6.5 cm Throat Erosion and some load development

[BryanCO]

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).

This is what I was doing, I started at 6jam and backed off all the way to 30 looking for something promising, all the 100 yard groups were junk, I did some more testing with 3x3 powder charge and seating depth at 41, 41.2, 41.4 at 16, 18, 20.
3 shots of each at 300, they were all around 1”-1.5” but ther was lots of poi shift and couple combos had pretty good flyers so I wasn’t to confident in any of them.

 

[Straightshooter1]

This is what I was doing, I started at 6jam and backed off all the way to 30 looking for something promising, all the 100 yard groups were junk, I did some more testing with 3x3 powder charge and seating depth at 41, 41.2, 41.4 at 16, 18, 20.
3 shots of each at 300, they were all around 1”-1.5” but ther was lots of poi shift and couple combos had pretty good flyers so I wasn’t to confident in any of them.

IIMHO, the test is flawed by mixing a wide range of seating depths (16, 18 & 20) with a narrow range of powder charges (41, 41.2 & 41.4). Even so, groups of 1" to 1.5" at 300 means you have an MOA of .318 to .477, which is not great, but not awful either.

You'd have been better off to choose just one of those seating depths (like the 20 off, if that's the one that looked the best) and load up a wider range of powder (like 39.2, 39.4, 39.6, 39.8, 41, 41.2, 41.4, 41.6). A wider range will show you group locations and the trend in POI shifts as well as changes in group shapes. Then if one of those loads is looking good, you need to verify what you see on paper shooting a narrower range around it. Once you've verified a powder load that looks good, you can then fine tune the cartridge with changes in seating depths in increments, like .003, to see if it'll tighten the groups up further.

 

[whatsupdoc]

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

No if you have 200 you are good to go.

 

[BryanCO]

I did a wide range of powder chargers early on I’ll post my target, but it was vary early and felt somewhere around 41-41.4 was a node…

I’m looking to put 10 shots into 2” at 600… should be possible my factory howa 1500 6.5cm shooting 123 eldm can put 10 into 3.5-4” at 600 off a bypod and rear bag…. This fclass gun should shoot better

 

[Frankm]

I d guess you re close to 2900 fps now with 200 rounds down that barrel. They speed up over the first 100-150 rounds.

Also, I d suggest throat erosion/growth is highly variable based on how hot you shoot it; how long of round strings.

 

[BryanCO]

I d guess you re close to 2900 fps now with 200 rounds down that barrel. They speed up over the first 100-150 rounds.

Also, I d suggest throat erosion/growth is highly variable based on how hot you shoot it; how long of round strings.

fastest i shoot strings is fclass style, which would be 22-25 rounds in 15-20 mins.. when i shoot groups its pretty slow and only 5-10 shots...

Ill chrono these next loads and see where im at

 

[BryanCO]

Here is some powder node testing at 100 yards after barrel break in process. 1,1,1…3,3,3….5,5,5….10

 

[BryanCO]

And then at 300 yards, seems like 41 and 41.5 group centers where pretty close which seemed to correspond to the 100 yard target I decided to play around there

It’s a 1” grid

 

[BryanCO]

This was then seating depth testing at 300 and the 41.3 charge (picked between 41 and 41.5 on the faster side)

The +6 was jam and then I moved to 6 thru 30 jump at 3k increments

It’s a 1” grid

 

[BryanCO]

From there I picked 18 jump and ran a test 2k on each side. And at 3 of the powder charges in my 41-41.4 range to see what happened.

1” grid at 300 yards

I wasn’t satisfied with anything cause of soo much poi shift if I was to over lay the group in either row or column

 

[whatsupdoc]

The 100 yard groups dont look promising. Go through the rifle first, check the bedding then have a known good shooter shoot the rifle. I would forget the 300+ yard tests until you get solid 100 yard groups.

 

[BryanCO]

I also decided to pick the 6k number cause it looked so good on the first 300 target and shot 10 at 600 yards, and they grouped around 3.5” high and 8” inches wide, but the mirage and wind was pretty tough so I would like to try more

 

[BryanCO]

The 100 yard groups dont look promising. Go through the rifle first, check the bedding then have a known good shooter shoot the rifle. I would forget the 300+ yard tests until you get solid 100 yard groups.

I agree I thought the 100 yards were shit but they were also shot right after initial break it, and the 300 yards started to tighten up so I didn’t know what to make of it.

 

[BryanCO]

Just for reference I shot these groups when I finally found the magic load with the factory 6br barrel using all the same setup as far as rest, bag and shooter(myself)… the 100 yards where all 5 shots and the 300 was 5 shots

I did lots of load development with that factory 6br barrel and couldn’t find anything I liked then one day I decided to jam the bullets cause some old guy I shot fclass club with in Oregon told me to try it and bam, the gun shot lights out.

 

[BryanCO]

I loaded that 6br and shot an fclass target on a heavy mirage and light switchy wind day at 300, 2 10 shot groups and only dropped 1 point on each 10 shot string and x count was 9 and 8… then I unscrewed the barrel and put the creedmoor barrel on, because I had lots of 6.5 components and not any 6 stuff

 

[Jet]

I would try a different bullet or powder

 

[Frankm]

+1 on bullet for sure

 

[bobcat93]

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.

I'm a bit rusty but doesn't the 6.5 creed have or require a long throat?..I think I remember measuring COL by dropping bullets in the chamber and using a rod..
I made up 50 loads and shot them off ..they were all mid loads right out of the book ,I had high pressure signs (flat primers)..
But I remember if I tried to kiss the bullet to the lands, and back it off for my C.O.L...the bullet would barely seat in the brass neck..thats a barrel right from Remington..
After gathering that info..I got busy with life but hope to revisit the 6.5 again soon

 

[Hohn]

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?

I’m betting your measurement of erosion has a lot of variability in it.