Bbl bands added to PCP’s, help or hurt?

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Tomygun1

Member
Dec 28, 2020
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OR, United States
I thought I knew what I was doing when I added a bbl band to my shrouded bbl Benjamin Akela 177 rifle for stability, it seemed to scream for one with soo much bbl flex. I haven’t shot it nearly enough to make a judgment, but early in this process to blame the loss of accuracy to the bbl band seems possible. It doesn’t take a PHD to guess that going from an moa @55yds for the first test in Dec, to a 5”spread in the second test in Feb after adding the bbl band and polishing the bore that it doesn’t like something I did. I wouldn’t think harmonics would be that sensitive with a shrouded bbl and will retest by sliding the band to different locations and then eliminate it. My non shrouded Cayden 22 has a factory installed bbl band and is sub moa.

Before jumping through all the whoops to figure this out I would like to ask others about their experiences when adding bbl. bands to your PCP rifles. Yet to come is a test for a Diana Stormrider that I also added a bbl band to but have yet to test (waiting for parts).

Tom
 
Tom,

With pretty much anything related to airguns...it depends.

I know that answer is unsatisfying, but its really the best I can do. With my Benjamin Marauder, the groups tightened and POI shifts stopped when I added an o ring to the bbl band so it would make full radial contact with the shroud. My Air Arms S-series guns absolutely benefit from a barrel band.

But other rifles? Not so much...made them shoot worse.

Have you chrono'd the gun? Sudden erratic shooting sounds like a blown breach seal or something similar to me (assuming simple culprits, stock/action screws torqued, shroud clipping, etc. are accounted for). 
 
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Leon, Thanks. In this case the band was added because the Akela bbl is very unstable, but I was still thinking it might help rather than hurt, apparently not.

Nico, Thanks. Sounds like your Marauder was sensitive to shroud tension and I will pay attention to that. I have yet to chrony the rifle but have played with the venturi controller down to half volume. It would be hard to blame this loss of accuracy on polishing the bore so the bbl band remains the suspected culprit. Just to put all the information out there I did ad a Donnyfl shroud addapter and silencer to the rifle while including the factory stack pack in the shroud but that was in place before adding the bbl band and in that configuration it shot moa.

Tom
 
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If your free float barrel is working well with your chosen bullet good. Stick with that. If it works OK with a different bullet ok use that. My experience is that barrels with barrel bands are not as accurate as free float if you can find the right bullet. The key is barrel harmonics. One particular bullet will work best with a free float barrel. My experience is that a barrel with a band will accept more variety of pellets at reasonable accuracy. So do you want 1 moa with a free float with one particular grain bullet or a 1.5 Moa with most bullets..... Most my hunting guns are banded and most my target guns are free floated. Hope this helps. My disco has 2 bands... Works great. My compatto is free floated. Slightly better but only with 10.5g pellets and everything else is worse than the disco. Does that make sense? Hope so. God bless 
 
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Raden, Thanks for the input.

like you, I believe free floating bbls. are free from other influences and all things being equal should be the most accurate. I will only shoot the Akela from the bench so it should be fine without a band. This rifle is considered a field gun, and while I have converted it to bench use it is still heavy, clumsy, and unbalanced, and the unusually long and floppy bbl/shroud that wants to twist and bend if touched seems to be the weak point. Looking to improve on that weakness I added the bbl. band and it seems to have made things worse. It could be that my initial question about bbl bands in general should pertain mostly to this and other shrouded rifles than PCP’s in general. However, I can’t help thinking that this problem wouldn’t exist if the rifle were unshrouded. Harmonics or unstable parts?

All opinions are welcomed.

Tom
 
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As others have said it depends on the gun, the ammo, the velocity of the ammo, how tight the barrel band is and where it is placed on the tube/barrel. So, harmonics is definitely at play here. I really would rather tension my barrels than put a band on them. But since tensioning is sometimes difficult to do I have put bands on a couple of my Crosman guns. I moved the bands around on the barrel/tube until the gun was happy with the placement and I was getting good accuracy. All but one of the guns I have with barrel bands on shoot very well now. The one I just need to find a suitable projectile for.
 
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“It would be hard to blame this loss of accuracy on polishing the bore…”

You’re probably right but there’s a difference between knowing and guessing and until you tested it you don’t know anything. Knowing whether the rifle shot better or at least the same after polishing would be helpful information. 
did you leave the breech oring in there when you polished the barrel? Is it still there? If you left it in there, did it get damaged when you polished the barrel? 

are you shooting the same tin of pellets? It’s not unheard of to have pellets from different batches have drastically different results. 

Could be a combination of barrel band and moderator. Remove the moderator and see what happens with just the barrel band. IMO I don’t think the Akela needs an additional moderator. I have both the .177 and .22. I do not have barrel bands either of them. 

As Bio said placement of the barrel band can also have an affect. Change the placement and try it with and without the moderator. 
lots of variables at play and you changed a couple at once. To better understand cause and effect it’s best to only change one variable at a time. 
 
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imo theyre needed more on a 'field use' gun to keep it from getting knocked out, because theyre gonna get bumped around .. as far as adding accuracy, ive never encountered that yet .. maybe it does on some setups i dont know for certain .. more likely it.makes a direct connection to to the barrel from something that flexes or transmits vibrations with varying holds but a good solid supporting stock reduces that ..
 
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I am someone who just can't leave anything alone, always want to try different things, my fx shoots lights out, better than me

as a stock barrel, 

I did try a carbon barrel liner sleeve on it and added more internal supports from the liner to the shroud, didn't work

so I bought a barrel band from england , and installed it last week, shot it inside on sunday, I could see the POI shift all around the X as 

I ran thru a magazine, trying 5 different grain pellets, it just didn't work either

so I am back to a stock barrel in a shroud, and back to shooting real nice groups, 

so I have found that barrel bands and additional supports just do not work in my gun

if I can just keep it that way, and not mess around with it, it would be nice.
 
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I think it depends on what you want to do with the rifle. If your a benchrester and can get the gun to the range and back without bumping it in any way, then by all means, free float that sucker! if, however, you want to go trapesing around in the bush and are constantly bumping the barrel on things, put bands on it. Group size MAY suffer a bit, but you'll hit that squirrel every time.

I run mostly the Disco based stuff, so not much support between the breech and airtube. A barrel band here is essential for strength. I generally run three bands on my guns...I want them solidly anchored to the rest of the weapon. Have I tried it without them? You bet! And you'd be ill-advised to repeat that experiment. The things are just so delicate, it's not even worth trying, unless, as I said, you can find a way to move the gun around without breathing on it.

In my centerfire benchrest stuff, my triple deuce and 6PPC have barrels that are free floated, you can run a piece of paper from the forearm of the stock to the action without interference. Those barrels are like an inch in diameter too, so very stiff. And I guard them with my life after zeroing them in.

Chris
 
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I think I should update this topic with new results as I started it and others may benefit. Todays testing was the proof in the pudding about adding a bbl. band. Yes, it will change the POI, and yes, it can screw up accuracy. I changed it’s position from near the muzzle to as close to the stock as possible and the old accuracy came back, sub moa @55yds.

this Akela rifle is one that really needs a band so I’m pleased it works. Thank you all for your opinions and experience.

Tom
 
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