Those things do get hot. Gloves or add a forward grip. I had a Midwest rail on mine and ended up going to a rubber hogue.

40 rounds get is mildly warm. I've run 500+ in a class day in an AK. They can get toasty. It's just a fact. They vent hot gas around the front of the handguard.

Wear a glove. I use kevlar lined gloves for gun stuff including suppressors. A glove on the support hand is nice for all sorts of things, heat, smacking the charging handle, mag changes, basically anything that might have a sharp edge.

As mentioned, all AKs can get a bit hot up there but the SLR Rifleworks rails mount by clamping to the barrel right at the chamber, so they basically are a heat sink.  Add some plastic rail covers to help a bit, and I usually wear some sort of gloves when doing any shooting anyway.