First post, y’all.

I’ve got a semi-auto vrbp 100 from RIA, which comes with both a light and heavy piston, and I’m having a little bit of a hard time understanding the distinction.

Manual says 2 3/4” shells get the light an 3” get the heavy, but isn’t that just shorthand? Are 3” shells always going to shoot more gas into the piston than 2 3/4, or are there 2 3/4 shells that would count as “heavy” loads? If so, what number should I be looking at, shot weight, FPS, or both?

Thanks in advance.

Keep it simple use the light piston for 2 3/4 shells and the heavy piston for 3 inch shells.

If there was a need to consider other factors the manufacture would have included that in the manual.

ALWAYS start with the heavy piston. Only if the gun does not cycle with the shells you are using, do you switch to the "light" piston.

Now that sounds like good, solid advice to me. Makes sense. Less wear on the firearm.

That makes a lot of sense. My main concern was causing damage by using heavy-load 2 3/4 shells with the light piston.

I'll switch over to the heavy piston, take it through the break-in period, then just keep sizing down my shells until the heavy piston starts having trouble.

Thanks for the advice