what is the best speed for .22 34gr H&N slugs

my question is what is the best tune or speed for H&N .22 34gr slugs. I am shooting them out of a FX maverick at 945 fps but it seems like I am getting some flyers but I am not sure if it is due to my tune or speed that I am shooting them.
I have been shooting the .218 H&N 34gr. heavy from my DRS.
I have found them to be accurate from 900 to 1000fps so 945fps should be fine.

I find I need to clean my barrel after 200 to 400 shots.
Try 5 to 10 bar more reg pressure and then reduce hammer spring tension to get back to 945fps.
 
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