Pentaxbros...if you haven't: Learn how to do AF Microadjustments.
https://www.pentaxforums.com/reviews/lens-align-front-back-focus/the-remedy.htmlMy Promaster 70-300mm LD needed a -6, My Quantaray 28-90mm Macro + Pentax DA 35mm f2.4 needed -1, and my Pentax DA-L 55-300mm SMC needed -9 after checking it on a LensCal ($18 off eBay) at multiple focus lengths, using my couch to steady the camera. Horrible front focus.
This helped increase my keep rate and got my already sharp pictures even sharper.
I'm gonna flirt with a different system (A390 + Minolta 70-210mm F4 and 100-200mm f4.5) and it makes me realize the good of these cameras (colors, ergos, features, AF surprisingly but the Sony is from 2010 and the Pentax is from 2016) and bad (Pentax lenses suck dick). I do like how much cheaper and better Minolta glass is.
>>441377355-300mm SMC is $50-70 all day long on eBay, jump straight to it. You don't have a new enough camera to drive the PLM on the good lenses, and the 70-300mms have a lot of aberrations...would only do those if its $20-30. But they're not bad either, pic rel is on one. Try to go new as possible if you do that and expect lots of sample variance, this comes up as a Sigma on LR (58mm Filter Thread) but I use the Tamron A17P profile for its viginetting.