I have a .300 rattler pistol, I would like to get a 5.56 upper with about a 10” barrel. May I ask what is compatible and where to find them?

I saw that there was a shorty 5.56 rattler branded upper, but they are nowhere to be found.

Thanks in advance.

You would need either a complete MCX/Virtus upper to put on your existing lower or a non-Rattler BCG and MCX/Virtus barrel for your current Rattler upper. If you go the latter route, you’d need to find a Rattler-specific handguard that is long enough to cover more of the barrel.

The Rattler, [legacy] MCX, and Virtus chassis (“uppers”) have different formats and their respective handguards are not interchangeable across platforms. The Rattler BCG (recoil assembly, not the bolt) is different from the MCX/Virtus and would have to be swapped with barrel changes if you tried to use the same upper. *ETA: MCX and Virtus bolts are also different and should be used with their respective barrels; but if you buy a new barrel kit, it will come with the proper bolt.

Much of this is covered in the Rattler and Virtus threads in this sub-forum.

Also, Sig does not appear to offer a 10” MCX/Virtus barrel but does offer a 11.5. Sig sells individual Virtus components separately, so you could piece together a solution that works for your goals and budget, or you could buy a complete upper kit that will also come with everything you need to adapt the system to a standard AR lower.

This is great info, thank you.  I have perused the other threads, but is couldn’t figure out for certain what parts could work.  Thanks again.

You exactly need:

Midwest suppressor handguard 10” for rattler
Sig 11.5 barrel, tapered bolt style
MCX Recoil. Assembly.

I run this on my rattler all day long.

Yep this is what you need. I went a step further and purchased a carrier. A new bolt came with my 11.5 barrel. All I need now is a firing pin and spring. Then I will have a complete bolt setup for my 5.56 barrel.