New DPMS SBR Mag Leaking CO2

[FuzzyGrub]

Started leaking out the back of the mag where the hammer hits, after the first shot.  After some lube and valve exercised, still leaked.   Crosman quickly sent out a new one, that works fine.   They said I could keep the defective one, so that meant I can try to fix it. 

It was easy to dis-assemble.  I do see a indentation in the O-ring from where the metal valve sits against it.  I was just going to flip it over, before I destroyed it, not knowing it was captured by the brass ring.      

From the schematic, it is #7-16, CO2-W1-TU, O-ring 1.9mm X 6.8mm (BLUE).  Unfortunately, it is not one of the parts that are indicated as available.  There is the same size O-ring at the front of the valve, but has a CO2-W1-T (GREEN) callout, which shows available.  The blue O-ring is hard, so assume the color difference is a hardness difference, but could also be material.  I'll call crosman on Monday to see if they have it or not.   Might have to try a GREEN vs BLUE, or a BN 90, since I could not find a poly O-ring near that size. 

[johnbrown]

That sure looks like a fun plinker and wanted to buy one for a while.
But, I have too many CO2 BB pistols which shoot around the same 380-420 velocity.
So  besides looking cool the DPMS SBR (or Crosman R1, AK  etc) would not give me anything I don't already have.

[FuzzyGrub]

Yes, it is plinking fun, especially in full auto.  Even in semi auto.  All have/will been converted to use HPA but getting back to CO2 is easy.  This would be just a spare CO2 mag.  For HPA, I use the QR mag which has a built in 300 BB res. 

My chrony won’t read the BB’s so haven’t tested higher pressures.  Others have them shooting much faster than stock.  For me, it might just mean more ricochets. 

[Dave S]

Started leaking out the back of the mag where the hammer hits, after the first shot.  After some lube and valve exercised, still leaked.   Crosman quickly sent out a new one, that works fine.   They said I could keep the defective one, so that meant I can try to fix it. 

It was easy to dis-assemble.  I do see a indentation in the O-ring from where the metal valve sits against it.  I was just going to flip it over, before I destroyed it, not knowing it was captured by the brass ring.      

From the schematic, it is #7-16, CO2-W1-TU, O-ring 1.9mm X 6.8mm (BLUE).  Unfortunately, it is not one of the parts that are indicated as available.  There is the same size O-ring at the front of the valve, but has a CO2-W1-T (GREEN) callout, which shows available.  The blue O-ring is hard, so assume the color difference is a hardness difference, but could also be material.  I'll call crosman on Monday to see if they have it or not.   Might have to try a GREEN vs BLUE, or a BN 90, since I could not find a poly O-ring near that size.

I had a similar problem with one of my mags. I coated the O rings and valve body with Dow Corning MolyKote 111 Di-electric grease. Problem solved! BTW, Avoid using Petrolem based oils as they have a tendency to harden the softer 70 Durometer Urethane O-Rings over time. dave

[FuzzyGrub]

Thx Dave, I'll use some Krytox on the valve and O-rings, once I have a replacement. 

I do think if I didn't ruin it, just flipping it over would have been fine.

This O-ring was "hard" at brand new, though. 

[FuzzyGrub]

FWIW: I stretched a -010 90D Urethane O-ring over the fitting.  Lubed the parts, re-assembled, and no more CO2 leak, and mag is working fine.