[T4nkcommander]

Hello all. I've been running a BBTac M62 (ASG M40A3 clone) for the past year, and wanted to share what I've learned about the gun so far, since there is a lot of misinformation regarding the platform (and scant correct info about it).

Stock my gun shot 450FPS the first outing, and quickly settled in the 410-430FPS range (1.6J). With hop up nearly maxed, the gun lifted both .36 and .4g bbs out to 200-220ft (laster straight), whereupon they'd fall like a rock.

The gun is easy to disassemble, and the stock hex screws are contained in the stock, making them impossible to lose. The stock is where much of the cost savings happened, and while it is certainly durable enough for play it doesn't feel high quality. Overall ergonomics are nice - to the point where I've gotten to quite like it. Interior part quality is sufficient for the price you pay - not top quality by any stretch, but not bottom barrel stuff either.

While stock performance was borderline impressive for an $80 rifle, I wanted my rifle to reach out quite a bit further. Given I was 1.2J lower than my field limit, I thought this would be pretty easy to accomplish. However upgrading has proven to be a challenge - not because there are not available parts, but because the gun is a mix of systems and no one really has figured out which parts are which. So, I decided to start this thread with my findings, so that others might have an easier time upgrading their rifles if they so desire.

Currently, my rifle is shooting accurately but still stuck at 1.8J - last tested with a Laylax SP170 spring. Seal is good everywhere except cylinder - best I can tell I'm leaking severely past the piston, causing my loss. I am about to purchase some new o-rings to hopefully address this issue.

Stock Specifications
Performance
.4g bb out to 220ft flat, then quick drop (hop up nearly maxed)

Spring

• Length = 8.5in / 216mm
• Outer Diameter (OD) .41 in / 10.5 mm
• Seems to be VSR-10 spec

Piston

• Length = 116mm
• Diameter = 0.75 in / 19.05mm
• Stroke length = 4.5 in
• O-ring is 20mm x 3mm (maybe 3.5mm)
• Inner diameter = ~12mm - does not accept 13mm springs
• 45 degree

Barrel

• Length = 456mm
• Bridged (unbridge with dikes to install Maple Leaf Buckings)

Cylinder

• Length = 9.5in (end to end, not including head nor bolt assembly)
• Diameter = 7/8in / 22.2 mm
• Estimated Volume = 44.34 cm^3 / 2.71 in^3
• APS2 spec
• Custom brass cylinder head (APS2 spec)

Hop Up

• Hop Up unit is VSR-10 clone. Only difference is bucking slit is on opposite side
• Maple Leaf buckings will fit, but will require shortening and removal of slit guide due to above.

Verified Upgrades
Springs

• S&T Upgrade Spring for M40A3 - 500fps when new, quickly dropped to 410-430 range.
• SSG springs do not work, as they are 13mm outer diameter and thus don't fit into stock piston.
• Laylax SP170 Spring for VSR-10 - Fits, and had great power initially. Quickly dropped to 1.8J range with heavy bbs.

Cylinder
- SSG96 Cylinder Head - Seals well without teflon tape, and extends further into the bucking (perfect length).

Hop Up

• Maple Leaf VSR-10 buckings - requires shaving off guide bar and shortening feed-size length. Mr Hop 2020 70 degree and 2021 80 degree work great.
• Action Army Hop Up Chamber - Requires magazine modification, and removes ability to quickly adjust hop up.

Barrel
- Maple Leaf Crazy Jet 430mm

Trigger Assembly
- L96 Trigger Sear - Only the sear itself fits - sear assembly does not.

Possible Upgrades
- Type 96/APS2 Piston - Not 45 degrees, needed for stock trigger-assembly.

Helpful Links

T4nk's Build Playlist
SiliconeSword's Upgrade/Mod Guide
BlackDog's Compatibility List
Jeppe's Notes

 

[T4nkcommander]

Reserved slot for future updates.

Update 1: The problem with this gun - and the cause of low power - is that it uses an APS2 chamber coupled with a proprietary piston. The trigger assembly (presumably to save cost) is 45 degree, instead of the 90 degrees usually utilized by APS2 systems. This requires the custom piston, which in turn doesn't allow normal APS2 springs (13mm OD) to fit. Since the VSR spec springs that do fit are too long, you can't get enough power out of them, even with ridiculously high ones such as SP170 spec.

Possible fixes include:

• Finding a APS2 spec 11mm OD spring
• Converting APS2 piston to 45 (heard some have done this), then installing APS2 spring
• Conversion of trigger assembly to 90 degree, then purchasing APS2 piston + spring

There is supposedly a facebook group dedicated to this gun, if you have a FB account it is probably worth checking out.

 

[T4nkcommander]

Nice work it's good to get some verified info on the platform and work out a good upgrade path as a lot of beginners pick up this rifle as it's cheap and iconic.

Possibly you might be able to use an Aps2 piston and 90' second sear?

Wonder if it's possible to drill new screw/mounting holes in a vsr trigger housing to fit the rifle. As they look very similar.

Also 44cm3 as the volume has to be wrong that's tac41/SRS levels of volume most aps2 stuff is around 30cm3 did you calculate it using the entire cylinder length or just where the piston head would sit from when cocked and the cylinder head?

Thanks! That was my thinking too.

Regarding the trigger - I believe one or two people have done this, although none of them went into detail on the process. I aware of a few people who bought an APS2 Piston and sanded it down to a 45 degree to work with stock trigger too.

Regarding mounting screws - I've wondered the same. It seems possible, but I'm not familiar enough with true VSR trigger assemblies to say for certain.

Regarding cylinder volume, I too thought this was too high. I used the stroke length and the inner diameter of the cylinder (so 4.5in and 20mm). I used an online calculator to convert and do it all for me. I was surprised at the number being so high so I ran the calc several times on different days. One would think if the volume is that high overvoluming the rifle would be trivial.

 

[T4nkcommander]

Used a different calc and got 35.9 cm^3, which seems to be a lot more reasonable. At 430fps, the rifle - coupled with Mr Hop bucking - is able to send a .45g bb flat out to 230ft (maybe up to 250ft), but starts dropping hard after that. With hop dialed up to 60% or so, it can be overhopped to target at 280ft. This seems anomalous to me, especially given seal is solid everywhere past cylinder head. When cylinder head is covered, my gun leaks out the back (towards me), sometimes all at once and sometimes slowly over a few seconds.

When I first installed the Laylax SP170 spring, I had a flat trajectory out to 270ft with .45g bbs, as expected. However, in short order this reduced to 250ft, and energy was chrono'ed to be 1.8-2J with .32, .4, and .45g bbs. I got 2.2J with .2g bbs. Note this was with piston weight increased up to ~50g from the stock 15g, which only appeared to have deleterious affect on power.

Shots 3-7 with .45g bbs, and 8-10 with .2g bbs. Laylax SP170 spring (seemingly defective?)

 

[T4nkcommander]

I'm hoping so. Proper sized replacements are in the mail to me as of today. Also going to run 2 - maybe 3 - for testing purposes. If it isn't that I've no clue what else it would be, unless I managed to get 3 different springs shooting 50-150fps lower than they ought to be.

I am using Ballistol as my lubricant as of right now.

 

[T4nkcommander]

Full seal on my piston - in fact, it is so snug it doesn't want to go past threads. Have about 10g of weight on the piston and my new Laylax SP170 spring in. No chrono at the moment, but I'd be surprised if I made 2.3J based on how it's shooting.

Still only getting to 70m (with .45g) before starting to drop/over hop, depending on setting. Overhopped for decent consistency it drops at 280ft.

 

[T4nkcommander]

Thanks for the kind offer, but I'm done with messing with it. I'm pretty confident everything past the cylinder is in good shape (the Mr Hop will overhop at will, it is just that energy is low).

Curious as to what it chronos - something about the cylinder/piston arrangement doesn't allow it to make much energy at all. Since the cylinder seems to be an APS2 system, it is strange that the power won't increase at all. I can only surmise that since the piston seems to be a one-off that something with it is curtailing the power production. It clearly doesn't like weight being added to it.

 

[T4nkcommander]

On a 170 you should be getting a bit more power then that.

This is my second SP170, same deal. I don't have leaks anywhere so I'm out of ideas.

 

[T4nkcommander]

The stock piston is APS2, but not 90 degrees like I understand the rest are. Thus, the piston is a custom 45 degree piston, designed to fit in the APS2 cylinder. The only successful changeouts I'm aware of were APS2 pistons that were shaved down to 45 degrees.

The stock piston and trigger unit have had no problems with two SP170 springs for over several months now, and a 500fps (supposedly) spring before that. Upgrading this is irrelevant at this point, given that two SP170 springs have proven incapable of bringing the power up.

The issue is that the gun does not produce more than 2J of energy, despite improvents to every area that would impact this. I realize that since the gun is APS2 spec cylinder, shortening the barrel to 430mm from 465mm probably lost me some power, but surely full seal and a beefy spring would substantially offset this? Apparently not.

Previously, the stock oring was insufficient to prevent leak by with my original SP170. With the new oring (Same size best I can tell) the piston is pretty snug. I wouldn't say it is hard to move but it does give full seal like it is supposed to.

The only other thing I can figure is that the cylinder head has not been aligned with the barrel correctly, which caused me to think my previous barrel was bent (it was, but the new one has the same problem)*. I'm going to rectify that, play a game or two with it, and maybe after that toy with piston weights until I purchase a SSG96 or SSG10A2.

As it stands, the gun's stock performance at $80 makes for a great starter gun, but despite dropping $170 into it at this point it shoots only marginally better than it did before. Why I cannot get the energy higher than 2J is beyond me, but from what I've seen nobody else has managed this either.

*Maybe that's not entirely true. I put a second o-ring in a extra groove for testing purposes. It may be causing extra drag. Still, aren't 170s supposed to give 3.3J min? Surely that's not causing a full joule to be lost, especially since this was not an issue previously

 

[T4nkcommander]

What BB weight are you using? 430mm should be .45.or .48g I think, anything lighter and it's wasted air volume.

Also the stock piston is so light I would assume more weight would only help.

Tested both .4g and .45g bbs. Using the latter, anything past 250ft requires a lot of hop. A half setting on my Mr Hop, the bbs will drop 20-30ft starting around 265ft. Crank that up and they might reach 310ft - maybe.

As for the piston - that was my thought too, but so far it has only made things worse. I've yet to get anything but reverse joule creep out of the gun. All of the springs tested with added piston weight (including the first 170) were shooting in the 400-460fps range with .2g bbs, so it appears they were not generating enough energy to compensate for the added weight.

 

[T4nkcommander]

Your using a vsr spec spring aren't you?

Might be why power is hitting a limit around 2j, aps2 springs are longer to keep the piston under a more even amount of pressure, action army t96 springs are 7/11mm so would work, aps2/t96 rifles can reach high joules so the issue appears to be the spring used.

I was wondering about this. How long are APS2 springs? The VSR10 Laylax SP170 spring is about an inch longer than the stock spring prior to install, and the same length after break-in.

 

[T4nkcommander]

An unused action army m150 for type96 is 23.8cm. Luckily I have a spare one in my gun bag.

Given the unused VSR SP170 spring is about 25-26cm new, this could explain why it would be shooting in the 450-480 FPS range, right? I have some DIY FPS adjuster rings I purchased that are 1cm long a piece - thinking maybe that'd help bring the power up now that I have a good seal. I'm hoping the reason this didn't work before is because I didn't have a piston seal previously.

I removed the second oring because it made for a very tight fit, adding a lot of resistance. I now have a very small amount of leakby, but with that and bring the piston weight back down I have gained a marginal amount of range back. I suspect I'm back in the 2J range again - I'll know for sure around Christmas when I borrow my brother's chrono.

 

[T4nkcommander]

Well, my suspicions were correct. Brand new SP170 gave 480 fps. I put one of my spacers in and got it up to 505 fps. I knew based on previous experience a second spacer would not latch, but desperate to get up to 530, I put another one in anyway - no avail.

The spring is already wearing in - it is barely shooting 2J with .2g bbs and 1.5J with .4g bbs, even with a spacer in now.

Varying piston weight (no weight, 1 wrap of lead tape, 2 wraps) made no appreciable difference to the lighter ammo and had a negative effect on the heavier ammo.

If I could find a APS2 11mm/8mm spring powerful enough I think this rifle would sing. Unfortunately, I cannot find such an elusive thing, and thus the power is capped in the 450fps range. The only upgrades that have made a difference is the bucking and spring. Other items are compatible but not worth the cost or effort.

I maintain this is an excellent budget rifle, great for beginners or those wanting to test the waters. I would recommend a bucking upgrade and spring upgrade - nothing else. That would put you at roughly $110 USD for a rifle that can fling .4g bbs flat to 250ftish.

For those wanting a rifle they can build up to 550fps and/or joule creep, this is not the rifle for you.

Now to decide if I'm buying a SSG10A2 or SSG96....