"HOT" bore groups opening up

[Vetmx]

That's why I excused my target in the original post. I have much better examples with multiple 10 shot groups. Just not handy. The knockouts end up making a clean 1" circle, worst case. .178 Nielsen's were hole in hole for multiple shots but would throw a nasty flier randomly. It seems like it does better with fatter slugs but maybe debris or some irregularity, maybe at the choke, sends them out of whack. Smaller diameter slugs like H&Ns, usually mic at .176, are a complete no go. The KO are spot on at .177 and have been most consistent. Along with the 13gr Zans. I'm starting to suspect either fouling at the choke or possibly the barrel not fitting snuggly within the shroud. The gun responded very well to a thorough cleaning. I keep hearing that the LW foul up quickly but I thought that was with the polygonal. I got maybe 75 shots before it was back to throwing fliers. I never clean my FX liners, and they do phenomenally with the proper slug.

I highly doubt that a 20” 15mm solid barrel is going to give you harmonic problems in .177. But way back when they introduced the Priest ll, I bought one and immediately built a slug barrel for it. It was a .25. I drilled my receiver or block to accept grub screws to secure my shroud. They eventually did this when they introduced the Prophet. Just make sure you don’t drill through where the orings are. That will insure you don’t have an issue there. Not sure if I still have any pictures from then but I’ll check.

 

[Vetmx]

Found a pic. It’s a good thing to do no matter what. Then you know your shroud is not floating on those silly orings.

 

[Blanks66]

I have seen this in rifle groups... After the first few I get lazy. lol
Sometimes they open up.

 

[Headshots]

Found a pic. It’s a good thing to do no matter what. Then you know your shroud is not floating on those silly orings.

View attachment 474903

Rubber has been used to deal with vibration on thousands of different applications. I think FX figured it was helping with accuracy by way of isolating harmonics . That's all I got . Lol

 

[Headshots]

I have a few pics of my groups getting better . Kinda the opposite but it's something I see when switching ammo . The ammo was Polymags .22 cal . The horizontal string of shots is similar on 2 different PCPs on the first 5 shots.?

 

[Vetmx]

Rubber has been used to deal with vibration on thousands of different applications. I think FX figured it was helping with accuracy by way of isolating harmonics . That's all I got . Lol

And somehow they wind up putting a barrel clamp on the M3. Orings change as the temperatures change.

 

[AaronKrebs]

I have a few pics of my groups getting better . Kinda the opposite but it's something I see when switching ammo . The ammo was Polymags .22 cal . The horizontal string of shots is similar on 2 different PCPs on the first 5 shots.?

View attachment 475671
View attachment 475672

It's interesting that it strings horizontally before grouping. Does that only happen while your barrel is seasoning to the different ammo?

 

[Headshots]

It's interesting that it strings horizontally before grouping. Does that only happen while your barrel is seasoning to the different ammo?

Yes , its the first time I noticed though .