Can I use birdshoti in my Ruger 22/45; even if single loaded; not asking if they will feed from the magazine.

Yes.

I've tried the CCI plastic cup stuff in my Mark II target. First round feeds fine from mag, won't cycle action, poor shot pattern.

Getting a little off topic, best commercial pistol shot cartridges I've tried have been the CCI 45 acp loads. Feed, cycle and produce fairly even patterns from my Colt govt model.

I have a case of 22LR birdshot. I spend a good time of my spring blasting carpenter bees. Mostly in a Ruger LCR but sometimes in a Ruger SR22.

It don't work the slide in the SR22, but it works just fine.

Yes.

It'll load from the magazine too. It just won't cycle.

Your Ruger model won't fire without the magazine inserted though.

Incorrect, as usual. It depends on which 'Mark' version he has.

Ah.

Dickheaded as usual is your MO. Continue on... Dorf.

If it was bought in the past several years, it won't fire without the mag, and you know it.

Older models may indeed fire, but more 22/45's have been made with that safety feature, than without. Why chance it? Wait til you have a rattler at striking distance only to find out you need the mag inserted?

Dumbass.

if it won't fire without the mag these are nice when installed: https://www.tandemkross.com/Steel-Hammer-Bushing-for-Mark-III-and-2245-Pistols_p_9.html

Thanksk to all gentlemen who replied: carpeter bees will be my first targets of opportunity

In my experience, the crimped 22 shotshell rounds generally stick in a semi-auto chamber. You'll find that out right away of course. The blue plastic tipped CCI rounds seem to work OK, as long as you don't break the plastic cup feeding them from a mag. An action full of birdshot can be a pain.

I wholeheartedly agree with the comment above on 45 Auto CCI shotshells; they work great on everything up to snakes and hand-thrown clays, and cycle every 45 I've tried them in. Patterns are best in a shallow-rifled 1911 barrel or Glock "polygonal" bore in my experience, more aggressive rifling makes doughnut shot patterns. (You'll see that in the 22 as well.) The 40 S&W version works great too, but don't waste your time with the 9mm as they are a different style.