Depends what you mean by "warm up."
For example, the AK. It's kinda fun to shoot an AK. Yes, I do live in California, but there are some pre-ban guns floating about. I don't have one, but I've shot them. However, I think an AK, set up with standard plank wood hardware, is not especially comfortable. It's fine for its intended purpose: peasant armies running around spraying bullets, and it's a fun toy. But it's not a gun I could really love, like take out of the safe and just shoulder and admire on a regular basis.
I have an SKS. It's still sitting in Cosmoline, as it has been for a long time. It's an interesting piece, and a relatively rare one for a Yugo. But I've never been obsessed with taking it out and shooting it. It was more of a "buy a 59 before they're all gone" purchase. I'd rather shoot my Mini-14 Ranch Rifle, which remains my favorite "long-range plinker."
My AR lowers remain without uppers. I bought them because of a legal window of opportunity in California. I'm not in any hurry to spend money on uppers.
I don't know. I think that any military/milsurp guns I've bought have been "get them cheap while you can", or "get them before they're banned" purchases, more than "I want a shooter!" purchases. Now that there's a kid on the way, I kinda wish I'd have put the money in the bank instead. Of course, one day, he'll get some cool rifles that aren't so readily available any more, so I'm not regretting it too badly.
I wish
my dad had picked up some M1 Carbines, Garands, GI 1911's, 98 Mausers, etc., when they came in Cracker Jack boxes.