FX 9 - Differences Between Gen 1 and Gen 2

The_Red_Rabbit

The_Red_Rabbit

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Hello CGN,

There seems to be two "generation" of the FX9 bolt. Appearently, for the Gen 2 Bolt to work in Gen 1, there needs to be a new feed ramp.

Can someone post a picture of their Gen 2? Together with measurements? Just wanted to see what the differences are.

Thank you!
 
The bolts are different lengths, the gen 2 bolt is ~1/8" - 3/16" shorter than a gen 1 bolt. I don't think they're interchangeable between different gen uppers.
When you put a gen 2 bolt in a gen 1 gun the bolt isn't flush with the back of the upper, it's inset by ~1/8". And the gen 1 bolt sticks out the back of a gen 2 upper by the same amount. I don't think a gen 2 bolt will function correctly in a gen 1 upper, and the gen 1 bolt is too long to work in a gen 2 upper.

Running a gen 2 upper on a gen 1 lower (and vice versa) should be fine. The gen 2 feed ramp works well on a gen 1 lower (tight fit), so once that's swapped you should be good to go for either generation of upper on a gen 1 or gen 2 lower.
 
Unholysavage said:
The bolts are different lengths, the gen 2 bolt is ~1/8" - 3/16" shorter than a gen 1 bolt. I don't think they're interchangeable between different gen uppers.
When you put a gen 2 bolt in a gen 1 gun the bolt isn't flush with the back of the upper, it's inset by ~1/8". And the gen 1 bolt sticks out the back of a gen 2 upper by the same amount. I don't think a gen 2 bolt will function correctly in a gen 1 upper, and the gen 1 bolt is too long to work in a gen 2 upper.

Running a gen 2 upper on a gen 1 lower (and vice versa) should be fine. The gen 2 feed ramp works well on a gen 1 lower (tight fit), so once that's swapped you should be good to go for either generation of upper on a gen 1 or gen 2 lower.
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Interesting. I only have a Gen 1. But I can tell you the upper itself did not change. But I suspect the barrel extension of a Gen 2 being longer than the Gen 1.

I say this because I came across two different barrels when I was building my second upper.

Lengths aside, is the under side cuts of the bolt different?
 
The under sides of the bolts are different, in that the cutouts extend further back on the bolt on the gen 1. Otherwise the cuts looked to be the same shape/width/depth.
We never pulled barrels off, but suspect that you're correct about the barrel extensions being different between the different generations. Apart from the charging handle slots the uppers themselves looked to be the same.
 
bigmouth said:
Gen 1=Garbage. Gen 2=Trash. Buy something else.
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Very useful contribution. Where can I subscribe to your news letter?

OP, another difference is the lenght of the charging handle slot in the upper. The Gen one CH slot is shorter by about .5" The Gen 2 the slot goes all the way to the front of the receiver.
 
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