Post by jnmodeller on Mar 29, 2011 19:22:15 GMT 8
Replacing the AGM Mp40 hop up with an AK hop up, i come up on this when i decided to change my stock barrel to a tight barrel, doc jim is very kind to email me a how to do it but you have to seal the hop up permanently, but my concern is how am i going to replace the hop rubber if needed in short i need a maintainable hop up chamber, since its a version 3 gear box i went to a shop to check the difference of an AK to my mp40 hop chamber, i noticed that it will only needs some adjustment, Im not a gunsmith ill simply use my scale modeling skills on this. have no measurement to give the key factor on this is comparing exactly the two chamber to know what to remove or add. Take picture of the original before dismantling it for the alignment guide.
fig 1
(left red ak hop camber, right black agm MP40 hop chamber) for adjustment compare closely the ear that you put the screw must have a washer as thick as the ear of the black hop chamber, cut BB feeder tube same length as the black .
fig 2
fig 3
as you see the ear for screw are not on the same aliment you have to make a washer /adapter for it. see fig 6 & 7
fig 4
file the hole of the mag well on were the hop goes trough because the AK hop has a bigger diameter.
fig 5
use a flat file to level after cutting, no. 1000 sandpaper for final cleaning.
fig6
you may use any plastic that is hard enough to hold it, i used a servo arm from my RC spare parts, a little sanding to have the right thickness.
fig 7
use two small screws similar from the original, the additional screw is a longer one use a copper tubing as washer so it can be place higher that the other one, as seen on the pic and hand file/grind the head of the shorter screw to give clearance to the other.
fig 8
fig 9
use the original (black hop chamber) hop lever switch and internal parts to replace the ak hop, enable to fit the MP40 front reciver.
fig 10
fig 1
(left red ak hop camber, right black agm MP40 hop chamber) for adjustment compare closely the ear that you put the screw must have a washer as thick as the ear of the black hop chamber, cut BB feeder tube same length as the black .
fig 2
fig 3
as you see the ear for screw are not on the same aliment you have to make a washer /adapter for it. see fig 6 & 7
fig 4
file the hole of the mag well on were the hop goes trough because the AK hop has a bigger diameter.
fig 5
use a flat file to level after cutting, no. 1000 sandpaper for final cleaning.
fig6
you may use any plastic that is hard enough to hold it, i used a servo arm from my RC spare parts, a little sanding to have the right thickness.
fig 7
use two small screws similar from the original, the additional screw is a longer one use a copper tubing as washer so it can be place higher that the other one, as seen on the pic and hand file/grind the head of the shorter screw to give clearance to the other.
fig 8
fig 9
use the original (black hop chamber) hop lever switch and internal parts to replace the ak hop, enable to fit the MP40 front reciver.
fig 10
I've heard other methods of using the AK hop chamber. One unsecured (friction fit) and one secured with zipties. But this is great. 
