What size blunt?

[Skipmaster1]

I was looking at the steel blunts in 3Rivers, but I'm not sure what the reason for different diameters is. Is it to match the shaft? wouldn't the larger give you a better chance at scoring a hit?

what would you reccoment for a Beeman MFX?

[Billy]

5/16 would fit 5/16 woodies.

11/32 will fit over the taper and sit deeper on a 5/16 wood.

Then you consider your blunt weight.

For the screw ins, you are considering head weight.

IF you have the skinny carbons...throw all of that out...I haven't tried those yet!

[Skipmaster1]

I should have specified. I meant screw in's and yes i shoot skinny carbons. i shoot 125's with this set up, but they offer a bunch of sizes in the same weight

[Billy]

Someone will be along to help...Sorry, I couldn't sort it out any better.
But, I'll be learning with you.

[Orion]

All shafts are not created of equal diameter.  The different blunt sizes are made for different diameter size carbon and aluminum shafts, such that they fit flush or perhaps a tad larger than the shaft when installed.  A tad larger than the shaft makes them easier to pull out of stumps.  The nominally larger size of the biggest compared to the smallest isn't going to make a difference re hitting the target.