I was shooting my rifle a week or so ago using a SiCo Sparrow suppressor for the first time, and I had a TON of failures to feed. No pics, but the bullet (American Eagle 45gr subsonic) was marred. My first thought was maybe the bolt wasn't going back far enough to properly strip the round out. Any ideas?

What do you mean by “failures to feed”?

Is the cartridge stripped from the magazine but fails to go into the chamber (a “failure to chamber”)?

Or is the cartridge simply left in the magazine and not apparently stripped off at all?

Failure to chamber. Round never went in, nose of the bullet had a gouge in it. Sometimes the base of the cartridge was still in the mag.

How does the gun do with other ammunition?

If that were the only type you fired with a specific magazine, it could be either the mag or the ammo.

But if other types work okay with the mag(s) you used, I’d have to say something odd was going on with the ammunition. One thought is that the ammunition doesn’t cycle the bolt far enough to pick up the rounds in the normal manner by engaging the rims. That seems unlikely to me, but not impossible. When a cartridge fails to chamber properly, does the case show any sign of damage such as a crease or dent?

Trying different ammo would be a test if you haven’t already tried it.

Even if only one type of ammunition has problems, I’d still try different magazine(s) if you can.

It's a combo of the ammo & springs need to be changed out...

Plenty to Read here

Just a place to start but do you have the same problem when removing the suppressor?

I'm gonna have to go experiment. I only had the subs with me at the time. I was thinking "recoil spring" but i think it operated fine w/o the can on it.

Which magazines were you using? My 10/22 takedown doesn’t like the BX-25 magazines but works fine with the standard 10 round box magazine. I may have to give this a try: BX-25 mod

If the gun is new run a couple hundred high velocity rounds through it for break in. Current production rugers are a bit rough, and this may help. I recently got a takedown and have been lucky in that it has run everything I have thrown at it. Haven’t tried with my can yet, but for so called sub sonic ammo ( synonym for standard velocity) I use European match ammo like eley or SK with good results.