G&G M16 range/accuracy problem
 

I have an older model G&G M16 - steel like black polymer upper with tinted plastic lower - put many thousands of rounds, has been shimmed twice since and has excellent compression for all stock parts:).

Got myself a Stainless Steel Madbull 6.03, same as stock length along with a Lonex hop-up unit.

All parts in and still getting the same range and did not improve the groupings at 100'. I am aware that I should replace the bucking but the hop-up doesn't appear to engage as the bbs don't backspin with hop on full

Could my bucking make such a difference, or is this another problem?

Thanks,
Joe

Yes, a hopup rubber can make a huge difference.

A new bucking might serve you right.

However, it sounds to me as though you could be experiencing problems with your hopup nub. Check to ensure it is sill seated in your hopup unit, it may have come out while you were swapping barrels.

Did you clean the new barrel before you installed it? They usually come very dirty from the factory.

The hop rubber alone is accountable for about 45% of your range. The BB weight being the other 45%, and the last 10% is everything else.