BB Feed Sleeve Mod.

[East Milford]

This is not necessarily a new mod but, i want to bump the idea to the present because ibe recently found it to have measurable gains. I chronographed this mod against the results of a previous mod, the (fixed mag head to breach mod) and the numbers were suprising. It picked up an additional 70fps average. I used a 25 shot string to get the data.

On to the mod. Its a 'sleeved BB feed tube' mod. Essentially it reduces the amount of 'blow by' that passes down the feed tube after the striker actuates the valve. Air propels the BB and follows it out the barrel. Additionally air will pass the chain of BBs in the feed guide and find its way out, this wasted air, albeit a small percentage is substantially enough to increase your velocity if it is redirected to it's intended path, the barrel.

To accomplish this i used a surgical  grade stainless steel syringe tube the outside diameter must be 5.00mm. The wall diameter of the tube  should be as thin as possible, mine was .050mm I believe.
It will press fit into the bottom of the mag head, that opening is 5.1-5.2mm, much larger than a BB.

Next i took a handfull of BBs and teat rolled them down the surgical steel tube, most all roll smoothly through it, but a couple would lightly bind up. So it was necessary to use a .177 BB barrel cleaning brush dipped in polishing compound to buff out/bore the tube so there are no hangups. I attached the barrel cleaning apparatus to a cordless drill and spun it for a while untill it was a mirror polish and no BBs would hang up.
Next i used a7mm  round ball diamond coated dremel bit to flare the end of the pipe just a tad bit, to assure a smooth transition of BBs into the tube. The length of tube i used was short but, it can be as long as you want to go, with attention that the feed channel eventually makes a curve.



Overall its a a simple mod with  a straightforward install. Anyone can do it. You will see that once BBs are in this tube it becomes nearly impossible to blow air through it. This is where the performance comes from, the escaping air is now forced to channel the path of least resistance, the barrel. Ultimately propelling the BB with the addition of the newly redirected air.

Here are some pics for reference
The BB 'feed tube sleeve ' and the 'fixed breach to mag  face' mod

Thanks to the guy who years ago used an antenna to stop the mag neck from 'puffing' by reducing the blow by. he gave  me the idea to pursue this further.  I think it was Dubb

[East Milford]

 Feed tube with the complete assembly. The air tube to air adapter is ported out, the factory port is the size of a pin, I enlarged it to 5mm then TIG welded the joints.

[camracer]

Nicely done. Great ideas!

I ported my whole air feed system from the inside of the HPA regulator on the tank all the way to the mag head. Anything that could be done. I posted photos and How-to about it all on the old forum somewhere some years back. It did make a very noticeable difference in power.

---Cam

[East Milford]

Nicely done. Great ideas!

I ported my whole air feed system from the inside of the HPA regulator on the tank all the way to the mag head. Anything that could be done. I posted photos and How-to about it all on the old forum somewhere some years back. It did make a very noticeable difference in power.

---Cam

Thanks Cam, I appreciate it.

Did you allign the intake hole that is on the bottom, between the O-rings (vertical air pipe section) with exit hole that is on the back aide of the ASA?
That is a major restriction in the system.

[camracer]

Yes, I did.

[East Milford]

Yes, I did.

Cam, what kind of velocity are you getting? Also what is your accuracy like?
Sorry for all the questions, but i have no one to talk about Drozd with lol

[camracer]

Hello East Milford,

I stopped taking velocity readings early on in my builds. It wasn't very important to me how fast it shoots. I was more into what it can destroy. Heh!
Also, I am not a huge fan of super fast RPM rates. I like to shoot at around 800 rpm. It feel more like a firearm at that rate, and is very satisfying to me (eh, ...to each his own).

As for accuracy, a "jelly bean" at 50' typically within one to three shots. I have thought about using Walther barrels, but never got around to it. I'm ok with my DrozdMax barrels Ray gave me years back.

---Cam

[DU-BB]

This is the same thing I did. I found an old telescoping radio antenna: it conveniently is an assortment of sizes in one package, and usually stainless steel. I used the piece that fit the best, which is pretty much the same as yours, it sticks in the bottom of the head. I like the polishing idea, too, I think I'll try that. I have all kinds of polishing compound. I just went though mine with 1000 grit sand paper, that worked well enough. 

[Parellax]

https://youtu.be/TekBE6sOgCs

[DU-BB]

One of the big issues I remember that this mod I made addressed was the "sta-puft marshmallow mag" syndrome. When we started running high pressure air, it would split the mag right open, and people were trying to put extra bolts through to try to prevent that from happening. There are several small vents on the neck to allow the air to blow out, but this fixed all that, and closes those holes. It does work. I knew it improved the velocity, but I could never measure how much. I'm glad someone finally put it to the test. I have a saying that in my experience, the secret to happiness is learning to sort the occasional good idea from an endless body of bad ones. This was a good one.

[Parellax]

Even though I didn't find any any fps gain something else I found was that it makes extreme ROF much more reliable. All I can guess is that it takes all of the flex out of the feed chute preventing double stacking. I'm releasing my first 6K bird back to the wild tomorrow. I'll see if I can find something to destroy with it first.