A&K Masada SPR - DMR Theory Crafting

[MrTea]

As i've posted within the "what have you just bought" thread, i've bought an A&K Masada SPR/DMR from another player however it's still got full auto and is at AEG limits of 350fps. I've been theory crafting a shopping list for turning it into an actual DMR. The different playstyle and technical challenge of making something reliable/consistent enough to be used as a DMR should be fun however, as always when doing something new, I would appreciate advice from those more experienced with this type of thing.

View attachment 112459

This is how it's currently looking. As always, any and all advice appreciated.

 

[Leo Greer]

Your list looks pretty good to my eyes.

There's probably no need for a delayer chip, but I've been wrong before...

I would personally recommend a Guarder spring, as I know AK2M4 has them, and they're incredibly consistent. I've easily gotten ~1 FPS variance out of AEGs using Guarder.

For the inner barrel, I would recommend polishing the stock barrel first and testing performance before you spend money, as stock barrels can be just fine a lot of times. Barrels are a lot of money for very little improvement over polished stock. In terms of what aftermarket barrel to go with and what inner diameter, you can build extremely accurate builds out of either end of the spectrum. I would personally recommend hunting down a Lambda SMART 6.08mm as the best balance of cost, performance, and forgiving inner diameter. For reference, Lambda are people who left PDI, so it's PDI performance at far cheaper prices, and with better hop windows.

I should note, you seem to be looking at very long barrels, which most likely won't be suitable for DMR BB weights. For reference, at those lengths, you have enough air volume for .2g or .25 if your setup is very efficient. You'll be wasting power and accuracy shooting DMR weights.

And finally, in my experience, the vast majority of your accuracy gain comes not from spring power, hop rubber, or barrel, but from stabilizing the inner barrel and hop unit inside the upper receiver, as well as making sure you have no nozzle wobble, and your hop arm is stabile as well.

I did a full write up on airsoft accuracy and accurizing a while back HERE for a more in-depth discussion.

 

[MrTea]

Thanks for the reply!

Delayer chip: That was my train of thought too. For £2 it's worth picking up just in case.

Guarder Springs: These are SPxxx springs. Should I use a SP120 or SP130 or just buy and test both?

Barrels: thanks for the info and suggestions. The barrel lengths I'm looking at are the stock barrel length which comes with the gun. I will look into potentially lapping the barrel depending on what the condition is like.

I'll read your link to try and learn more about stabilising the hop, nozzle, hop arm and inner barrel.

 

[Leo Greer]

Thanks for the reply!

Delayer chip: That was my train of thought too. For £2 it's worth picking up just in case.

Guarder Springs: These are SPxxx springs. Should I use a SP120 or SP130 or just buy and test both?

Barrels: thanks for the info and suggestions. The barrel lengths I'm looking at are the stock barrel length which comes with the gun. I will look into potentially lapping the barrel depending on what the condition is like.

I'll read your link to try and learn more about stabilising the hop, nozzle, hop arm and inner barrel.

In general for "SP" springs, they're about the equivalent of the "M" rating + 20. So an SP100 = M120. Vaguely. I would personally go SP120 and see where you land before spending more, but it's nice to have extra springs onhand anyways.

In your case, it may be worth using a shorter-than-stock barrel, depending on how heavy of ammo you're wanting to fire. For the spring strength you're looking at, I'm assuming you'll be shooting .36g or higher, which would seriously undermine your power if you use such a long barrel.

 

[MrTea]

In your case, it may be worth using a shorter-than-stock barrel, depending on how heavy of ammo you're wanting to fire. For the spring strength you're looking at, I'm assuming you'll be shooting .36g or higher, which would seriously undermine your power if you use such a long barrel.

You'd be correct about the BB weight. I was planning on using 0.36G.

For the barrel, I can't measure the stock one until it arrives in the post but listings online are stating 509mm.

How much of a reduction in length are we talking about?  Would this make it harder to stabilise the inner barrel inside the outer barrel or is the tape method mentioned in your linked post still applicable?

Secondly, my understanding is this where "bore-up" sets come into play specifically to avoid the reduction in performance with longer barrels however I've seen loads of conflicting comments from people saying that you only need bore up for 600mm+ and some saying they're used when your barrel exceeds 450mm+ The current cylinder I was planning to use is one without any ports and is advertised as being suitable for 450mm - 660mm barrels. Checking different brands I see a similar cylinder length and internal diameter and they're advertised as being suitable for 450mm-550mm barrels.

Thanks for the advice so far and continued help.

 

[Leo Greer]

You'd be correct about the BB weight. I was planning on using 0.36G.

For the barrel, I can't measure the stock one until it arrives in the post but listings online are stating 509mm.

How much of a reduction in length are we talking about?  Would this make it harder to stabilise the inner barrel inside the outer barrel or is the tape method mentioned in your linked post still applicable?

Secondly, my understanding is this where "bore-up" sets come into play specifically to avoid the reduction in performance with longer barrels however I've seen loads of conflicting comments from people saying that you only need bore up for 600mm+ and some saying they're used when your barrel exceeds 450mm+ The current cylinder I was planning to use is one without any ports and is advertised as being suitable for 450mm - 660mm barrels. Checking different brands I see a similar cylinder length and internal diameter and they're advertised as being suitable for 450mm-550mm barrels.

Thanks for the advice so far and continued help.

Hop over to THIS thread for a more detailed discussion on what BB weight goes with what barrel length. The stabilization method still works fine.

"Bore up" is an unspecific term. Without knowing the diameter increase and being able to calculate the true increase in air volume, it's impossible to know. It's also related to BB weight--heavier BBs require more energy to accelerate and accelerate more slowly, thus requiring more air volume.  You could use a bore up kit for a 350mm barrel shooting .48g and be correctly volumed.

The full cylinder is suitable for a 450mm barrel... but only when using light weight BBs. Keep in mind that a lot of this advertising is written by people who don't know much about it--660mm is crazy long, and you're losing power even on .20g with that long of a barrel.

As a note, voluming rules can be played by loosely. There are so many factors here, and the exactitudes don't matter as much as being in the general vicinity.

 

[MrTea]

Having had a quick read over that, the writer is saying the ideal barrel length (for a non ported cylinder) is 380mm when using 0.36g BBs where the cylinder to barrel volume ratio is 2.48:1.

Using the calculator they linked, I've input the cylinder size that I was planning on buying 23.7mm inner diameter X 72mm length minus the length of the cylinder head/piston. While i'm not sure on the exact size, i'm using the 12mm measurement they provided in the article.

Using the calculator, assuming I'm using 6.03mm barrels, the 380mm length they specify gives a ratio of 2.44:1. I tweaked the barrel length setting until I got the 2.48:1 ratio and ended up with a barrel length of 374mm. The writer also states that AEGs are 'forgiving' and during their testing you can go 50mm each way with only approx 0.05joule loss which would take me up to a maximum of 424mm.

Am I using this information and the tools provided correctly or is the lack of sleep after a night shift addling my brain?

If I buy an ideal barrel length of 374mm (or similar) within the plus/minus 50mm range depending on what is available, what are the chances of the BB striking the inside of the outer barrel?

Edit: I've updated the shopping list with the relevant barrel choices moving forward. If you wouldn't mind casting your eye over it. I tried finding Lambda SMART ones in stock but had no luck.

 

[Leo Greer]

Your math looks correct to me.

There's basically no chance of it striking the outer barrel... unless something goes seriously wrong.

Your choices on barrel all look suitable to me. I would be wary of PPS, since I've heard that some bad things about their barrels in the past, but it's the cheapest of the bunch so that gives it some "try and see" merit in my eyes. You may also have trouble getting the ML rubber to work with the PDI hop windows, but you could always go flathop, or use a Macaron and make it work easily.

One question I do have; have you done any research on the durability of the stock gearbox shell? Most are okay, but when boosting power up this high it's always something to consider.

 

[MrTea]

You may also have trouble getting the ML rubber to work with the PDI hop windows, but you could always go flathop, or use a Macaron and make it work easily.

Is the contact patch too big for some barrel windows on the ML MR hop rubbers for brands like PDI or is it PDI have a smaller window? I usually use ML Macaron in everything I build as it's always served me well but fancied trying out their MR hop rubber.
 

One question I do have; have you done any research on the durability of the stock gearbox shell? Most are okay, but when boosting power up this high it's always something to consider.

Yes and no. I've read that 'Radiusing' the gearbox is, more than likely, necessary however given it's a standard V2 gearbox shell i'm not too bothered if I prematurely destroy it. Also, given it's made in China and the stock parts on the gun are pretty crap (i.e. the nozzle, piston, spring guide etc.) it wouldn't surprise me if the gearbox shell is also crap. I've pulled a gearbox from an A&K Masada before and it felt like one of the poorest quality ones i've handled and had stange marks on the outside and inside, pic related from the boneyard Masada AR I bought ~6 month ago;
 

View attachment 112478

I didn't jack up the wiring or double up the spring in the gearbox which is shown in the picture, that was all the previous 'tech' who 'fixed' the gun.

Thanks again for all the help. Hopefully in a month or two i'll be back with an update on the build.

 

[Colin Allen]

A&K gearboxes are not great; the alloy is rather soft, making it very easy to strip threads.  That would not make me hugely confident regarding their durability at higher powers.

I have two of their Masadas; neither of them has the original gearbox.

 

[MrTea]

A&K gearboxes are not great; the alloy is rather soft, making it very easy to strip threads.  That would not make me hugely confident regarding their durability at higher powers.

I have two of their Masadas; neither of them has the original gearbox.

Looks like i'm going to be the experiment then. Can you can remember how long yours lasted at 350fps or did you change it prematurely? I'm still running the stock gearbox shell in the AR version and i'll try seeing long the stock gearbox shell lasts in the DMR version obviously checking it after each time I play.

 

[Colin Allen]

Looks like i'm going to be the experiment then. Can you can remember how long yours lasted at 350fps or did you change it prematurely? I'm still running the stock gearbox shell in the AR version and i'll try seeing long the stock gearbox shell lasts in the DMR version obviously checking it after each time I play.

I changed them because threads kept stripping so I cannot really offer any guidance; you are indeed the experiment.  However, I guess that being somewhat soft might be better than being brittle when it comes to resisting cracking.  Just remember to radius those front corners!

 

[MrTea]

I guess that being somewhat soft might be better than being brittle when it comes to resisting cracking.  Just remember to radius those front corners!

That's what I was thinking. Most people associate weak gearboxes with brittle rather than soft metal. Radiusing was always on the cards as it's such an easy thing to do to alleviate pressure on the gearbox shell and it's basically just rounding the corners of the shell where the cylinder head meets it, especially when the gearbox is going to need totally stripping for cleaning anyway. When I took apart the AR Masada gearbox and cleaned it, my hands were black afterwards. I had to use 'industrial cleaner' to get the crap off. Not sure what they're using inside the gearbox for lube but it's awful to clean.

 

[Leo Greer]

Lemme ask around and see if I know anyone who's used ML rubbers with PDI barrels--I know the shape of the window is a little weird, but I haven't tried it out myself, so no hard statements.

 

[Adolf Hamster]

Lemme ask around and see if I know anyone who's used ML rubbers with PDI barrels--I know the shape of the window is a little weird, but I haven't tried it out myself, so no hard statements.

I've used macarons with pdi, cant say had any real issues.

 

[DerDer]

From what I remember there were several different cuts of window in PDI barrels. Was one of the reason why they were a bit of a nightmare to R-Hop, together with the angles of certain cuts.

 

[concretesnail]

I've found zci barrels very good and solid fit with maple leaf rubbers when it comes to the window. I used them for a dmr setup and again when I changed the barrel length.

 

[MrTea]

I've found zci barrels very good and solid fit with maple leaf rubbers when it comes to the window. I used them for a dmr setup and again when I changed the barrel length.

I use them on my other stuff and tbh it's decent for the price except their longer barrels are a pretty penny and come into range of other, better, brands. You might be interested to know that AK2M4 is making (or getting made) his own inner barrels and they're supposed to be a similar price point to ZCI while having an ever better internal polish, he's calling them "XT standard and XT performance. He even bought a scope cam to show off the internal of the test pieces. Supposed to be arriving in September. Here's a link to his FB page where he shows the inner surface of stock brass, aluminium, ZCI and the test pieces he's received so far.

My only gripe with ZCI is that they only make 6.02mm as far as I know.

 

[concretesnail]

If ak2m4 is doing his own barrels then I'd be tempted to try those too to be fair. Ak2m4 is my usual go to for parts. 

 

[MrTea]

If ak2m4 is doing his own barrels then I'd be tempted to try those too to be fair. Ak2m4 is my usual go to for parts. 

Same. For the few times i've spoke to him, he's always been helpful and insightful. Couldn't fault the guy over anything so far. I'm hoping he gets those new barrels in soon