D-boys SPR MK12 Question

Hey all, i got a lot of good feedback last time I had a question so I'm back again for a little help. I recently purchased the D-boys SPR MK12

http://www.airsplat.com/Items/ERM-BI-SPR5381M.htm

rifle and I'm looking to do a couple of small upgrades to it due to my own personal screw up. While trying to get the front flash hider off I ended up torquing the inner barrel and shreading my hop up bucking.

Anyway, to make a long story short, I am going to go ahead and add a tightbore barrel and new hop up system to it while I have it apart and I was wondering if the M16 style internals is what I'm going to use here or M4 or if they are the same or what. I would think it would be the M16 style internals but wanted to check with some peolpe with more experience on internals that I have. So hope someone can help. Thanks!

The hopup unit will be the same for M4 and M16, but the barrel length is what will differ. I would suggest you take out your barrel and measure how long it is, and then purchase a tightbore that is equal to or a little less than that length. That's all really that you'll have to worry about.
-Bob.

Remove the barrel and measure it for Millimeters. I believe it will be the same size as a standard M16. The internals from M4 to M16 are the same, completely interchangeable.