This might seem to be a problem with the front of the body, like the breeching up ring, but it's very probably a worn out REAR of the body. Wear at the rear that you can see/feel by rocking the bolt around. On some old bodies, putting the bolt in is like throwing a sausage down the High Street. While the wear seems to be minimal at the rear end, the accumulative effect at the front end is exaggerated to the extend that the bolt is lifted up and therefore touches the breeching ring
I wouldn't mind betting that if you lift the rear of the bolt upwards while you're sliding it forwards, you'll have overcome the problem. Alas, it's not a cure and the body is still what we in technical circles define as 'shagged'. There is a greater degree of wear and that is defined by us REME types as 'well and truly shagged.............' Isn't that right Son, Tankie and Skippy?
Next phase, the can of white paint and a ZF on the butt