[Faitfull]

There is many different platforms and gearboxes out there.

If we where to design a det rifle from scratch, what gearboxes would be the better for dmrs?

I see that people often use v2.5 however rumors go that like the v2. It have a tendensy to crack

V3 and v6 should be durable. V3 have a trigger assemply many dislike to handle in the tech part.
V6 is very easy to work on. However its trigger makes it difficult to have many mags on.
Dont hear so much good on the t3 (svd) however in teory. Motor Cage plus v2.5 cylender.
V7. Some claim it is durable. Some say it is weak like v2.

I find it difficult to figure out, what route to go. I would like to design a dmr from scratch. How much does the longer cylender do? What gearbox to start from.

 

[Leo Greer]

V2.5 is your best bet if you want power above 2.5 joules.

V2 and V3 are your next best in my opinion thanks to the parts compatibility and options.

If you’re not wanting to go over 2 Joules, I’d stick with a V2–you’ll have the most choices and the easiest time working on the hop unit and such, and the V2 has some advantages over others, like a relatively short air nozzle (longer air nozzles make worse DMRs).

I also factor size into my rating, since at my field it doesn’t matter if the replica is an actual DMR caliber, and I can tell you, V2.5 guns are almost always a heck of a lot larger than your standard V2. Since you really shouldn’t be using past a 400mm barrel with your V2, you really don’t end up with a huge gun.

Actually, shorter barrels lengths become more and more optimal the heavier your BBs get (for AEGs), so you can make a DMR with a 300mm inner barrel no problem, and it won’t be less accurate than a longer barrel.

V2 also has the trigger advantage, as you mentioned.

For what actual gearbox to use, figure out what your base gun is and then we’ll be able to suggest better stuff—a lot of stock gearbox shells are really strong, and sometimes better than “upgrade” parts.

 

[Faitfull]

The v2.5
If I get a cyma v2.5, how strong a spring can it handle?

V2.5 is your best bet if you want power above 2.5 joules.

V2 and V3 are your next best in my opinion thanks to the parts compatibility and options.

If you’re not wanting to go over 2 Joules, I’d stick with a V2–you’ll have the most choices and the easiest time working on the hop unit and such, and the V2 has some advantages over others, like a relatively short air nozzle (longer air nozzles make worse DMRs).

I also factor size into my rating, since at my field it doesn’t matter if the replica is an actual DMR caliber, and I can tell you, V2.5 guns are almost always a heck of a lot larger than your standard V2. Since you really shouldn’t be using past a 400mm barrel with your V2, you really don’t end up with a huge gun.

Actually, shorter barrels lengths become more and more optimal the heavier your BBs get (for AEGs), so you can make a DMR with a 300mm inner barrel no problem, and it won’t be less accurate than a longer barrel.

V2 also has the trigger advantage, as you mentioned.

For what actual gearbox to use, figure out what your base gun is and then we’ll be able to suggest better stuff—a lot of stock gearbox shells are really strong, and sometimes better than “upgrade” parts.

 

[Leo Greer]

That’s all dependent on other variables. If you install a decent cylinder head buffer and potentially do things like radiusing, I’d guess the shell could handle up to an M140. However, that’s just my best estimation—sometimes you can have good shells and bad shells. CYMA uses different OEMs for everything but their AKs, so it’s dependent on model how good it is. It even depends between sportline, standard, and platinum of each model.

Unless you have specific FPS goals you’re trying to get to though, I’d think an M130-M140 would be fine as long as you do the rest of it right.

Someone else who has more personal experience with the Cyma SR-25 will be able to give you a better recommendation. I know a few guys have built them out over on Airsoftsociety.

 

[Doctor Jest]

How much power do you need?

I did a quick search and it seems on some fields you're allowed 3.5j on some fields, 2.9j with a 3 second trigger delay on others......the v.2.5 is about 10mm longer than a V2 with the same internal diameter so in theory, it should allow you more latitude. That said, it does have proprietary parts in that the gears have more teeth, the piston is longer, the cylinder is longer of course....

One video:

In terms of withstanding internal stress I believe Classic Army, Matrix and A&K all make shells and should all be good for around an M130 and M140. Retroarms make a CNC V2.5 but there have been reported issues with Retroarms and I have no idea if these are still current or were addressed at some time. Assuming that they are "to specification" then they should manage an M150 or M160......

There was another thread recently about high-powered AEGs and the caveat there also applies here: The Internal stress beyond 2.5j on any build can limit longevity in terms of parts life.

 

[Faitfull]

I am allowed up to 2.89j on my local field with 25m safety, however at 2.25j i have shorter safety at 20m distance at over 2.25

if 2.89j a max of 3 bullets in the air at the same time.

There is no demand for semi locked or delay or looks.

 

[Doctor Jest]

Either a good V2 with a bore-up cylinder, or a V2.5. With decent air seal and perhaps (if you choose) a bit of joule creep you should get to wherever you choose to be fairly reliably. I mean, I ran a V2 + bore-up cylinder +M140 for 2.4j for ages, but equally I've seen people running similar power and cracking their gearbox in a couple of months.

 

[Leo Greer]

You don’t even necessarily need a bore up cylinder, though it can be useful.

 

[Doctor Jest]

I like them just to alleviate some of the gearbox stress when running larger springs tbh mate. M130 and upwards for a DMR build...the MSG-90 was a case in point as the barrel was pretty darn long and I ran lighter BBs at the time (.29s for their sheer amazing accuracy) but they're not essential, just an option.

 

[Leo Greer]

Above M130 I think that makes sense. I just don’t usually want to go above M130! Actually, some of the time I’m wanting to use a stronger spring, since everything I have shoots ~30RPS and PME is an issue.

 

[Doctor Jest]

Understandable, for my MP5k (300 fps or so with a .2g) it's still got an M120 in there for that reason.

 

[Leo Greer]

This M4 I’ve been working on came with a ridiculously heavy piston, so it’s been a chore taking the weight down. I won’t knock Arcturus for making their piston indestructible, but if you get PME going over 23 RPS it needs some help.