Issue with 4th+ round fliers

JARHEAD1371

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I'm working up a load for my new 25 SST, H1000, BR2, and the Blackjack 131. I'll shoot 5 shot groups and always have shots 4 and 5 as fliers. All 5 shots are in about 90 seconds.

If I shoot 3 in about a min, then wait for about 10 min, and shoot 2 more, then they all group together tightly.

I've never come across this situation and I appreciate any shared info. My barrel is a CarbonSix 7 tw and 24" long.
 

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Or looking through heat waves coming off the barrel.

To be honest, I hardly ever (99.8% of the time) shoot 5 shots in a row, and definitely not in 90 seconds. And not with a laser beam load like a 25SST with 60ish gr of powder at 3100+fps.

You already know it shoots 3 in a row well, then letting it cool keeps the group tight. Not sure why you keep shooting 5 in a row with the same results.
 
Or looking through heat waves coming off the barrel.

To be honest, I hardly ever (99.8% of the time) shoot 5 shots in a row, and definitely not in 90 seconds. And not with a laser beam load like a 25SST with 60ish gr of powder at 3100+fps.

You already know it shoots 3 in a row well, then letting it cool keeps the group tight. Not sure why you keep shooting 5 in a row with the same results.
90 seconds is longer than you think, and probably shorter than I typically shoot the 5 rounds. If a barrel beats up that fast, than it's not worth having IMO. While a one shot kill is ideal, sometimes this doesn't work out. Besides, if you shoot any type of PRS type matches then you are screwed. I sprecken the 25 SST is a hotter round than you typically see at a match, but 3 rounds is several less than it should be for this situation.
 
90 seconds is longer than you think, and probably shorter than I typically shoot the 5 rounds. If a barrel beats up that fast, than it's not worth having IMO. While a one shot kill is ideal, sometimes this doesn't work out. Besides, if you shoot any type of PRS type matches then you are screwed. I sprecken the 25 SST is a hotter round than you typically see at a match, but 3 rounds is several less than it should be for this situation.
Is your 25SST a PRS gun?
Have you checked barrel is 100% tight? Could be moving a bit as the tenon heats up.
Try tightening (or loosening) action screws? Had rifles that shot "ok" improve greatly with changing action screw torque.
Barrel channel clearance?
Did you quit cleaning it?
No suppressor, right? Had errant shots when a suppressor would heat up when not tight.
Muzzle brake? Tight? Slight baffle strike if not centered or sized? Moving when heating up?
 
Make sure your barrel is 100% free floated and has no chance of touching the stock. Some times a dollar bill is not enough clearance. Another thing to try is putting a pressure point in the front of the stock. Sometimes with shifty barrels a pressure point will settle it down. I know some smiths will bed the full channel on slim barrels to help with it also. I've never had to do a full channel bedding but I have had to put pressure points on a few Remington mountain rifle barrels. Easy to see if it will help. Just fold up a business card and slide in under the barrel while pulling down on the stock. Should be very snug. Try different thickness and see what works then you can put bedding there using the shim to hold it off till it sets up. Then you can remove the shim. A bad glass bedding job can cause shift also. Don't give up on it you will get it there. Good luck. Shep
 
90 seconds is longer than you think, and probably shorter than I typically shoot the 5 rounds. If a barrel beats up that fast, than it's not worth having IMO. While a one shot kill is ideal, sometimes this doesn't work out. Besides, if you shoot any type of PRS type matches then you are screwed. I sprecken the 25 SST is a hotter round than you typically see at a match, but 3 rounds is several less than it should be for this situation.
Lance is dead on and I'd say quite familiar with shooting and the Sherman Cartridges. The Carbon barrel isn't helping you with heat dissipation like many manufacturers would like you to believe. They are great for saving weight but show POI shift from heat just like lighter contour steel barrels ( think #3 bartlein or less, they are turned down quite a bit for the carbon wrapping). They don't typically show mirage in your scope which is why a lot of people buy off on them not heating up as fast, but it's not true. If you built this gun for PRS or any style of competition shooting, a carbon wrapped barrel was the wrong choice. I have quite a few carbon barrels on rifles so from my experience that's why I am saying this. Not trying to ruffle your feathers, just my take from some experience
 
Have you tried a different primer. Just analyzing but your groups aren't shooting in the same spot. 1/2" here 1/4" there. Just doesn't seem like a solid load. What are your velocities and spreads like?
 
Is your 25SST a PRS gun?
Have you checked barrel is 100% tight? Could be moving a bit as the tenon heats up.
Try tightening (or loosening) action screws? Had rifles that shot "ok" improve greatly with changing action screw torque.
Barrel channel clearance?
Did you quit cleaning it?
No suppressor, right? Had errant shots when a suppressor would heat up when not tight.
Muzzle brake? Tight? Slight baffle strike if not centered or sized? Moving when heating up?

I'd have to check my logbook, but I'd guess it's at about 80 rounds since the last cleaning. No suppressor or brake. Completely free floated I the XLR, no bedding. I took it out of the chassis to double check the torque. Besides the barrel heating up, I can't find a reason for the fliers.

Here shortly I'll switch to an identical steel barrel and see if there is a difference.
 
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