Sudden Speed and ES/SD Change

[mbeavers1]

I am shooting a 6br in a 28" bartlein barrel, Impact action, lapua 3x fired brass, and Berger 109s. The barrel has just under 2k rounds down it, most using 30.4gr of Varget running at 2830 fps w SD of 5ish and SD 10-12. My loading process has remained the same.

I shot a match in Feb and all was great, rifle was hammering then I left for 6 weeks for work. I came back and shot about 50rds to get ready for the next match - all good. Unfortunately, i procrastinated on loading and waited until Thursday night before realizing that I have used up my last of the current Varget lot. There was no time to get back to the range so I just loaded up my 250 rds dor the match using the same load - i know, i know.

I get to the zero line and run a few foulers from my last batch and then load one of the new ones - BOOM. First speed was 2910. It settled down to about 2890 as the average. SD and ED higher but manageable.... amazingly, no pressure. I survived the match.

I went home and cleaned - including copper (i think this was my mistake). I bore scoped it and all is good. A couple more trips out to the range and now my speeds are all over thr place. I loaded up a couple ladders from 29.3 up to my original load. I got back to my normal speed of 2830ish with 29.9gr.

Now it wont group worth a damn and SD and ES suuuucks - 20 and 40. I have about 60rds down it since the cleaning. I thought maybe it just needed fouled back in but that didnt seem to help. I put a tuner on it and spun it all the way around almost 3 times. The attached pic shows the poor groups - each target is a different tuner setting.

I am kind of at a loss for where to start to clean this mess up.

1. Im surprised there was THAT much variation between the lots of Varget.

2. I decided to clean the copper so I could just start over with the new lot of varget. I now think this was a mistake. I have 60ish rounds down it since that and it has not settled. Maybe I need more to 're-break' it in?

3. I tried to use the tuner instead of seating depth. The tuner is a change from before, so my first thought is to take it off and do a seating depth test?

4. Barrel shot out? Really doubtful. Shot well 300 rds ago and 2k rds is on the low side for a 6br. The chamber still looks pretty good with a bore scope.

Thoughts? I am again travelling and get back with 15 days before my next match so trying to put a plan together.

I have another new barrel, but Id have to break in and do load dev for that and time would be short.

 

[Halfnutz]

Annealing?

 

[mbeavers1]

Annealing?

Every firing. No change to loading process:

Clean (walnut vib)
Anneal (AMP)
Size and deprime
Clean (walnut vib)
Lube neck ID
Mandrel
Trim/chamfer/deburr
Prime (CPS)
Charge (auto trickler v3)
Seat (Wilson arbor w force pack)

 

[nn8734]

Following…I hope you can figure this out in time for your next match…it’s frustrating as hell when this type of shit happens.

the two changes you mentioned:

1) Varget Lots - I have several one lb cans of Varget, all different lots and haven’t noticed that type of performance difference that you have seen when going from one can to the other. Though maybe your new lot is that different than the previous (I personally doubt it but it’s possible I guess)

2) Cooper fouling removal - this may be the bigger contributor to your barrel’s behavior change

3) Barrel shot out - also possible. But I’d think the progression from hammer to dud would be more gradual…

Do you have any other lots of Varget to try just to rule that out?

 

[whatsupdoc]

Cleaning the copper will not make a barrel that hammers into a dud so it must be something else.
If you are following the same reloading procedure using the same components except for
powder I would run a small ladder with the new powder and see if you can find a good spot.

That being said your barrel may have reached its end. Never had a 6BR so not sure what its average life span
is but some barrels for whatever reason die early.

 

[nn8734]

Cleaning the copper will not make a barrel that hammers into a dud so it must be something else.
If you are following the same reloading procedure using the same components except for
powder I would run a small ladder with the new powder and see if you can find a good spot.

That being said your barrel may have reached its end. Never had a 6BR so not sure what its average life span
is but some barrels for whatever reason die early.

I’ve noticed some “odd” behavior after cleaning in a couple of my SS barrels over the yeas but they would settle back down after about 10-15 rounds, flyers would go away, etc.

Looks like he also did a ladder w/the new lot but didn’t do seating depth testing so perhaps that’s the next step.

All that said, if seating depth doesn’t work, he doesn’t discover something wrong with his equipment and can rule out the powder itself then it very well could be the barrel.

With limited time until the next match he will have to decide quickly to swap to the new barrel or run with the existing.

@mbeavers1 Here’s an article about 6br barrel life/cost to shoot. It mentions a lifespan of 2200-3000k rounds of accurate life for the 6br.

Barrel Life and The Cost of Shooting

6mmBR.com is the best guide for 6mm BR Benchrest precision shooting, complete with 6BR FAQ, Reloading Data, Shooter Message Boards, Reader Polls, and Photo Gallery. Match event calendar and rifle competition accuracy training tips. Equipment reviews (.243 bullets, 30BR cartridge, 6mm Norma...

www.6mmbr.com

 

[918v]

Every firing. No change to loading process:

Clean (walnut vib)
Anneal (AMP)
Size and deprime
Clean (walnut vib)
Lube neck ID
Mandrel
Trim/chamfer/deburr
Prime (CPS)
Charge (auto trickler v3)
Seat (Wilson arbor w force pack)

If you over anneal the case will not be able to hold on to the bullet long enough for the powder to ignite consistently unless you jam.

 

[mbeavers1]

If you over anneal the case will not be able to hold on to the bullet long enough for the powder to ignite consistently unless you jam.

Agree, but Im running the same AMP aztec code i have for the first couple firings. Also, my neck tension is pretty much the same on my force pack gauge when seating.

 

[918v]

I have an AMP as well, but what I have noticed is that with my reloading process one reload cycle does not harden the brass to the same level it was before annealing. So if I anneal every time I reload the cases get progressively softer and eventually too soft.

 

[918v]

I would retest with brass that you did not anneal, something with hard necks.

 

[mbeavers1]

Interesting....i thought the annealing temperature set the final grain structure/stress state that the brass returned to, not the initial stress state after work hardening. Basically every piece of brass should return to the same grain structure regardless of the amount of work hardening for a given temperature.

 

[sinister]

With 2,000 rounds down the barrel my first guess (after cleaning and de-coppering) is your throat has advanced .001" per thousand rounds. Two thousand rounds would be close to .002", giving you a little more of a running start before bullet ogives skid into your rifling leades (rather than starting with minor jump or "Kissing" the lands). Not sure if you're not maybe getting just a little more gas blow-by as well.

Is your walnut media treated with rouge (like Lyman's). That stuff can be a little rough if you're not tumbling it off with corn, or perhaps wet-tumbling.

Do you have a Stoney Point or Hornady LNL gage? Have you measured your jump since new?

 

[918v]

Interesting....i thought the annealing temperature set the final grain structure/stress state that the brass returned to, not the initial stress state after work hardening. Basically every piece of brass should return to the same grain structure regardless of the amount of work hardening for a given temperature.

That is the theory. In practice, however, it doesn’t pan out. I use a Lee collet neck die and can tell the necks apart by their hardness.

 

[mbeavers1]

With 2,000 rounds down the barrel my first guess (after cleaning and de-coppering) is your throat has advanced .001" per thousand rounds. Two thousand rounds would be close to .002", giving you a little more of a running start before bullet ogives skid into your rifling leades (rather than starting with minor jump or "Kissing" the lands). Not sure if you're not maybe getting just a little more gas blow-by as well.

Is your walnut media treated with rouge (like Lyman's). That stuff can be a little rough if you're not tumbling it off with corn, or perhaps wet-tumbling.

Do you have a Stoney Point or Hornady LNL gage? Have you measured your jump since new?

I have a gauge but i have been subscribing to Eric Cortinas theory on the lands. Only the initial measurement matters. Use that to set initial jump and then every couple hundred rounds, shoot a group with current jump and then one with 0.003" more. If group improves, use new jump value. His thought process is that its simply not a good measurment after torching that many off.

That being said, I have been adjusting my jump but have never seen groups open up like this.

 

[Supersubes]

With 2,000 rounds down the barrel my first guess (after cleaning and de-coppering) is your throat has advanced .001" per thousand rounds. Two thousand rounds would be close to .002", giving you a little more of a running start before bullet ogives skid into your rifling leades (rather than starting with minor jump or "Kissing" the lands). Not sure if you're not maybe getting just a little more gas blow-by as well.

Is your walnut media treated with rouge (like Lyman's). That stuff can be a little rough if you're not tumbling it off with corn, or perhaps wet-tumbling.

Do you have a Stoney Point or Hornady LNL gage? Have you measured your jump since new?

Is the .001 and .002 a typo?