I have an C&H Avant Toute 12 gau. boxlock, ejector. The ? is would this gun be a good candidate for a conversion to say - #1 choice .303 British but likely to much pressure---right?, then #2 say a .38x55, #3 a 20 gauge rifled slug-gun---likely the best choice. The main object is something handy, fairly light, and not too punishing on the shoulder. I would appreciate any opinions pro. & con. on an endeavour like this from someone who has travelled the road. Thankyou in advance --- John Can.