading is great but testing is how we know stuff. Tuning is best described as timing bullet exit with optimal muzzle position, by one means or another. In a nutshell, we speed or slow the bullet exit time with load changes. We speed or slow the bbl with tuner adjustments. Either way, we're timing bullet exit with optimal muzzle position. Not trying to make this a tuner thread but just pointing out how they both essentially are doing the same thing in regard to timing. IME, best accuracy happens at anti nodes, not nodes...but we all know what we're referring to when we refer to "nodes" in the context of rifle accuracy. To keep this from going into the weeds with tuners, I'll leave it at that unless someone wants to start one of those threads.
The target doesn't lie though. You can see what I'm talking about yourself with a sine wave test.
Multiracer
Gold $$ Contributor
"The target doesn't lie though."
Erics video shows just what to look for when testing seating depths with the same powder charge.
Erics video shows just what to look for when testing seating depths with the same powder charge.
Ok. Thanks!
I assume you mean that seating depth matters with your comment, to which, I agree. There again, he states that he doesn't "chase the lands", to which I also agree. But we both use tuners, too.
You guys, again all are over complicating something simple
First off, lets look at leade angle, 1.5 degrees
that is suuuuuuch a slight slope, the bullet can ease into the lands and you not feel it
Secondly
looking for square marks - this is not a very exact number because you do not know how much the bullet has eased into the rifling
---
using a loose fitting neck so the bullet can slide- the lands can and will grip the bullets ogive because the two angles are so close together its almost a taper press fit and the bullet can be pulled out a few though
not giving repeatable results
All those methods arent bad per se, will get you in the ballpark anyway
but
---
if you instead take your cleaning rod
1) insert from the muzzle until it hits the face of the closed bolt
mark the rod at the end of the muzzle with something defined like painters tape
2) then open bolt and drop your bullet down into the chamber and "LIGHTLY" tap it into place from the base so its against the lands
the bullet will stop at the same place every time if you give it the same light tap on the base
Vs. all the leverage of closing a cammed bolt on a dummy round which I doubt we can feel as deftly
3) re-insert your cleaning rod from the muzzle and lightly insert it until the end stops lightly against the meplat of bullet - (I like my Dewey because it has a flat blunt end)
4) mark the rod again at the end of the muzzle
5) measure between these two taped points
=== this is your OAL for a dummy round where the bullet just kisses the lands
WITH THAT BULLET ONLY
since every bullet can be slightly different from base to ogive
Assemble your dummy round with that one bullet
6) Now using your comparator measure CBTO
this is exactly touching the lands
EVERY TIME
repeatable, as long as you use some fairly consistent pressure and dont be a gorilla it will repeat within 3 thou MAX of touching lands merely by how off you will be from measuring tape to tape with your caliper
I have done this so many times I now get within 1 thou every time
if you're a machinist and know about light fringing or can see a dif of 5 though naked eye ---
--- you'll know how to line something up squarely and repeatable to mark your rod with the tape.
(you get better as time goes on)
anyway
within 3 thou, is good enough, if you feel youre off add 3 thou, or 5 thou, and call THAT
touching
Now simply start working back from there
---
Tools
Cleaning rod (everyones got one)
Electrical or painters tape (everyone has it)
Dummy rounds (everyones made one or two if they reload)
Now keep that dummy round as a gauge
in 1000 rounds, do this again and you can measure throat erosion by comparing to your original dummy round
---
I like to make a chamber gauge from the reamer that cut the chamber in the barrel and use THAT
as touching the lands since the reamer will cut the same leade and throat every time
but if you dont got that, or didnt cut the chamber yourself
This method works every time, repeatably (or you need some practice with balancing on one foot and chewing gum at the same time if its too difficult lol)
First off, lets look at leade angle, 1.5 degrees
that is suuuuuuch a slight slope, the bullet can ease into the lands and you not feel it
Secondly
looking for square marks - this is not a very exact number because you do not know how much the bullet has eased into the rifling
---
using a loose fitting neck so the bullet can slide- the lands can and will grip the bullets ogive because the two angles are so close together its almost a taper press fit and the bullet can be pulled out a few though
not giving repeatable results
All those methods arent bad per se, will get you in the ballpark anyway
but
---
if you instead take your cleaning rod
1) insert from the muzzle until it hits the face of the closed bolt
mark the rod at the end of the muzzle with something defined like painters tape
2) then open bolt and drop your bullet down into the chamber and "LIGHTLY" tap it into place from the base so its against the lands
the bullet will stop at the same place every time if you give it the same light tap on the base
Vs. all the leverage of closing a cammed bolt on a dummy round which I doubt we can feel as deftly
3) re-insert your cleaning rod from the muzzle and lightly insert it until the end stops lightly against the meplat of bullet - (I like my Dewey because it has a flat blunt end)
4) mark the rod again at the end of the muzzle
5) measure between these two taped points
=== this is your OAL for a dummy round where the bullet just kisses the lands
WITH THAT BULLET ONLY
since every bullet can be slightly different from base to ogive
Assemble your dummy round with that one bullet
6) Now using your comparator measure CBTO
this is exactly touching the lands
EVERY TIME
repeatable, as long as you use some fairly consistent pressure and dont be a gorilla it will repeat within 3 thou MAX of touching lands merely by how off you will be from measuring tape to tape with your caliper
I have done this so many times I now get within 1 thou every time
if you're a machinist and know about light fringing or can see a dif of 5 though naked eye ---
--- you'll know how to line something up squarely and repeatable to mark your rod with the tape.
(you get better as time goes on)
anyway
within 3 thou, is good enough, if you feel youre off add 3 thou, or 5 thou, and call THAT
touching
Now simply start working back from there
---
Tools
Cleaning rod (everyones got one)
Electrical or painters tape (everyone has it)
Dummy rounds (everyones made one or two if they reload)
Now keep that dummy round as a gauge
in 1000 rounds, do this again and you can measure throat erosion by comparing to your original dummy round
---
I like to make a chamber gauge from the reamer that cut the chamber in the barrel and use THAT
as touching the lands since the reamer will cut the same leade and throat every time
but if you dont got that, or didnt cut the chamber yourself
This method works every time, repeatably (or you need some practice with balancing on one foot and chewing gum at the same time if its too difficult lol)
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Seems like a lot of typing that can be replaced by just making a dummy round at the best seating depth and work off of that going forward.
Multiracer
Gold $$ Contributor
When you "re insert the cleaning rod" what is on the end of it ? Something flat ? What I am getting at is how do you know it hasn't swallowed some of the tip or gone alongside the tip ?
Multiracer
Gold $$ Contributor
Its still winter time....Lol
I edited to add I like to use a Dewey rod because it has a male thread flat blunt tip that meets the point of the bullet nicely
my Dewey rod measures .200" dia, so youd have to have a bore of at least .400" for it to move off center enough to slip past the point of the bullet.
Thats for 22-7mm, if you have a .308 you should be using a .30 cal rod anyway due to flex
If you got like a Carbon Fiber Tipton with female end, I'd cut a brass jag squarely flat on the end and use that
---
the rod dia. should over half of bore dia. so that it will not slide along side the tip of the bullet
with a Dewey there is a very definitive stopping point when you feel it hit the bullet meplat
just dont gain momentum and knock the bullet loose, ease the rod in slow and easy and you will feel it stop
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it is a lot of typing, but a quick and simple process once you do it
(How do you know where best seating depth is? Most of use use touching lands as a starting point first right?) More importantly...it has been proven over and over again, that rifles HATE to be used with the bullet just touching the lands, so we also want to avoid that seat depth
Knowing where it is to avoid it is also good data.
if you find best seating depth is .020" off, you can then mark your dummy round as needing .020" off or simply make another dummy round with best seating depth,
But the original touching the lands Dummy round can also be used to monitor throat erosion from day one because you can always reuse my method and measure it again at any time to see where the rifling has moved out to.
I mean some of us get used barrels, used rifles etc and need to see where the lands are as a starting point
this takes only a couple minutes,
or you can at least know this method and gauge it against your other favorite and see how they compare or how repeatable each one is and judge for yourself which one you like better.
its a tool in your toolbox to know since everyone has the tools needed for it is all
I just like not having to buy some silly tool just to do this since thats not necessary
-
I used to use a blue sharpie and mark the bullet, insert, close bolt, nothing, or too much
adjust etc and do it again and
Once I realized when I was seeing rifling marks that seemed to measure about .030 long and,
that did not mean I was into the rifling .030" I began using my method instead.
you could see .030" rifling marks on a bullet ogive but only be into the lands .005" because the angles so closely match, or every ogive angle is different so the marks will not correlate to the same amount of depth into the rifling
I like what I described because it seemed perfect and repeatable and got me there much quicker in load development, with no guessing
---
with my method could be done before marking the bullet with a sharpie twice
---
I often use this method when chambering a barrel and instantly start at .015 - .030 off if its a flat base round like a 22 BR or 6 BR and just see what the rifle acts like at first, so often it is already shooting clover leafs right there.
Adjust .010 in then .010 back - and see which one closes up
then fine hone in
done within 30 rounds usually
I dont like wasting barrel life trying to find a good seating depth to start load development because I like to try so many different powders as well
---
if it's now already shooting in the .2's its practice barrel life now and you can use that practice life to super fine hone seat depth in .001" increments if you like
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I don't disagree, or at least not enough to argue about. Either way though, dummy or touch, they're both a reference point. That's it!
Tesoro
Non-compliant
I am feeling stupid right now because I can't see how using the Hornady tool can short you on the true kiss/touch measurement? I can see the nicks on the bullet with a 10x loupe that indicate I was lightly kissing.Tom Peterson, the original designer of the Stoney Point 'Chamber-All' (now known as the Hornady Lock-N-Load OAL tool) told me that the difference between the measured 'touch' distance with that tool would be from .010-.015 shorter than the true touch point....for consumer safety.
I broke out my original 'Chamber-All' tool today and used it in one of my 30BR barrels. Then did my normal 'Touch Point/Wheeler Method'.
T.P./'Wheeler Method: 1.642"
Chamber-All Method: 1.631"
Pushing as hard as I could on the rod on the Chamber-All, the most I could get was 1.633". By the way, the original rods were aluminum, not the current plastic ones.
Good shootin'-Al
I can even simulate a jam and measure the land scrape marks with a caliper to measure the jam.
The only measurement one is taking is from cartridge base to the point of contact. If the case shoulder was extended 20 thou then that would make no diff. Plastic or Alum push rod no diff cause I use the inertia of bullet to find its spot in conjunction with a female tipped dewey rod. Each measurement takes 3-4 back and forths, one finger drives the bullet and the other drives the rod.
Not to argue or disagree at all but my findings were exactly opposite. Once I began using the Wheeler method it was plain as day that I was jamming far more with the L & L device than the Wheeler method was giving me.Tom Peterson, the original designer of the Stoney Point 'Chamber-All' (now known as the Hornady Lock-N-Load OAL tool) told me that the difference between the measured 'touch' distance with that tool would be from .010-.015 shorter than the true touch point....for consumer safety.
I broke out my original 'Chamber-All' tool today and used it in one of my 30BR barrels. Then did my normal 'Touch Point/Wheeler Method'.
T.P./'Wheeler Method: 1.642"
Chamber-All Method: 1.631"
Pushing as hard as I could on the rod on the Chamber-All, the most I could get was 1.633". By the way, the original rods were aluminum, not the current plastic ones.
Good shootin'
kelbro
Silver $$ Contributor
Close, .... but actually use two stop collars on the rod. Lock the second one from the muzzle on the bolt face (not the firing pin!). And lock the first one on the bullet. Measure between them.
If you have trouble figuring how much to tap the bullet in, use one of these to get repeatability on your 'push' rather than tapping. The insertion force gauge is like a trigger pull scale that works in reverse. Oh, and put a blunt jag on the rod, or just use 0.187 stock from the shop that has benn faced off, not just sheared.
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