Sentinel on HPA

[Smoothpumper]

I recently picked up a sentinel that hasn't been used on HPA. I'm hoping someone can help me out on the best route to get it going. It currently won't recock on an 800psi or a 650 psi output tank using the stock barrel. I was able to get it to recock about 90-95% of the time with a slight underbore and the velocity at 320-330. Should I try a spring kit first? File another flat on the valve pin?

Any help would be appreciated.

[Brokeass_baller]

This might sound obvious, but have you given it a good cleaning and oiling? That's more than enough pressure for it to function properly.

[Smoothpumper]

I stripped, cleaned, replaced orings, and oiled.

[Brokeass_baller]

These guns have the velocity adjuster in the front, right? The screw controls the valve spring? Maybe try reducing the spring tension? That might allow the hammer to open the valve longer, giving the blowback air more time to act against the hammer.

Otherwise, I can't think of anything else. Sorry.

[flyweightnate]

I still have some high flow valves for these. My experience is they allow a bit more control over velocity, sweetspot around 650psi, and have ports that are piloted 90% deep - chase them with a 5/64" drill - to increase blowback gas. One port is my preference for Sentinels, and obviously 0 for Illusions. They're not magic, but they are a whole lot more durable than stock and let you use a reg more effectively.

But most of these guns cycle very reliably at 800psi. Make sure you're using a 016 o-ring on the hammer (or was it 017), and lightly polish any corrosion off the hammer. The zinc plating gets sticky. Check that your sear spring isn't worn out - they'll stutter if they don't have enough tension to catch every time. The little spring behind the trigger-mounted sear latch is a common culprit, too. Those pivots wear out, and the slop makes things get jumpy.

[gabe]

I've never had a problem getting mine to run at tank pressure. The HP valve from flyweightnate really made it much smoother though.

Try shooting it with a squeegee in the barrel or better yet, paint. If it won't recock on paint the there's something wrong.

[Smoothpumper]

Thanks for all the tips.

I changed out the hammer spring but then I was having trouble getting to a decent velocity. I need to find some more time to test but I think I'm getting closer. I hadn't thought about the sear spring and that might certainly explain the inconsistent recock. I'll check it out.

Flyweightnate - I do have one of your valves in my Illusion and it works great. I chrono'd prior to and then after install and I had a 50fps gain from your valve. Allowed me to run a lower pressure and is noticeably quieter.

If I was going to keep this, I would certainly buy another one of your valves but I'm planning to give this one away to a young person next time I get out to play.

[flyweightnate]

No better way to ensure he finds MCB, sooner or later... rare, check, old, check, mech, check!