So, I took my gun out today to get it dialed in for a competition tomorrow.

Group sizes with my Sparrow on the end were not acceptable, especially after seeing how others shot. I pulled the can off and got groups that were touching all the way around at 50 yards using Eley Force and some Wolf. Winchester bulk was not nearly as good.

Can was on the gun using the Gemtech QDA. After getting it worked out without the can, I removed the QDA mount and threaded the silencer on directly to see if the mount was causing the problem. Same issue again using three different kinds of ammo.

Anyone have any suggestions as to what to look at or am I just SOL with this can on this gun?

How big of a group are you talking?

There should be a POI shift for sure, but sounds like you could be having a baffle strike if the groups are all over the place.

I didn't grab pictures but at least double in size.

Looked inside the can. No strikes. Pulled it apart to see how dirty it was and it wasn't bad.

Interesting...If no baffle strikes, I am out of ideas.  I used to have that exact rifle and had no issues with my SilCo Sparrow.  Even a little lead shaving on one of the baffles or the muzzle of the suppressor will affect the groups.

Are the threads on that barrel too long?  I seem to remember the Savage threads being too long for the SilCo Sparrow, and that a spacer should be used.  If the barrel muzzle is bottoming out on the blast baffle, that could cause some irregularities.

I'd check thread concentricity.

I'm a big fan of Savage, but they have been known to turn out some non-concentric threads.

If the sico is monocore maybe try without the cover and put up cardboard on each side of you to see if you are shaving lead

I've had the same issues with my old sealed can and professionally threaded match guns. 22's can be very fickle and a slight change in barrel harmonics can severely effect accuracy which is a big reason tuners are so popular with those trying to shoot tiny groups. I might try another can if you have one available or know someone with one, then bedding the rifle, possibly a slide on barrel de-resonator.

ETA: Like others have said that's all moot if there's any shaving happening.

The threads on the fvsr are to long for suppressor use without a spacer. I run a spacer on mine that someone on silencer talk made for me years back. I believe silencerco and gemtech both have spacers available on their site

Another vote for having the threads checked.  My RAR with Spectre II if anything is MORE accurate than unsuppressed.  It does have about an inch POI shift at fifty though.

Ok. I'll check into that.

Yea, POI shift isn't something I'm worried about. I could zero for that. But when it's not grouping consistently...

QDA works fine for me on a T-bolt with an Axiom suppressor

I have two Mk II FV-SR rifles and the threads have been fucky on both of them. It was like whomever read the thread spec of 0.4" didn't interpret it correctly (0.4" from crown to shoulder) but instead made the thread length 0.4" and then added a thread relief on top of that. So it's something like 0.46" or 0.47" OAL (the exact length escapes me).

The SilencerCo cans have an o-ring in the endcap and a 0.4" thread will butt right up against the o-ring. Any longer and you will run it into the o-ring causing weird compression and maybe misalignment.

You could (1) trim the threads back a bit to get 0.4" OAL (2) use a peel washer which gets you about the right thickness to get 0.4" threads or (3) use SiCo's 1/2x28 to 1/2x28 with o-ring engagement adapter.