Harmonics of a shrouded barrel

[Martin]

I have a Benjamin Marauder and soon will be getting a FX impact X, I have been doing some reading on the subject of harmonics and have seen nothing about the effects a shroud has on them. The FX evidently has no problem with bad vibes but that could be due to the O rings on the barrel, could the marauder Benefit from such or are the O rings on the FX for something other than harmonics?

 

[mtnGhost]

It's due to the floating nature of the barrel. Not as a big of an issue with non-floating types. Think about the harmonics like if you hung a metal pipe to a tree with paracord, put an object inside of the pipe, and then hit the pipe with something. 

 

[JCD]

Airguns with no firm mounts between action and muzzle may have more 'harmonic' action but they are also far less prone to muzzle 'shift' from tube fill pressure or hold tension. So many variables... but none matter until there is an issue .And not a huge issue with design f the impact. I have not heard of an Impact having any issue related to the fact that the barrel is held firm for the first 11 inches (appox) or because of the shroud vs LDC on the end. POI changes for the latter but if you zero for one vs the other you should be okay. The extendable shroud on some are less than completely repeatable but that the shrouds fault.

If you have info to the otherwise, I'd appreciate a reference. On the other hand, if you use an LDC on the end of the stock shroud.... that CAN change things. A Sumo on a shroud adapter on my .25 with a 700mm barrel changed my 75y POI by 7 MOA. Rather than try to figure it out, I just went to a lighter LDC. with MUCH less POI change.

 

[Martin]

Hey JCD,

Thanks for the heads up on the sumo, I’ve got my eye on probably A DonnyFL TANTO or maybe the TATSU if I decide on the .25, still haven’t decided on caliber yet but I’ve just about been swayed toward the .30. From your experience as an owner of the .25 what’s your take on the two if you don’t mind me asking? 

 

[edosan]

This may help to solve your doubt, not only for harmonic, vibration also (related)

https://www.youtube.com/watch?v=OxP2VSjgrD8

 

[John "spysir" Blount]

Normally in airguns, shrouded or not hanging 12-16oz of the muzzle end will effect harmonics. And normally in a calming way. Your resuts may very.



John

 

[JCD]

Hey JCD,

Thanks for the heads up on the sumo, I’ve got my eye on probably A DonnyFL TANTO or maybe the TATSU if I decide on the .25, still haven’t decided on caliber yet but I’ve just about been swayed toward the .30. From your experience as an owner of the .25 what’s your take on the two if you don’t mind me asking?

Hi Martin, If you're asking about the LDC's, all I can say is that I found the Sumo to heavy for my use on the 700mm barrels' shroud. I was trying to zero at 75y and have a good aim point on the scope at 100y (or do the same in reverse) . On my rifle the Sumo was heavy enough to make that awkward. When I've mentioned this in the past, others have hopped in and said they did not have the same level of POI change from the weight. Nothing at all against Donny's stuff but I'm using Huggets now.

If asking about the .25 vs .30.... I have no experience with the .30. My shooting is mainly to 75y max with lots of 50y shooting mixed in. If I had a .30 I'd prob want it shooting on the hard side and that just seems like overkill for my use. Now come summer and more frequent 100y plus outings, I might try a .30 barrel...

 

[Martin]

Hey edosan, 

Thanks for turning me on to the video, it explains in detail what I was saying about the O rings between the liner and the sleeve inside the barrel of the FX. With a design of this type dampening the harmonics of the Barrel and fact that the FX rifle is a very accurate rifle leads me back to the question as to weather a gun like the Benjamin Marauder and other guns like it that have the barrel running bare through the Shroud without a sleeve and O rings might could benefit from such.

 

[Guest]

I have an experiment for you guys to try which will demonstrate the effect of your barrel shroud and moderator on your accuracy.

1) Shoot a couple groups at 50 yards with just the naked barrel with nothing on it. Just keep the same point of aim for each shot and look at the group size you get. 

2) Shoot some groups with just the shroud on the barrel.

3) Shoot some groups with your silencer attached to the shroud. (Try each silencer you own).

4) Shoot some more groups with just the silencer only on the barrel. 

Now I want you to repeat this experiment at 100 yards. I believe you will be surprised by what you see...