My TM VSR Doesn't Make Sense

[Styrak]

OK, so I have a TM VSR GSPEC, and stock (how I got it), it was shooting around 400fps on stock parts except the spring. I added some parts and it's shooting LOWER!

I bought:
Laylax PSS10 M150 Spring
Laylax PSS10 Bearing Spring Guide
Laylax PSS10 6.03mm Barrel
Laylax PSS10 Zero Trigger Set

Now, first of all I found that the Zero Trigger piston was binding in the stock TM cylinder ($250 trigger/piston set, what the fuck?), so I had to sand down the (what I assume to be) delrin/plastic guides on the side so that it would freely float back and forth inside the cylinder. This was my first reasoning behind the low FPS, but like I said I sanded it and still the same results.

After adding these parts (minus the tightbore, because I wanted to compare apples to apples) it was shooting around 380fps, 20fps lower WITH AN M150!

After doing said sanding and making sure the piston didn't have any interference with the cylinder, I put it together and got the same results.

I swapped the TM piston back in and got 440-450fps. Wat.

I swapped the Zero Trigger piston back in, and put on the stock TM oring, and the best I could get it up to (including installing the tightbore) was about 430fps. I would assume with the M150 it would be closer to 480 or 500fps.

My last thought which I haven't done anything about, is that I'm using a Firefly soft hop rubber (I know, but hards are out of stock everywhere). Would this be a factor in that it isn't holding onto the BB hard enough so the piston can impart enough energy on the BB?

Any suggestions would be helpful, thanks. Right now I have all the parts in except I'm using the stock TM piston @ 430fps.

[bean]

Are you using the air brake the bit that screws into the piston. That can drop FPS. That's all I can think of. I put the Laylax cylinder in mine when I built one and the stock in another. Both ran great.

[Drakker]

Did you test the airseal with the Laylax piston? Assemble the trigger set with the receiver and the cylinder and cylinder head. Cock it, put your finger on the nozzle to block the airflow and shoot. If the air seal is good the piston should move slightly forward then stay in place. If it keeps moving forward, even very slowly, you have an air seal problem and it could explain the lower FPS.

Also, what weight of BBs are you using to chrono? My G-Spec, with the stock barrel and perfect air seal shots 370 fps with .20g, 370 fps with .25g, 365 fps with .30g. You read that correctly, that's the equivalent of around 445 fps with .20g when shooting .30g BBs.

The G-Spec has a lot of over volume, so in mine the air brake doesn't seem to affect FPS much if at all. It might be worth it to try to remove it though.

[Hectic]

also if not using the airbreak, is the grub screw in the piston? There is a hole in the center of the piston if.its not plugged up it will leak like crazy.
also is the spring installed with the tighter coils at the spring guide

[Styrak]

Not using the airbrake, using the grub screw. Also yes I have to test the airseal.

Drakker, I was chronying with 0.20's at 430fps, and when using 0.30's it was at about 370-380fps which made sense.

[Ricochet]

Check how your cylinder head seats into the hop-up chamber. Have you switches out buckings for an after market one? The upgrade buckings, such as the firefly, are slightly larger, and I find produce a better airseal with the upgrade cylinder sets.

[Styrak]

Originally Posted by Ricochet

Check how your cylinder head seats into the hop-up chamber. Have you switches out buckings for an after market one? The upgrade buckings, such as the firefly, are slightly larger, and I find produce a better airseal with the upgrade cylinder sets.

My last thought which I haven't done anything about, is that I'm using a Firefly soft hop rubber (I know, but hards are out of stock everywhere).

Yes I'm using a Firefly soft. I haven't changed the cylinder or cylinder head, it's stock TM.

[Hectic]

i think i.know what your problem is. Its a gspec. The short barrel in the gspec had a negative effect on fps. The cylender in the vsr is perfectly matched for an inner around 500mm, shorter barrel = wasted compression = low fps numbers (hence why once u increase bb weight your losses are far less) try some 36's see how those work for you. Ill try to dig up the link for a custom build a guy did with a gspec. What he did was shorten the compression (by porting the cylender) the shorter he made it, the less waste the higher the fps.

[Hectic]

i dunno, my google fu is lacking and the times i have posted about it here havemt shown up in my old posts or in a search.
however, i do know that all things the same internally, going from a 330-500mm inner has netted about 100fps the same goes for extending the window on the cylinder (to shorten the compression zone) to compensate for a shorter inner.
if u have one that u can use try stickin a longer inner in and see how much fps u gain. Its crazy really. Going from a 500 to a 455 in my gun lost me about 25fps so goin to a 330 in theory would loose me about 85

[bean]

That would be why I never had this issue I put a longer barrel in mine right off the batt.

[Styrak]

Originally Posted by Hectic

i think i.know what your problem is. Its a gspec. The short barrel in the gspec had a negative effect on fps. The cylender in the vsr is perfectly matched for an inner around 500mm, shorter barrel = wasted compression = low fps numbers (hence why once u increase bb weight your losses are far less) try some 36's see how those work for you. Ill try to dig up the link for a custom build a guy did with a gspec. What he did was shorten the compression (by porting the cylender) the shorter he made it, the less waste the higher the fps.

Hmm, looking at the BB Bastard MSED, a 0.30 at 370fps is equivalent to a 0.20 at 453fps, but I chrony 0.20's at 430fps so it's affecting it a little. But I should still be up near 480-500 with that spring. Not that I would do it, but would porting the cylinder bring me back up to standard rates?

Things to test now I guess would be compression, and a longer barrel if I can find one.

[Hectic]

yup, porting will fix the issue (if all else is good)
i really wish i could.find the link for u so you could see the data its quite impressive lol.
easiest "test" would be a longer inner. Thats why i went to the pss hop up for easy barrel selection lol. But the vsr is prety good for airseal so i doubt thatsmuch of an issue unless u got a wonky piston (i know the rings were off sized u said so something.else could.be off too)

[Hectic]

heck yeah!! i found it lol.
scroll down a ways youll see the results of porting the cyl. so its matching the barrel volume

[ThunderCactus]

if you're getting the equivalent of 450fps with .30s and only 420fps on .20s, it just means you have joule creep. Which is GOOD because it means for SURE that you can enough air volume to make use of your barrel length.
besides, you're not using .20s so who cares what the performance is like on .20s?

[Hectic]

i agree TC, thats why i suggested tryin some.36's if you get that 370-375 range yer right on target with yer 500ish on .20's with tue heavier bb traveling slowwer may make better use.of the short barrel/big cylender