Picked up one of the used stainless GB's.  I am thinking of turning it into an SBR.  Should I cut the barrel down, or does anyone make replacement barrels?

If you look on GunBroker occasionally an AC556 parts kit or barrel will show up. I've also seen reproduction Gas Block Front sights available that are a copy of the AC556 version.

https://www.gunbroker.com/item/860804638

There's a copy of the front sight.

Not sure on the barrel, I'd think having it cut down would let you decide on how to open the gas port yourself, if you wanted to tailor it. Not sure how hard it is to change a barrel anyway for the mini14.

Yep, that is the reproduction sight I was thinking of.
Obviously an AC556K kit would be the most foolproof, if expensive, way to set up an SBR'd Mini. Everything is already tuned to the shorter barrel setup.
However I don't see an issue with having a form 1 in hand and having a quality smith like Morgan at Class 3 Machining cut and re-thread the barrel. The gas port and such would need to be tuned but its very doable. Now that Samson has a reproduction folding stock, it would be a cheap way to get a AC556K clone.

I don't know about the AC556, so everything I say is theory. A lot of the factory SBR's are badly over-gassed for reliability, and if someone wants to put on a silencer, it'd probably be better to go with cutting the barrel to get the port you want. Either way I'd probably get an adjustable gas block.

It's one of the things keeping me from SBRing my 300blk, seems a very expensive SBR by the end of it. The fun level vs % of fun money ratio is just way out of whack. :)

I was able to do my own barrel cut-down SBR without removing the barrel using tools from CNC-Warrior and Brownells. It was fairly easy to do and it is is accurate as it was before and handles a suppressor - I cut, refaced, re-crowned and threaded mine with 1/2-28 and didn't re-use the 9/16-24 factory flash hider I used a modern upgrade that was modern Ruger production.

Here is the thread I did on it.  Ruger DIY AC556K clone SBR thread

The only consideration (assuming your GB is one of the recent stainless ones on the current market) that I am uncertain is if the Ruger stainless steel is harder to hand thread than the blued steel.  I bet a call to CNC warrior should help clarify.

I was glad I did it myself - it wasn't that hard and costs less than sending it out for re barreling.  i also added a binary trigger from a bygone era and it works well enough for a fun ride at the range.

Twist the barrel off and save it.  ASI can fix you up with a short barrel and front sight.  That barrel is going to be a collectible/in demand barrel in the future if not all ready.

kwg

I believe an alternative is what some members have done is to have a gun cut down with a perm attached muzzle device to a 16"+ length.

This may give you the look you want without the Tax Stamp Hassle and expense.

I wouldn't be happy with anything less than the short length myself, but you may feel otherwise.  Some of these look great with the right muzzle device.

Stolen pic off of a google search

I've got 8 stamps already, so no issue there.  The easiest is to cut the barrel, but I can't bring myself to cut the GB barrel.  A new barrel is probably the route I'll go.

That's an absolutely beautiful rifle.

Send it to John Thomas he can do the barrel work.