All I can tell, the original sako 995 clip is aprox 0,100 longer than the AI and is already useless. This is why I built on a single shot action and will sell the sako when I get a chance
To cycle 300gr bullets, you need to cycle 4"+ long amo
Bile......have your smith throat the chamber to accept the OAL of your choosing ( if that's with a deep seated 300 then so be it) then load accordingly you will still have plenty of room to get the velocities the 338 Lapua was designed for! I'm running an HS Precision custom rifle ( built for me) and the throat is too long for the 300's but perfect for the 250's. All I do is run the 300's single feed and the 250's thought the mag. Give the 250 Lapua Scenars a go......had mine hold up enough to get to a mile at 1900 ft/elev. and the boy was able t shoot a 10-12" groups at 1 mile with it as well!!
Your mag length is plenty long for what your asking to do!