Just finished making a roller plunger for my BSA plunger gearbox. Got two in my other A series, and the difference compared with the standard pointy thing is substantial. Quicker and smoother changes - may not be as good as a modern, but not far off.
T'was when assembling my latest that I examined the original unit, wondering if the'yd made a hole to relieve the hydraulic pressure created when the cam plate compresses the plunger. Yes, they did, but in my opinion it's too small. Were I refitting the original I'd drill a second hole, possibly 4mm, high up on the side to help. There's not much oil to shift as the plunger only moves around 1/4, but what's relevant is the fact it has to move in a fraction of a second. I can't vouch a better hole would transform the gearchange, but I reckon it should improve - for very little work. I've made the release hole in my roller unit 5mm.
