the thunderbolt ammo is really dirty in my guns...after about half a brick. you can scrub out chunks of crud...but I have not seen that type of keyholing...

I think the unit 2 uses a 10# spring..as compared to a 9# in the unit 1..the website says high velocity ammo too..

am very curious about that..as trying to decide on a unit 1 with iron sights or a unit 2.