Barrels and slugs

Hi
I have a Hatsan 125 air rifle which loves Barracuda 21.14gr and Gamo competition 21.75gr pellets both great around 40 yards, putting holes accurately through a metal plate.

My Mrs got me several tins of different pellets and slugs to try for Christmas:

The JSB Match jumbo 15.89gr which seems a bit flighty at longer distance.

Also a tin of H&N slu HP which are .218 27gr. These fit very tightly into the barrel and the rifle makes a harder sound when I tried them. Is it safe to use them? I'm new to slugs.

Also she got a tin of JSB Knockout slugs 25.39gr .216 which just fall out of the barrel if I'm not careful closing it as they are very loose. Is it worth shooting these?

Thanks for any advice.
Happy new year
 
Hi
I have a Hatsan 125 air rifle which loves Barracuda 21.14gr and Gamo competition 21.75gr pellets both great around 40 yards, putting holes accurately through a metal plate.

My Mrs got me several tins of different pellets and slugs to try for Christmas:

The JSB Match jumbo 15.89gr which seems a bit flighty at longer distance.

Also a tin of H&N slu HP which are .218 27gr. These fit very tightly into the barrel and the rifle makes a harder sound when I tried them. Is it safe to use them? I'm new to slugs.

Also she got a tin of JSB Knockout slugs 25.39gr .216 which just fall out of the barrel if I'm not careful closing it as they are very loose. Is it worth shooting these?

Thanks for any advice.
Happy new year
@goatboy Suggestions - If .218 slugs fit too tightly and .216 slugs fall through the barrel, consider slugging your barrel by taking a wooden dowel to push some .218 slugs through (one at a time from breech end to muzzle). Then measure the raised impressions left by the barrel’s grooves using a good set of calipers or a micrometer. Which should provide more accurate readings. Or consider taking a chance on buying and trying some .217 slugs.
 
Even heavy pellets are not recommended for a break barrel. Slugs seem to be even more extreme than that.

From a performance point of view I would expect poor results also. Even medium-high power pellet PCPs usually shoot slugs poorly. The really accurate slug guns seem to be operating at the top end of PCP outputs.
Thank you, I thought I would try slugs for better pest control. Perhaps a flat nose pellet around 8 gr. would work better. Accurate shots will help too .