Author Topic: SOLVED: bad barrel - work on it or replace it? (Read 41244 times))

nervoustrigger · « **Reply #60 on:** July 28, 2014, 02:57:18 AM »

Well, it continues to confound me. What follows are some results from the "no barrel band" experiment.

Removing the barrel band means removing the bottle and that means dumping the pressure. And pumping up from zero is a bit tedious and time consuming so I didn't have time this evening to run through the full set of different pellets again but I wanted to at least try the two best performers from the "tight barrel band" experiment.

No sense in dragging it out. They didn't do as well and there was a bizarre amount of vertical stringing. Check out the photo. So surely there must be a velocity issue, right? Nope. Ran several of each pellet across the chrony and the ES was 10-15fps for both pellet types.

How about the AA 10.3gr that grouped well yesterday without a barrel band? Could I reproduce that result? No, not really. They grouped but in two distinct places. Attached is a photo of a couple of examples. Naturally I suspected that the barrel was not firmly secured to the receiver but both the factory set screw and the one I added were nice and tight, and I had taken care to make sure the barrel was settled in the receiver as I tightened them...precisely because I wanted to minimize any tendency for the barrel to move. I also kept the rifle benched and did not lift it nor touch the barrel for the duration of the test.

What's next? Well, I think I'll run through at least a few more of the different pellet types and see if anything shows promise. If not, back on goes the barrel band. And while I have the bottle off, I'm going to take the opportunity to give the internals a good deburring and light polish and inspect the valve.

More later.

palonej · « **Reply #61 on:** July 28, 2014, 02:17:38 PM »

Can you say PERSEVERANCE Jason???
I commend you bro and am really hoping you get it sorted!!!

nervoustrigger · « **Reply #62 on:** July 28, 2014, 03:10:08 PM »

Thanks, Joe! It may beat me yet but I will go down swinging! I figure there is a useful bit of knowledge to be gained from this experience. I just hope when I'm done, the lesson is something other than not to try making a tackdriver out of a spitball soda straw.

vigilandy · « **Reply #63 on:** July 28, 2014, 03:14:59 PM »

I'm starting to feel bad about asking Jason for help. I had no idea how involved it was going to get... AND he's handpumping the 13CI bottle!

nervoustrigger · « **Reply #64 on:** July 28, 2014, 03:36:19 PM »

Nah, no worries Andy

Sorry if I'm coming off like a complainer. While I did underestimate the difficulty in diagnosing the issue, I knew it might go deeper and I was (and am) prepared to deal with it. Just looking to learn something in the process!

K.O. · « **Reply #65 on:** July 28, 2014, 03:38:41 PM »

Jason what you just did was proof that this rifles trouble after all the other work done to get it at its best, has a harmonics problem...

It will change a bit with hold, state of fill etc. etc. etc. ...

in PB they will work up a load that works for that rifle/barrel etc.

well the load in this case will change a bit with the tanks state of fill so that is a no go...

So seeing as we are near rimfire guys in velocity lets take a look at what they do to tame harmonics...

and the group without the barrel band the other day probably was a bit of luck and a matter of having hit a sweet spot...

from what you have already done the first thing I would try is the tight band and your heavy shop made LDC...

we could try to interpet the above results but honestly it is a very complicated subjective thing with guesses guided by science...

I would also try some of the cheaper seemingly cockeyed things that sometimes do work like o-rings on the barrel, ect...

the big problem is changing ammo and state of tune will change the nodes and the method needs to be more of a general damper such as some shrink tube on the barrel and then find a spot with a slightly heavy weight that works for a broad range of nodes caused by the differing state of tune/fill...

Otherwise I thing the .5"-.75" inch groups are about it... IMO...

http://www.rimfireshooting.com/index.php?/topic/2653-suhl-homemade-barrel-tuner/

If you make one like the ones with the set screw make it so you can slip it over shrink tube on the barrel it does make it more effective as a damper and plus you are marking up the barrel less..
http://www.network54.com/Forum/79537/thread/1122672923/Question+about+light+barrel

just a general search on rimfire harmonics...

https://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4ADFA_enUS508US508&q=rimfire+harmonics+barrel+

So yep the last battle and no guarantee of success but it if taken on just might grow some cloverleafs...

But remember this is all just IMO...

K.O. · « **Reply #66 on:** July 28, 2014, 03:49:00 PM »

http://www.network54.com/Forum/79537/thread/1118616857/%26quot%3BHOW+TO%26quot%3B+make+a+%26quot%3BBARREL+HARMONICS+TUNER-MUZZLE+WEIGHT------

just in case you did not click the above link that is in the other link...

K.O. · « **Reply #67 on:** July 28, 2014, 04:02:36 PM »

AND he's handpumping the 13CI bottle!

Jason kicks butt...

I just hope I do not come off as annoying and could be off track (but honestly do not think I am)

I was hoping that some of the real tuners would take the time to advise you...

To be fair though they are concentrating on their bread and butter making a good rifle great...

I like the challenge of getting a problem child good and just some times very good... which does not always turn out...

vigilandy · « **Reply #68 on:** July 28, 2014, 04:16:57 PM »

Quote from: nervoustrigger on July 28, 2014, 03:36:19 PM

Nah, no worries Andy Sorry if I'm coming off like a complainer. While I did underestimate the difficulty in diagnosing the issue, I knew it might go deeper and I was (and am) prepared to deal with it. Just looking to learn something in the process!

You're not coming off as a complainer-- it sounds more like you're working too hard on this problem! I've been learning alot reading KO's comments and following your progress. Right now, I have BZ's QB in hand and my neighbor is laid up temporarily so definitely take your time on this project.

K.O. · « **Reply #69 on:** July 28, 2014, 08:18:08 PM »

Here I go again and I am pretty sure you already checked but

is it well seated in the stock with everything hanging so much it would be critical on these...

I look at the tank and it looks to me like an effective seating the tank block would be a good move in order to help control resonances...

pretty basic stuff so I just sort of assumed plus I do worry about offending if it has been checked.

nervoustrigger · « **Reply #70 on:** July 28, 2014, 09:25:42 PM »

Quote from: vigilandy on July 28, 2014, 04:16:57 PM

Right now, I have BZ's QB in hand and my neighbor is laid up temporarily so definitely take your time on this project.

Cool, that's good news. While thinking over things today, I came to the conclusion that if I don't give the valve and striker assemblies a careful inspection and tune up, that I would always wonder if they were contributing to the lack of shot-to-shot consistency. So with your blessing here, I'm stripping it down tonight and taking a closer look at things.

nervoustrigger · « **Reply #71 on:** July 28, 2014, 09:34:21 PM »

Quote from: K.O. on July 28, 2014, 08:18:08 PM

Here I go again and I am pretty sure you already checked but is it well seated in the stock with everything hanging so much it would be critical on these...

I look at the tank and it looks to me like an effective seating the tank block would be a good move in order to help control resonances...

pretty basic stuff so I just sort of assumed plus I do worry about offending if it has been checked.

Well, don't worry about offending me

but I have indeed considered that and have tried shooting with the tank block screws and stock screw both loose and tight, without any particular improvement. And after the .22 barrel swap, I knew I could pretty much rule that out. That points to the barrel pretty solidly as the culprit...whether the bore or harmonics or a combination of the two.

nervoustrigger · « **Reply #72 on:** July 28, 2014, 09:39:16 PM »

Quote from: K.O. on July 28, 2014, 04:02:36 PM

I like the challenge of getting a problem child good and just some times very good...

Kirby, I want to give you a big thumbs up for hanging in there with me on this rescue mission and keeping the ideas flowing. I probably would have thrown in the towel otherwise.

Quote from: K.O. on July 28, 2014, 04:02:36 PM

which does not always turn out...

Haha, yep. Such is life.

K.O. · « **Reply #73 on:** July 28, 2014, 09:55:57 PM »

Quote from: nervoustrigger on July 28, 2014, 09:34:21 PM

Quote from: K.O. on July 28, 2014, 08:18:08 PM
Here I go again and I am pretty sure you already checked but is it well seated in the stock with everything hanging so much it would be critical on these...

I look at the tank and it looks to me like an effective seating the tank block would be a good move in order to help control resonances...

pretty basic stuff so I just sort of assumed plus I do worry about offending if it has been checked.

Well, don't worry about offending me but I have indeed considered that and have tried shooting with the tank block screws and stock screw both loose and tight, without any particular improvement. And after the .22 barrel swap, I knew I could pretty much rule that out. That points to the barrel pretty solidly as the culprit...whether the bore or harmonics or a combination of the two.

I felt that it was a barrel thing also after the .22 did well, but does not rule it out totally sort of like the valve...

sometimes it just a bunch of small things and any one of them changes the gestalt.

Not being there all I can do is try to give ideas by running my thoughts by you...

and it is easy to come off like a know it all type arse especially when you are the one doing the work, the only one who can feel and see

what the rifle is doing...

So I want to keep my tone as humble as I can but be as thorough as if I was there talking with you

And I feel you have just as much and more experience as I, I just have the time to type some of this stuff out for some of the newer

airgunners to see and ponder.

K.O. · « **Reply #74 on:** July 28, 2014, 10:01:24 PM »

Quote from: nervoustrigger on July 28, 2014, 09:39:16 PM

Quote from: K.O. on July 28, 2014, 04:02:36 PM
I like the challenge of getting a problem child good and just some times very good...

Kirby, I want to give you a big thumbs up for hanging in there with me on this rescue mission and keeping the ideas flowing. I probably would have thrown in the towel otherwise.

Quote from: K.O. on July 28, 2014, 04:02:36 PM
which does not always turn out...

Haha, yep. Such is life.

I think when you get done with the valve and get it back together with the barrel band it will give at least .5 groups...

But I think you are shooting for better and hey you do have a good chance of getting there...

you could have tried another .177 barrel but then that can be bigger crapshoot than dealing with what you know you have...

K.O. · « **Reply #75 on:** July 29, 2014, 02:48:11 AM »

" Kirby, I want to give you a big thumbs up for hanging in there with me on this rescue mission and keeping the ideas flowing. I probably would have thrown in the towel otherwise. "

I am sort of playing the role of kibitzing cheerleader

(should it bother me that it has been an enjoyable pastime)

I do think you would enjoy the experience/challenge without me also though, and thanks for sharing.

Just do not ask me to put on the uniform I guarantee it would not be a pretty sight

nervoustrigger · « **Reply #76 on:** July 29, 2014, 10:04:03 AM »

Well, I stripped it down tonight and inspected the internals. The only unexpected thing I found was that the valve stem is a loose fit to the valve body. Normally the parts are a slip fit but I could see a slight gap which means some air will be wasted during the firing cycle. I imagine that explains the slight puff of air I was feeling even after fixing the bent bolt probe. I'm planning to try a -005 O-ring slipped over the stem to see if that takes care of the issue.

Otherwise, the parts were just rough as usual. The slots in the air tube had burrs that put scuff marks on the hammer and spring guide, and the cocking pins and valve stem had pronounced machining marks. So I deburred and polished everything up with exception of the inside of the hammer which I'll take care of tomorrow. That, and smoothing out the exhaust port. I'm also thinking about doing an RVA if I get motivated. Seeing as it has enough hammer strike to handle ~1100psi air, I imagine it's overkill for CO2 duties. And hopefully back together Wednesday evening.

nervoustrigger · « **Reply #77 on:** July 30, 2014, 01:16:42 AM »

I got ants in my pants this evening after work. Added a RVA, milled the valve inlet, radiused the valve exhaust, replaced the valve spring, ported the tank block, made a new cocking pin, and drilled the hammer for the new cocking pin location.

Here's the major parts washed up and ready for assembly.

Tater · « **Reply #78 on:** July 30, 2014, 01:48:14 AM »

Quote from: nervoustrigger on July 30, 2014, 01:16:42 AM

I got ants in my pants this evening after work. Added a RVA, milled the valve inlet, radiused the valve exhaust, replaced the valve spring, ported the tank block, made a new cocking pin, and drilled the hammer for the new cocking pin location.

Here's the major parts washed up and ready for assembly.

I've followed this entire thread and some of this stuff is SOOOO way over my head. Fascinating stuff and I'm learning a bunch.
Thanks for sharing this entire process, it's a good troubleshooting model.

palonej · « **Reply #79 on:** July 30, 2014, 02:05:56 AM »

Jason my friend.....you gotta have some WOP in you bro!!!
Stubborn to a fault and fight till you drop!!
I am loving this thread and rooting like crazy for you!!!

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SOLVED: bad barrel - work on it or replace it?

Author Topic: SOLVED: bad barrel - work on it or replace it? (Read 41244 times))