DAR... We Have A Problem...

[Firewalker]

I have an issue with my DAR that I am hoping this post will be a place to collaborate and discuss a fix that is permanent and affordable.

Here we go: The shroud is moving my barrel and throwing pellets into the shroud cap!

Please see the targets attached below, #5 shows an "on target" shot that I was able to repeat in the next three shots with the barrel shroud removed but with the shroud attached, the pellets all fly up (#1 & #2 went 7" & 6" above and to the left) and even loosely threaded on and the front O-ring removed, the pellet hits above and to the right as much as an inch with #7 showing a 2.5" rise when tightened but with the endcap removed and the interior nut loose.

Target #9 once again with the shroud removed is right on the bull.

Looking at the second picture, you can clearly see lead on the edge of the cap where pellets have been striking.   

[tracker1955]

Haven't touched a gen 2 but assume they are still using the same barrel to shroud support and cone-shaped baffles as the gen1. I never had an issue with clipping, but did notice how fragile the aluminum air cylinder to shroud barrel band was, and how easy it was to strip the set screws if not careful. I would check that when attaching the barrel band you are not accidentally getting the shroud skewed in relation to the centerline of the action and air tube. If skewed it will throw your shots left or right and can affect vertical poi. 

[Firewalker]

The grub screws and threaded holes on the barrel band are good to go, the shroud is left to float and the grub screws are set evenly from side to side so as to not skew the band.

The baffles are tubes with a "washer" end seen below.

Trust me, this is not an issue on my end, everything is tight and properly torqued, I have millions of PB rounds sent down range in my lifetime including 1000yd open sight competitions in the late 80's with Garands.

I took correspondence courses for gunsmithing in the early 90's and have certificates in many mechanical disciplines so lets focus instead on the gun and how to correct the setup at the factory that is allowing for the misalignment that is causing clipping. I dont mean to sound like a jerk, I'm just frustrated and dont want to waste time with basics unless there is good reason to do so.

Actions taken so far:
-Removed the shroud and barrel band from the DAR awaiting return, swapped them out after checking runout (the original was MUCH better with only 0.002" of runout while the replacement is at 0,007" of runout at the center!!). I also swapped out the baffles, alignment block and cap. POI and POA are better but still off about .097" overall at 10m.

I hesitate to remove the barrel due to the fourth grub screw being at the bottom of the barrel band above the  reservoir which would have to be removed and replaced, voiding may warranty. Removing the shroud does not affect the warranty according to Joe at DAR.

Do I jack the barrel up after loosening the three grubs holding the barrel to the breach and see if that helps or will this deform the mild steel the barrel made from?

Haven't touched a gen 2 but assume they are still using the same barrel to shroud support and cone-shaped baffles as the gen1. I never had an issue with clipping, but did notice how fragile the aluminum air cylinder to shroud barrel band was, and how easy it was to strip the set screws if not careful. I would check that when attaching the barrel band you are not accidentally getting the shroud skewed in relation to the centerline of the action and air tube. If skewed it will throw your shots left or right and can affect vertical poi.

[Pelletjunkie]

What does your crown look like?

[Firewalker]

Fantastic! The unsupported barrel shoots great, see targets 5 & 6 below.

[Firewalker]

I checked the barrel alignment with the three top screws in place, it's almost 0.018" out, drooping in the front, I am going to loosen the three screws and "jack" up the barrel to match the height at the receiver.

(later)

I got the barrel raised to be even at a gap of 0.0212" across the whole length. Wish me luck!

[RDB]

The shroud support that slides on the end of the barrel. How loose is it on the barrel? And how loose is it in the shroud? I suspect bother are a little on the loose side causing your problems. 

[Rat Sniper (AKA: PaulT58)]

What happen if you remove all the baffles and the spacer that goes over the narrow part of the barrel and put the end cap back on?  Are the pellets clipping the end cap?  It seems something inside the shroud is pushing the barrel off center.

[Pelletjunkie]

Is the muzzle on a DAR barrel threaded?

[Pelletjunkie]

It looks like the rear shroud mount slides over the barrel and is secured with grubs. How sloppy is the fit on the barrel. Remember, a little off on the back of the shroud is a lot off by the time you get to the front.

[RDB]

What happen if you remove all the baffles and the spacer that goes over the narrow part of the barrel and put the end cap back on?  Are the pellets clipping the end cap?  It seems something inside the shroud is pushing the barrel off center.

He would blow his end cap to smithereens .

[RDB]

Is the muzzle on a DAR barrel threaded?

It is not.

[Firewalker]

On the DAR, there is an o ring holding the barrel to the clamp and two grubs holding the clamp to the reservoir, its tight and there is zero movement.

 

The shroud support that slides on the end of the barrel. How loose is it on the barrel? And how loose is it in the shroud? I suspect bother are a little on the loose side causing your problems.

[Firewalker]

With the barrel sag, I was very hesitant to do that since I knew it would clip the cap really badly! The barrel was sagging 3/64" front to back.

What happen if you remove all the baffles and the spacer that goes over the narrow part of the barrel and put the end cap back on?  Are the pellets clipping the end cap?  It seems something inside the shroud is pushing the barrel off center.

[Firewalker]

No, sorry, its just turned down.

Is the muzzle on a DAR barrel threaded?

[Pelletjunkie]

So the piece they use to center the business end of the shroud is a slip fit I’m guessing. I would be looking at correcting the issue from the breech end of the shroud. It just depends on how tight their tolerances are.

[Firewalker]

Its very tight, there is an o ring in the clamp and 2 grubs in the clamp for the reservoir.

It looks like the rear shroud mount slides over the barrel and is secured with grubs. How sloppy is the fit on the barrel. Remember, a little off on the back of the shroud is a lot off by the time you get to the front.

[Pelletjunkie]

If the rear shroud mount is a nice tight fit you are going to have to chuck the barrel up and check the runout on this.

[Firewalker]

I "jacked" the barrel up and got shim to fit 0.0212" across the barrel length. I also tightened the inner nut over the baffles and then turned the shroud by hand on very tight. I am hoping to add some stabilization to the barrel assembly this way. 

[Pelletjunkie]

If this is a Chinese gun, you might want to have a few drinks before you start to spin the barrel. I have seen plenty that the bore wasn’t even centered in the barrel.