RT tuning

[athomas]

You should be able to set the trigger up to operate very similar to what you are used to. The ULT force requires about 15oz of trigger force where it contacts the trigger pin. The return force is more than 15oz. Its the mass of the sear assembly that causes the problems with the mag. The inertia required by the sear assembly takes time to accelerate, which slows the response of the system. This why tuning is so critical. One of the losses is causes when the bolt returns slower than it should. When you release the trigger before the bolt is returned, the top of the sear rubs against the returning bolt, slowing it down even more. This is the level 10 tuning issue. The ULT tuning issue is just a timing issue as to when you release the air after the sear has engages the bolt. Too soon and it stops the bolt from resetting. Too late and it doesn't open the on-off far enough to charge the front chamber fast enough.

The ULT requires about 15oz of force to activate the trigger and gets about 6lbs of return force based on a 850psi tank. The differential is about 6:1 but some of that is negated by the inertia of the sear assembly or your finger resting on the trigger.

The retro on-off assembly requires a 2lb trigger pull, and has about a 8lb return based on 850si tank output. Thats a differential of 4:1 which is less than that of the ULT but the higher return force overcomes the inertia of the sear assembly much better so it has less issues.

If you wish to tune your ULT to have a 20oz trigger pull the same as your handgun, change the point at which the trigger pin contacts the sear. Moving the contact point up increases the force and shortens the movement and also gives the on-off pin more leverage on the trigger so your finger will have less of an effect on the overall return of the sear. Search for the thread where Jack & Coke did a test on it. You can get the specs.

[Ando]

I think Luke offers this mod.

[38super]

With a 6:1 return ratio I should theoretically be able to get pretty close to what I want just by tuning the stock components. I don't mind it pulling less than 20 ounces; what I'm really after is overall travel and quick reset.

This trigger sear mod looks like it might be worth attempting. I'm wondering though, if mass/inertia is an issue on quick resetting of the trigger, has anyone tried skeletonizing the sear to reduce weight?

Going out later today to try a few things.

[athomas]

I think lightening of the sear should be tried. I'll bet it makes a big difference in the operation of the ULT.

[38super]

So I got to the field last night and promptly blew the burst disk on my tankand had to borrow a 3000 psi rental from the field (sigh). Man, that thing was like carrying around a `57 Chevy!

In any case I spent about an hour and a half tuning, trying different things and ended up settling on the ULT with five shims. That in combination with the better L-10 tuning job per athomas' instructions, take-up and over-travel screws adjusted to delete all unnecessary slack and it's definitely a lot better. Combine this with a little change in technique (I simply have to stop thinking of it as if I'm shooting a carbine or pistol) and it seems I'm good to go. No more chuffing after that "adjustment" either. By the end of the evening I had it shooting a LOT faster and while still no match for the ramping crowd in protracted strings of fire, it was certainly fast enough. And there's something to be said for accuracy over volume.

Interestingly; the kid (early 20's) who was reffing had never seen a Mag, didn't know what it was and couldn't figure out how it worked without batteries. Then I let him try it and he just looked at me, not quite believing it. I always get a kick out of that and it does happen quite often. I still can't figure out why more people aren't using these things.

Maybe I'll experiment later with the sear job, but for now it's doing what I want it to so I probably won't change anything for a while. I think I'll keep it at standard pressure as well.

Thanks again to all for your kind assistance.

[athomas]

Good to hear you got it working better.

[38super]

If you wish to tune your ULT to have a 20oz trigger pull the same as your handgun, change the point at which the trigger pin contacts the sear. Moving the contact point up increases the force and shortens the movement and also gives the on-off pin more leverage on the trigger so your finger will have less of an effect on the overall return of the sear. Search for the thread where Jack & Coke did a test on it. You can get the specs.

I spoke to Luke and decided to go ahead and have this mod done. Should be back in a few days.

Regarding the sear/bolt drag in the system during the reset cycle; I note there is some burnishing on the top (non-engagement) surface of the sear and also some pretty obvious tooling marks there. This would increase drag, yes? I realize that changing the angle of this surface would only introduce another problem so I won't look there for gains. But since the sear is only surface hardened, would there be any percentage in polishing these tool marks with a fine India stone and then lubricating with spray graphite? Or would this be likely to damage the sear and/or contaminate the system?

Has anybody tried this?

Thanks

[athomas]

The drag due to a less than perfect top surface is usually not an issue. The bolt should not be rubbing on the top of the sear.

The tuning of the level 10 helps reduce any bolt/sear drag. By having a properly tuned level 10, the bolt fires and resets quickly, before the sear can be released and has a chance to get pushed against the resetting bolt.

[38super]

The drag due to a less than perfect top surface is usually not an issue. The bolt should not be rubbing on the top of the sear.

The tuning of the level 10 helps reduce any bolt/sear drag. By having a properly tuned level 10, the bolt fires and resets quickly, before the sear can be released and has a chance to get pushed against the resetting bolt.

Excellent. Thank you.