I'm sure some of you have seen this post in the Facebook groups, but in coming here to hopefully reach eyes that aren't on Facebook. I'm really hoping that there IS something wrong that I can fix and that I am not going to have to run some extreme LPR pressure and CDEL. There are plenty of MQ2 halfblock builds I see that don't mention these issues. A super high LPR pressure and CDEL value doesn't really work anyway as a solution. Maxing both out will get me to velocity, but I still have insane blowback up the feedneck. Here's the troubleshooting I've done so far. This is the post copied from Facebook. Please read it all as it shows that I've crossed off issues like regs and seals (to some extent).
Long one here, but please read and help if possible. My bolt is moving back BIGLY when firing leading to low velocity and big blowback***!!!¡¡¡!!!
I need help with a problem on a MQ2 halfblock build where I'm experiencing blowback with the bolt and back block moving back nearly the full stroke of the ram when firing even though the cocking noid is unplugged!!!! This is a freshly assembled and back from ano. The MQ2 and sci-fi were pulled from another working build I've been running for a season with very conservative timing for a soft shot. Some specs:
MQ2
Half block
Evo ram with two PE QEVs
AKA SCM III LPR
AKA 2L+ low pressure spring
Eclipse pops V2 ASA
Inception trident halfblock bolt. I tried a resurrection bolt and another halfblock bolt that didn't have a front o-ring groove but had o-rings around the inlet port and had grooves for the detents. This 3rd bolt and the resurrection bolt were better than the trident by about 20fps, but still showed insane blowback and low velocity because of it.
Timing:
SON 3ms
CDEL 5ms
CON 60ms
COFF 36ms
When firing a ball the back block shoots back in reaction to shooting the ball, velocity is low around 230-250 FPS, and there is massive blowback that shoots the next ball out the feedneck. Jacking up the LPR really high increases the velocity and can get me to 300fps. This is because there is more pressure holding the ram forward during the firing process. I do not want the ram jacked up. That defeats the purpose of the MQ and I could always use a low LPR pressure before with much more reciprocating mass and the same regs. This wouldn't address the blowback issue either.
It seems like air is blowing by the internal ram shaft o-ring. Upon removing the front plug and listening there was no air leak. When I forcibly pull the bolt and sled back the ram shaft maintains the seal. No air comes out the plug or front QEV exhaust. If any air exhausts out the front or rear QEV when I pull the sled back it's out the rear QEV as you'd expect. I put some grease over the rear QEV exhaust port and pulled the sled and bolt back to make sure the air exhausted out the rear QEV and pushed the grease out. It did. The front QEV will suck some air in and let it go back out when I pull the bolt assembly back. This is visible by watching the grease I shoved in it's exhaust hole.
I've sprayed soap water all around the ram, LPR, ram, and QEV assemblies. There is a very, very small air leak around the o-ring between the rear QEV and ram body. It is very, very minimal and only visible with soap water. There are no other audible or visible air leaks. The u-cup seal doesn't bubble at all at rest or when I pull the bolt assembly back. The u-cup seems to be sealing tight against the ram shaft.
The LPR seems to be functioning. I can lower it and the bolt pulls back easier. Raising the LPR will eventually cause the cocking noid to leak. This indicates it's changing the pressure. The AKA 2L HPR affects velocity with changes made, and it will cause the MQ2 to vent when raised to high. I also tried another known working 2L reg. It made no difference. I've tried 2 cocking noids but have more.
I have unplugged the cocking noid from the board, manually loaded a ball in the chamber, and shot many times. You can see the bolt move back in this state when firing even though there is no power to the cocking noid. If I hold the bolt forward with my finger and have 2 balls in the feedneck the ball with shoot at velocity and as high as 330FPS depending on where I have the reg set. The balls in the neck will not blow out. This tells me that the bolt o-rings are sealing the chamber, but the force of shooting the ball is moving the bolt back, causing low velocity, and causing massive blow back.
I'm at a loss. I've tried different cocking noids, ASAs, and HPRs. I pulled the rsme apart and installed a new shaft o-ring and bumpers. Could the manifold be imperfect and leaking internally between ports on top of the cocking noid manifold? Could there be blow by in the ram or out its cup seal ONLY when firing from the instant high impulse of the shot? This seems unlikely. Could something be wrong with the LPR that causes its pressure to drop during a shot when a lot of air goes out the valve? Please help.
This video is ⅛ speed shooting a ball with the cooking noid unplugged and LPR higher than I'd like.
Long one here, but please read and help if possible. My bolt is moving back BIGLY when firing leading to low velocity and big blowback***!!!¡¡¡!!!
I need help with a problem on a MQ2 halfblock build where I'm experiencing blowback with the bolt and back block moving back nearly the full stroke of the ram when firing even though the cocking noid is unplugged!!!! This is a freshly assembled and back from ano. The MQ2 and sci-fi were pulled from another working build I've been running for a season with very conservative timing for a soft shot. Some specs:
MQ2
Half block
Evo ram with two PE QEVs
AKA SCM III LPR
AKA 2L+ low pressure spring
Eclipse pops V2 ASA
Inception trident halfblock bolt. I tried a resurrection bolt and another halfblock bolt that didn't have a front o-ring groove but had o-rings around the inlet port and had grooves for the detents. This 3rd bolt and the resurrection bolt were better than the trident by about 20fps, but still showed insane blowback and low velocity because of it.
Timing:
SON 3ms
CDEL 5ms
CON 60ms
COFF 36ms
When firing a ball the back block shoots back in reaction to shooting the ball, velocity is low around 230-250 FPS, and there is massive blowback that shoots the next ball out the feedneck. Jacking up the LPR really high increases the velocity and can get me to 300fps. This is because there is more pressure holding the ram forward during the firing process. I do not want the ram jacked up. That defeats the purpose of the MQ and I could always use a low LPR pressure before with much more reciprocating mass and the same regs. This wouldn't address the blowback issue either.
It seems like air is blowing by the internal ram shaft o-ring. Upon removing the front plug and listening there was no air leak. When I forcibly pull the bolt and sled back the ram shaft maintains the seal. No air comes out the plug or front QEV exhaust. If any air exhausts out the front or rear QEV when I pull the sled back it's out the rear QEV as you'd expect. I put some grease over the rear QEV exhaust port and pulled the sled and bolt back to make sure the air exhausted out the rear QEV and pushed the grease out. It did. The front QEV will suck some air in and let it go back out when I pull the bolt assembly back. This is visible by watching the grease I shoved in it's exhaust hole.
I've sprayed soap water all around the ram, LPR, ram, and QEV assemblies. There is a very, very small air leak around the o-ring between the rear QEV and ram body. It is very, very minimal and only visible with soap water. There are no other audible or visible air leaks. The u-cup seal doesn't bubble at all at rest or when I pull the bolt assembly back. The u-cup seems to be sealing tight against the ram shaft.
The LPR seems to be functioning. I can lower it and the bolt pulls back easier. Raising the LPR will eventually cause the cocking noid to leak. This indicates it's changing the pressure. The AKA 2L HPR affects velocity with changes made, and it will cause the MQ2 to vent when raised to high. I also tried another known working 2L reg. It made no difference. I've tried 2 cocking noids but have more.
I have unplugged the cocking noid from the board, manually loaded a ball in the chamber, and shot many times. You can see the bolt move back in this state when firing even though there is no power to the cocking noid. If I hold the bolt forward with my finger and have 2 balls in the feedneck the ball with shoot at velocity and as high as 330FPS depending on where I have the reg set. The balls in the neck will not blow out. This tells me that the bolt o-rings are sealing the chamber, but the force of shooting the ball is moving the bolt back, causing low velocity, and causing massive blow back.
I'm at a loss. I've tried different cocking noids, ASAs, and HPRs. I pulled the rsme apart and installed a new shaft o-ring and bumpers. Could the manifold be imperfect and leaking internally between ports on top of the cocking noid manifold? Could there be blow by in the ram or out its cup seal ONLY when firing from the instant high impulse of the shot? This seems unlikely. Could something be wrong with the LPR that causes its pressure to drop during a shot when a lot of air goes out the valve? Please help.
This video is ⅛ speed shooting a ball with the cooking noid unplugged and LPR higher than I'd like.
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