Manufacturers are all over the place on car weights. Some are over, many are under, and some are meet the RP. I would say the most likely is underweight.
But some people like them light because they can run longer trains.
Others like them heavy because they track better and behave better during switching.
Personally, I try to have all of mine meet the RP.
Paul
A recommended practice is not a standard, so there's no requirement to meet it.
There's a degree of personal taste in the weight of rolling stock in the first place. We're not talking about the track gauge, which is a standard because otherwise the whole things doesn't work in the first place. An overweight or underweight car can still work perfectly fine.
NMRA Recommended Practice 20.1 sets out the proper weight by scale and length of car for model railroad rolling stock. My club tests every item of equipment proposed to be operated on the club layout for conformance to the applicable standards and RP's to ensure good operation. OK, I'm fine with that. But I have a problem with car weights. I was just reading a review in MR and the car is almost dead on in its dimensions, has RP 25 contour wheels on needle point axles in easily swiveling trucks, the couplers are mounted at proper height, it operates through common turnout numbers and curve radii and has smooth paint work and seperate grab irons and is properly lettered to the point you need to use a magnifying glass to read the fine print. Truly, we are blessed to have such quality products at reasonable (not inexpensive, but not too many years ago, this would have been a contest quality model) prices. Then why oh why, ye Deities Above, does the car not meet RP 20.1....Yes, I know, "Just and some washers, lead fishing weights, etc", but why should we have to. Fortunately, the roof of this boxcar came off easily for the reviwer to bring it up to snuff but I've encountered plenty of equipment where getting inside and adding weight was a problem. So from now on, I'm writing to the manufacturer and letting him know that I have a problem with his products and requesting he change his ways. Your opinions, please.