Groups open up on a 50 round day

[wsftr]

Hi,
this is .308 FTR
Barrel has 450 rounds on it
Load dev has gone well with vertical holding between .3 - .6 moa 300 - 1000
Generally speaking load dev has been in cooler temps by say 10 - 12 deg c and no more than 24 shots in a day.
First time using it in a comp in hot sunny days with 4 x 10 counting matches, I have found that the groups open up ~ 30 rounds.
Generally speaking I have to bring the POI 3 - 5 clicks (1/8 click) down to help center the group for the later relays.
It seems like it wants to shoot as I'm not chasing vertical like I would a barrel that is fouled out but the groups are larger and I have to click down during the shoot.
A month a go on a clean barrel it held .5 moa vert for the first 10 shots (first counting relay)- it hammers on the early relays.

What would you all do to fix this?
I suspect I am on the hot side and the extra round count and heat is taking me over the top as the day goes on.
I manage the carbon and copper in the barrel and use a borescope for cleaning. Could I be cleaning too much - but I don't need fouling shots to be confident of a clean in points for the first relay.
I don't think its a barrel issue as it seems like it wants to shoot - I have had barrels that have fouled out and those are just wild rides - its not like that.
I'm thinking of knocking it back a couple of 10ths in powder.

Any thoughts appreciated.

[MattyG]

What is the barrel profile, how long is it and what loads are you using?
These are all factors that will be at play.

[Barossa_222]

It sounds like you haven't developed your load properly. Where is the top and bottom of your powder node and where are loading within it? You said you suspect that you are "on the hot side". You need to test properly. Could be barrel fouling, but I think you need to recheck how you tested. Good luck with things.

[AlanF]

...A month a go on a clean barrel it held .5 moa vert for the first 10 shots (first counting relay)- it hammers on the early relays.

What would you all do to fix this?

I have rule of thumb about barrels. If you have one that shoots well clean, then clean it more often e.g. middle of the day just before a hard target like 700yds. It does depend on how long your cleaning method takes of course, but if you clean often then it can be done more quickly.

[MarkS]

As Barrossa says, drop down to the next node and see what happens.
If you think you're running too hot a load you probably are.
A good stable load the barrel likes won't care if it's 6deg or 36deg

[mike H]

...A month a go on a clean barrel it held .5 moa vert for the first 10 shots (first counting relay)- it hammers on the early relays.

What would you all do to fix this?

I have rule of thumb about barrels. If you have one that shoots well clean, then clean it more often e.g. middle of the day just before a hard target like 700yds. It does depend on how long your cleaning method takes of course, but if you clean often then it can be done more quickly.

I am with Alan,clean the barrel at lunchtime,it won’t need too aggressive a clean.