Rem Model 4 rolling block rimfire hazard?

I have an old Remington rimfire. Shoots really well with standard velocity ammo. My dad said not to use high velocity, so I stick to standard. Well, twice now, out of several hundred rounds, there has been gas blow out of the case near the rim and back into the face of the shooter. It would seem the action needs some attention. No local smiths I have talked to have experience in this (or much else frankly).

It is a really sweet gun to shoot. The first time my friend shot any gun, she had a .2" 3 shot group at 50 yards with it off of sandbags. It doesn't scare anyone or cause flinches.

I would like to safely let more people shoot this.
Any suggestions?

Sounds to me like a headspace problem. Years ago, I bought a brand new Colt "Colteer" .22 single shot that did that with standard and high velocity ammo. Took it to my gunsmith and he said it was a headspace problem and that Colt had quietly recalled a bunch of the rifles. He'd sold me the rifle so he gave me the option of a refund or another .22 in the same price range. I took the money.
Paul B.