Tac-one body out of spec?

[jpdgas]

I built a Xvalve Tac-one and it just never cycled right. I'm not lightning on the trigger, but it felt like it couldn't keep up with a 850psi tank and ULT, and would RT (with an RT on/off) literally at 2bps with 1.1kpsi behind it. I spent a lot of time tuning the L10 and sear adjustments with no luck. Pressure tested in to the reg and no drops there. I gave up and started systematically swapping out parts. Trigger, sear, bolt, xvalves, frame, rail... I tried the body last. I stuck a ULE mainbody on it and everything just started working as expected.

I have no idea what would be wrong with a mainbody that would cause this, no idea where I would even start. Any suggestions? I suspect I'll probably be sending it out to Sandman, but if there is something I should look at first I'd rather fix it myself. Thoughts?

[Trbo323]

I know some of the micro mags had issues making velocity but if I remember right that was due to the body being drilled too far... Or not far enough, can't remember which.

Few things I would check

1) detent, if it causes too much drag on the bolt, I could see this issue

2) I forget what it's called but that steel ring in the body that the spring sits against. If it's missing, I don't know what that would do to the spacing

3) also, if the steel ring is missing or has been for a while then replaced I could also see the aluminum mushrooming up and I don't see any scenario where that would be good

First thing I would do is put the bolt in the body alone and see if there's any extra drag anywhere

Did you put fresh o rings in it? Agd spec or whatever you had around?

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[superman]

Make sure the feedneck does not extend down into the breach. Feel where the body screw would be in the breach and make sure it isn’t dimpled inward.

[jpdgas]

To Trbo323 points:

1) I took the detent out completely, no change
2) The steel ring is there. I took it out to check for clearance around the bolt, it isn't even close to touching it, so no drag there.
3) I can't see or feel any deformity in the breech.

When I drop the bolt in without a spring it travels freely. With a spring, the only resistance is the bolt sliding in the spring. The performance is the same with a completely different xvalve assembly and both xvalves perform great in the ULE mainbody.

superman The feedneck is clear, and I don't see or feel any deformity in the breech around the feedneck, body screw, or detent.

If something is causing drag, I can't tell where its coming from.

[Trbo323]

Do you have the rail bushing in?

https://www.airgundesigns.com/product-p/000129.htm

If not, I'm wondering if the rail is moving around a little between each body switch

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[jpdgas]

Yep, bushing is in there. Also torqued the valve screw a bit to make sure nothing was shifting. Also tried it hand tight, no change.

[Socalpumpballer]

What feed style is the Tac body? If it’s a warp body check to see if the feedneck clears the rail properly

[jpdgas]

It's center feed, the ULE is also centerfeed

[mercpb]

Have you asked Tim about it yet?
I don't see him around MCB but he's active in the AGD FB groups. Or just ring him up

[jpdgas]

I'll give him a call. He just inspected the ULT I thought was my problem so hes already sort of aware of the issue I suppose

[LukeAO]

LMK if you want to hire someone to go through it.

[jpdgas]

Definitely not of the table, I'll see how far I get this weekend with my tinkering

[tunaman5]

just swap it out with a known good ULE body...then you will know if the body is bad. Not very likely though...as I have never seen one that didnt work.

[jpdgas]

That's what I did and it was happy with the ULE body. Sandman has it at the moment, so I'm sure it'll get sorted out soon.

[jpdgas]

Got some resolution on this one, I had Sandman take a look at it. I ended up in IL for the first time in my life and I happened to be working 30mins from the Fox store front.
Firstly, awesome guy Tim, and he has some amazing mags on that wall! Secondly, he worked his magic and the tac is working as intended. He did a full rebuild, tune, and tweaked the trigger rod a bit and all my problems are gone. I had only rebuilt downstream from the reg. I have no idea why the valve was shooting fine in other mags, or why it was fine with a ULE body on it, and I'll probably never know. I guess one takeaway is when its not working and you don't know why, just rebuild EVERYTHING.
I'm just glad I can actually play with this one now. Thanks Sandman!