6.5 cm Throat Erosion and some load development

[BryanCO]

I just put a criterion 6.5 Creedmoor barrel on my savage f12, trued the action, bolt face and lugs.... I have shot the berger 140 during break in and an unsatisfying attempt at load development.

41.3 h4350
varying seating depth during load development 5 jam to 20k off
lapua LR brass, fed 210m
seeing 2850 area out of a 30" tube

I measure 13 thou of throat erosion in 206 rounds? does this sound normal, it seems high to me.

 

[Straightshooter1]

I just put a criterion 6.5 Creedmoor barrel on my savage f12, trued the action, bolt face and lugs.... I have shot the berger 140 during break in and an unsatisfying attempt at load development.

41.3 h4350
varying seating depth during load development 5 jam to 20k off
lapua LR brass, fed 210m
seeing 2850 area out of a 30" tube

I measure 13 thou of throat erosion in 206 rounds? does this sound normal, it seems high to me.

What was your regimen for cleaning?

Which Berger 140's?

What was the cartridge's COAL's?

 

[BryanCO]

So far I have cleaned about every 80 rnds, 3 wet nylon scrub, 3 wet, sit, 3 dry

I don’t really measure coal as I’m shooting single shot fclass and only really care base to ojive for consistent jump

I’m doing seating depth test but don’t understand how I could find a 6k window if by the time my tube has 100rnds down it, the lands have potentially moved 7k leaving my jump window…

So I’m wondering if that erosion seems standard…

Cause I’ll look for a bigger jump window somewhere farther away… like 60-90k… idk I’m still learning

 

[BryanCO]

140 hybrids

 

[barefooter56]

140 hybrids

Bryan,
A general rule of thumb with the Berger Elite Hunter and Hybrid Target bullets is to start your bullet seating depth testing at .015" off the lands. Then you work back into the cartridge case in .015" increments (.015",.030", .045", .060"). When you find a bullet seating depth that shows promise, you can test .005" to either side of that CBTO if you wish to see if accuracy can be improved. All bullet seating depth testing is done using the starting powder charge!

 

[BryanCO]

Thanks for the info! I do most of my load testing at 300 or 600(on good wether days) I was wanting to try seating depth first and then move to powder charge. I have got my other 6.5 to shoot good using different methods but I think I just stumbled across the good load via luck.

But my question still stands, does 13k of erosion after 200 rounds sound normal?

 

[BryanCO]

sounds good, im not 100% on the measurement, just when i used the alex wheeler method of finding the lands the bullet sat out 13k farther then when i first did it with no rounds down the barrel. I used the same bullet to measure.

do the lands go a little faster at break in and then slow down?
i guess ill see after the next 200..

 

[HTSmith]

So far I have cleaned about every 80 rnds, 3 wet nylon scrub, 3 wet, sit, 3 dry

I don’t really measure coal as I’m shooting single shot fclass and only really care base to ojive for consistent jump

I’m doing seating depth test but don’t understand how I could find a 6k window if by the time my tube has 100rnds down it, the lands have potentially moved 7k leaving my jump window…

So I’m wondering if that erosion seems standard…

Cause I’ll look for a bigger jump window somewhere farther away… like 60-90k… idk I’m still learning

I'm betting you have a really dirty barrel.

 

[BryanCO]

I’ll scope it and see what’s up, it’s been cleaning up pretty easy

 

[Straightshooter1]

sounds good, im not 100% on the measurement, just when i used the alex wheeler method of finding the lands the bullet sat out 13k farther then when i first did it with no rounds down the barrel. I used the same bullet to measure.

do the lands go a little faster at break in and then slow down?
i guess ill see after the next 200..

In my 6.5 PRC with a Preferred Barrel Blank's barrel I had .014 throat erosion after 238 rounds. At 899 rounds I've had .037" of throat erosion, which averages to ~.004" per 100. I would expect a 6.5CM to have substantially less throat erosion. But I do notice from other new barrels that I've had, the erosion is substantial to start off, which kind of makes sense to me, even for barrels that have been lapped.

I only asked about COAL because how far you're off your lands doesn't really tell me anything about the specs of the cartridge since chambers are different sizes. I was tying to get an idea how hot you're loads might be as a seating depth could results in high pressures.

Like HTSmith suggests above, it doesn't appear to me your cleaning technique isn't getting your barrel clean enough. And a throat that remains dirty will contribute to faster throat erosion. Scoping it is a good idea as just looking at patches doesn't really tell you much about how clean everything really is.

 

[BryanCO]

Ok sounds good, I’ll measure the coal the next time I make up some rounds and let you know. I’m also gonna start from square one trying to work a load now that the barrel has 200 rounds down it and is “broke in”

I don’t have quick load or anything I’m just going off pressure signs on my case/primers which have been showing none at 41.2, I have even shot 42 without signs.

I would like to hear all people have to say to help me learn quicker

 

[Jet]

Was your first measurement taken on a new unfired chamber? If so, in the future recommend you fire 50-100 rounds prior to taking your first measurement so you can break in the barrel/throat area. I wouldn't worry to much about it. Take another measurement in 200rds and you will likely see .004'-.006" of growth.

Good Shooting.

 

[whatsupdoc]

Your erosion is normal, I measured erosion at one time (tried to anyway) but it was a waste of time.

Your velocity is very good for 41.3 gr of H430 and a 140 hybrid, typically 41-42 gr of H4350 is the sweet spot for 140's in the 6.5 Creed but you say load development has been unsatisfactory.

What kind of groups are you getting? Shooting of a rest or bipod?

 

[BryanCO]

Your erosion is normal, I measured erosion at one time (tried to anyway) but it was a waste of time.

Your velocity is very good for 41.3 gr of H430 and a 140 hybrid, typically 41-42 gr of H4350 is the sweet spot for 140's in the 6.5 Creed but you say load development has been unsatisfactory.

What kind of groups are you getting? Shooting of a rest or bipod?

Yea 2850 was back at break in rounds too, like 20 rounds in, I haven’t chrono’d since but I assume it will be faster now, I think the 30” tube is helping that.

I felt like I was getting good speed also

shooting from a SEB neo with the seb rear bag, I thought I was shooting 6 off, but it turned out to be around 18 off most likely, at 600 I put 10 shots into prolly 3.5”of vertical 8” or horizontal, but the mirage and wind in CO is tough…. The other seating depth I thought was 16 off but most likely 30 off shot prolly 6.5”, it would group tight 11oclock outside the 10 then group 4 o’clock outside the 10 nothing inside the 10 and no x’s. It would keep switching each shot in those 2 spots

 

[BryanCO]

I’m thinking of loading at the true 18k mark and seeing where 10 land… and also loading seating depths like suggested above to see what happens.

15, 30, 45, 60, 75, 90, 105 4shots at each round Robin

I’m will to post the data here if people wanna see

 

[BryanCO]

Was your first measurement taken on a new unfired chamber? If so, in the future recommend you fire 50-100 rounds prior to taking your first measurement so you can break in the barrel/throat area. I wouldn't worry to much about it. Take another measurement in 200rds and you will likely see .004'-.006" of growth.

Good Shooting.

Yea first measurement was on unfired barrel, so quick erosion during Initial break in is the first thing I thought. I’ll see where I’m at after and other 200.

 

[josebd]

I just put a criterion 6.5 Creedmoor barrel on my savage f12, trued the action, bolt face and lugs.... I have shot the berger 140 during break in and an unsatisfying attempt at load development.

41.3 h4350
varying seating depth during load development 5 jam to 20k off
lapua LR brass, fed 210m
seeing 2850 area out of a 30" tube

I measure 13 thou of throat erosion in 206 rounds? does this sound normal, it seems high to me.

This is my savage with bartlein barrel
.020 off lands

 

[Straightshooter1]

I’m thinking of loading at the true 18k mark and seeing where 10 land… and also loading seating depths like suggested above to see what happens.

15, 30, 45, 60, 75, 90, 105 4shots at each round Robin

I’m will to post the data here if people wanna see

That's fine to use those increments off the lands . . . to start with. Just don't confuse that with "seating depths". Once you choose one of these distances from the lands that looks the best, you should change your thinking to "seating depths" where you're measuring by how much you adjust your seating die; like in .003 increments from that cartridge measurement that's looks good (say it's .060 of the lands, but now ignore where you are from the lands and focus on the measurement of those seating die adjustments).

 

[whatsupdoc]

Everyone has their own methods, but I would save them hybrids and shoot cheaper ELDMs until
you get a good 100 rounds down the bore then put the hybrids .010 off and get the powder charge set then play with the jump.

 

[BryanCO]

I have 200 down the bore already, are you saying 100 more?

Everyone has their own methods, but I would save them hybrids and shoot cheaper ELDMs until
you get a good 100 rounds down the bore then put the hybrids .010 off and get the powder charge set then play with the jump.