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AirMax: Add an 11mm O ring to tighten the SRS and barrel to the spinning back bushing

May 18 2017 at 10:04 PM
H.E. Potter  (Login Hepotter)
YF12

The breech loading port is actually a barrel bushing that is not solidly attached to the breech block. I don't know the purpose for which it spins, but it vexes me greatly.

The first thing I tried was pressing my thumb tightly against the bushing, trying to hold it in place while spinning on the front barrel bushing/SRS system. That helped, but you can only apply so much force to the tiny enclosed loading port before it starts spinning again.

I found that putting an 11mm O-ring around the front barrel bushing and rolling it up against the SRS system helped to apply an outward force against the breech bushing and thus allow a tighter fit. Not a perfect solution, but fast and inexpensive at this point of experimenting and finding "fixes" for the little problems we come across. Note the pics/comments below...
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[linked image]

In this picture we note the four components affected. The pistol's frame and loading port/rear barrel bushing, the top rail that slides off by simply pulling forward after removing the SRS system/front barrel bushing, the SRS system with the front barrel bushing sticking out, and a common 11mm O-ring.
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[linked image]

Slide the O-ring onto the front barrel bushing. Roll it up against the SRS system's rear baffle. Now, when you put the top rail back on and screw the SRS/front bushing back on, you should notice less rotation of the rear bushing/loading port when you tighten the front barrel bushing. Don't over do it...just make it tight enough to compress the O-ring a bit.
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[linked image]

There's a reason not to over-tighten and that reason is shown here...note the vent holes in the front barrel bushing. Why are they there? To vent into the shroud? Seems to make sense,
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[linked image]

But, look what happens when you tighten the front barrel bushing all the way down...the barrel threads block the vent holes!

They almost got it right. However, the barrel front threads are too long. By putting the 11mm O-ring between the shroud and the SRS system, we get a couple of millimeters extra space so the holes are not completely blocked. This will allow part of the muzzle blast to exhaust into the top rail/shroud, and reduce the load on the SRS system.

Is it perfect? No. I am considering a fatter 11mm O-ring, or possibly a washer/shim between the O-ring and the shroud. Meanwhile, until you or I can get down to the O-rings store, and find a thicker O-ring, or an 11mm washer/shim...this fix will have to do for now. There's plenty of threads on the barrel, and I did consider cutting off a few millimeters, but then I take a chance of buggering up the threads on either the barrel, or the front barrel bushing. Better to K.I.S.S. it and slap something in between to bring those front bushing vent holes out away from the over-long barrel threads.

Comments? Advice? A better way? Let's talk!

Hepotter


    
This message has been edited by Hepotter on May 18, 2017 10:06 PM


 
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