FX Not convinced an FX Crown bottle clamp is a good idea

Jump to latest Follow Reply
I think they kind of suck and not because they will damage anything. They are difficult to get the bolts tightened equally. When you do they don’t seem to stay that way and are susceptible to moving. If I hav to do it over for the 65 bucks that clamp costs I would have bought a rail for my m3 off of here for a little more.
 
  • Like
Reactions: coastal drifter, swNCsw and Dairyboy
Upvote 0
No experience, no bottle guns. But as a retired mechanical engineer I tend to think in terms of stress. One potentially important point to remember is the stress on the bottle from the air it contains is pushing out of the bottle trying to make it bigger. A clamp on the bottle is pushing the other direction. I do not see how that can hurt anything. I think it reduces stress.

As you handle the gun there is a possibility the stress redistributes some because there is a stress transition on the edges of the clamp. That could amplify the stress at the edge of the clamp. I don't think that is significant unless the handling is very unusual. It just isn't much stress for a bottle that supports 3000 to 4500 psi.

The bottle attachment was probably not designed to support this stress. But it has to support the same pressures, I think. That might be the biggest concern, it would take an actual calculation to see how stress changes. But again I think it's probably minor. The further out on the bottle you attach the clamp the greater this stress would be. It would be lower with the clamp closer to the bottle attachment.

A poorly designed clamp could damage carbon fiber but I doubt the available products are poorly designed or manufactured. I would inspect it still to make sure no rough edges will contact the bottle.

The other thing that makes me more confident is I think the failure mode of the bottle will be a leak and that is highly unusual. The only item I would be a little concerned about is the bottle attachment. If that were damaged the bottle might become the projectile but I think it's pretty unlikely and a gun would probably show signs, like a leak in this area, before a big "failure". The fact that there seem to be no reports is also comforting.

I like my bipod as far towards the muzzle as possible. If I had a bottle gun, I would probably use an attachment like this so I could move the bipod forward.
 
  • Like
Reactions: MEC17670
Upvote 0
engfred said:
Hi Edward,
My experience is that a Bipod on the bottle causes a lot of Poi shifts if you like shoot a benchrest target. The POI becomes unpredictable unless you carefully lifts the legs on the bipod and put them down again. If you shoot a mag, on the same target without moving the rifle and the eye, I can shoot a magazine down the same hole.

I successfully use bottle clamp placed on the middle of the bottle, for attaching the bipod on my Redwolf - this is no problem the Redwolf is sturdy like a tank.

My Crown is very lightweight compared and will be much more sensible to shoot.

I find it better when I shoot with the bipod mounted on a picatinny rail fixed to the end of the Crowns wood stock.

But also remember to tighten the two screws holding the stock semi tight.
It is totally unpredictable if the screws are not properly tightened.

With that said I have really been fighting the POI shift on my Crown.
I have tried many different ways to avoid not only sideways, but also up and down depending on the load distribution on the bipod vs. hold vs. reas support.
Best is to have a bipod that can rotate when you rotate sideways. And secure to hold the same way every time so you get the same weight on the bipod every time you press the trigger.
If the bipod legs is 45° degrees forward - be sure to have feets with very little friction from bipod feets to the table.
This should allow the bipod to easily slide into the same position between every shot.

I know this is probably basic information for most shooters - but I just learned by comparing different ways.

But one thing is for sure Bipod holder on the bottle did not work for me at all with my FX Crown.

The Crown will never be like my Redwolf. I can take the redwolf out of box and shoot at a target from 50 m and it will hit the same spot as last time - from the first shot.
Lets just say it as it is - They Crown needs some massage to wake up and perform - just like men in my age ;-)

Best regards Claus from Denmark

Old photo from when I just received my Crown Today I use mainly 700 mm barrels - It is so long.
View attachment 386326
Click to expand...
here is my challenge....
instead of all of us being armchair pcp engineers "lets ask the manufacturers of our pcp's" if they want us to do this!
the follow on question is: do the manufacturing companies sell bottle adapters.... i think not... all aftermarket so in affect they have no responsibility if something goes amiss.
 
Last edited:
  • Like
Reactions: Ta-Ta Toothie, coastal drifter and swNCsw
Upvote 0
Hello again
The OP here
I have decided not to use a bottle clamp on my Crown MkII
Not only do I want to introduce any potential POI shift to a gun that has none, more importantly do I want to put any stress or strain on parts that restrain/retain 250B of high pressure air.

When a bipod is needed I'll attach to the stock

Thanks again for each of your point of view
I am glad I asked
Edward
 
  • Like
Reactions: MEC17670, Solo1, Dairyboy and 2 others
Upvote 0
It's a bad idea for all the reasons already mentioned. As Mr. Monk would say, I might be wrong, but I doubt it. There are few rifles that don't offer a safe and stable place to attach a bipod. I read of one person who was going to use a bottle for attaching a sling to be used in position shooting. If this guy was going to seriously sling up as one would in service rifle competition, that is a story that might end badly.
 
Upvote 0
cavedweller said:
Interesting - it says it’s outgoing? Same as being discontinued?
Click to expand...
This clamp is actually enginered to be a sling mount, thus supporting the weight of the entire rifle.
And the clamping area is much smaller than the larger style bottle clamp, which would distribute stress more evenly.
And it was marketed by FX, so apparently, their engineres approved ???
Ive not heard of any negative mishaps from these style of clamps.
I like this bottle clamp method much better, as opposed to drilling holes in a beautiful walnut (or synthetic) stock, as it allows the bipod to be moved much further toward the muzzle end.
 
  • Like
Reactions: MEC17670
Upvote 0
Long_Gun_Dallas said:
Rail broke out of my original stock. Don't feel like mutilating the walnut stock. Overall construction of the crown is extremely strong. I'd wager under 3500lbs of pressure it can take 30 or so more.
Click to expand...
Yes, but air pressure isn't really the issue. With a bottle clamp mounted up front, you are creating maximum leverage against the bottle/action connection. Under normal use, it shouldn't be a problem, and many folks use it, but, using the stock as the mounting platform is strong, and creates no potential pressure on the bottle connection. And it's a very simple job, no stock mutilation required. It's just a matter of opinion and preference.
 
Upvote 0
Before I made wood stocks for my 3 P35s I attached a bipod using a 34mm scope picatinny adapter. The air tube of the P35 is about 33mm so I put some tape in the adapter to take up the clearance. It worked well but you had to get the rotation right, of course, or you were building in cant. Now I have metal picatinny rails bolted to the stocks.

The air tube is an aluminum pressure vessel which I believe there is more reason for concern than there is for carbon fiber bottles. I believe that because of destructive tests on aluminum and carbon fiber tanks documented on video and included here by another member. The aluminum tank failed at a much lower ration of failure pressure to working pressure. In addition, the carbon fiber tank had a chunk machined out of it greatly increasing the stress in that area. And it still failed at a much higher pressure. But without any data or design information it is hard to know how the margin built into the tanks tested compares to the margin built into the guns and tanks we use. Still, I believe carbon fiber tanks in general have more margin against mechanical failure than aluminum pressure vessels. The carbon fiber is not uniform, it is woven and impregnated with resin and it would be irresponsible to assume it is homogeneous when designing the thickness. So the only real choice is to make it plenty thick which in the real world means higher margin.

The twisting force on the bottle from load being applied to the bottle through does stress the reduced diameter near the attachment point. I am confident the clamp squeezing the bottle is not harmful because that stress is in the wrong direction (compressive versus tensile) to be harmful. But the neck down area would have compressive loading on the top and tensile on the bottom. It would take a real calculation to know the significance but I believe it is not important because of the margin in the tank design. If I buy a bottle gun I would consider a bottle clamp for picatinny attachment. I don't think it's a risky thing to go. I don't think any of the manufacturers recommend against it but if they did, that could change my mind. They have the design data and could easily do a calculation to have a much better informed opinion. But since they apparently are not, I think that is another sign it's not risky.
 
  • Like
Reactions: MEC17670 and Long_Gun_Dallas
Upvote 0
4C65E04B-1813-4BC5-AA06-F68705268B62.jpeg

Not a problem.
 
  • Like
Reactions: MEC17670 and Long_Gun_Dallas
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu