Recent content by nervoustrig

Short answer: Yes, you want some spring force holding the valve closed. Longer answer: You can get by without it, but a couple of caveats to bear in mind: Having no valve spring can sometimes cause problems when filling from zero pressure. Hitting it with a quick blast of air from a bottle...

Got it, thanks. Yeah I saw the other thread and thought this was the same rebuild project.

x2 on John’s advice regarding the poppet. Even if it still seals okay, a plastic poppet would be an improvement over the soft OEM one, especially for a big bore like that. Much easier to knock it open. It would allow you to significantly reduce the hammer spring tension, making the cocking...

Yes, the valve assembly pictured is immediately recognizable as a QB7x. The O-ring is a size -113. Buna-N 70 durometer is good.

Looks like those four found out at a level of 10.

My buddy Anton installed a big can on his gun and it also began producing 2" groups. But in fairness, his was a shotgun and distances were quite close. In all seriousness, a slight POI shift is to be expected, but if groups open up considerably, that's symptomatic of clipping the baffles...

Please pass the eye bleach.

Yes, a -006. It's prone to extrusion so use a 90 durometer if possible.

Hardening of the O-ring at the small end of the regulator’s piston is a result of thermal stress. For adjustable regulators, the same occurs with the O-ring on the adjuster screw. An elastomer with better high-temperature properties will last longer. Viton, or its generic material callout...

Agreed, there is something very enjoyable shooting an easy-to-cock rifle with a sedate shot cycle. One of my favorites is a very modest QB78 bottle conversion with a PEEK poppet and super light MDS nylon hammer. In .22 cal shooting 18.1gr at 30fpe, it’s similarly quiet and recoilless as my...

Whew, that sounds frustrating. Divide and conquer. A regulator functions by passing air until such time as the force against the piston’s large end compresses the spring sufficiently to force the small end against the seat and halt the flow of air. So start by forcing the piston to stay off...

That's a tough one to diagnose from the available information. Let's get a baseline without changing the hammer spring tension. Normally that would mean doing a full string but since... ...so instead try collecting velocities at different reservoir pressures and report back. 3 shots at...

Dressing the seat surfaces is indeed the way to improve it. It's actually not that bad, though, A decline from 124 bar down to 114 bar is a change of about 8%. Anything under 10% is usually rendered inconsequential if the gun is adjusted for the velocity knee. Has the gun been difficult to...

Either way will work in most cases. The initial goal is just to find the amount of hammer spring tension necessary to reach the velocity plateau (max velocity achievable with the current regulator setpoint). However in some cases you can get confusing behavior when starting with maximum hammer...

You are on the right track, but you can approach it as more of a cookbook recipe by lowering the regulator a bit and then dial the hammer spring tension to the velocity knee (95-97% of the maximum velocity). https://www.airgunnation.com/threads/regulator-pressure-vs-hammer-spring-tension.1133487/