FX Flexibility of a Crown Gen 2 barrel.

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.20calguy

.20calguy

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May 6, 2021
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Greetings
I just got my Crown back from UA for repair, and I haven't shot it in this heat yet. Since it got hot I put a shop fan out that has a vibration to it. Fan off I can shoot pennies at 75 yards. Fan on It shoot all over the place. I even had two shots hit the ground thirty or so feet ahead of the back stop. Turn the fan off, pennies again.
This my only gun that can't shoot with the fan on.
That much at flexibility is crazy to me.

Thoughts?
 
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.20calguy said:
Greetings
I just got my Crown back from UA for repair, and I haven't shot it in this heat yet. Since it got hot I put a shop fan out that has a vibration to it. Fan off I can shoot pennies at 75 yards. Fan on It shoot all over the place. I even had two shots hit the ground thirty or so feet ahead of the back stop. Turn the fan off, pennies again.
This my only gun that can't shoot with the fan on.
That much at flexibility is crazy to me.

Thoughts?
Click to expand...
How is the vibration from the fan transmitted to the gun? Is it resting on the same table that you're shooting from?
 
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MrP said:
How is the vibration from the fan transmitted to the gun? Is it resting on the same table that you're shooting from?
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Actually through the floor which is 5/4 board decking. My table is rickety and transfers the vibration like a record needle. Its a 5/4 board table top sitting on a keyboard stand, similar to an ironing board.
There's a good 2 moa vibration in my scope picture, but it doesn't affect my springers. They still shoot nicely with the fan on.
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.20calguy said:
Actually through the floor which is 5/4 board decking. My table is rickety and transfers the vibration like a record needle. Its a 5/4 board table top sitting on a keyboard stand, similar to an ironing board.
There's a good 2 moa vibration in my scope picture, but it doesn't affect my springers. They still shoot nicely with the fan on. View attachment 486405.
Click to expand...
Are you shooting the springers from the same rest or bags as the crown? If you’re shooting the crown from a bipod and the springers from a bag that’s your answer. I don’t see how you could shoot good groups with any gun with 2 moa of vibration going on though.
 
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forrest342 said:
Are you shooting the springers from the same rest or bags as the crown? If you’re shooting the crown from a bipod and the springers from a bag that’s your answer. I don’t see how you could shoot good groups with any gun with 2 moa of vibration going on though.
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Yes the same everything except pellets. .20 cal vs .30 cal. Remember the Crowns barrel is a 600mm, and it's a 300mm on my main springer an HW97K. The springer barrel will not flex, and the Crowns barrel obviously does.
 
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My mk1 crown was always wicked accurate but their barrels are a flat out terrible design. If you drop it barrel first or bang it hard all of that force is put on 3” or whatever that is held in the breech. Utter joke. In fact I bought the gun and it arrived to me with a slightly bent barrel. Not sure what exact part but couldn’t even sight the scope in. Had to buy a new barrel tube (part transfer port screws into) and barrel liner housing. All was good then.
 
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Trucker3573 said:
My mk1 crown was always wicked accurate but their barrels are a flat out terrible design. If you drop it barrel first or bang it hard all of that force is put on 3” or whatever that is held in the breech. Utter joke. In fact I bought the gun and it arrived to me with a slightly bent barrel. Not sure what exact part but couldn’t even sight the scope in. Had to buy a new barrel tube (part transfer port screws into) and barrel liner housing. All was good then.
Click to expand...
Wow.
I don't think that the barrels termination to the receiver is a bad design at all. I just think that the barrel is a bit flexible without some aft support, but its done for the sake of weight, astetics, and bottle access.
I have a new 380mm .22 cal kit for it to make it more yard freindly, and get the shot count up. It is currently a 600mm .30 cal.barrel.
 
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.20calguy said:
Wow.
I don't think that the barrels termination to the receiver is a bad design at all. I just think that the barrel is a bit flexible without some aft support, but its done for the sake of weight, astetics, and bottle access.
I have a new 380mm .22 cal kit for it to make it more yard freindly, and get the shot count up. It is currently a 600mm .30 cal.barrel.
Click to expand...
It’s an extreme weak point. Dont drop it barrel first or ram it into something hard. All that leverage (esp a 6-700 mm barrel)is put onto the small transfer port actually attached to the gun by the set screws in the block. Not saying it’s the only rifle made like this but it’s a weakness in my opinion. I would put a barrel band on for extra support and rigidity
 
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Hi Guys!
Just my two cents - Most of the really fine shooting air rifles have a "floating barrel". Look at the Steyr, Thomas, Walther, Air Arms, etc. and you will find those barrels with the only attachment at the breach block. I believe that this "cantilever beam" model gives a very low natural frequency of vibration so that when the rifle is shot the high frequency vibration induced will not be in the range of the natural vibration frequency and the deflections of the barrel caused by the induced vibration will be minimized. So the concept of connecting the barrel to the block with mere inches of mating surface is very commonly used.
In the Crown Mk II the barrel liner is held within the aluminum shroud with a couple of delrin spacers. The shroud acts to reduce the noise of firing the rifle (air stripper at the muzzle with directs air back into the shroud) and helps prevent damage to the barrel liner from accidental knocks. The barrel/shroud system is actually quite stiff as the large diameter shroud provides a lot of bending resistance (Moment of inertia of a cross section increases by the cube of the radius).
What I am trying to say is that the Crown Mk II's have done really well in many shooting competitions and in general are fine shooting rifles. Look at the leader board for the AGN 30 and 40 yd challenges and you will see as many Crown Mk II's as other really nice rifles. I admit that I take care to avoid bumping my barrel at FT matches - and have seen others whose rifles have fallen and barrels end up with POI shifts.

Cheers,
Greg
 
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.20calguy said:
Greetings
I just got my Crown back from UA for repair, and I haven't shot it in this heat yet. Since it got hot I put a shop fan out that has a vibration to it. Fan off I can shoot pennies at 75 yards. Fan on It shoot all over the place. I even had two shots hit the ground thirty or so feet ahead of the back stop. Turn the fan off, pennies again.
This my only gun that can't shoot with the fan on.
That much at flexibility is crazy to me.

Thoughts?
Click to expand...
Hi Again,
I was just doing some more thinking about your issue. You said you just got the rifle back from Utah Air after some work. Based on your symptoms I think you have something that was not properly tightened by the techs. Have you checked the four barrel set screws? If they are not tight then the whole barrel assembly could be vibrating. The other possible weak spot could be the position of the two or three spacers on the barrel liner. I usually put some electrical tape around the barrel on each side of the spacer once I have them positioned. One should be about an inch of the end of the barrel (but not any less) and the others evenly spaced along the length of the barrel. They have a tendency to move when the shroud is put on or taken off.
Good luck.
Cheers,
Greg
 
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NAProf said:
Hi Again,
I was just doing some more thinking about your issue. You said you just got the rifle back from Utah Air after some work. Based on your symptoms I think you have something that was not properly tightened by the techs. Have you checked the four barrel set screws? If they are not tight then the whole barrel assembly could be vibrating. The other possible weak spot could be the position of the two or three spacers on the barrel liner. I usually put some electrical tape around the barrel on each side of the spacer once I have them positioned. One should be about an inch of the end of the barrel (but not any less) and the others evenly spaced along the length of the barrel. They have a tendency to move when the shroud is put on or taken off.
Good luck.
Cheers,
Greg
Click to expand...
Actually the rifle is in perfect working order. The barrel is flexible enough to take on harmonic vibration. The speed of the fan was the right frequency to set it in motion.
rcarlisle said:
What NAProf said. My similarly constructed Dreamline barrel suffered gradually increasing fliers as the front spacer was slowly pushed back by the muzzle blast from each shot. Making sure those spacers don't move is key.
Click to expand...
I just got this one back from a total going through at UA, and I'm not experiencing flyers. Just like a wing flutter, it locked on to my fans frequency and began an oscillation. I bet that I could have tuned it out with barrel weights.
 
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