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-   -   AK Guru's help needed - LCT AKMSU modded front end (https://airsoftcanada.com/showthread.php?t=170902)

HackD March 10th, 2015 18:21

AK Guru's help needed - LCT AKMSU modded front end
 
An AK Guru's help/advice is definitely desired, purists might want to look away..

I'm trying to get this season's boom-sticks all setup to my taste, and i'm running into a few issues, regarding mating of an (AABB?) compact 'shorty' PBS-1 suppressor purchased from airsoftdepot (http://airsoftdepot.ca/catalog/produ...oducts_id=2337) , to my Tactical Fantasy LCT AKMSU. I actually ordered the regular length (http://airsoftdepot.ca/catalog/produ...roducts_id=284) and the shorty appears to have been sent in error, instead. I'll need to rectify that issue, tomorrow when open. Even with the correct PBS-1 that i ordered, the basic issue still likely remains.

I got the idea from the below image:

http://img01.militaryblog.jp/usr/car...n/DSC_0395.JPG

from this Japanese blog, translates fairly poorly through Google .. http://carbinesan.militaryblog.jp/e252542.html

I'm not trying to direct copy, but get a similar approximation flush fit to the sight block/gas tube of the AKMSU muzzle, as seen on the above photo

.. and this is my result, so far.

https://lh4.googleusercontent.com/-t...310_172549.jpg

As can be seen, i am using a Hephaestus Aluminum Silencer Adapter for GHK AK Series (24mm CW to 14mm CCW) .. the AABB PBS-1 in turn uses an internal thread insert that converts from 14mm CW to 16 or 18mm CW (I think). This is not ideal to me .. i would much prefer it being flush fit against the sight block, as already said, and as shown in the inspiration photo.

What do i need to do, to rectify this? Do i need to go to a different airsoft manufacturer sight block (LCT uses an integral 24mm threaded sight block/gas tube assembly) to make this work? Different PBS-1? Machine out and tap the PBS-1 to get to 24mm CW? What am i not getting here, in this equation to my ideal of perfection?

Thanks for any help/pointers..

beta678 March 10th, 2015 19:14

You need a PBS-1 w/ the 24mm threading.

He's got a UFC PBS-1 if I'm not mistaken, I think 5KU and Building Fire also make one with the 24mm threads with a 14mm insert.

But since you've already gotten a PBS-1, your best bet is to just get it drilled out and tapped for 24mm threads.

HackD March 10th, 2015 19:30

Thank you, sir.

Tap, it will be.

MADDOG March 10th, 2015 19:38

Quote:

Originally Posted by HackD (Post 1937976)
Thank you, sir.

Tap, it will be.

I could trade you my long version with both flush mount adaptors for your short version.
It is a little banged up but I would prefer a short option

But if you removed the Hepastus adaptor and took out the PBS insert, will it not just screw on to the front sight threads directly?

beta678 March 10th, 2015 20:07

The short one from airsoftdepot which he has doesn't have the 14mm-24mm insert, think its just a 14mm CW/CCW adapter in it.

The regular length one which he actually ordered, looks like it might have the 24mm threads with the insert is removed. Best bet is to have it exchanged to the one he actually ordered and see if that's the case, if not, drill and tap then.

I have a mild suspicion the shorty they have pictured is the Building Fire PBS-1, which would mean 24mm threads.

HackD March 10th, 2015 20:13

Quote:

Originally Posted by MADDOG (Post 1937978)
I could trade you my long version with both flush mount adaptors for your short version.
It is a little banged up but I would prefer a short option

But if you removed the Hepastus adaptor and took out the PBS insert, will it not just screw on to the front sight threads directly?

Banged up, it depends on just how much.. If it is well worn, paint-wise, with very minor dings, not an issue. If it looks like it has been used as a pry-bar along the way, something of an issue. :confused:

I did a bit of checking after Beta678's post - it's a removable 14mm CW to 18mm CW threading insert adapter in the suppressor base. As such with the PBS-1 Shorty, unless tapped out, it's not going to fit the LCT sight block/gas tube assembly, of which the 24mm CW muzzle threading base is integrated onto, and slips over the end of the unthreaded outer barrel itself.

So yes, if your's is a 24mm CW threaded PBS-1 and in somewhat good shape still, I might well consider a trade, just to get 'er done. The whole point of this in the end, is to change out my inner barrel to something a bit longer than the LCT AKMSU barrel, and get some what-if Commie Tacti-cool while i'm at it.

I've already got a 24mm CW tap sourced out.. just got to hit the 'fuck my VISA further' button, to go ahead with that route.

HackD March 10th, 2015 20:19

I'm 99% sure that it is this one, that airsoftdepot sent me, in error. You can see the 14mm CW to 18mm CW threading insert in the back-side view.

Mis-labeled PBS-3, to boot..

http://shop.ehobbyasia.com/aabb-pbs-...l#.VP-JfdJ4qlw

beta678 March 10th, 2015 20:20

Quote:

Originally Posted by HackD (Post 1937984)
I'm 99% sure that it is this one, that airsoftdepot sent me, in error. You can see the 14mm CW to 18mm CW threading insert in the back-side view.

Mis-labeled PBS-3, to boot..

http://shop.ehobbyasia.com/aabb-pbs-...l#.VP-JfdJ4qlw

Can you get them to send you the other one? Cause if I'm not mistaken, that one has the threads you need.

Plus the review seems to confirm it lol, probably the element/building fire PBS-1 after checking the engraved numbers on it.

http://airsoftdepot.ca/catalog/produ...&reviews_id=25

HackD March 10th, 2015 20:27

Quote:

Originally Posted by beta678 (Post 1937985)
Can you get them to send you the other one? Cause if I'm not mistaken, that one has the threads you need.

Plus the review seems to confirm it lol, probably the element/building fire PBS-1 after checking the engraved numbers on it.

http://airsoftdepot.ca/catalog/produ...&reviews_id=25

I'll give airsoftdepot a ring tomorrow about my issue.. i don't even know if i saved the boxing for it, receiving it the day before recycling day..

Thanks for the help on this.

ebfud March 10th, 2015 20:37

You could always change out the gas block for a 14mm threaded version.

HackD March 16th, 2015 15:15

Welp, that's a fail, x2.

Airsoftdepot sent the longer one, 'as ordered', except it isn't the one as pictured on the website. Same as the short, just longer. Same threading insert as the other one, going from 14 to 18mm.

So, i guess it's off to find a machine shop to tap it out to 24mm.

Disco_Dante March 16th, 2015 16:33

Quote:

Originally Posted by HackD (Post 1938878)
Welp, that's a fail, x2.

Airsoftdepot sent the longer one, 'as ordered', except it isn't the one as pictured on the website. Same as the short, just longer. Same threading insert as the other one, going from 14 to 18mm.

So, i guess it's off to find a machine shop to tap it out to 24mm.

I'm not sure how much money you want to spend on this but you can also buy Dummy suppressors for real AKs that will be 24mm. I was looking into that when I couldn't find a PBS4 with 24mm threads. I ended up going with a DTK4 replica, which is the modern suppressor for the AK series, and comes in either 24mm or 14mm. You can get them both from Samoon.

HackD March 17th, 2015 20:41

Not really interested in pursuing this further - this suppressor is enough of a close approximation to what i need/desire in terms of form and function.

However, thank you for the Samoon suggestion.

Dropped the suppressor and the gun off at a machine shop today - they'll have the suppressor base modified pretty quickly/cheaply this week, and returned back to me in satisfactory form.

Definitely on par, for the cost in time and money of posting them back to airsoftdepot.

brock0 March 17th, 2015 21:56

Depot sucks. I'm sure it's a shop filled to the brim with the nicest people in the whole wide world but they simply fail hard at shipping.

Not that it's helpful in this situation but I'm not at all surprised.

HackD March 18th, 2015 20:11

Quote:

Originally Posted by brock0 (Post 1939139)
Depot sucks. I'm sure it's a shop filled to the brim with the nicest people in the whole wide world but they simply fail hard at shipping.

Not that it's helpful in this situation but I'm not at all surprised.

Yes, i have had a few odd mis-picked orders in the past also .. this 2x in a row FUBAR is pretty much the deal breaker for me.

HackD March 19th, 2015 13:30

.. and, end result of coming out of the machine shop for modifying of the suppressor base, was this:

https://lh6.googleusercontent.com/--...e%28HDR%29.jpg

Mission accomplished.

brock0 March 19th, 2015 15:58

Looks amazing! Very nice

MADDOG March 19th, 2015 18:02

Quote:

Originally Posted by HackD (Post 1939357)
.. and, end result of coming out of the machine shop for modifying of the suppressor base, was this:

https://lh5.googleusercontent.com/-z...o/2015%2B-%2B1

Mission accomplished.


Now you just need to make sure your exit hole on the silencer is big enough. I had to widen mine slightly (drill it out) as the BB's would sometimes catch the side depending on how the silencer was oriented/screwed on the front sight. Love the cheap manufacturing tolerances, quarter turn one way straight, quarter turn the other hit the side of the silencer. Have you test fired yet?

HackD March 19th, 2015 19:08

Not test fired yet.

I have heard that this is an issue. If push comes to shove, i will be using a longer inner barrel, and re-springing to adjust FPS.

The Machinist noted the sloppy tolerance for the sight-block threading on the LCT .. "This was Not 24mm - it was an approximation only". He took the difficult path with boring out and threading the suppressor mount, on a lathe. At the moment, the threading is very precise and tight, but he also warned that the alloy on the suppressor base is very soft. He could offer no guarantee that the threading wouldn't lose definition and get sloppy over time.

As an aside - part of this exercise was in finding a new machinist to take on side-work related to some of my airsoft and non-airsoft related projects - finding one that actually takes pride in his work, and the time to do it in, is a fairly hard thing to do. His handling of the project, passed muster. Although - funny story - his after hours cleaning service found the gun inside the gun bag in his office - his cleaner (his daughter in law) wanted to know what was up with the gun - thereafter, it was known as the "Terrorist Bag".



Quote:

Originally Posted by MADDOG (Post 1939419)
Now you just need to make sure your exit hole on the silencer is big enough. I had to widen mine slightly (drill it out) as the BB's would sometimes catch the side depending on how the silencer was oriented/screwed on the front sight. Love the cheap manufacturing tolerances, quarter turn one way straight, quarter turn the other hit the side of the silencer. Have you test fired yet?


MADDOG March 19th, 2015 20:20

Quote:

Originally Posted by HackD (Post 1939426)
Not test fired yet.

I have heard that this is an issue. If push comes to shove, i will be using a longer inner barrel, and re-springing to adjust FPS.

The Machinist noted the sloppy tolerance for the sight-block threading on the LCT .. "This was Not 24mm - it was an approximation only". He took the difficult path with boring out and threading the suppressor mount, on a lathe. At the moment, the threading is very precise and tight, but he also warned that the alloy on the suppressor base is very soft. He could offer no guarantee that the threading wouldn't lose definition and get sloppy over time.

As an aside - part of this exercise was in finding a new machinist to take on side-work related to some of my airsoft and non-airsoft related projects - finding one that actually takes pride in his work, and the time to do it in, is a fairly hard thing to do. His handling of the project, passed muster. Although - funny story - his after hours cleaning service found the gun inside the gun bag in his office - his cleaner (his daughter in law) wanted to know what was up with the gun - thereafter, it was known as the "Terrorist Bag".

If you go to a longer barrel you need to be careful of a few things:

1) Barrel vibration and stability past the front sight, I tired this and the accuracy was crap due to the fact nothing was supporting the barrel for 8-10 inches. This can cause even more BB's to hit the front of the silencer unless the barrel end is actually held in place and stabilized in the end of the silencer (tough to d0, not impossible). I had a barrel that was sticking slightly out past the end of the silencer and you could hear it vibrate in the end of the silencer.

2) You need to change the cylinder as well for the porting to match the new length of barrel for proper air pressure. Your current cylinder is for the short AKSU barrel, which I have found to be highly accurate and have not messed with it

Just an FYI

HackD March 20th, 2015 01:06

Thanks for the tips.. if a longer inner barrel is inadvisable, without requisite gearbox work (I'm of the school that believes if it ain't broke yet, don't #@#! with it) then an alternative solution might be going to metal supermarket and getting a section of oversize brass tubing to fix in place inside the suppressor.

Firing up the bench drill and fabbing up a suppressor base inner spacer to sleeve the oversize brass tubing over the stock inner barrel, drill out the nose of the suppressor to the OD of the tubing, and interference fit in place, flush through the nose of the suppressor. In essence, creating a larger diameter "outer/inner" barrel that shouldn't affect the piston's volumetric pressure characteristics, near as badly as an extended length 6.03 inner barrel. BB's might bounce, but they won't be shattering against the interior of the suppressor nose, or otherwise becoming wild flyers.

I've yet to pull a battery out and charge it up for a test, but if the hop-up setting doesn't eliminate this issue, it might be worthy of a Saturday afternoon garage project experiment/solution.


Quote:

Originally Posted by MADDOG (Post 1939430)
If you go to a longer barrel you need to be careful of a few things:

1) Barrel vibration and stability past the front sight, I tired this and the accuracy was crap due to the fact nothing was supporting the barrel for 8-10 inches. This can cause even more BB's to hit the front of the silencer unless the barrel end is actually held in place and stabilized in the end of the silencer (tough to d0, not impossible). I had a barrel that was sticking slightly out past the end of the silencer and you could hear it vibrate in the end of the silencer.

2) You need to change the cylinder as well for the porting to match the new length of barrel for proper air pressure. Your current cylinder is for the short AKSU barrel, which I have found to be highly accurate and have not messed with it

Just an FYI


HackD April 14th, 2015 17:18

It took me a little while to get back to it.. but the sleeved over barrel idea worked fabulously. 1/2" OD stainless tubing, with the end cap of the suppressor countersunk to accept the end of the OD stainless tubing in a friction fit .. still has same nominal bore outlet as the stock suppressor does, looking end-on. The outer sleeve is kept centered by the suppressor 'packing foam' in the suppressor body, and slips loosely over the stock brass inner barrel that protrudes from the gas-block/sight assembly.

It's following the same principle of construction, of a 'suppressor' tracer unit, that i had on hand.

https://lh6.googleusercontent.com/-J...o/2015%2B-%2B1



Quote:

Originally Posted by HackD (Post 1939472)
Thanks for the tips.. if a longer inner barrel is inadvisable, without requisite gearbox work (I'm of the school that believes if it ain't broke yet, don't #@#! with it) then an alternative solution might be going to metal supermarket and getting a section of oversize brass tubing to fix in place inside the suppressor.

Firing up the bench drill and fabbing up a suppressor base inner spacer to sleeve the oversize brass tubing over the stock inner barrel, drill out the nose of the suppressor to the OD of the tubing, and interference fit in place, flush through the nose of the suppressor. In essence, creating a larger diameter "outer/inner" barrel that shouldn't affect the piston's volumetric pressure characteristics, near as badly as an extended length 6.03 inner barrel. BB's might bounce, but they won't be shattering against the interior of the suppressor nose, or otherwise becoming wild flyers.

I've yet to pull a battery out and charge it up for a test, but if the hop-up setting doesn't eliminate this issue, it might be worthy of a Saturday afternoon garage project experiment/solution.


Piper Jacob January 16th, 2018 01:57

Can you PLEASE help me with my AKMSU
 
Hey,
So I'm pretty new to Airsoft, and I recently upgraded from my combat machine to an LCT AKMSU NV. A problem I'm having with it is that it's insanely innacurate. Less accurate than the cm16 for sure. I don't think it's the barrel because I took the flash hider off and the barrel had no apparent wobble. Does anyone else have this problem? Could someone with experience please tell me what is wrong with my gun or is this just how it comes.

Styrak January 16th, 2018 10:20

Try cleaning the hopup rubber and barrel?

Desmodus January 16th, 2018 11:27

This ^

Give them a once over and make sure everything is nice and clean. What kind of issues are you having specifically?


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