You just need to remove the FSB and replace it with a low-pro block. I live in Loganville and have the tools to make this happen if you want to bring it over.
What length is the new barrel? You could measure the old tube, measure the difference between where the gas tube on the old barrel and the new barrel are and that's your gas tube length.
Here's what I can find, mid length gas tube should be 11 3/4 inches long.
Carbine length gas tube measures 9 3/4"
Midlength gas tube measures 11 3/4"
Rifle length gas tube measures 15 1/8"
Like Allsmiles said I would check for fouling or debris. Is it one round in particular doing it or a few different rounds?
Oh, also, is the Ammo from the same lot as the stuff you've been shooting? The COAL may be off.
I've thought about doing this with an FVSR, but I want a little longer barrel so I was looking at the standard heavy barreled Savage and then having it threaded.