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Discussion Starter · #1 ·
Hi all, I have an Ares msr700 which I've upgraded from what was absolute mess of a replica.

It's now got an AA cylinder, m150 spring, and SCW trigger and piston.

Problem I'm having is that the front o-ring on the piston has deteriorated twice now, and I'm not sure why.

I don't think that there's much fps/compression loss but that's probably due to the double o-ring design and I don't have a chrono so can't be 100% sure. See the photos attached.


Audio equipment Gas Tool Auto part Coil spring

Hand tool Bumper Office supplies Hood Wood

thats how far back the piston gets held by the 90deg trigger


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Theres also scoring on the rubber seal on the rear end of the piston

Automotive tire Rim Bicycle part Auto part Nickel


This can't be normal for these o-rings to deteriorate like this right?

I'm using wd-40 silicone spray inside the cylinder, and it's not scored at all on the inside or has any debris. I completely cleaned it out and resprayed the silicone spray when I replaced the o ring.


I have a feeling perhaps that it's due to the piston moving back farther than the opening of the cylinder as shown in the image above, and then being forced forward fast against the pressure and maybe its catching on the edge of the opening? But i dont believe this explains the scoring on the rear end, and lack of deterioration on the second o ring.

Looking for any explanations and suggestions as to what I can do to stop or limit this. Any more photos required just let me know


Thanks in advance!
 

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Isn't WD40 a petroleum based lubricant? I would stay away from that since it could make rubber expands. I prefer to use normal silicone oil. They might dry faster, but it's a good thing for me since it makes me service regularly, preventing possible fatal failure by services early.

As for the damages, it might be the cylinder wall has some scratches. Or there might be some metal debris inside the cylinder. My piston with delrin/teflon ring behind it also has those scratches even barely 100 shots after installment, and turns out it's because the latter reason.
 

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Discussion Starter · #3 ·
Isn't WD40 a petroleum based lubricant? I would stay away from that since it could make rubber expands. I prefer to use normal silicone oil. They might dry faster, but it's a good thing for me since it makes me service regularly, preventing possible fatal failure by services early.

As for the damages, it might be the cylinder wall has some scratches. Or there might be some metal debris inside the cylinder. My piston with delrin/teflon ring behind it also has those scratches even barely 100 shots after installment, and turns out it's because the latter reason.
Thankyou for the help.
Just had another look, cylinder wall doesn't have any scratches or debris or anything at all. I will consider getting pure silicone oil instead, however the wd40 I'm using should technically be fine for this purpose I believe.
Automotive tire Fluid Paint Tin Drink


Given that theres no scratches or debris in the cylinder and provided its not caused by the lubricant, I'm leaning towards it being due to the cylinder port.
Would it be harmful to file down/sandpaper and smooth off the inside edges of the cylinder port?
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There's no harm in doing it. Rather, it would only gives you benefit as far as I can think. Just make sure you do it properly and not leaving any burr/debris lest it will worsen your problem.

Also, to make sure, how is your piston in cocked position? If the o-ring goes behind the end of the slot, then it might be well the reason for the damages.
 

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Discussion Starter · #5 ·
The piston does go further than the opening of the slot. It goes back to about here as shown
Hand tool Bumper Office supplies Hood Wood


I will try to smoothen the inside edges of the slot, and of course make sure it's clean before reassembling.

I'll let you know how it goes!
Thank you again for your insights
 

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At this point I'm sure that's the cause. The front o-ring collided with the edge of the slot, the result is it would completely center the piston so that's why the second o-ring is undamaged because it doesn't hit the edge like the first one does.
 

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The front o-ring is probably hitting internal threads of the cylinder.
 

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Discussion Starter · #8 ·
Ahhhh that makes alot of sense. I smoothed down the sharp edges of the cylinder port anyway, but yes that sounds like that is it or is at least contributing.
How can I stop that? Would my only option be to cut the spring or something?
 

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Discussion Starter · #11 ·
Much better I think.
Wedged an o ring that just quite fits into the cylinder right at the front and let the head push it into place when being screwed in against the piston.
Thank you both of you for your awesome advice. You both have helped me solve this final problem (of many) I hope in this headache of a project lol. Cheers
 

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This should make your gun sound quieter too, as it's a dull thud vs a sharp crack.
Even if it's just as loud, it's actually better, as lower sounds travel slower and not as far as high pitched sounds, which is why the MK23 sounds like nothing at a distance.
 

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Discussion Starter · #14 ·
Huh....

Apparently I didn't do enough research lol I have the 308 and went PDI because it's all I could find for aftermarket parts
The msr 338 version? Or something different? Yeah most of the msr parts are vsr compatible apart from the proprietary hopup chamber I believe.
PDI is meant to be pretty good or at least one of the best anyway right?

Edit: oh and trigger is proprietary. Got the SCW msr trigger v3
 

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The msr 338 version? Or something different? Yeah most of the msr parts are vsr compatible apart from the proprietary hopup chamber I believe.
PDI is meant to be pretty good or at least one of the best anyway right?

Edit: oh and trigger is proprietary. Got the SCW msr trigger v3
I got the springer trigger as well, and not mad I got the PDI set.

Moreso just glad it's more compatible than I apparently initially thought, especially with PDI maybe going out of business lol

Edit: yes the 338 not the 308
 

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Discussion Starter · #16 ·
I got the springer trigger as well, and not mad I got the PDI set.

Moreso just glad it's more compatible than I apparently initially thought, especially with PDI maybe going out of business lol

Edit: yes the 338 not the 308
Yeah, compatibility is pretty good I'd say, though this is my first sniper replica so not sure comparatively to others.

How long have you had it and how does it shoot? Do you have any problems with the tdc hopup loosening over time? I can imagine mine will become loose. What nub and rubber are you using?
Thanks

Here are a couple resources I used to learn about it, if you haven't seen already

Fourth paragraph, explains vsr compatibility

Useful information, I think a few problems mentioned have been sorted out in later produced replicas. For example mine doesn't have any stock wobble


This should make your gun sound quieter too, as it's a dull thud vs a sharp crack.
Even if it's just as loud, it's actually better, as lower sounds travel slower and not as far as high pitched sounds, which is why the MK23 sounds like nothing at a distance.
Definitely right, big difference. And with the benefit of reducing wear and tear overall I'm very glad you advised this :)
 

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Yeah, compatibility is pretty good I'd say, though this is my first sniper replica so not sure comparatively to others.

How long have you had it and how does it shoot? Do you have any problems with the tdc hopup loosening over time? I can imagine mine will become loose. What nub and rubber are you using?
Thanks

Here are a couple resources I used to learn about it, if you haven't seen already

Fourth paragraph, explains vsr compatibility

Useful information, I think a few problems mentioned have been sorted out in later produced replicas. For example mine doesn't have any stock wobble




Definitely right, big difference. And with the benefit of reducing wear and tear overall I'm very glad you advised this :)
Got mine like 6 months ago maybe off Evike. Mine had a tiny bit of stock wobble, fixed with a piece of electrical tape between the two parts.

For right now, stock barrel and a PDI W Hold bucking. Ordering a PDI barrel + r hop soon, already have flat VSR buckings to pair that with. + a concave hop arm I found a print file for on here.

I took the TDC screw out and put in a longer one that sticks out a bit from the receiver, if yours does loosen over time just try some blue loctite.

Hoping it fixes the massive air leave I have between the barrel and cylinder, shoots like ass due to that atm so I haven't used it.
 
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