The 204 Ruger was/is made in the "A", "AB", "B" and "V" configuration. I think that all except MAYBE the "A" have been discontinued
I have a "V, available ONLY as a stainless/laminate rifle, a standard "B" and an "AB" that I changed over to an "AH" to use as a walk around rifle for smaller varmints.
At first I sort of stayed away from the 204 as I already owned and shoot semi custom/custom #1s in various .17 caliber cartridges, 17 Mach IV, 17/222 and 17 Remington. The tiny bore rifles, including #1s are a niche rifle that fill a very small "Hole" but do that well and are fun to shoot. I built my first ".17" when I moved and lost my spotter and needed something to shoot varmints that didn't recoil off the sight picture. The 17s were perfect for that. You get what amounts to zero or near zero recoil and can actually see the bullet hit and correct if needed.
My brother RG bought a "B" in 204 when they first came out but I hesitated buying a 204 after talking to him. His and my later experience suggests that once you go to bullet weights above the mid 30s and a scope much bigger than 18x you lose the ability to "watch" shots" hit. There is JUST enough recoil with bullets in the 40 grain range to carry your eye off target under recoil with a BIG scope. If you are with a scope much bigger than 18x you lose the ability to see the shot hit. Now if your using heavier bullets and a scope below 12x or so that probably isn't an issue.
The other thing to think about with the 204 is that like the various 17s it starts out very fast BUT due to light bullets weight and a very low BC they shed velocity and thus energy REALLY fast and are highly subject to drift at range with ANY wind. As a general rule I consider the 17s and the 204 Ruger along with the 204 VarTarg and the rest as 250 yard cartridges at best. Inside that they are effective on thin skinned varmints, even up to coyotes BUT after that the energy is so low they become iffy. It also become iffy hitting a picketpin at 250+ yards.
Object lesson I shot some steel silohuette targets with my 17 Remington and a 30 grain Berger bullet. They blew right through the 1/2 plate steel of the chicken on the 200 meter rail. If you hit the javelina on the 300 meter rail, high on the back it would knock it off the rail and leave a shallow crater in the steel. In order to topple the turkey on the400 meter rail you had to hit it within 1/2 an inch of the top of the head and then it would SLOWLY turn and fall off the rail. The bullet just pecked the paint off the target. I can't remember EVER hitting the Ram on the 500 meter rail and certainly never knocked one over.
I have killed a few antelope and deer with the 30 grain Berger in the 17 Remington and my brother has killed a few with his 204 also. That said it's more of a stunt than anything else and not to be recommended and even then only within very narrow parameters with a really good sight picture at yardages under 150 yards or so.
On the other hand they are an absolute riot to use on ground squirrels, jack rabbits etc as long as you don't try and stretch it too far. They will kill coyotes and badgers and big rock chucks out to 250 or so but shot placement is critical and wind drift becomes an issue.
I would never recommend one as a guys sole varmint rifle. But if you already have a 22 CF the 204 is a LOT of fun with virtually zero recoil as long as you understand it's limits
My other walk around close range varmint/squirrel rifles are a #1 AH in 222, another in 223 (used to be an "AB") and the 204 "AH" that started life as an "AB" Oh also a #2 in "AH" in 17 Mach IV (17 Fireball). No sights as all are scoped.
RWT
Your knowledge on this fine rifle design is appreciated. 
