Today I am going to show how I fixed the trigger mech (briefly), installation of a tight bore and MAD BULL Accelerator hop bucking.
Ok so I got a bit of carried away the other night and fixed the trigger block and polished it inside without taking photos.... The SHS sears were already installed. The fault was the sear return spring which is highlighted below. I simply swapped it out for a longer and stronger one. The old one was not original.
The insides of the trigger box were polished with a dremel and Autosol polishing compound. Only took 10 minutes to make it all shiny inside, little bit of grease and a rebuild. Not an essential mod but gives me piece of mind that everything would be pristine inside and not packed full of cruddy grease.
So with a fully working VSR I went to the chrono and it was firing 530fps! That's with a standard inner barrel. I also managed to order a LayLax 430mm 6.03 inner barrel. Below shows the dismantling of the hop unit. I won't be showing the complete strip down of every part in this project, if you are looking for a full strip down then YouTube is your friend. A VSR though is dead easy to strip down fully.
With the hop unit taken apart by only undoing 4 screws I could take out the internals and get to the hop arm. For now I am just going to biro hop mod the hop arm. The "TDC" hop mod will be done in the near future once the hop rubber has had time to bed in.
The above picture shows the hop arm with a piece of biro (the ink tube) cut and glued to fill the gap. I have then lightly filed the piece of biro to be perfectly level and follow the shape of the hop lever arms / prongs.
Re-construction of the hop unit could then commence. The new tight bore was added along with the MAD BULL Accelerator hop rubber. I PTFE taped the rubber to the inner barrel to create a better air seal. The new hop rubber is also half a mm shorter than the old standard TM VSR hop rubber.
With everything lined up, BB gate catch installed and screws set back in place The hop unit was now complete (until I do a TDC hop mod in the near future).
First impressions of the MAD BULL accelerator were great. The rubber is thinner than a standard TM VSR but is very cleanly cut. Hop is instantly applied now with the biro hop mod, but more so with the new bucking. The "bulge" that is produced from applying hope is also perfectly even and very hard. The bulge is more square too whereas I was used to having the TM version having a more oval shape as pictured below. Proper testing in a week or so will determine just how good the MAD BULL rubber actually is (MAD BULL on the left -RED):
So with the gun fully upgraded with the following I managed to hit: 545fps
# ASPUK steel cylinder
# ASPUK steel upgraded cylinder head
# ASPUK high pressure piston
# ASPUK steel VSR spring guide
# VSR M150 spring - Already cut down
# SHS steel sear set
# LayLax 6.03 430mm inner barrel
# MAD BULL accelerator hop rubber
# Biro hop mod
With a standard M150 spring I'd expect this to be over 600fps before cutting it. This is the end of the project for today. The next stage will be making it fire under 500fps (but as close as possible) and filling the stock to start the sound deadening. More pics and blog updates should be up mid next week, time to go and buy some Plasticine 😉
Written by Karl, who has written a total of 202 posts.
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