Weren't the 20-gauge federal heavyweights 7's? I've got a box or two but am too lazy right now to dig them out of the safe and look.
The original Federal "Heavyweights" were some type of HTL tungsten, but not as "heavy" as Federal's current TSS pellets. Those original "heavyweights" were closer to a #5 lead in terms of penetration & weight. I saw two longbeards die from them this past weekend.
I've killed either 3 or 4 longbeards with #7 1/2 lead in times long past. My reason for using 7 1/2 lead was because I was using guns more suitable for quail than turkeys. The more open chokes and #7 1/2 lead was very adequate out to about 30 yds (head/neck shots only). And, that era pre-dated today's superior HTL and TSS specialized turkey shells.
IMO, #7 1/2 lead loses too much of its penetration/energy to be very effective beyond 35 yds, although no doubt many turkeys have been killed with it at 40 yds & beyond.
Considering how few shells need by fired for an annual limit of turkey,
the cost of far superior TSS loads seems reasonable.
Save your 7 1/2 lead for smaller birds or sporting clays.