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Throat erosion
- Thread starter Dunraven
- Start date
Grab a cup of coffee and read through this. In terms of “what has always been done” this is pretty groundbreaking work and data. It’s not enough yet to consider it all encompassing for all calibers, bullets, etc, but worth considering.
https://precisionrifleblog.com/2020/03/29/bullet-jump-load-development/
https://precisionrifleblog.com/2020/03/29/bullet-jump-load-development/
i dont check or adjust anything until theres a problem...im at 1100 rounds in my 6BRA and am going to play with some 109s so i checked this morning....ive lost .008 off the lands sense new...i started at .005 off the lands with a 105 hybrid now im at .013 off now and shoots just as good as when i started.
You had less than 0.001” throat erosion per 100 rds? That’s nuts. Is it your powder? Long neck of the BRA? Only shoot 1 round then water cool the barrel? Lol
I typically use Berger Hybrids in all my loads for their jump tolerances. If I find that it shoots about the same from .005 to .020, I'll load at the .005 and not worry about it until I start seeing something on target that warrants concern. I just went over 1600rds on my Dasher and thought the accuracy was falling off a bit. Rechecked everything and I was off my old numbers by .025. Reset jump back to .005 and everything came back like it was. Didnt have to mess with powder charge this time although every now and then a couple extra tenths of a grain are necessary to keep a load in tune.
started at 1.803 BTO with a 105 touching the lands now 1.811 BTO with the same bullet touching...im running 105s with varget at 2975fps and i do not baby barrels...like hookers...run em hard and put em away wet LOL!
im not a smart guy but i dont buy into all the long neck..shoulder angle..slower powder ECT for longer barrel life i think it boils down more to the barrel itself...ive had a few go WAY before their time and a few go longer than i thought they would...had a few hummers and a few that just would not shoot.
for a long time id run the chrony and check and recheck everything all the time...i dont anymore and its the best thing ive done...put 100-150 rounds through a new barrel...find a load...shoot that load till theres a problem(other than the shooter)..try making a few small adjustments and if said problem persists a new barrel goes on...life is simple....1150 rounds now.
Hijacking this old thread.
After about 1,200 high velocity rounds in my 6.5 Creedmoor with 140ish bullets, my throat went around 1.5" towards the muzzle.
To long to load.
So I will go on like Steel Head said and see what happens.
But I´m thinking about how to prevent high erosion in the future.
Less temperature, less pressure, less velocity and so on.
Easy said, but if you want to shoot your bullet to the max?
There is not much you can do in my opinion, to stretch barrel life significantly, but to shoot another caliber like the ol´.308 Win. or something.
After about 1,200 high velocity rounds in my 6.5 Creedmoor with 140ish bullets, my throat went around 1.5" towards the muzzle.
To long to load.
So I will go on like Steel Head said and see what happens.
But I´m thinking about how to prevent high erosion in the future.
Less temperature, less pressure, less velocity and so on.
Easy said, but if you want to shoot your bullet to the max?
There is not much you can do in my opinion, to stretch barrel life significantly, but to shoot another caliber like the ol´.308 Win. or something.
I typically make my ammo in fairly large batches, but when time permits, I will try to start with a smaller finite number to "Prove" my load again, pausing production pending range results.
If the results differ by significant accuracy variations; the jump is one of my first inquiries, and I try to keep a mental archive on that.
But this is really driven by knowing one's rifle and its current level of accuracy. It's seldom wrong.
You can still shoot effectively with a receding throat. I helps to be a handloader, and to redevelop the load occasionally; but eventually it becomes a cumulative exercise in dodging problems. Chasing receding throats is often impossible, especially when the shooting discipline requires magazine feeding.
Where I can, I try to use W748, which is listed as having a lower combustion temperature.
While not as popular a choice in the literature, I will work up loads with it that also list IMR-4064, Varget, and IMR-4895. Working with unpublished loads carries its own special perils and sometimes has advantages.
Greg
If the results differ by significant accuracy variations; the jump is one of my first inquiries, and I try to keep a mental archive on that.
But this is really driven by knowing one's rifle and its current level of accuracy. It's seldom wrong.
You can still shoot effectively with a receding throat. I helps to be a handloader, and to redevelop the load occasionally; but eventually it becomes a cumulative exercise in dodging problems. Chasing receding throats is often impossible, especially when the shooting discipline requires magazine feeding.
Where I can, I try to use W748, which is listed as having a lower combustion temperature.
While not as popular a choice in the literature, I will work up loads with it that also list IMR-4064, Varget, and IMR-4895. Working with unpublished loads carries its own special perils and sometimes has advantages.
Greg
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Well, thank you.
It is not always easy to find the combustion temperature of a powder.
Is that shown in QL for example?
I will take a look at this, never thought about it.
I´m a bit limited to European powders, because there are sadly times where you have to wait months to get the US stuff.
But what I remember, if not wrong, is that single based powders in general are somewhat less hot (and slower).
It is not always easy to find the combustion temperature of a powder.
Is that shown in QL for example?
I will take a look at this, never thought about it.
I´m a bit limited to European powders, because there are sadly times where you have to wait months to get the US stuff.
But what I remember, if not wrong, is that single based powders in general are somewhat less hot (and slower).
I load in batches of 3-500. Every batch I do a test at the same length. +.003 +.006 +.009
Takes 12 rounds and about 10min. Run what shows the best for the next 3-500rnds.
I don’t measure the chamber after the initial measurement when the barrel is new.
Takes 12 rounds and about 10min. Run what shows the best for the next 3-500rnds.
I don’t measure the chamber after the initial measurement when the barrel is new.
Now that´s a good one.
So you are always on track with the ongoing erosion and don´t have to worry to much about false measurements.
Because that´s what happened to me yesterday, I had a hard time finding the lands with my bullet.
But now my thinking is how to prevent erosion if possible.
Running heavier bullets at a lower velocity and with powder that won´t burn very hot.
How do I find out the temperature a load produces?
So you are always on track with the ongoing erosion and don´t have to worry to much about false measurements.
Because that´s what happened to me yesterday, I had a hard time finding the lands with my bullet.
But now my thinking is how to prevent erosion if possible.
Running heavier bullets at a lower velocity and with powder that won´t burn very hot.
How do I find out the temperature a load produces?
Now that´s a good one.
So you are always on track with the ongoing erosion and don´t have to worry to much about false measurements.
Because that´s what happened to me yesterday, I had a hard time finding the lands with my bullet.
But now my thinking is how to prevent erosion if possible.
Running heavier bullets at a lower velocity and with powder that won´t burn very hot.
How do I find out the temperature a load produces?
You’ll always have throat erosion. No two ways around it. You can slow down, but that will only buy you a little time.
And yea, the way I posted above I learned from a pretty knowledgeable source in another discipline. You don’t have to worry with measurements. Also, erosion isn’t always the same or uniform. So, just do a quick jump test and see what’s working. Have to make sure your barrel is clean so you don’t induce some other error.
interesting. I just hit 1000 on my xcal 65CM MTU and remeasured. I was .195 when it was new. and Im only .198/9 now. either im not measuring correctly (most likely) or my hot high pressure rounds are something magical.
for most people its a measuring issue or cleanliness issue
the barrel needs to be pretty clean because carbon in areas will cause short measurements, and most "gun cleaners" suck something fierce at actually getting carbon out...ive seen really dirty barrels deep cleaned and the lands be found .050"+ further away than the owner thought they were
also depends heavily on the users rate of fire, and how much he torches the barrel...really hot loads fired slowly wont wear as much as light loads fired rapidly, etc
ive measured before leaving for a 2 day match on a clean barrel, then fired 250-300 rounds, pushed a couple wet then a couple dry patches (what a lot of people consider "cleaning"), remeasured and gotten a shorter measurement than original...re-clean the barrel good, checked with a scope, and then the measurement is .008 longer than original
couple nights ago, i wetted this chamber w/ 75-100 rounds to clean the neck out...with wipe out + accelerator for 45 min, probably 5-6 wet patches over that time, then pushed a nylon brush for 10 strokes, spun it for ~60sec ...and looked with a scope...
then i wetted a felt patch with vinegar+h2o2, spun it in the throat for 30 seconds...this isn’t uncommon for what I’ve seen in others either
of course you will always have barrel to barrel variation in caliber, loads, and steel...so its possible you scored a great one and it lasts for forever lol win win
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I got off the phone with my rifle builder and we both agreed im not aggressive enough in my cleaning. likely the cause for sure. I used the tool and the bullet seat/feel method and got the same measurements but with the scope, the gun "appears" to be "clean" but for sure it isn't based on what I have been doing.
I check when cleaning doesn't bring my groups back.
Every barrel is different on amount of erosion per # of rounds, of course. Although, most high(er) speed stuff nowadays run about 3 thou/100 rounds. There are exceptions, of course. My last 6.5CM ate away .045 in a little over 1300 rounds. Whereas, another 6.5CM has a tad over 2200 on it and only set back .030. Palma contour running 2875 vs M24 @ 2600 has a lot to do with it, too.
Every barrel is different on amount of erosion per # of rounds, of course. Although, most high(er) speed stuff nowadays run about 3 thou/100 rounds. There are exceptions, of course. My last 6.5CM ate away .045 in a little over 1300 rounds. Whereas, another 6.5CM has a tad over 2200 on it and only set back .030. Palma contour running 2875 vs M24 @ 2600 has a lot to do with it, too.
Jake Vibbert uses the same load on every barrel, he doesn't load to a seating depth and doesn't change his load at all over the life of a barrel. I also believe he doesn't even clean his barrel during its life. He seems to do pretty well.
Kinda reminds me of the 6.5 saum shenanigans.
Oh yeah they last 3000+ rounds,,,,,,,if you set them back after every match.
He could probably load them backwards and still outshoot most of us ! I think he knows how to win a match or two and not get lost down a rabbit hole.
I think the point is you don't need to do seating depth tests every few hundred rounds to win national level matches and doing seating depth testing won't on its own move you from middle of the pack to the podium.
you cant convince them lol people have personally seen what ive done with random loads, over and over....and at the end its usually "well you dont count...that wont work for me" lol let them have their load work/tuning fun
He cleans his chamber/throat. He also arrives at matches sometimes with barely a 1MOA gun.
He's not shooting bench rest or F-class, so he doesn't get hung up on bench rest or F-class precision.
Erik Cortina just released an enlightening video on how he determines seating depth, and how he maintains precision through throat erosion.
I think if you have the time and inclination, if done properly, tuning throughout the life can only help.
However when I say “have the time” I mean you’re not picking load development over barricade practice. Having a .2 gun won’t help you beat guys with a .7 rifle if you can’t get as steady as them or read wind.
Take the .2 gun and shoot 1” dots off props @ 100yds. If you ain’t doing so well, then you need to be working on other things more so than adjusting seating depth.
However when I say “have the time” I mean you’re not picking load development over barricade practice. Having a .2 gun won’t help you beat guys with a .7 rifle if you can’t get as steady as them or read wind.
Take the .2 gun and shoot 1” dots off props @ 100yds. If you ain’t doing so well, then you need to be working on other things more so than adjusting seating depth.
