Is their a difference in strength between the steel and aluminum recievers on the BLR?

I can't imagine there would be since they handle all the same calibers. It would be business suicide to use weaker materials in a society as litigous as ours, especially when it comes to firearms.

Personally I like the little extra weight from the older steel recievers.

I don't think strength is a concern (to those who care), but simply aesthetics.

You have a steel bolt locking into a steel barrel. Strength is derived from this union - not from the walls of the receiver.

I had a BLR in 7 mm Rem mag that would shoot the maximum load with ballistic tips, RL19, 140 grain bullets. I had the aluminum receiver, to anwser your question, no, the aluminum is also very strong. I think the BLR is a great rifle. Trigger needs help, my only complaint with it.