Need advice my 6xc load fell apart in the heat of a match

[Shawnba67]

Ok so I worked up a load for my 30 " XC 270 neck .267 loaded. .0025 neck tension
Norma brass 210m 39.4gr H4350 Barts 105 Gungnirs. This load in practice averaged 14fps ES for 5 shot groups and sub half moa average accuracy. This could very well be my ability.
Shot it in an f class match with electronic targets and the fps at target was pretty decent for first relay, omitting one wierd one other 27 shots had an ES spread of about 40fps not great but entry angle affects the targets fps reading, so no alarms. By the third relay and a hot rifle in the hot sun. I was getting SD of 70fps. SD!
My buddy's sd was 9fps, other fellow on lane was 5fps, so targets probly ok
Ammo and rifle were all out in the hot sun
So obviously I need a better tuned load. Any advice on how to do this?

 

[JohnKielly]

Ammo and rifle were all out in the hot sun

Try keeping your ammo out of the sun - in a Styrofoam box for example.

 

[tbeasley]

Ok so I worked up a load for my 30 " XC 270 neck .267 loaded. .0025 neck tension
Norma brass 210m 39.4gr H4350 Barts 105 Gungnirs. This load in practice averaged 14fps ES for 5 shot groups and sub half moa average accuracy. This could very well be my ability.
Shot it in an f class match with electronic targets and the fps at target was pretty decent for first relay, omitting one wierd one other 27 shots had an ES spread of about 40fps not great but entry angle affects the targets fps reading, so no alarms. By the third relay and a hot rifle in the hot sun. I was getting SD of 70fps. SD!
My buddy's sd was 9fps, other fellow on lane was 5fps, so targets probly ok
Ammo and rifle were all out in the hot sun
So obviously I need a better tuned load. Any advice on how to do this?

What velocity was your load at?
Also have you shot slightly above and under 39.4 grains to see where your load falls apart?
My 2 and several others XC's I know of hold together better at 38.0-38.5gr. H4350. I've seen 6xc hold a wide accuracy node in the 2900-2950fps range.
Also what is round count?

 

[Shawnba67]

What velocity was your load at?
Also have you shot slightly above and under 39.4 grains to see where your load falls apart?
My 2 and several others XC's I know of hold together better at 38.0-38.5gr. H4350. I've seen 6xc hold a wide accuracy node in the 2900-2950fps range.
Also what is round count?

3035fps. 200-ish round count.
I have loaded to 40.2gr. Never saw any pressure, but the repeatable ES was always at 39.4 regardless of bullet used.

 

[tbeasley]

3035fps. 200-ish round count.
I have loaded to 40.2gr. Never saw any pressure, but the repeatable ES was always at 39.4 regardless of bullet used.

It's just me, but I'd back down the velocity. By any chance have you checked trim to length and neck clearance? If you back down powder charge a bit and still see a problem, make sure brass is uniform and never hurts to try another bullet to see if same problem persists.

 

[R.Morehouse]

I know this is most likely a no brainer but be sure your round isn't cooking in the chamber for any length of time while you are aiming. Things will go south quickly from one round to the next.

Regards
Rick

 

[Zero333]

I think the hotter a barrel gets the worst it is on the jackets and will affect the accuracy and the ES/SD. Thicker jackets will obviously fare better as the barrel gets hotter.

 

[Dusty Stevens]

Those rounds cooking in the sun plus a hot barrel is to blame im sure. Looks like you had a good load- mother nature has her way with fixing loads for you

 

[Shawnba67]

I have about 15 left over from the match. I plan to chronograph them and see If they are still 14fps ES. If they are I will need a plan on how to fight the sun!!

Has anyone ever done any research into how long it takes a round to cook in the chamber? I have seen veteran shooters pull out a live round after waiting a moment or two for condition to stabilize. But never asked or thought to count while I was watching.

 

[Milo 2.0]

I'm going to go a diff route than most. Do you have a borescope? In the last 1 1/2 yrs we've been seeing serious carbon building problems in tubes, and carbon rings, do not have it figured out, but could be atmosphere, humidity etc.. or the downloading of cases resulting in incomplete burns, just gunking things up. And it has caused some big problems resulting in barrels getting scrapped early, and your rd count is right in line with when we made our first observations.
Here is a quickload model, I entered a 30" tube. I'd thoroughly clean my gun and retry.

 

[Shawnba67]

I'm going to go a diff route than most. Do you have a borescope? In the last 1 1/2 yrs we've been seeing serious carbon building problems in tubes, and carbon rings, do not have it figured out, but could be atmosphere, humidity etc.. or the downloading of cases resulting in incomplete burns, just gunking things up. And it has caused some big problems resulting in barrels getting scrapped early, and your rd count is right in line with when we made our first observations.
Here is a quickload model, I entered a 30" tube. I'd thoroughly clean my gun and retry.
View attachment 1055525

Thank you for that!
My normal cleaning regimine is Butchs until patchs come out clean, then Wipe out/patch out until clean. Usually takes 12 of Butchs in a row. 3 of Wipe out let sit for an hour or more. Any recommendations on modified cleaning, I'm very apprehensive to use any abrasives this early on, but if you need em you need em right!

 

[Milo 2.0]

Thank you for that!
My normal cleaning regimine is Butchs until patchs come out clean, then Wipe out/patch out until clean. Usually takes 12 of Butchs in a row. 3 of Wipe out let sit for an hour or more. Any recommendations on modified cleaning, I'm very apprehensive to use any abrasives this early on, but if you need em you need em right!

I'm not the best at cleaning my guns, for you, it would be best if you could see what is happening in your barrel. How many times have you cleaned this barrel? You had a lot going on that day, and I may be way off.
I cleaned my 2 xc's yesterday, no copper solvent, just Boretech C4, I soaked, brushed, soaked more, added a little Kroil mid aft, finally last night I jagged them clean. When I borescoped both of them, they both looked like a decent prairie trail, not bad, but not clean and I'll most likely shoot them and clean like an idiot next time. The barrels do not really copper foul.
A borescope is handy, especially for a guy who competes.

 

[Dusty Stevens]

Thank you for that!
My normal cleaning regimine is Butchs until patchs come out clean, then Wipe out/patch out until clean. Usually takes 12 of Butchs in a row. 3 of Wipe out let sit for an hour or more. Any recommendations on modified cleaning, I'm very apprehensive to use any abrasives this early on, but if you need em you need em right!

Looks like you need some bronze brushes and these 3 items: red and blue JB and a tube of iosso. This combined with a bottle of butchs will clean any barrel on earth and most (95%+) use only these items and dont have issues.

 

[Ledd Slinger]

Thank you for that!
My normal cleaning regimine is Butchs until patchs come out clean, then Wipe out/patch out until clean. Usually takes 12 of Butchs in a row. 3 of Wipe out let sit for an hour or more. Any recommendations on modified cleaning, I'm very apprehensive to use any abrasives this early on, but if you need em you need em right!

Sooooo...you never scrub with a brush??? If not, you got fouling in your barrel bud. I used Butch's Bore shine for a lot of years long time ago. It don't work all the way without a brush.

Still need to do a ladder test with H4350. I bet your load falls apart as is goes faster.

 

[Shawnba67]

UPDATE
Shot another 3x1000 today. same load without the scorching hot sun held together fairly well.
SD stayed about 10fps. overall fps did go up about 30fps over course of the day this seems to be normal.

 

[1shot]

Thank you for that!
My normal cleaning regimine is Butchs until patchs come out clean, then Wipe out/patch out until clean. Usually takes 12 of Butchs in a row. 3 of Wipe out let sit for an hour or more. Any recommendations on modified cleaning, I'm very apprehensive to use any abrasives this early on, but if you need em you need em right!

As with a lot of shooters, i have a rhythm, or sequence of events from one shot to another. The last thing I do in that sequence is close the bolt to minimize the amount of time that round sits in the chamber. If I see a condition change after the bolt is closed that I can't compensate for with hold-off, that round comes out, and another goes on the loading tray with the bolt open as I wait it out.
On the topic of cleaning, I switched from Butches to C4 and greatly reduced my cleaning time as evidenced with my Hawkeye.

 

[Killick]

Are u jumping or engraving ur bullets? Also, I only use .001” neck tension for my 6xc.

 

[Shawnba67]

Are u jumping or engraving ur bullets? Also, I only use .001” neck tension for my 6xc.

jumping I think .025 or so. I had 20 rds of ammo left over from the first match a month ago. It shot well once I got it outa the sun!

 

[Killick]

jumping I think .025 or so. I had 20 ers of ammo left over from the first match a month ago. It shot well once I got it outa the sun!

I use 115 JLK VLD’s so I’m soft seat and engraving them. That seems to solve the overheating spiking for me.

 

[Shawnba67]

I use 115 JLK VLD’s so I’m soft seat and engraving them. That seems to solve the overheating spiking for me.

Well, I will put this info into my tool kit!
Thank you