I bought Orpingtons for a good dual-purpose chicken and I was wondering if anyone has done the same. I'm new to all of this and really would like advice about when the average age is to butcher an orpington?
Orps are classic DP birds. They've been around now for over a hundred years. At one time they were highly recommended and were in the top five for meat and egg production.
The average age to butcher is when you want to. No one can tell you what is absolute, especially nowadays, when everyone is into "Doing Whatever Moves You."
However, there are some generally accepted (traditional ) gradings for poultry, which include loose timetables. This applies to what we like to call "heritage" birds.
Keep in mind that this name,"heritage," didn't exist until recent times. Through the 1960's, the dual purpose bird was really the only game in town. The genetically selected "meat chicken" common today was still waiting in the wings (no pun intended).
That being said, it seems fair to use the criteria that has historically applied to the dual purpose bird:
8-12 weeks - "Broilers" 2.5 lbs dressed weight
14-20 weeks - "Fryers" 3.5 lbs dressed
5-9 months - "Roasters" Over 3.5 lbs, dressed
You may find that these weights undershoot today's results somewhat, especially in the backyard flock. There have been significant advances in both breeding and feed composition, and to be honest, backyard birds have a better life. Meaning, of course, they have the chance to grow bigger in their allotted time!
When to butcher also has much to do with your situation. Cockerels are better at the table when butchered young. If they are to be held longer to achieve higher weights, they should be confined - and far away from females.
Remember the point of the dual purpose bird: to lay eggs
and provide an acceptable carcass for eating. In all ways, it is a compromise.
... if they start crowing, does that make the meat bad, or no?
Crowing in and of itself has nothing to do with meat quality. But it is a harbinger of climbing testosterone levels, which in turn signal the growth of fibroid muscle tissue.
Once they start to crow, and if left to simply wander, breed and fight, they will become tougher and less succulent at the table.
Coincidentally, this occurs at about 12 weeks.