ARA has two divisions: Unlimited Rifles and Factory Class. I'm assuming your speaking of the Factory Class division. The ARA started the Factory Class a few years ago as a way to get more people involved in the sport, and I think their thinking was along the lines that if you started shooting benchrest with a .22 you have in your safe, at some point you would want to upgrade to the Unlimited level of competition. As it turns out, the Factory Class has grown much faster than what they expected. Two years ago, we had 6 to 8 Factory Class shooters at a match. Last year we had 12 to 16 shooters show up. I think the idea of a Factory Class was meant for the more common "sporting" type of rifles. The target rifles, such as a Winchester 52, was never allowed. A few of the lessor known target rifles slipped through and dominated the competition a couple of years ago, and so they outlawed that group of rifles and set the $1,000 limit, but for some reason, allowed CZ rifles that were in current production, (the 457models). By the end of the year, CZ was producing certain 457 models that were well over the $1,000 limit. This year they've updated their list of approved rifles and raised the dollar limit to $1,250. The list of approved rifles is on their website. There are a very few modifications you can do to your factory rifle, but the intent is to shoot something as it comes off the self.
https://www.americanrimfire.com
and after reading that, if you still have questions, contact Dawn at Killough Shooting Sports as they are the headquarters for the ARA.
For all your shooting needs, browse the full collection of ammunition and accessories at Killough Shooting Sports. Same day dispatch on orders before 2 pm.
www.killoughshootingsports.com
My personal opinion- The Factory Class grew faster than the ARA anticipated. The ARA is dominated by the Unlimited crowd, and they have their own mind-set about the sport of benchrest shooting. If I had $10,000 invested in my hobby, I'm sure I would have my own ideas of what benchrest shooting is. They were caught flat footed by the popularity of the interest in shooting factory class benchrest. The changes they made this past year is an attempt to get caught up with the reality of what was happening in the Factory Class. It needed to be done and I'm glad they have finally given some attention to the fastest growing area of the sport.
Find a range that hosts an ARA shoot and take your son, I think it would be a wonderful father/son thing to do. You'll need to join the ARA, and you can do that on their website and it's free. You'll want a front and rear rest; the front can be a bipod. You can shoot from a magazine. Most matches are 5 or 6 cards of 25 targets each plus unlimited spotters, so you need at least 125-150 rounds for the target and then maybe another 50 for spotters, so you'll each want 200 rounds at a minimum. Bring hearing and eye protection. Don't worry about anything else; just show up and shoot.