Bullboss accuracy loss (after cleaning)

Jump to latest Follow Reply
rwbarrett

rwbarrett

Member
Dec 20, 2017
25
2
North Carolina
Hi, 
To quote the Beatles "please, please help me". I cleaned my new Bullboss (.22) barrel recently with a bore snake. I didn't notice it had that embedded wire brush on the end and it got very difficult to pull through. I stopped pulling when it got super tight and I looked at the muzzle to see the little brush wires so i removed the bore snake and thought "well that's clean enough". Before I cleaned it I shot maybe a full tin (500) of JSB 18gr through it and I was getting 10 shot groups 1/2"-5/8" at 25 yards. Which is better than my Gamo Urban getting about 3/4"-1" groups at 25 yards.

It seems that after the cleaning my accuracy has dropped off. I now get 1-1/2" groups at 25 yards and that has lasted about 200 JSB pellets before I started to investigate what was going on. So I removed the barrel, cleaned and inspected it while it was out of the riffle, then I leaded the barrel up with 40 shots before shooting it again and by now it has had probably 200 JSBs through it. I have also tried different pellets since the accuracy loss. Different JSBs, H&N match, sniper mag, the list goes on. Same results.

I've removed the barrel again, it looks fine, crown looks fine, no apparent scratches in the rifling, basically it looks fine to me. No apparent damage to the layman here.

Now I'm thinking its the scope. I know I have sat my case down to hear it fall over on its side behind me at least twice. So maybe the scope has been whacked too hard. Well I did the Pepsi challenge on my scopes. I swapped them this morning, remounted them on each other's guns and then shot BOTH guns. The Urban still shoots as it always has and the Bullboss is still disappointing me.
I also checked the orings on the barrel. I feel no puff of air when I shoot, but I have some nitrile orings so I will replace the outer ones on the barrel for sure. One of those looks a tad flat spotted, but no real damaged there. The probe oring looks great.

The chrony still reads consistent 940-950 fps +/- 10 fps, no huge variations in muzzle velocity. When it shot great it was shooting at 1000fps. But it was still set to 1000 fps when it started shooting bad so I made that 1000 fps to 940 fps change well after it started shooting bad.

One last thought, the bore snack brush wires likely never got to the barrel. I could see them on the threaded shroud end cap when I stopped cleaning with it and there is about 4"-5" from that to the barrel crown.

I am at a lost, is there anything on these guns that can suddenly take a turn for the worse? Its frustrating.
Before this happened I loved this gun. It has tons of power and although its no 100 yard shooter, it shot great in my opinion for backyard plinking.
Thanks guys, hopefully with some help I can figure this out, but as of right now I am stumped.
 
 Recently had same issue (.25 Bullboss). Never had a problem with the bore snake though and find them highly useful. 

I thought I had been clipping the shroud as well, so I just removed the entire thing and shot it without the QE shroud. Barrel only. Kind of loud. Same issue. I think I had not seated the barrel correctly upon the previous cleaning. That was the main "delta".

I have also had hammer spring issues that have impeded consistent accuracy. I routinely have to crank on the allen key all the way CCW until the rifle wont fully cock, then back it CW a turn or two until it will.

However, back to subject at hand. I had not properly re-seated the barrel. Accuracy back on track.

I have a love / hate relationship with this rifle. It needs to get a tune.
 
Upvote 0
I didn't remove the barrel the first time I cleaned it, but that's a great point. I have made sure to slightly tighten those two set screws and then rotate the barrel some, that way I can feel it drop into the right spot for the screws. Next time around (my barrel is currently out) I may dot those spots with a paint pen if I have one handy, That way I can see them with the set screws removed.
I don't think my hammer spring has been the culprit, but I need to bring out the chrony when I shoot without the shroud and recheck my fps. My shot pattern is completely random and looks circular when 10 shots are through. No vertical or horizontal stringing, just completely random.

One other thing I will do is oil that pellet probe oring. I just though maybe the bore snake rubbed it dry. The fabric of the bore snake was hard to pull through by itself, it was for a 22 / 223 I think. And when the brush wires came into play there was basically no way that would pass through the barrel. It didn't even make through the shroud cap. So now my fingers are crossed that oring is extremely dry when I get home. A little silicon grease may be the trick.

Strange that your hammer spring needs to be turned out, mine is run as far in as I care to go without taking it apart to see it. I've run mine in to the point it is tight and it still shoots pretty fast.
 
Upvote 0
Ok, I've only run 10 shots through it, but it seems to be back to good.
I oiled up the pellet probe o-ring, it was bone dry. Dave without your info I would have torn that o-ring to pieces. I have rebuilt many hydraulic cylinders and i consider myself good at getting behind a seal or o-ring without damaging it, but that thing would have been impossible to remove in one piece. And if you didn't tell me the cap unscrewed I would never have known. So thanks Dave.
I also put an o-ring on the plastic nut that secures the shroud to the barrel. The Hatsan schematic looks like it is supposed to have one, but mine never did. So I added that which gave the nut-to-shroud fit a much better feel. Also, when I tightened the shroud securing nut, I torqued it down tight. I didn't make it gorilla tight, but its very secure now.

Pictures . . 
1524830805_14399290155ae312556ba208.40049298_0427180720[1].jpg

That above is the Gamo Urban at 12 yards. 3/8" C/C- 10 shot
1524830866_3079967735ae3129272c639.57790948_0427180720b[1].jpg

Lower left above is the bullboss at 25 yards.
Top center is the bullboss yesterday at 12 yards (about 5/8" maybe 3/4" C/C).
Top right is the bullboss this morning without the shroud. It's the first string I've seen. The first shot is low and so was the last. Otherwise not a bad group and that low shot was the first shot after lubing the pellet probe o-ring and changing out the outer barrel o-rings.
1524831146_13738999165ae313aaa1cdd6.38539917_0427180720c[1].jpg

Here is a 3/8" group at 12 yards after I put the shroud back on.

I am curious to see on lunch if the accuracy is here to stay and if it gets any better, because it used to be a bit better at this close range.

If it is indeed fixed I have an important note. It really matters how tight you screw that plastic nut back on that holds the shroud. It puts the barrel in tension and the shroud in compression. It really changes how loose or stiff the barrel is.
It's only one group, and its not even that great of a group, but man-o-man I am hoping this thing is fixed!
And fixed or not I will get it in front of a chronograph some more and also try to get the fps down some more too. That adjustment feels like it is near the end of its range though, time will tell.
Thanks everyone.
 
Upvote 0
1524853587_4439751255ae36b53ab5df6.05540611_0427181214[1].jpg

Very top is about 7/8" C/C at 25 yards. The right group is also at 25 yards. I don't like to dismiss flyers for better accuracy, but I think this means my bullboss is back to being mostly the same. I know it's not very impressive, but that is a vast improvement. It feels like night and day when looking through the scope.
It now shoots at a different speed, so i need to fine tune my power and maybe try some more pellets at the current power level and I am pretty sure it can get back to the accuracy it had before; maybe better :). It was out of the box at 1000 fps, I didn't tune it that high. Then it started to shoot bad so I lowered it and tried more pellets.

I think what happened was that shroud nut worked loose. It didn't have an o-ring like shown in the schematic. It's possible that I rubbed the oil off of the pellet probe o-ring and got some intermittent blow by causing issues, but the probe itself says pretty slick with oil so I don't think that was it. And I didn't change that o-ring, just oiled it.
Link to schematic:
https://cdn.shopify.com/s/files/1/1711/3177/files/BULLBOSS.PDF?18406802655913783755

Or here for a clickable link.
I see the url says shopify, but it really is Hatsan's site
 
Upvote 0
I did not read all of the responses but here is my opinion. Your boss is done. Unless you can figure out how to put a new Barrel on it. I have heard that you should not use a bore snake on an airgun even though it is a soft thing. Apparently it has a hard piece on it that screws up airguns. So everyone needs to use something called the crown saver from Mac 1 airguns. It cost about $10 and it is the only way to clean your airgun http://www.mac1airgunshop.com/mobile/Product.aspx?id=37642
 
Upvote 0
Mine just STB 15 min ago. Stopped firing all of a sudden. Was having a great time as I finally got a chrono yesterday. It’s a .25. Would not get past 775fps with 26gr JSBs. Anyhow, suddenly no fire. Removed air cylinder to prevent accidental discharge, then half of the hammer + one other oddball piece fell out of rifle. I have not modded in any way. Happy Friday! There will be some happy ground squirrels this weekend. Guess I’m gonna be sending the rifle back for repairs. Bummer. This thing has never quite been right.
 
Upvote 0
rwbarrett-Maybe you're already aware of this but in case not-- it's VERY important that there's clearance between the shroud & the barrel for it's entire length. Hold up the rifle with good lighting behind it to check. If it's touching anywhere that'll definitely mess up your accuracy. Get the shroud positioned so that it's slight flat area is on the barrel side. This is usually with the letters QE topside.

Ed
 
Upvote 0
Wow, Nainoa, that's terrible. I hope they straighten it out for you quickly.

OldCorps, yup mine has a good gap all along the length of the tube and barrel.

I lowered the hammer spring tension some more to get the JSB 18gr shooting about 880 fps (870-890). It was back to its old self! I also shot some monster redesigns through it and they did pretty bad, but there are two groups from those in the pic below. They shot about 100 fps slower. 
1525110463_1185559645ae756bf9eb5f7.38269314_0428181541[1].jpg

1525110507_3470646975ae756ebeb71a5.38998998_0428181542a[1].jpg

Best group was in the center, about 1/2" And that's 10-shots at 25 yards. .22 bullboss / JSB 18gr / roughly 880 fps
 
Upvote 0
"agnthooziast"That F.P.S. change was very key advice in my experience. Glad you're back in business!
Click to expand...

Yes, 
Jking you were right on.
"RW, I think 940-950 might be a little fast. I’d back it off to about 870-880 and try it there. Who knows, a clean barrel and lower velocity might make a big difference. Probably one of the easiest things to try as well. Hope you get it straightened out.
jk"

Thanks!
 
Upvote 0
Here is a follow up, it still shoots great. Great, for this gun IMO, is about a half inch group at 25 yards. 10 shot groups. The FPS advice was key, as another member pointed out. And the best part, I get 50 shots per 3000 psi fill. I could probably get more too, but I stopped at 50 and still had about 125 bar according to the gauge. When I refilled off my tank I was able to here the cylinder's check valve open right at 2000psi. Which i think is close to 125 bar without looking up the conversion. This gauge stays in the green down to 100 bar, but I was basically out of targets at 50 shots.
My guess for why it acted up is still probably that i dried out the probe o ring when cleaning the barrel. All i really did to remedy it was lube that o ring and adjust the hammer spring. I also lubed the barrel's outer o rings, but since they see no air pressure that only assisted reassembly. 
i did also disassemble and reassemble a few times but again, lubing that o ring was really all i did different, that and lower the velocity.
I really enjoy this gun. Its heavy, but it is priced well for what it does.
thanks again to everyone who helped!
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu