A&K Masada SPR - DMR Theory Crafting

[RostokMcSpoons]

@MrTea, I nearly went to Halfords too, as I need a spade connector to resurrect my Classic Army M16. I realised I didn't know if they had the right ones - what size do I need to ask for?

 

[MrTea]

@MrTea, I nearly went to Halfords too, as I need a spade connector to resurrect my Classic Army M16. I realised I didn't know if they had the right ones - what size do I need to ask for?

I used these.

These should also work.

I will say, the actual spade connector which goes onto the motor tab is crimped a touch too tight and I had to use a small flathead to pry them open a bit more so they went onto the motor tab without forcing it on and potentially damaging the motor. If you don't have one already, i'd suggest getting a crimping tool.

 

[Haru]

i needed spade connectors too I just got mine from ak2m4

 

[MrTea]

New hop unit from AirsoftPro ordered. Hopefully this one actually works. Prolly going to take 2 weeks to arrive so the DMR won't be viable for my next outdoors session.

 

[MrTea]

The hop unit from AirsoftPro arrived and was installed. Went in like a treat with none of the issues from the Wiitech one. What I didn't do is change the nozzle to the AirsoftPro one because I was short on time and just wanted to see if the hop unit fit.

I decided to do some testing to get some initial FPS readings and it's not good. The single highest FPS reading I got was 274.4fps on 0.36g (1.26joule) which is 368.3fps on 0.2g. In addition to the low FPS, it's also massively inconsistent with a ~50fps difference between the highest and lowest FPS reading. I'll have to go back into the gearbox and use the AirsoftPro loading ramp and nozzle to see if it makes a difference in the FPS in testing. The airseal from the compressions parts (with the nozzle on too) was great when I tested during installation so I know that's unlikely to be the issue. For reference; the limit on 0.36g is 313fps (420fps on 0.2g) or 1.64 joules. As long as i'm over 300fps on 0.36g with a max variance of 3-5fps i'll be happy.

Fixing the inconsistency is key in my mind. If the FPS was consistent but low, I wouldn't mind. Boosting FPS is easy through spring strength, it's the inconsistency that's got me wondering.

In other news; the spring guide for the A&K Masada SPR is a non-standard size. I ordered a QD bearing spring guide and that's also too big. I measured it with calipers and cannot find any spring guide with a similar size. I've also 'shimmed' the inner barrel to the outer and that thing is rock solid now, zero movement at all.
 

View attachment 116393

 

[MrTea]

Back again and i'm moving in the right direction, FINALLY. I sat down this morning after mulling over my options and remembering someone having a somewhat similar issue with their AEG being massively inconsistent and it turned out their bucking was causing the issue. I stripped the rifle and disassembled the hop unit.

Here's what the hop unit looks like with the ML MR Hop rubber installed.

View attachment 116744

 

I took the hop unit apart and compared it to the stock hop rubber as seen below. Apologies for the poor focus.

View attachment 116745

Interestingly the stock hop rubber is a few millimeters longer than the ML MR Hop rubber. I put the stock hop rubber into the hop unit and as you can see below, despite being longer, the feed lips(?) don't protrude into the hop unit as far.

View attachment 116746

I PTFE taped the hop rubber and hop unit in keeping with my first attempt at assembling the hop unit just in case the PTFE was somehow causing my issues. I rebuilt the gun and went to test it on 0.2g BBs and then 0.36g BBs. Results are below;

View attachment 116747

Now i'm getting somewhere! Interestingly the power has gone UP from before and, thankfully, it's consistent! I'm impressed that on 0.36g BBs i'm getting 3.2fps difference across 20 shots, that's probably my best yet of any of the AEGs i've worked on.

My issue now is; does this gun require a different length or type bucking to work correctly or is possibly just the ML MR Hop rubber causing issues? As for the power it's producing, i'm aware it's well short of the 420fps on 0.2g BB (313fps on 0.36g)/1.64Joule limit i'm looking for and I do have an M150 spring kicking around in my spares box somewhere. I would have slapped it into the gearbox but my screwdriver fell to bits on me this morning and i'll have to wait for another to arrive on Sunday which is a bit annoying but still... progress!

@Leo Greer I'd like to pick your brain over the hop rubber issue. Have you ever ran into anything like this before? Should I just try trimming the feed lips by a millimeter or two so it matches the stock bucking length when installed?

 

[Lozart]

Maple Leaf rubbers quite often have rather long feed lips. You could try GENTLY sanding it down to the point that it feeds OK. Can be a bit of a gamble if you take too much off and knacker your airseal.

Alternatively you could flat hop or R-Hop with a prommy rubber.

 

[Adolf Hamster]

Can be a bit of a gamble if you take too much off and knacker your airseal

There's also ensuring that the lips remain square and dont have blemishes etc that could cause an air leak.

much like trimming a nozzle its often easier to just buy a different part.

Interestingly the stock hop rubber is a few millimeters longer than the ML MR Hop rubber

It's relatively common to see some variation in what for want of a better term i'm going to call skirt length on a hop rubber.

Too long generally is an issue if you can't get the c clip to stay put, within reason shorter is ok.

My issue now is; does this gun require a different length or type bucking to work correctly or is possibly just the ML MR Hop rubber causing issues?

Some guns just dont like some buckings, typically i like pdi w-hold when a gun doesnt want to play ball with maple leaf, although certainly at 1j the w hold can struggle to lift north of ~.32's, you might be ok at dmr power though.

 

[MrTea]

@Lozart @Adolf Hamster

Thanks for the insight, i've never ran into this issue so it's a new one for me and all the previous ML stuff i've used has just worked a treat. I've got two ML MR Hop 70 degree buckings so I might try "adjusting" the lips of the bucking to see if I can improve feeding.

As for the PDI W-hold, the stock bucking looks pretty similar in it's contact patch/mound shape.

I'm at a bit of a loss as for what other buckings/nubs to use in a flat-hop setup (if I screw up fixing my current buckings). I know Prommy/Laylax sell a hard (red) flat hop bucking and the pack of two nubs but i've seen some forums posts elsewhere saying that Prommy purple is more than enough for 400-450fps with a hard flat hop nub.

 

[Leo Greer]

On the ML issue, Lozart and Adolph pegged it—you can try sanding the lips, but ultimately it’s a spec issue. ML rubbers are designed to fit Taiwanese units like Maxx, G&G, etc. 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.

I would personally suggest either flathop ping the stock rubber as a free try, or buying a flathop rubber. I don’t have experience with the unit you’re using, so I’m not sure what exactly will fit the best, but you can flathop pretty much any rubber.

The PDI W-Hold is usually contained with units that don’t like ML, and so are the Modify Flathop rubbers. Prommy should fit as well (I’d recommend purple), but they tend to be kinda expensive. And, of course, you can always just buy stock rubbers that are made from half-decent material like Guarder, Arcturus, G&G (similar to ML but may fit better), Krytac Blue and Orange, etc. Flathop really depends on the rubber and the nub, so the current contact patch shape doesn’t matter.

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.

 

[MrTea]

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.
 

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

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]

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

They are in the Czech Republic.

 

[Leo Greer]

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]

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:

View attachment 130797

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:

View attachment 130799

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

 

[Leo Greer]

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]

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.

 

[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]

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.

 

[grumio]

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?