I have a couple of the SRC & SRC Bulldog's sportsline
I also bought a busted one off somebody who tried to replace the brittle receiver with a metal one
Think the classic TM plastic tabs broke off the original top receiver and thought he would reshell it
But didn't quite go according to plan so he cut his losses and sold it on....
https://airsoft-forums.uk/index.php?/topic/23093-src-m4a1-for-sale-or-swaps/
The problem is the tiny 3mm drift pin was slightly out when the SRC box was installed
we are talking about half a milimeter out - not much but enough that it wasn't going go through without force or a mod
another "regular" box aligned perfectly
To be brutally honest with that info:
Either expect a little bit of work - but it can go
or
cut your losses now & get another gun
What you decide is up to you and depends on your base gun and what not...
if you have the 6mm green bushings cheapo gearbox with the two piece hop unit then consider another gun perhaps
Not that a one piece hop unit will cost much but it is one more thing that will changing on a metal receiver
The 6mm plastic bushing replace, the gears are toffee - the sector is absolute dire quality
The rest of the box isn't bad at all if you have the double o-ring brass cylinder head etc.....
But think SRC are not in same league as G&G & ICS from Taiwan
The cheap Sportsline SRC's should be stopped and retailers should maybe stock the cheap Cyma's imho
Don't get me wrong - it is do-able but don't go paying top dollar for a receiver then still have a bit of grief
plus no matter what it will still be cheap basic gearbox in a better receiver is what I'm saying...
No matter what people do their SRC's or G&G's it will still be nigh on a SRC or a G&G is what I mean
Look around but weigh up the options I would suggest