Terminus Zeus / Curtis Vector Quick Change Issues?

[littlepod]

For those running the Zeus/Vector with quick change / hand tight barrel setup, has it been repeatable for you? I've been prepping for a class out of state so I'll be taking off the barrel to minimize the pelican case size (running a shorter case). I zeroed last week, and went to do a final chrono and zero check.

Put on the barrel, elevation was spot on, shooting 1 mil left - not .1, 1mil. Adjusted the 1mil. Took off the barrel, put it on again. Shooting .2mils right, and .4mils high.

Now I probably can check a few more things, maybe unmounting / remounting the suppressor is causing some issues. It's a TBAC Ultra 9 so I wouldn't think that would cause problems. I'm going to do a few more tests with putting the suppressor on/off to see if there's any shift.

I mounted my 6GT barrel (with a muzzle brake) and it retained the same zero as I had jotted down.

Any tips for people who have this working repeatably? What I'm doing is hand tightening the barrel till it shoulders, and putting a little more oomph to my twist like if I was going to hand tighten anything. Then I put the barrel set screws to 10in/lbs with my fixit it torque wrench.

Thanks for any tips.

 

[Dthomas3523]

When you take everything into account, shooter, lighting, and the rifle system itself, “return to zero” is almost never going to be better than .1 - .4 mil or so each way.

There’s just too many tolerances stacking to be truly 0,0 everytime.

 

[KimberGuy]

My Zeus goes back to POI every time. I’d look hard at your suppressor first, especially if you’ve got another barrel that is showing consistent repeatability. I’d also put a witness mark on the barrel/action to ensure that you are indeed “torquing” the barrel on the same amount each time.

 

[Lunchbox27]

I switch between my 6mm and my 308 barrel just about every range session. It often takes about two shots to return completely to it's zero, but it's never more than .2-.3 mils off for those first two shots. I have witness marks (as KimberGuy mentioned) but the hand snap always puts it in the same spot either way.

I'm curious... was this just a few shots on target, or did you shoot a few groups to confirm that shift?

 

[FisherT&C]

Theoretically a barrel tightens a little bit as its fired. Even a barrel torqued to 90ftlbs can be slightly more difficult to get off after being fired and it's not because of being dirty. The idea is that a bullet traveling down the barrel creates a rotating force opposite the twist of the barrel which tightens it down a little to a point.

So the barrel may just need a few shots to settle.

 

[Dthomas3523]

Theoretically a barrel tightens a little bit as its fired. Even a barrel torqued to 90ftlbs can be slightly more difficult to get off after being fired and it's not because of being dirty. The idea is that a bullet traveling down the barrel creates a rotating force opposite the twist of the barrel which tightens it down a little to a point.

So the barrel may just need a few shots to settle.

So, does a left hand twist barrel become slightly looser? Serious question.

 

[FisherT&C]

I imagine it is possible. I never have tested it. I just know from my personal experience and other guys have said the same thing that a barrel is torqued more after it's fired.

Slight digression, I know most 1911s have left hand twist because it will drive the pistol into the right hand. So I'm not the only one that considers this theory.

 

[Dthomas3523]

I imagine it is possible. I never have tested it. I just know from my personal experience and other guys have said the same thing that a barrel is torqued more after it's fired.

Slight digression, I know most 1911s have left hand twist because it will drive the pistol into the right hand. So I'm not the only one that considers this theory.

Driving the recoil is a common understanding. Torquing the barrel is another thing. Not that I believe or disbelieve it’s possible.

Would be curious to see if the barrels are actually tighter or looser with real tests.

 

[littlepod]

I switch between my 6mm and my 308 barrel just about every range session. It often takes about two shots to return completely to it's zero, but it's never more than .2-.3 mils off for those first two shots. I have witness marks (as KimberGuy mentioned) but the hand snap always puts it in the same spot either way.

I'm curious... was this just a few shots on target, or did you shoot a few groups to confirm that shift?

I shot a few groups to confirm.

I need to put the witness marks just to see if there's anything going on.

When I put my 6GT barrel on, it grouped immediately. Shot 5 shots, all within .7" at 100 yards. Never had any settling which was nice. Shot a few more groups, stayed spot on.

When I put the 308 back on, first shot, was .8mils high, then all the following shots were .4mils high. This is based on the last measured zero settings for the scope (not based on the 6GT's settings).

I'll do the witness marks this week and try again. I'm going to also take on / off the suppressor to see how that might cause poi shifts.

 

[bb505]

apologies for asking in this thread, but it seems to be the most recent regarding Terminus Zeus'. So, just picked up a Zeus that came with 2 6mm barrels. Bought it to "consolidate" my traditional r700 style collection. I have a defiance which I now need to move, but want to keep the barrel(proof carbon bull in 308). Has anyone had luck with refitting a r700 pattern barrel to the Zeus, as in, an easy task for the gunsmith to do, maybe without the need to re-ream the chamber? This would be for the hand tight version, where i believe a flat spot is cut (no threads) for the set screws to press against.