• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Throat erosion progression

What is your experience as to how throat erosion progresses? Is it a straight line increase as rounds increase; or is it more erosion in the beginning and then tapers off; or less erosion in the beginning and more as time goes by?
 
What is your experience as to how throat erosion progresses? Is it a straight line increase as rounds increase; or is it more erosion in the beginning and then tapers off; or less erosion in the beginning and more as time goes by?

There are so many variables where any changes in one of them can effect the rate of throat erosion. For example, things like: Rate of fire; using various loads from mild to hot; using different powders (some powder effecting throat erosion more than others); cleaning procedures; etc. In my limited experience, the rate varies. But that's because I use and load my guns in different ways. Given all things are actually constant, I'd say throat erosion tends to be a linear. But, I've never experienced it to be so.
 
So how has experience been with need to “chase the lands” vs maintaining established BTO as throat erodes? I’m thinking there may be a more important bullet seating depth related to barrel length and the point the projectile exits the barrel.?? Complete theory at this point but wondering what everyone’s experience has been.
 
So how has experience been with need to “chase the lands” vs maintaining established BTO as throat erodes? I’m thinking there may be a more important bullet seating depth related to barrel length and the point the projectile exits the barrel.?? Complete theory at this point but wondering what everyone’s experience has been.

There are other threads that have talked about this. In my own experience, I've found that keeping the same CBTO kept me in an accuracy node for a long time. So I don't change it as the throat erodes . . . until I find my accuracy degrading, then I'll make some seating adjustment. But those adjustments really have little to do with distance to the lands.

Of course, I'm not seating any bullets to touching or jamming the lands.

 
For several years I followed the "chase the lands" theory , and it worked well . Then ; strictly by accident , I found a CBTO that "HIT" the accuracy node , and I figured I'd seat at that number till accuracy began to deteriorate . Eight hundred rounds later , I'm still using the same seating depth , and still shooting very high numbers . This may be workable for this barrel only , but I can't give a opinion at this point . Barrels are like children . Everyone of them is different , in everything .
 
Yeah, if you test and find best CBTO off the lands then erosion doesn't matter from there.
But that doesn't answer OP's question(I don't think). And I don't know the answer to that.

The last few barrels I've burned out had relatively low land erosion. Seems like lands had moved ~.080" with the last. But I didn't pay mind to the rate..
 
I am a Follower of, Cortina and Satterlee, concerning the "Jump" Issue ! I look for, a good Bullet and FIND, a "Jump" Accuracy Node THEN, shoot, the piszz out of them !
And HOPEFULLY for, quite,.. a while !
I shoot, Secant Ogive and Hybrid, Design Bullets for, the most part, in 3 Tikka's and 2 Rem 700's with, "Jumps" from .025 to .105 ,.. WORKS for, Me ! Agree with, D-4279
LOVE, the ELD-M's and Berger, Classic Hunters for,.. Accuracy !
 
For several years I followed the "chase the lands" theory , and it worked well . Then ; strictly by accident , I found a CBTO that "HIT" the accuracy node , and I figured I'd seat at that number till accuracy began to deteriorate . Eight hundred rounds later , I'm still using the same seating depth , and still shooting very high numbers . This may be workable for this barrel only , but I can't give a opinion at this point . Barrels are like children . Everyone of them is different , in everything .
Before wear, was your seating into the lands? The reason that I ask is that in the short range group game, seating somewhere between touch and jam, I have seen competitive accuracy go away and then be restored with as little as a .002 adjustment, seating the bullet longer. I think that the overriding principle here is to do your own testing and believe your targets. If you are looking for answers on the internet that you can easily determine for yourself, doing your own testing. My question is, why?
 
Yeah, if you test and find best CBTO off the lands then erosion doesn't matter from there.
But that doesn't answer OP's question(I don't think). And I don't know the answer to that.

The last few barrels I've burned out had relatively low land erosion. Seems like lands had moved ~.080" with the last. But I didn't pay mind to the rate..
EVERY Barrel, ( Steel Quality / Hardness ) and EVERY Powders HEAT Index Number, is DIFFERENT and answering the OP's Question, AIN'T gonna,.."Happen" as it's pretty much, UN-knowable, "across the board",.. IMO
Yes, you can Test One Barrel and One Powder but,.. EROSION is, a Guaranteed,.. Fact of Life !
And will VARY from, Barrel to Barrel and Powder to, Powder THEN, "throw in" RATE of Fire and Cleaning Regimine,. LOL,.. I won't lose, ANY sleep thinking about, THIS,.. "Chit" !
 
Last edited:
Before wear, was your seating into the lands? The reason that I ask is that in the short range group game, seating somewhere between touch and jam, I have seen competitive accuracy go away and then be restored with as little as a .002 adjustment, seating the bullet longer. I think that the overriding principle here is to do your own testing and believe your targets. If you are looking for answers on the internet that you can easily determine for yourself, doing your own testing. My question is, why?
No . I was seating .015 off touch to begin with . Typical seating for the Juggernaut in F-TR shooting . I have no idea where it is now , and don't care as long as it keeps giving me a good X count , and high numbers . When it goes away , I'll figure out what to do next . Hopefully .;)
 
The OP may have found a good load with an in-the-land (ITL) relationship, and then he's wondering what it's gonna take to manage that.
 
Based on measurements to just "touching" the lands, new barrels in my hands seem to show an initial higher rate of land erosion in the first couple hundred rounds or so, then they settle down to a more uniform rate over the rest of the life of the barrel. I suspect the initial "higher" rate may have more to do with smoothing down any sharp corners, edges, or tooling marks that may have been in the throat of the fresh chamber, rather than being actual land erosion. Of course, the cartridge, powder choice, bullet weight, etc., all have a big impact on the rate of land erosion, as can the barrel steel composition and the land/groove configuration.

It's also worth mention that the lands don't simply move further out in the throat over time while maintaining the exact same shape they had originally when the chamber was first cut. The lead angle can readily change as the lands erode, making the process of predicting exactly what will happen to the seating depth optimum for a jumped bullet, or even a jammed bullet, more difficult to predict than simply "chasing the lands" via simple measurement of land erosion. The good news is that with a relatively small number of fired rounds we can determine the optimal distance relationship between bullet ogive and land engagement empirically (i.e. optimal seating depth), without actually having to understand in detail what the changes that occur in throat geometry are doing over time.

For that reason, I'm a believer in doing regular seating depth testing. Regular seating depth testing will generally result in any observed changes with respect to land erosion and/or seating depth optimum being relatively small, meaning you don't necessarily need to cover as wide a seating depth test range as you might the first couple times you do a seating depth test with a given bullet/powder/primer combination in a new chamber. That way, it should be possible to maintain the highest level of precision for a given load throughout the expected life of the barrel. It will also allow you to adjust charge weight to maintain velocity as necessary, in the event where a significant rate of land erosion necessitates a change in seating depth sufficient to effectively change the usable internal case volume and therefore pressure/velocity.

Over time, it may be possible to reliably predict the behavior of a given barrel with respect to land erosion and the effect it may have on seating depth optimum. Many shooters do this with jammed bullets routinely (i.e. chasing the lands), and it clearly works in many cases. The same may not always be true for jumped bullets. I've had loads with jumped bullets where the optimal seating depth followed land erosion very closely, and others where it did not follow land erosion at all. Thus, doing actual seating depth testing can help to remove any ambiguity about optimal seating depth in such cases.
 
If your load relies on a starting pressure set up by land relationship, then you would have to chase that.
Otherwise, you don't (that I've seen).
Like if you initially choose a good seating node out there ~100thou OTL, then land erosion won't affect anything for the accurate life of the barrel(with that load). Even just 10thou OTL has seemed immune to erosion for me.
You could tweak on things and redo a crown or barrel setback(life extension), and stretch a couple hundred more out of it, but it's not worth it IMO. Better to have a new barrel in the waiting.

It makes no sense to me that someone with a hunting capacity cartridge would set up a load while ITL.
They should know this would be precarious given erosion rates associated with burning a lot of powder.
There also is no advantage to it for them, like there is with small underbore (competitive) cartridges.
 
Throat erosion progression? Sometimes faster than you would like.
That's why I go with ZERO free bore from day 1. I know where to go from there. ;)
 

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
166,264
Messages
2,214,881
Members
79,496
Latest member
Bie
Back
Top