Once they are fully feathered they should be ready to go outside. The heat lamp probably isn't needed, if they get cold they will huddle. If you really feel that they need the heat lamp, then hang the lamp in the coop not as a heat lamp but as a heat source for the coop. The heat from the lamp will maintain an even warmth in the whole coop, no need to maintain a brooder setup once they are feathered and outside.
My current flock have been outside for almost a week now. The chicks were hatched the first week of April and are fully feathered. They love being outside and I love that they love being outside.
They greet me every morning when I open the coop for the day. Night time temps here in Colorado have been in the low 40"s to upper 30's. Their body heat keeps them warm inside the coop, and if they get cold they snuggle. If you don't keep Feed Hoppers & Waterers in the coop with the chicks, make sure that they get a nice drink of water before they are locked up for the night.
I put them away each night at around sunset. They will complain and make noise, they are not ready for bed and will want to stay up longer...some people's kids.
At this stage they are still learning about the world around, everything is going to be new to them for the next year.
Your biggest concern once they are first outside is wet weather, wet cold chicks are dead chicks. I was late getting my little ones outside this year due to the rains we've been having lately. (Even more rain forecast for this weekend) If it rains, your little ones may or may not know to seek shelter. So if weather rolls in, you will want to be around to ensure that the chicks stay dry and out of the weather.
yes i have a 125w heat lamp bulb about 6 feet above my dog run floor. The room is inside my garage and is insulated on every side.
I kept the light on just to keep the entire room warm (it stayed about 60) during the night. During the day however they are outside wandering around
Tonight is there last night with the heatlamp on.....we are getting a slow warmup and low temps are suppose to be 40 degrees or warmer at night
They are fully feathered so i figured they are ready for it....even tho that room will still stay 45-50 at night.
6 weeks and fully feathered, they are ready!!! Get them out there! (remember, years ago people raised chickens with no heat lamps, and chickens made it just fine)