A&K Masada SPR - DMR Theory Crafting

[MrTea]

10 hours ago, Leo Greer said:

I have no clue where AirsoftPro falls on the lineup of Tawain/China/HK, but they all have different specs, courtesy of the wonderful airsoft industry.

 

It's a 1:1 copy of the stock A&K hop unit but CNC aluminium. IIRC A&K is a Chinese brand.
 

10 hours ago, Leo Greer said:

Prommy should fit as well (I’d recommend purple), but they tend to be kinda expensive.

 

I managed to find a Prommy purple (just in case I fuck up adjusting the ML hop rubber) and the pack of soft/hard flat nubs for £24. Will be a nice backup and if not needed just sit in my spares until next time

 

10 hours ago, Leo Greer said:

For a nub, I usually just use a piece of 8mm tubing cut into a rectangular patch, glued to the hop arm. This creates a concave contact patch and ultimately a similar effect to an MR. Hop that works with any rubber and barrel. You can adjust the height by either sanding it or adding layers of tape. Or you can simply cut your own nub out of hard plastic using small files. It can be flat or concave, either works. Then attach it to your hop arm (maybe sand the hop arm flat), with superglue.

That's a nice bit of info going forward, cheers.

[Colin Allen]

12 hours ago, Leo Greer said:

I have no clue where AirsoftPro falls on the lineup of Tawain/China/HK

They are in the Czech Republic.

[Leo Greer]

1 hour ago, Colin Allen said:

They are in the Czech Republic.

 

The question is what specs they're using. Chinese/Japanese/older units are often designed for thinner, shorter rubbers, whereas Taiwan/HK/newer units are often designed for thicker rubbers with longer lips. If it's a perfect 1-1 copy of the A&K unit that'd be awesome, and it should work better with the Prommy rubbers, Modify rubbers, and PDI rubbers, though @MrTea will be able to tell us more as he works on it. 🙂

 

[Colin Allen]

5 hours ago, Leo Greer said:

 

The question is what specs they're using. Chinese/Japanese/older units are often designed for thinner, shorter rubbers, whereas Taiwan/HK/newer units are often designed for thicker rubbers with longer lips. If it's a perfect 1-1 copy of the A&K unit that'd be awesome, and it should work better with the Prommy rubbers, Modify rubbers, and PDI rubbers, though @MrTea will be able to tell us more as he works on it. 🙂

 

Ah, in that case, it definitely prefers the older style rubbers.

[MrTea]

So, over the winter i've not really touched this project until a week or so ago. Previously, I had stopped working on it at the stage of finding out that Maple Leaf hop rubbers don't work too well in this gun. I've still not fixed this and so far i'm just working with the stock bucking because I know it works and, at the minute, i'm trying to boost power closer to the limit for DMRs. On an M130 spring I was getting the following:



These reading were taken back in October. As a preemptive measure, I had ordered an M150 spring and dropped it into the gun a week or two ago but only just got around to testing it today to get the following:



A nice bump in power bringing it closer to the limit. This translates to about 420fps on a 0.20g BB with the max joules being 1.88J. I've still got some additional headroom but i'm hoping the Maple Leaf bucking will give a slightly better seal and creep that number up a little bit more. I'm going to have a go at smoothing down the Maple Leaf bucking tomorrow and retesting it then but failing that i've got a Prommy Purple ready just in case.

On a standard V2 gearbox and full cylinder I don't know if i'm able to get much more power out of this. M160 and M170 springs exist but i'm wondering at what point do the working parts fail to compress the stronger springs. Ideally, i'd like to get this right on the border of 1.88J

Edited May 30 by MrTea

[Leo Greer]

On 30/05/2024 at 21:05, MrTea said:

On a standard V2 gearbox and full cylinder I don't know if i'm able to get much more power out of this. M160 and M170 springs exist but i'm wondering at what point do the working parts fail to compress the stronger springs. Ideally, i'd like to get this right on the border of 1.88J

I run an M170 (SP150) in my V2 DMR @ 2J exactly on .48gs. I run it on XYT 18:1s and a T238 33K @ 11.1v and it has no trouble cycling.

 

You can also pair a good high torque with something like a 20:1 set or even 32:1 if you really wanna be careful.

[MrTea]

7 hours ago, Leo Greer said:

I run an M170 (SP150) in my V2 DMR @ 2J exactly on .48gs. I run it on XYT 18:1s and a T238 33K @ 11.1v and it has no trouble cycling.

 

You can also pair a good high torque with something like a 20:1 set or even 32:1 if you really wanna be careful.

Thanks for the insight. I've gotten a M160 spring in prep for modifying and testing the ML MR Hop 70 degree bucking but I seem to have misplaced that hop rubber... somewhere??? Not sure how i've lost it but i'm on a drive to consolidate all of my spare parts + tools into something that I can carry onto an airsoft field (due to a recent crappy experience) and work with so it may turn up in a random box when I break everything down.

This is why I haven't updated the post since last week plus yet another boneyard rifle made its way to me... which I still haven't started work on.

Edited June 8 by MrTea

[grumio]

Out of interest did you get the ambi selector working well? I'm currently working on one of these and I've got it functioning but it is extremely sloppy and awful to use.

[MrTea]

18 hours ago, grumio said:

Out of interest did you get the ambi selector working well? I'm currently working on one of these and I've got it functioning but it is extremely sloppy and awful to use.

The left side of the rifle is solid and functions great. The right side functions but I wouldn't use the right side to change which fire mode. It's somewhat loose but it does move the way I'd expect.

Edited June 10 by MrTea

[grumio]

2 hours ago, MrTea said:

The left side of the rifle is solid and functions great. The right side functions but I wouldn't use the right side to change which fire mode. It's somewhat loose but it does move the way I'd expect.

 

Nice thread by the way, found it really helpful just reading through.

 

That's also funny that the right side on yours is worse, on mine the left side binds and feels coarse but the right side is really easy to to move. Is there anything you found that helped with getting it working smoothly?

[MrTea]

4 hours ago, grumio said:

 

Nice thread by the way, found it really helpful just reading through.

 

That's also funny that the right side on yours is worse, on mine the left side binds and feels coarse but the right side is really easy to to move. Is there anything you found that helped with getting it working smoothly?

I didn't do anything special honestly. I just re-assembled it and left it how it was. Sorry I can't help more.

[Leo Greer]

On 09/06/2024 at 00:38, MrTea said:

Thanks for the insight. I've gotten a M160 spring in prep for modifying and testing the ML MR Hop 70 degree bucking but I seem to have misplaced that hop rubber... somewhere??? Not sure how i've lost it but i'm on a drive to consolidate all of my spare parts + tools into something that I can carry onto an airsoft field (due to a recent crappy experience) and work with so it may turn up in a random box when I break everything down.

I put together an “Airsoft Medkit” that’s basically a briefcase filled with tiny plastic shelving units. I can carry all my tools, adhesives, and enough spare parts for a complete internal rebuild of two RIFs. It’s saved my butt a few times. Just make sure you include the essentials; super glue, emergency crackers, a backup to your backup screwdriver…

[MrTea]

@grumio Have you found a hop rubber that will work properly with this hop unit design or are you still using a standard/stock one?

[MrTea]

Actual progress this time around but additional confusion.

I tried sanding down the Maple Leaf MR hop rubber feed lips. No matter how little I took each time, I could never get a rubber that resulted in consistent FPS readings - at one point I got an FPS reading of ~800 so IDK 😅

I've been messing with different hop rubbers trying to find one that consistently works especially when the stock hop rubber ended up splitting when changing it over. I was going to try the a ML Macaron 60 degree as i've never had an issue with them before and they just worked. During the process of installing it I noticed that the hop unit wasn't applying hop evenly, it was applying too much pressure on the right side resulting in uneven hop. I think this is simply due to the way the hop unit is designed that makes the hop arm slightly off center. Happily I managed to remedy this quite quickly by using a small o-ring that I had lying around which I think is for a MOSCART fill valve? All I did was just put this between the body of the hop unit and the hop arm. Before anyone mentions it, yes the screw is in the wrong side of the hop unit and no, this isn't what was causing the issue with the misaligned hop arm




Now that I had sorted that I moved onto changing the hop rubber. I have a prommy purple I was going to try out but for some reason I just wanted to try a Maple Leaf Macaron yellow/60 degree just because they've worked flawlessly on everything I've put them on. I also installed the bucking with the Gearparts Omega 70 nub from AK2M4 and it worked. I am so mad. I am confused as to why this works. Before I tested this, i'd bought and installed a SHS M160 spring to creep up the FPS. The spring is very twangy (if that makes sense) and it's pretty annoying.



Since starting this build, i've changed which outdoors site I go to and they allow 450fps for DMRs so i've still got a bit of headroom that i'd have to buy an M170 equivalent to get to. Is a SP160 the same as a M170?

Could it be the MR hop bucking didn't work as the hop window on the inner barrel is too small causing inconsistent contact?

I am at a loss as to why this suddenly works... I want to buy another ML MR hop rubber and try it but I feel like if I disturb the hop rubber in the slightest it's gonna throw a fit and not work anymore.

Edited June 20 by MrTea

[Lozart]

13 hours ago, MrTea said:

Since starting this build, i've changed which outdoors site I go to and they allow 450fps for DMRs so i've still got a bit of headroom that i'd have to buy an M170 equivalent to get to. Is a SP160 the same as a M170?
 

 

For the love of GOD don't start chasing FPS limits.

 

Use it, see if it's actually lacking in range/accuracy first.

 

 

As for your other question, yes absolutely if the window on your barrel is too small or if the rubber hasn't gone on properly then an MR hop will catch on the edges.

 

SHS springs can be quite wide tolerance. Pick a spring brand you like and trust (*coughs* XT @ak2m4 *cough*) and stick with it.

[Colin Allen]

1 hour ago, Lozart said:

SHS springs can be quite wide tolerance. Pick a spring brand you like and trust (*coughs* XT @ak2m4 *cough*) and stick with it.

XT springs are great; they are very consistent.

[MrTea]

1 hour ago, Lozart said:

SHS springs can be quite wide tolerance. Pick a spring brand you like and trust (*coughs* XT @ak2m4 *cough*) and stick with it.

That was what I was going to do initially however it appears his XT springs don't go past M150. Up until this point, it's exactly what I was using.
 

1 hour ago, Lozart said:

For the love of GOD don't start chasing FPS limits.

Not yet. Now i'm closer to the limit, and have it chrono-ing consistently, i'm going to give it a test on 0.36g BBs to see how it's performing.

[ak2m4]

M160 are arriving in a few months however what's going on with that build?  Never worked on a Masada personally but why so low power ?

[Lozart]

3 minutes ago, ak2m4 said:

M160 are arriving in a few months however what's going on with that build?  Never worked on a Masada personally but why so low power ?

 

 

I was wondering the same, my MK12 is doing 420 FPS on a M120 spring!

@MrTea just to go back to basics, I assume you've checked that you're actually getting good compression with all the new cylinder/piston parts?

[MrTea]

54 minutes ago, Lozart said:

I was wondering the same, my MK12 is doing 420 FPS on a M120 spring!

@MrTea just to go back to basics, I assume you've checked that you're actually getting good compression with all the new cylinder/piston parts?

That's annoying. The air seal was perfect when I originally changed out the stock compression parts but I can definitely go back and check again when I get the time.

[ak2m4]

@MrTea what's the inner barrel length, is it 6.12mm?  what's cylinder type is it? 

 

[MrTea]

44 minutes ago, ak2m4 said:

@MrTea what's the inner barrel length, is it 6.12mm?  what's cylinder type is it?

 

6.12mm yes, 360-ish long IIRC and a full/non-ported cylinder.

[ak2m4]

4 hours ago, MrTea said:

 

6.12mm yes, 360-ish long IIRC and a full/non-ported cylinder.

 

I've never run a 6.12mm so can't comment, however I'm guessing it loses a fair amount of power.   I'd love to test one and get my borescope down one.

However I suspect the issue is you're using a full cylinder with a 360mm barrel, you should be using either a 4/5 or 3/4.  You should be able to hit you're required power with a M120 spring. (Unless there's something else I'm missing).  I've not the time to read through the whole thread, so don't know the whole story.  The 6.12mm however does introduce more unknown variables.

[MrTea]

I'll take the current setup and use the stock barrel and see what happens to the FPS. Should give an idea as to whether the barrel is causing significant FPS drops.

If this turns out to not be causing large FPS drops, i'll test the airseal afterwards.

 

Sound good?

[Colin Allen]

1 hour ago, ak2m4 said:

 

I've never run a 6.12mm so can't comment, however I'm guessing it loses a fair amount of power.   I'd love to test one and get my borescope down one.

However I suspect the issue is you're using a full cylinder with a 360mm barrel, you should be using either a 4/5 or 3/4.  You should be able to hit you're required power with a M120 spring. (Unless there's something else I'm missing).  I've not the time to read through the whole thread, so don't know the whole story.  The 6.12mm however does introduce more unknown variables.

I went down the wide bore rabbit hole with an SVD I had many years ago; the drop in power was significant compared to a tight bore barrel.