moderator troubles

[zzr1100]

hi folks, ive got problems with my fn19 and accuracy with a mod ...
the mod attaches by use of a collar ,
without a mod on it groups pellet on pellet, with the old parker hale on it it groups like a shotgun, with the SAK from my rimfire its a bit better but not much,
initial thoughts must be that the collar/adaptor must be misaligned a the pellet is touching the mod on the way through,
the thing is .. there are no pellet debris in either mod.. the adaptor cant really be mis-aligned as its a very very tight fit and is all the way on the barrel ...
any advice ???

[ovenpaa]

Is it possible to fit the can and then look from the breech end towards a reasonable light source, if so check for any slight vignetting which would suggest it was a tad out of line.

[Graham M]

It only needs the smallest of contacts to de-stable the pellet and you won't see any debris at all.
The same thing was happening with my .308 and the T8. The bullet was barely skimming the edge of the hole at the front but the first shot was 8 inches right. The next shot was 4 inches right and all shots after that were in a group. I think the heat caused the moderator to expand enough to remove the problem until it cooled down again.

It was only when the exit hole was examined under a strong light with a magnifying glass that a tiny "V" became apparent. Opening up the hole to 9mm did the trick, but otherwise no evidence of damage or debris was visible at all.
It would suggest that your SAK is out of line, and because your PH is longer than the SAK it would make the hole even further out of line making it even worse.

G.M.