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In the PPS/SHS Shock Transfer System (STS) Review, we provided explanation to the purpose of a M4 gearbox bracer. In this article, we will compare the Modify Well Lock Bracer to the PPS/SHS Shock Transfer System.
The retail package for the Modify Well Lock Bracer is rather simple. It's in transparent plastic glued to cardboard (shown in the photo below).
The Modify Well Lock Bracer is practically the same as the PPS/SHS Shock Transfer System (STS) from the outside. It also has two 2mm hex screws to lock the impact pins (see photo below). However, it's the internals that differ as we will show later.
The side differs in the branding trademark and structure (see photo below). But the structure different should not make any difference in rigidity.
Looking at the other side of the two bracers, it seems the PPS/SHS STS has more metal (see photo below). The Modify Well Lock Bracer cut a corner in this area.
From the front, we can see one improvement of the Modify Well Lock Bracer. The Modify Well Lock Bracer's metal pins are much smoother and uniform than the PPS/SHS STS (see photo below).
There is very little difference between the two bracers when looking at them from the bottom (see photo below).
The biggest improvement in the Modify Well Lock Bracer is in its internals. The following video demonstrates the internal difference pretty clearly.
The technical difference is shown between the diagram below. As you can see, the Modify Well Lock Bracer uses angle notches to prevent any motion once it's locked down. The previous bracers has a flat notch, meaning that when the pressure exceeds the perpendicular locking pressure, the impact pin will move.
There are several differences in the APS M4 receiver that made the Modify Well Lock Bracer installation a bit different than standard installation.
First of all, the APS gearbox is typically a electric blowback (EBB) model. Therefore, the EBB plate strikes the STS. The solution I chose is to disable the EBB on the gearbox. (See "Disable Electronic Blowback on APS Airsoft Guns" thread).
Second, the APS M4 receiver magazine well has more metal and is more sturdy than the standard M4 receiver. Therefore, the magazine well actually blocks the hex screws (see photo below). The correct solution is probably to file out the receiver to reveal the hex screws.
I used a rotary tool with a metal circular file to drill out two half circle pattern in the lower receiver. The photo below shows the spots that had been filed on the lower receiver. With the holes filed, I was able to insert a 2mm hex wrench to tighten the Modify Well Lock Bracer.
Although the idea for the Modify Well Lock Bracer is a good one, the execution is not too good. Even with the set screw tightened, it never locked into place. They always loosen as the AEG cycles. After a while the set screws fall out. The photo below shows the set screw falling out only after playing two nights. The set screw is lost after falling out of the magazine well. I only found out after taking the gun apart for maintenance.
Note that I have used the PPS/SHS Shock Transfer System (STS) far longer than the Modify Well Lock Bracer and the PPS/SHS version never had this problem.
The shinny silver aluminum set screws on the Modify Well Lock Bracer are pretty. But they don't function well inside the AEG. They are too smooth and loosen easily.
I went to Lowes and found that the set screw size is M4x0.7 (see photo below). It's about 5mm in length. Unfortunately, Lowes doesn't have any metric set screws. The lady at Lowes mentioned that Hillman.com may carry them. Luckily, Home Depot does have metric set screws and I was able to pick up two black steel ones.
The black steel set screws seem to fit more snug in the Modify Well Lock Bracer. They also don't seem to be as easy to loosen as the aluminum set screws. We'll see how these steel set screws perform over time. If they don't work either, then maybe some Loctite will do. In the future, I'll stick to the PPS/SHS Shock Transfer System (STS) instead.