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MagPul PTS MASADA ACR

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I carefully removed the stock rubber pad, scraped the glue and rubber pieces off, it wasn't perfect but clean enough. Then I cut (carefully with a sharp razer blade) out a piece of Sorbothane in the same shape as the original stock rubber piece and glued it in with Loctite Super Glue. Any glue that is CA (Cyanoacrylate) will bond to it. I waited about 20 minutes before I installed the cylinder head just to make sure it was cured.

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And this is only for the cylinder head? Sorry, new to internals... learning fast though!

 

Is there and problem with having a a ball bearing piston head with a 400 fps set up? And is it worth replacing the cylinder aldon with the cylinder head? Once again, im new so i dont want to mess anything up because i have a budget :) thanks a bunch guys it really helps.

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Yeap. Bearings arent good to have on a high stress gun. I wanted to bin the bushings and bearings that came stock with the gun but was told that they've actually held up. FPS in the 350 range is enough for me. My TM Next Gen M4 gets my sub 400 power.

 

The stock tappet plate has been working for me so I haven't had to replace it and I don't have any spare tappet plates for a v.3 gearbox laying around. I might pick one up when I'm close to making my mind up as to what the final setup for the gearbox will be.

Hm... I will try to fit in a V3 tappet plate then. I'll keep you posted when that happens.

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Shaved the front part of the tappet plate and tapered part of the lip air nozzle-tappet plate retainer so my nozzle went farther forward. Same spring...same setup..instead of up to 318 fps with hop set for .25g bbs, I ended up getting up to 330 fps with .25g bbs. I replaced the hop bucking with a Prometheus soft/purple hop bucking and made shims out of shrink tubing. Now I'm getting up to 335 fps with .25g bbs.

 

Also installed a jg mosfet in my masada akm. Could have went with a fancier mosfet but this will do.

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I don't have photos of the shrink tubing shim job. I try to keep take down of the outer barrel to a minimum to keep the figure 8 nub from getting too beat up. What it is is a stack of 2 or 3 shrink tubing. Then cut down to fit on the slot and directly over the hop bucking.

 

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Photo of the JG mosfet assembly:

 

IMAG1973.jpg

 

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The MAGPUL PTS Masada ACR seems like it needs a cripeload of tweaking. I'm finding out little things about it here and there.

 

A guarder SP100 spring used to shoot up to 355 FPS for me after adjustments were done to the gun. With a little bit more tweaking, the same spring now shoots up to 375 FPS with .20g BBs.

 

Initially, my MAGPUL PTS MASADA ACR AKM was shooting up to 345 FPS with .20g BBs out of the box. I will have to double check the FPS of the gun with the stock spring.

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Ive had to sand down the front of the tappet plate, taper the air seal nozzle forward retainer lip, and tapper the inner part of the gearbox shell so the air nozzle moved farther forward to improve the seal between the air nozzle and the hop bucking.

 

*As a result of that, feeding on full auto at 20 RPS became an issue. I have installed a Sector Chip Delayer that has since fixed the issue*

 

Previously, with the piston all the way forward (spring installed), nozzle all the way forward....I could blow into the inner barrel and air would leak which indicates that the seal between the hop bucking lip and air nozzle isn't perfect.

 

After the modification I could blow into the inner barrel and air will not leak out which undoubtedly resulted in the FPS increases I've been getting.

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My stock Magpul PTS Masada ACR AKM chronoed up to 350 fos with .20g BBs with the hop off when it was brand new.

 

I have made the following changes:

 

-TM Inner barrel 6.08mm x 317mm

-TM ported cylinder (m4)

-KWA G36C Cylinder Head

-Prometheus Soft Hop Bucking

-Systema Turbo Motor

-Systema Aluminum Piston Head w/ Bearing

 

Tappet plate was modified as did the air nozzle (as noted in previous posts)

 

Using the stock spring and that set up, the gun chronoed a high of 379.8. Without decimal numbers, the gun shoots 373-379 FPS with .20g BBs with the hop set for .25g BBs. I'm sure it would shoot a couple ore FPS higher with the hop turned off.

 

Out of the box, the guns air seal was not perfect. Right now, I would say that the seal is as close to being perfect if not as perfect as can be. End result is up to a 30 FPS increase with the same spring.

 

My other Masada ACR AKM was shooting up to 383 FPS. I stuck that spring in a different set up which yielded FPS up to 413 FPS (another 30 FPS that the gun should have been shooting).

 

I'm not saying these two guns are representative of a whole production run. I'm just saying that the gun could be made to shoot harder with tweaking here and there....quite a lot actually. For those following everything that I have been writing...congratulations, you know exactly what to look for when tinkering around with your Masada.

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I just did a quick check to see if my ACR was sealing well with a bb loaded. It didn't appear to seal that well as blowing air into the end of the barrel easily leaked through.

The only things that I've switched out parts wise are the (sealing) air nozzle, piston/head, sorbo pad.

 

sacairsoftsn00py do you know how much you moved your parts forward?

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Got my shs CNC aluminum cylinder head. Version 3 long. The shaft is 23.45mm. Bore is 4.31. Shaft diameter is 5.35mm***

 

***I didn't use the same caliper for this. I might re-measure with the same caliper when I get home.

 

Jeff. Make sure.your nozzle and piston head are both all the way forward.

 

Photo of the shimmed Prometheus Hop Bucking

 

IMAG1993.jpg

 

Photo of the JG MOSFET switch assembly for v.2 gearbox (rear wiring) installed into the PTS Gearbox. Had to cut the wires to length

 

IMAG1988.jpg

Edited by sacairsoftsn00py

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Thanks for the Hopup picture, i had assumed thats what youd done but wanted to clarify, i see youve opened up the area around the bucking, has that made a big difference? the hop up arm is very narrow anyway?

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I opened it up some so the nub does not get caught in it. It's a just in case thing for me. I don't think its necessary if you don't take down your gun that much. At the zero hop setting, I have enough hop for .20g bbs. It's surprising how much 3 layers of heat shrink tubing does to increase the hop.

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I opened it up some so the nub does not get caught in it. It's a just in case thing for me. I don't think its necessary if you don't take down your gun that much. At the zero hop setting, I have enough hop for .20g bbs. It's surprising how much 3 layers of heat shrink tubing does to increase the hop.

Wow! This would help me a lot dude. I hope to see more work and experimentation from you. ThanKs!

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No dice with the shs cnc v3 long cylinder head. The holes that lock it down to the gearbox are a little big which allows for axial rotational play. I'm sticking the KWA ver. 3 cylinder head off of their g36 and am waiting for my sorbo pad from ars.

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Stock barrel hop window/slot measures 3.55mm. A Marui barrel hop window/slot measures 3.70mm...a difference of .15mm. While that may seem insignificant to many...it is significant to me as that means more of the hop bucking is sticking down the barrel.

 

I have pics of other things I have done...like the nozzle tapering, sanded down tappet plate, and tapered gearbox shell interior. People will just have to compare theirs to mine.

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Nozzle and tappet plate all the way forward

 

IMAG2010.jpg

 

Tapering on the air nozzle retainer lip (Allows for the nozzle to go forward farther)

 

 

IMAG2013.jpg

IMAG2014.jpg

IMAG2014.jpg

 

Tappet plate sanded down (Allows for the tappet plate to go forward farther)

 

IMAG2016.jpg

IMAG2017.jpg

 

Tapering inside the gearbox shell (Allows for the nozzle to go forward farther)

 

 

IMAG2019.jpg

IMAG2020.jpg

 

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I have my gearbox opened and laid out on the table. If there are other picture requests please let me know as I wont be taking any more after I close it up. ARS is supposedly shipping my Sorbo Pad the next 24 hours. Its been 13 days since I placed the order from them. Supposedly, he just came from Shot Show 2012 in Las Vegas, NV.

Edited by sacairsoftsn00py

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I've not had any issues my ACR since getting it in 2010, however I got around to chrono'ing it over the last few days and with 0.2g bb's its been smashing them out at 410 fps!! The only changes I have made have been a new motor and thats it. Comparing it to my M4 which did 340fps on an M100 I swapped springs around between the guns and found the M100 from the M4 was pushing 420fps in the ACR and the spring from the ACR was pusshing 328fps in the M4.

 

Strange! Now to cut down the springs to 370fps in the ACR and a bigger spring for the M4!

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Spring ratings differ from brand to brand. Guarder SP100 springs shoot up to 370-80 FPS. Systema M100 springs shoot up to 365 FPS. SHS 100 springs shoot up to 390 FPS. PPA SP100 springs shoot up to 400 FPS. For this reason, I stick with springs I know base line FPS figures for in a Marui M4 AEG. If I'm not getting the expected FPS I want from the spring, then I start looking into things.

 

I was able to get up to 413 FPS on a stock spring with a 6.08mm (not the 6.04mm stock inner barrel). Also, I'm using the shorter 317mm inner barrel. And not the standard 365-385mm inner barrel that come with the carbine length outer barrel assembly

 

I'm not saying my experience with sub par air seal on my masada is representative of whats out there...I'm just saying...if its an issue with mine...its probably an issue with other people's as well. For those with the same issues that I have...I've posted up possible fixes. :)

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