Lets see if I can describe this well enough...
Back in the day, I used to have issues with how far back the pump on my Bushmaster SI would travel. The grooves on the side of the body where the pump attaches to the bolt would eventually lengthen, especially with the constant use of auto-trigger. Basically, the screws would keep pounding the end of the slot.
Eventually, this would cause all sorts of problems, because now I'd be hammering on the power tube, and they broke often enough on their own without my help.
But then Unique Sporting Goods set me up with this ring thingy that could be placed right behind the back of the pump arm. Once you measured where you wanted it, you'd screw the two halves together, and now the pump arm was limited as to how far back it could travel.
Not sure if these rings were actually massed produced or they were just an in-house thing for Unique. I can say I never saw anything like them again.
And naturally, I'm looking to get my hands on one now.
Does anyone know what I'm talking about?
I don't know what you are talking about the Unique Sporting Good, but one thing you can do is to put a split collar on your barrel so your pump going to stop on the split collar and not on the slot of your body. Just watch-out to not squeeze your finger or hand between the pump and the collar!
Something like this:http://www.mcmaster.com/#cadinlnord/6436k18/=ithu9h
Hope this help!