GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: redlined_b16a on January 23, 2018, 11:10:32 PM
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.25 cal BullBoss.
Groups arent as tight as Id like them to be.
I re cut my barrel crown on my AT44 .22 to an 11 degree target crown.
I machined a bore alignment tool.
Shimmed my 3 jaw chuck until I got a about a 1/2 thousands run out.
The at44 bore was about .005" from being center of the barrel.
The bullboss measures .024" off center.
My 3 jaw or my ablities do not allow me to compensate that much accurately.
Next step is to buy a 4 jaw or get an outside machinists involved.
My question is:
How much off center is too much?
My scope has to be shimmed already or I can not zero.Shimmed to the left.
Gun is about 4 months old.
I already modified the crown so I think sending it back to hatsan is not gonna fly
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Google searches show its a common old rifle issue.
Some say it effects some say it does not.
With a LDC it would effect with clipping and two of my plastic hair curler baffles are chipped
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Instead of doing 11deg. just cut it off square and use a brass round head machine screw in a drill with abrasive lightly both directions on the bore. Works the same but hole doesn't have to be in the center. Regards, Tom
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I'll give it a try.
I like to over think stuff.Figured I have a lathe I can machine it!
The phrase that always gets me in over my head.
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That, and since you have a lathe, I would move the breach forward, cut the rear off, and re-locate port to be at 6 o'clock and the bbl bore centerline indexed the 12 o'clock.
Has been done for decades on older out of center bbls and modern AG barrels quite a bit. ;)
Knife
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Instead of doing 11deg. just cut it off square and use a brass round head machine screw in a drill with abrasive lightly both directions on the bore. Works the same but hole doesn't have to be in the center. Regards, Tom
If the bore is off center, then even if you cut the barrel square the crown will still be at slight angle won't it? Will the round head screw method correct that by removing some more material from one side then?
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No Sir. The end, (Crown will be at 90* to barrel. Regardless whether it is centered in the actual barrel steel. Look at many Smith & Wesson Revolvers. With the rib, and underlug being from the same piece of stock, it is not in the center of the piece of steel. Same/Same.
The screw will index off the edges of the actual bore, not the outer walls of the barrel. Therefore, it will still find dead center. ;)
Knife
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I remember about a year ago a guy on this forum was putting a LW barrel on his gun, he even showed a video of the barrel in his lathe chuck spinning to show how badly it was off center, I don't recall if he ended up sending the barrel back or not nor even if he used the barrel. This is really bad news especially of you have a long LDC, it's likely you'll get clipping, I'd let them know about the situation myself, chances are they're going to say sorry, no can do. Five thousand's is way too much for sure.
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My bullboss bore is .025" off center.
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Actually although I am a proponent of the brass screw method, i want to point out it only has a self-indexing, auto-squaring feature if the bore is drilled off center AND completely parallel to the outside of the barrel. Well, at least for the last inch or so near the muzzle. My understanding from having cut and recrowned a number of barrels is that it’s more common that the bore wanders along the length of the barrel, following an arc for example. That being the case, the axis of the bore is more likely at a slight angle relative to the OD, so if you square off the end based on the OD, the bore intersects the muzzle at a slight angle.
If that doesn’t make sense, let’s look at an extreme example. If you imagine a solid block of steel with a grossly mis-drilled hole that goes through at a 30 degree angle, the hole you see on the outside of this block is an obvious oval. This oval hole is our muzzle in this hypothetical example. No amount of spinning a round head screw against that oval hole is going to produce a “muzzle” that is precisely perpendicular to the axis of the hole. As such, a pellet sent out of it would not experience an even release of expanding gas around its skirt and therefore would leave somewhat destabilized.
How would one go about solving that? Well, it seems you would need to index off of a snug gauge pin inserted into the muzzle and then make your facing cut.
With that being said, my experience tells me it’s all pretty academic. I’ve recrowned a few barrels whose bores were probably 0.020” or more out of concentricity at the muzzle and, after making a beveled crown with the brass screw method, on average they grouped as well as barrels that didn’t have this issue. I know at least some of these had a wandering bore because the concentricity offset moved when I lopped off a short section from the end. To be fair, there are far too many variables at play to proclaim it makes no difference whatsoever but from a practical standpoint, I think that’s a close enough approximation to be useful.
Tl;dr Don’t immediately blame poor groups on a bore that is off center. More than likely the problem lies somewhere else.
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I contacted Hatsan just to see.
Rolling my barrel across a flat surface ir wobbles too.
Ill recrown and hope for the best.Right now I can get 3/4" groups at 35 yards which is fine for my hunting needs but at 50 yards groups are just above 1".
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The bore being not concentric to the OD of the barrel is common on all guns. Every PB that I've threaded has had this issue(Remington, Savage, Ruger). Not too much of an issue with air rifles, as the barrel doesn't heat up with use. I use gauge pins to indicate the bore in with the four jaw to thread or re-crown.
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My used QB78D came to me with the .22" barrel chopped to 14". Not only was the last 1/2" of the bore scratched up from some lame effort someone made at guiding a crowning device of some kind, but the bore was over 1mm off centre. As I wanted to use a long-ish air stripper this was a problem. I cut it down to 13.4" where the bore was still intact, then centred on the bore in my 4 jaw and trimmed the 15mm OD down to 1/2" and threaded it, then crowned the new muzzle on the lathe. Worked out nicely. But lacking the lathe I wouldn't have bothered.
You seem also to have a warped barrel, if I'm understanding the wobble on the table thing. I'd put that against a straight edge and get to work correcting the bend, using whatever improvised means come to mind. Sighting down the bore combined with a good straight edge and rolling on a known-flat surface would eventually help in adjusting it to truly straight, using whatever leverage I could put together.
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Indeed, straightening a barrel can be done reasonably easy by hand with the barrel clamped between wood blocks in a bench vise, provided the curvature is over a fairly broad distance. But it’s also unlikely to affect your group sizes in a meaningful way, just where they land relative to where your scope is pointed.
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A little update
Played a few hours with the boss.Got the barrel strighter.
Did not measure it but against a stright edge it was about a .050c bend.A slow steady long curve.
The o.d. runout was within .005 thousandths measuring breech midle and muzzle read outs.
I noticed if you look down the barrel o.d. you can see a bunch of hills.The barrel o.d. has about 10 spots ranging from .010"-.022" diffrences in heights.I guess that's part of the fordging process.
Used the drill and brass with lapping compound method.
Barely tightened groups up if any.
35 yards and I tried many diffrent holds.
Best I can do is a 13/16" ctc.
The intresting thing was I tried with no baffles or end cap to eliminate clipping(even though baffles are already clipped)and the group opened to a 1.125" ctc group.
Install baffles in the q.e. and tightened back up.
I think I need to chop off 5/16" off of my barrel to get that damaged land out to rule that out.
Perhaps it is the shooter but my at44 can pull 1/2" ctc at 50 yards
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Sorry if I missed it but try pushing a couple different pellets through from breech to muzzle and see if you catch any rough spots or loose spots. And at the crown, if you feel any increase in resistance as the head of the pellet emerges, there's a burr. I think your barrel is choked, so it won't be quite as obvious an an unchoked barrel because you will already be encountering a restriction near the muzzle but if you watch carefully, you can distinguish the difference. It's pretty easy to raise a burr if you put a little too much pressure when spinning the screw against it...it's the most common problem I see when helping people with the process for the first time. There's a more comprehensive DIY accurizing article in my signature if you are interested.
[edit]Just re-read and noticed your comment about a damaged land. Yeah if you can see damage, I agree address that first.[/edit]
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Just to be sure we're taling the same thing here. Which of the two are we talking about here?
Are barrels that aren't stright along the outside, which willnever run ture (at least unless you straighten them).
Are barrels with a bore that is off-center, that will run a true as can be on the outside, but the bore is well off of dead center.
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I have both a curved barrel that I strightened today
And my bore is not concentric with the barrel o.d.
But that is no longer my concern.The damaged land is now.
I will post up a picture.
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(https://imagizer.imageshack.com/v2/150x100q90/923/C0q7c7.png) (http://imageshack.com/f/pnC0q7c7p)
(https://imagizer.imageshack.com/v2/150x100q90/924/WvYsdb.jpg) (http://imageshack.com/f/poWvYsdbj)
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Not that I wouldn't LIKE the bore to be on-center, but I don't sweat it if it isn't so long as the barrel shoots well.
This one is off center. Does make an LDC a bit more of a problem, but other than that, the barrel shoots so well I've no plans to replace it.
(http://i157.photobucket.com/albums/t50/ribbonstone/QB%20mods/f5a62be2-7e44-48ca-a8cd-b50770dc6721.jpg) (http://s157.photobucket.com/user/ribbonstone/media/QB%20mods/f5a62be2-7e44-48ca-a8cd-b50770dc6721.jpg.html)
And if you want to get all "ticky" about it, this RWS 34's bore at the breech is likely slightly off center too...but it hasn't kept me from shooting it for the last 24 years.
(http://i157.photobucket.com/albums/t50/ribbonstone/springers/DSCF2181-1.jpg) (http://s157.photobucket.com/user/ribbonstone/media/springers/DSCF2181-1.jpg.html)
If it makes a rat'srump of difference, I can't proove it. These aren't firearms, so uneven heating/expansion isn't going to play a part like it would in a powder burner,
I won't condem a crooked outside barrel, or a straight outside/crooked inside barrel until I've shot it. If it shoots well. I'll leave it alone (as there are many more viusually perfect barrels that won't shoot real well).
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Like I stated the off center is of no concern anymore.When I first noticed it I had never heard of this issue.
I have email Hatsan and filled out a form plus sent a picture but on the customer service form it ask specifically if I tried to repair it myself.
I was honest so I already know im on my own and thier reply will be that they can sell me a replacement barrel.
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True enough. It it ain't broke, don't fix it. Problem is, the guy's gun isn't shooting well at all. Big groups, off to one side so he has to shim his scope. Not good. Sounds to me like that disturbance in thee rifling might be the worst of it. Time to chop and crown.
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That ding on the land is a problem. Not something I'd want to fix unless I had no other choice. (it's a PIA to cure). Best would be a new barrel if possible.
But if it were a barrel I couldn't replaced, would counter sink the barrel...likely bored back to a 3/8" hole just past the land-ding, then crown the deeply recessed crown. That way, you get to keep the outside (and threads) just as they are...cutting the barrel and recorwning will lose at least part of the threads.
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I was going to ask that question next on the counter sinking,If tgat has been done.Ofcorse Id let a machine shop do that.
Probly cheaper to buy a barrel from Hatsan.
That ding on the land is a problem. Not something I'd want to fix unless I had no other choice. (it's a PIA to cure). Best would be a new barrel if possible.
But if it were a barrel I couldn't replaced, would counter sink the barrel...likely bored back to a 3/8" hole just past the land-ding, then crown the deeply recessed crown. That way, you get to keep the outside (and threads) just as they are...cutting the barrel and recorwning will lose at least part of the threads.
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Options on repair
1: Counter bore as suggested but If I do that it would be a professional machine shop and how would I crown a counter bore.
2:machine off the damaged portion and re crown,make a new shroud retaining nut longer to reach all of whats left of the threads.I did not measure but that damaged land is about 5/16" into the barrel.
3: cut and machine just run shroudless and use a standard LDC which worries me cause its detachable and may cause legal problems.
Bull Boss is very loud shroudless
4: Buy a new barrel
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new barrel
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This was supposedly still accurate after the "mod" they did, lol...
(http://www.airgunhome.com/images/feinwerkbau2.jpg)
"After one of the big SHOT trade shows, the owners of the Westinger & Altenburger Co. (Feinwerkbau) of Germany presented us with this amazing feat of airgunsmithing - a Beeman/Feinwerkbau Model 2 CO2 pistol with the barrel making a complete twist around the gas cylinder! The gun actually shoots quite well! Note that the all-important final inch(25 mm) or so is straight - that and the crown are the only really important parts of the barrel as far as accuracy is concerned. When some shooter would say " I think I see some little defect in the rifling way down inside my barrel, or the middle is a little off, or the barrel is not quite straight, and that is why I am not shooting well" , the airgunsmiths loved to bring out this gun and ask if his gun was more off line than this one!"
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I see a lot of guns like that have had to eat several ldcs because the barrel bore is off center especially qbs and hatsans, hatsans worst is the threads are crooked on the barrel. David
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I see a lot of guns like that have had to eat several ldcs because the barrel bore is off center especially qbs and hatsans, hatsans worst is the threads are crooked on the barrel. David
David on the LDC's that I've gotten from you there's plenty room in them to work just great as long as they're not real crooked, I haven't had any crooked threads that I can tell on any of my SPA guns.
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Hatsans reply
Micky,
We are sorry to hear that you are having issues with your Bullboss.
Your RMA number is xxxxxxxxxxxxx.
Please send it to the address below, along with copy of your receipt and
a copy of this email. We will repair your item. If it's determined that other
issues were caused by something other than manufacture's defect, i.e.
user error, tampering, abuse, etc., we'll contact you with a cost of the
repair and return shipping before we do any work.
For Pre-Charged Pneumatic (PCP) guns, we WILL NOT process your
repair unless the air cylinder and at least 1 magazine are included.
I asked if I could send just the barrel.
I have a feeling it is not worth sending since I recrowned it.
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Yeah based on the statement about PCPs must include the air cylinder and magazine, there’s nearly zero percent probability they would accept the barrel only. From their point of view, I can totally understand that. The visible rifling defect is perhaps the only thing that would justify sending just the barrel so make your case (or reiterate it) along with the photo and see if they will accommodate you.
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I don't expect them too just take the barrel but worth a shot.
If they decline just taking the barrel for inspection I'll move to plan B.
Try to use needle files and get rid of that dent.Check for group Improvement.
Plan C.
Try to counter bore barrel
Plan D.
Look into machining off the damage and making an extended shroud nut to catch threads futher back.
Plan E. Buy a replacement barrel
I just dont want to waste money mailing a gun for Hatsan to Say the gun has been altered and your repair cost will be $$$.
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I pushed a Jsb 33 grain through the barrel and the pellet is tight all the way through the barrel and its tight all the way through.
The pellet did catch on that damaged spot.
So I followed through with plan B.
Carefully filled down the ridges.Pudshed a pellet and cleaning patches.No more catching.Took several attempts.I will group Tommorow to test results.
I looked at the shroud nut and only half of the threads hold on.
If I make barrel shorter to machine out the bad spot I will have to trim the shroud on the muzzle end to make it work but I think its do able.
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Good news from Hatsan via email.
They reviewed my photos and after I asked I can send just tge barrel and they will send me another one.
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That’s great, glad to hear they are willing to work with you. Most places would rigidly stick to the written policy of sending the whole rifle back.
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I sent another email asking specificlly that since I re crowned and tried to file out that dent if they will charge me for a barrel.
Hatsan said no they will not because I tried to correct the issue.
Thats pretty cool
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The bullboss measures .024" off center.
My 3 jaw or my ablities do not allow me to compensate that much accurately.
Next step is to buy a 4 jaw or get an outside machinists involved.
I know you have the barrel being taken care of by Hatsan but one suggestion on crowning an off center bore the next time would be a hand turned crown cutter with brass pilots. It centers in the bore so regardless of the outer barrel shape, the tool is squared in the bore. I've used this tool on many centerfire rifle barrels when I was working as a gunsmith. Polished the crown with a brass crowning tool and fine compound.
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Hatsan USA is finally mailing me a new barrel.
Was just about to give up.
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New barrel arrived.Crown looks nice.
Transfer port shaves pellets.....easy fix but 6" from muzzle end tgere is a larger i.d. spot the the pellet gets loose in and it catches when pushed through.
None the less I will see how it groups.
It was the dirtiest barrel I had ever seen.
The black dirty ring is where the i.d. is larger and patches can not clean there.
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Excellence is upon me so far.
Benji 27grain and jsb 25 grain hole in hole at 35 yards
The crappy 33grain jsb first gens about a 3/4" group
Happy so far
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It likes the 30grain barracudas and I pulled a 1/2" ctc at 50 yards.
865 fps average for 51fpe.
I finally like my gun.
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Great hearing your results- a 35-yard one-holer is a keeper, no doubt. But the bottom line is your gun is shoo9ting up to your expectations now. a 50-yard 1/2" group is nothing to sneeze at :)
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Hope it stays that way for ya and does not lead up at the ring to much... If it does you might want to consider fire lapping with paste...(JB bore/tooth(the ones with hydrated silica))
right now... if it aint broke don't fix it.. 8)
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To be 100% satisfied Id have to open the transferport to .180"
And try to get more out of the hammer to get 33 grains at 900fps.
850fps is the guns limit.More hammer preload loweres the fps and stops the trigger from working.
I do like its performance with the 30 grain cudas though.
18 shots only use 2800 down to 2100 psi and thats with the extra valve holes plugged and one .165" port hole.
I can shoot 4 mags easily but .........more pumping.
I should have bought a bt65 short instead
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Glad to see Hatsan step up & send you a new barrel. Since you have a lathe, a 4 jaw chuck sure would come in handy the next time you need it. I don't use mine very often, but for some jobs, its a must have item.
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As a hobbyist a mini lathe is a must have tool.