<< Previous Topic | Next Topic >>Return to Index  

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...
.
.
.
[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.
.
.
.
[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.
.
.
.
.
[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,
.
.
[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


 
 Respond to this message   
AuthorReply
Richard
(Login tobyjoe)
YC

What about drilling new holes forward do you think that would work?

May 19 2017, 8:14 AM 

Its just a thought that popped up in my mind. And thank you H.E. for all the awesome input into the pistol , I received mine last night working perfectly fine but I cant get the front barrel bushing off , guess i'll have to make a spanner wrench. Thanks again for all your in put into the pistol.

Richard Pollard aka Tobyjoe in Maine USA

 
 Respond to this message   
H.E. Potter
(Login Hepotter)
YF12

Vent holes in AirMax shroud...things to consider

May 19 2017, 1:30 PM 

First...I considered drilling more holes above the barrel threads, but I lack the drill press equipment to firmly secure the font bushing in order to drill it, so I decided reducing the thread length on the barrel might be the better method. The first thing I would do is find a nut that fits those threads and put it on the barrel threads BEFORE I cut off the excess. That way I can unscrew that nut and force any disturbed threads back into proper alignment after the cut.

There was evidence of loc-tite on my front bushing. I used two small stiff nails, placed them into opposing holes, held them in place with my fingers, then put a screwdriver between them and turned slowly. That additional leverage broke the loc-tite loose and off it came.

Once those bushing holes are opened, one way or another, I do believe that adding a few small vent holes in the back of the top rail/shroud will help reduce air pressure on the LDC/SRS system. It might change the "tone" of the muzzle exhaust, or simply reduce the air pressure coming out of the muzzle, perhaps making it a bit quieter. Maximizing the efficiency of the LDC is done by permitting air expansion in the shroud, and lightly venting some of the pressure out before it gets to the LDC baffles.

My experience with venting shrouds goes back several years. One thing I learned is a few small vent holes work better than numerous or big vent holes. I suggest 1.0mm to 3.0mm size, buy a new drill bit to do the job cleanly, and after examining the AirMax shroud, I'd go about an inch forward of the breech block to avoid that small nylon sleeve on the back end of the barrel, and this would still permit the high pressure air to use the full length volume of the shroud to expand before it vents out.

Starting with two 1.5mm holes on each side of the shroud is what I'm considering. Keeping these holes small keeps their exhaust noise very quiet.

Another forum member is considering placing his vent holes in the SRS tube. If you decide to try this...keep these holes especially small and few! Too big/too many and they will produce their own noise, or adversely affect the SRS system function.

I can't over emphasize that venting is not a total solution...it's just one efficiency aid for the LDC, and it's very very tempting to over-do it. Be satisfied with the results from a few small vents strategically placed!.


(Afterthought: If you over-vent, and get excessive exhaust noise, you can always plug excess holes with JB Weld epoxy putty. It fills holes nicely, can be sanded smooth, then touched up with a black permanent marker to make it disappear.)
Hepotter

 
 Respond to this message   
H.E. Potter
(Login Hepotter)
YF12

UPDATE: two 1.5mm holes drilled in each side of shroud...suggestions...

May 19 2017, 5:52 PM 

I drilled two holes in each side of the flat middle of the top rail/shroud. 1.5mm and when I blew hard into the muzzle and air vented from both sides.

Suggestions from this experience:

1) Don't go much larger than 1.5mm

2) The first hole was 2" from the rear of the flat section.

3) The second hole was 3" from the rear of the flat section.

4) Extreme caution when drilling...the distance from the shroud wall and the barrel is a fraction of an inch. Use caution NOT to drill too deep. If in doubt, take off the LDC and blow into the muzzle. You should feel a strong vent of air from the hole. Drill no further!!! On one side I felt the drill bit go through the shroud wall and hit the barrel. However, on the other side I did not get this sensation and wasn't certain if I had drilled deep enough. When I blew into the muzzle I felt a strong vent of air come from that particular hole.

5) A black permanent marker dressed up the holes nicely.

6) Use a ruler and a pencil to mark the exact drill points at 2" and 3". Line the holes up carefully so they match. I used the thin center line going down the length of the flat portion as a vertical guide.


Thoughts....the expansion inside the top rail/shroud is limited. Drill shallow and stop early and test for venting. Two holes on each side are where I am stopping for now. I needs to take some test shots to see if it helped or made matters worse.

Hepotter


    
This message has been edited by Hepotter on May 19, 2017 5:55 PM


 
 Respond to this message   
H.E. Potter
(Login Hepotter)
YF12

Test shot update....4 vent holes....

May 19 2017, 6:06 PM 

Upon firing, there is definitely air coming out of all four holes.

Did they make a difference? I believe it helped. How much? I'm 74 and my hearing is not acute as some of the younger forum members...BUT, all I heard was the hammer slap and pellet impact. I could not distinguish any muzzle blast. Younger ears should be better at noting muzzle discharge, especially if they are ten feet away from the shooter.

For now, I'm stopping at four holes. It's the quietest pcp gun I now own and I've learned to stop when you reach acceptable results. I've gone too far too many times to risk losing what I've gained.

I hope this helps anyone considering maxing out the gun's features. The regulator is next on my list. I have no idea which way to turn the hex wrench, or how far. Suggestions?


PS: Crosman pellets don't fit well in my gun. I've got to really push hard to seat them. The JSB pellets are just right and load easily.
Hepotter


    
This message has been edited by Hepotter on May 19, 2017 6:09 PM


 
 Respond to this message   
Bob
(Login bpratl)
YF12

vent holes

May 21 2017, 6:11 AM 

Do you have any photos of the 4 vent holes or the spacing from the rear of the shroud?

 
 Respond to this message   
Frank Zuccarini
(Login Frank_Zuccarini)
YF

Once again..........

May 19 2017, 10:02 AM 

........... We are in your debt.

Thanks for sharing your work with us..................... Frank

 
 Respond to this message   
Mrodair.com
(Login Mrodair)
YF12

The factory vent holes aren't covered, when inside the barrel jacket.

May 19 2017, 10:51 PM 

Count the turns when installing in the barrel jacket when installing.

Then remove as you pictured and screw on the same number of turns.

Doesn't cover the holes.

Big difference between on the bench and installed in the jacket.

If the oring is thicker than the shoulder of the barrel nut, it will not allow it to center the barrel properly.

If you choose to use one there, be sure it is very small cross section.

For the other end, a dab of locktite would be much easier in my opinion, and would keep the breech depth constant.

The SLRS, was counter stepped a very specific amount, to ensure the barrel says centered and the holes were not covered.

Check it out.

 
 Respond to this message   
H.E. Potter
(Login Hepotter)
YF12

Thanks for the info. Part of the new product learning curve. nt

May 20 2017, 12:17 AM 

Hepotter

 
 Respond to this message   
Mrodair.com
(Login Mrodair)
YF12

I believe our ideas, have complemented each other, the

May 20 2017, 1:56 PM 

Holes, when revisiting, are a bit small for the amount of "dwell time" as the pellet passes that spot.

Further, by increasing the number of holes, or in my case elongating them, the sound level was much lower.

As you stated, to a degree that it could be noted by ear alone.

I would very much like to visit with you after you have used the MK II a bit more and compare notes.

My views, are a bit jaded and of course one sided from a parts design point of view.
(Not to mention being a retailer)

Actual user input, is much more important and as recently proven our manufacturer is willing to make changes based from our findings.

Looking forward to your findings, and as always.

"Stay Tuned"

We Are Mrodair

 
 Respond to this message   
H.E. Potter
(Login Hepotter)
YF12

A thought for the next owner's manual...or perhaps a quick video?

May 20 2017, 3:30 PM 

By adding a photo of the regulator adjustment hole, and describing how to raise/lower the setting would be most helpful.

This is also true for the two stage trigger adjustments. Several owners have indicated they needed to adjust/fine tune the trigger...in my case, the hammer wouldn't cock. Fortunately I realized the sear was not engaging and was able to quickly remedy the problem. However, a few pics and explanation of the trigger's first and second stage adjustment would be most helpful.

Perhaps a video of you making these two user available adjustments on your Youtube channel would be more timely!

So far it's proven to be a great gun, and I love that two stage trigger...second stage is crisp, and breaks cleanly with no rubbing or "creep" that I can detect! It is surprisingly powerful, but still maintains a very large shot count for it's size!!! Seems a lot of thought went into this gun.

Hepotter

 
 Respond to this message   
 
  << Previous Topic | Next Topic >>Return to Index  

Airgun Calculators    Num of fills calc    Capacity Calc

******** Kalibrgun High quality, superb Accuracy, outstanding Value. ********





D I S C L A I M E R
JK's Airgun Forums, moderators, and administrators are not responsible for any problems that may occur from reading or using content posted on this forum, as they are the exclusive responsibility of two parties: the person who posted it and the person who acted on said posted information.Use of our forums by people under 18 years old is allowed only with legal guardian(s) present.