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

[K.O.]

Hi Kirby, I'll give that a try and report back this evening.  I always push the pellet from breech to muzzle.  With a good barrel I expect to feel uniform resistance as it travels down the bore to the muzzle.  In the suspect barrel, it was very loose.  It occurred to me that initially that may have been a symptom of damage to the pellet as it raked across the sharp transition to the bore.  However I tried again after breaking the sharp edge and it became much easier to get the pellet past the leade and into the bore, but it still felt too loose as I continued pushing.  Uniformly loose, but too loose.

I've only seen that behavior with one other barrel, the .22 cal one that came with my dual-cal Beeman RS2.  The .22 didn't group too badly as I recall, but after slugging the .177 barrel and finding it to have uniform, moderate resistance when pushing a pellet through, I was subsequently blown away when I began shooting 1/2" groups on average at 25 yards with a cheap springer, and occasionally having groups in the high .2's and low .3's.

That experience is why I'm suspicious of the bore on this QB, and partly what prompted me to start this thread with the pics of the faint rifling marks and a presupposed assertion that I was dealing with a bad barrel.  But given my limited experience, I wanted to get some other opinions.  That the thread has gone on for this long without anyone agreeing with me, maybe I was wrong. 

But I haven't tracked down the problem yet so there's still hope that I was right

I think you are probably right about the bad barrel but sometimes they can be saved it depends on how it is bad, if the breech end is tighter then you know the drill lap it and it just may fix it.

Me I can not help myself I want to figure out the why.

Me I think these things should be smooth bore till the last  1/4 of the barrel (as long as the pellet skirt seals) with hammer forged rifling heck they are softer metal than PBs so it would be better and in IMO cheaper to make barrels in the end...

[K.O.]

If you find it is tighter at the breech you might depending on what you find try hand or fire lapping   or  a combo of most of the way by hand if just one small area and finish with fire lapping.

but depends on what you find...

I am pretty sure you already know about it but for those that do not...

second result down is a fire lapping tutorial,

https://www.google.com/search?sourceid=navclient&aq=&oq=&ie=UTF-8&rlz=1T4ADFA_enUS508US508&q=fire+lapping+air+rifle&gs_l=hp..0.41l44.0.0.0.5318...........0.

it sometimes does the job,

[nervoustrigger]

A couple of quick updates:

.177 barrel - pushing a couple of pellets from muzzle to breech revealed no evidence of a tight spot near the breech.

.22 barrel - not choked

I converted the rifle back to .177 and omitted the barrel band in preparation for another round of testing with a floated barrel.

[vigilandy]

Thanks for the info on the 22 barrel and I'm keeping my fingers crossed waiting for the results of your next shooting session!

[nervoustrigger]

Hi Andy, man I'm really hoping floating the barrel helps (with the addition of the second set screw in the receiver) but I'm skeptical considering how near the QB79 band is to the receiver in the first place.  Meaning if the band were way out near the muzzle, I could see it make a difference.  I guess we'll see. 

If it does not, I have some other things in mind to try to ascertain if barrel harmonics are the fly in the ointment.

BTW, when I slugged the .22 barrel with a JSB 18.1gr pellet--which grouped really well--the rifling marks on the head were very slight.  So maybe what I was seeing with the .177 barrel isn't necessarily a bad thing which would support one of Kirby's earlier comments.

That reminds me, Kirby also called attention to the smeared lead trailing off the skirts in my initial photos.  That was gone after breaking the sharp edge at the start of the rifling.

I'll keep any eye out for the additional pellets as well.

[K.O.]

Hi Andy, man I'm really hoping floating the barrel helps (with the addition of the second set screw in the receiver) but I'm skeptical considering how near the QB79 band is to the receiver in the first place.  Meaning if the band were way out near the muzzle, I could see it make a difference.  I guess we'll see. 

If it does not, I have some other things in mind to try to ascertain if barrel harmonics are the fly in the ointment.

BTW, when I slugged the .22 barrel with a JSB 18.1gr pellet--which grouped really well--the rifling marks on the head were very slight.  So maybe what I was seeing with the .177 barrel isn't necessarily a bad thing which would support one of Kirby's earlier comments.

That reminds me, Kirby also called attention to the smeared lead trailing off the skirts in my initial photos.  That was gone after breaking the sharp edge at the start of the rifling.

I'll keep any eye out for the additional pellets as well.

I think  #1 .177 is more difficult to tune the lighter pellets are more sensitive so it can be a real challenge some times...

there is a finer line between to loose and to tight  , to loose leads to precession/spiraling because it is coming out the bore because of tilted


 to tight mangles  the pellet leading to imbalance and precession/spiraling (then there are pellets such as the Daisy pointed that just seem to be prone to it for cg or aero reasons)

now the thing is then you throw in barrel harmonics at the same time and  you have a big group that is hard to figure out

ok so the .22 is not having the harmonics prob well it may just have some but smaller just because of the freq is different and different for the rifle as a whole.

removing the barrel band on the .177 may help or hurt for a couple reasons.

1. it is already a long unsupported barrel that would be prone to harmonics but the band allows a bit of shifting changing the nodes slightly shot to shot

2 the longer unsupported barrel(without band) changes the freq (lower IMO) but may do so in the same way every time or just move it to a

freq that the barrel is more resistant or susceptible to... also imagine a very slightly bent barrel or one with the bore just a touch off center...

here is some food for thought
https://www.pyramydair.com/article/Airgun_accuracy_It_s_not_a_given_Part_1_The_barrel_September_2009/67
https://www.pyramydair.com/blog/2009/07/do-pellets-spiral/

ok so harmonics can be tamed a bit with barrel weights that beak up the nodes...

more food for thought just cause it has the HOTS...
https://www.pyramydair.com/blog/2011/10/pellet-velocity-versus-accuracy-test-part-1/


if it is a problem with harmonics only there is no keyholing and movement of groups left or right(precession) at different ranges, they just get

bigger at longer ranges.

and the above link shows the spiraling effect they will tend to keyhole also

So what is my point,





reading bad groups for hints on what is going on...

and at different distances...

roll the barrel is it slightly bent, shine a light make sure it was bored strait, I have had a PB that had an off center bore (cheap .22 that shot great).

 Some times it is one thing some times its many...

Then there is one of these if the pellet is being destabilized by the high pressure needed to get it near 900 fps and transonic...
https://www.pyramydair.com/product/hatsan-air-stripper-for-select-177-cal-hatsan-air-guns?a=4556#Reviews

this is probably old hat but not for those just getting into air rifles.

[K.O.]

Then sometimes there are barrels that you just get whooped on by...

Sometimes you get to feel good because you solved the mystery and tamed the durn thing...

this is just my approach and there are many that have a ton of experience that have better methods or even disagree with some of my ideas

that's a good thing cause it may be I am off course a little I am not a pro...

[K.O.]

Can not resist a couple more links...

http://www.arld1.com/nutation.html

http://www.network54.com/Forum/79537/thread/1254290801/CM+group+showing+yaw%2C+implying+nutation+and+precession--Real+world+example

[K.O.]

Those that may want to try an air stripper here is a thread about using a marauder part to make one...

http://www.gatewaytoairguns.org/GTA/index.php?topic=42482.0

[nervoustrigger]

Kirby, thanks for the ongoing ideas.  I got busy today and haven't yet had a chance to fully read and absorb everything in the links but I plan to.

I worked on the rifle some more today.  As I was about to get started shooting some groups, I noticed a puff of air escaping during the firing cycle.  A little baby powder sprinkled around the transfer port and the bolt revealed it was leaking at the bolt.  So I went in and disassembled the receiver to have a closer look.  I had previously noticed the bolt was bent so I had rolled it on a piece of plate glass to determine how it was bent and then corrected it.  Corrected the body of the bolt to be more specific.  I could not tell if the probe was bent.  This time around, I chucked it up in the drill press and quickly identified that it was so I straightened it.  I then applied a couple of coats of lacquer to the O-ring groove and let it dry, then installed a new O-ring.  Got the rifle reassembled (no barrel band) and went outside and shot this group with Air Arms 10.3gr.  The second group wasn't nearly so good so there's still more to be done, but this is the first indication I have seen that the barrel may be capable of grouping. 

The additional pellets that Andy sent arrived today so I have plenty of pellet types to test now!  Keeping my fingers crossed.

[K.O.]

(>")> <("<)  (>")>  a short getting close to victory dance for ya from Kirby the cream puff...

I can tell you are trying for at least a touch better...  was that at 700 or 800+  I wonder what the twist rate is on those barrels?

Honestly I just think it is cool to see you take on the challenge and even  getting to act like it wants to group is an accomplishment... 

It has to feel good  after the effort

[nervoustrigger]

I didn't run the AA 10.3gr over the chronograph but it was doing about 815fps with the 10.5gr CPUMs (15.5fpe).

I'm not quite ready to celebrate just yet but that one group is very encouraging after countless times watching pellets spray all over the paper.  I was so shocked that I accidentally did a 6-shot group instead of the usual 5!

[K.O.]

Not quite out of Ideas yet...     be the pellet tune the pellet

Jason I wish I was there with you because I could do some of the scut work that I think would be one of the next steps...( plus it is just easier to makes sense )

Getting out the Vernier calipers and sorting a few pellets  first  the air arms ant then the next best so on I am betting it would like

the  4.51-4.52s best ( from looking at the  at the pic at beginning of the thread.)

it is not easy because of how you need to be very consistent but it can be done for small testing  sets of pellets.


I do not know for sure if it is worth the effort but it did seem to make a difference with the few I did but it is such a pain that its is just good for finding out what  a barrel likes...

 If you have a co² revolver  measure  to make sure and push the pellets through from the big side to the little one through its

magazine, could be modified for different sizes with sand paper and dowel or a reamer... for them  to hold the pellets without them falling

out the have to be about 4.51 or so on the small side and bigger on the other to make loading easy...

http://www.walmart.com/ip/Speedloader-Clips-for-Crosman-357W-Air-Pistol/20753525?action=product_interest&action_type=title&placement_id=irs_top&strategy=PWVUB&visitor_id=83946928908&category=0%3A4125%3A546956%3A1107532%3A1224812%3A1080384&client_guid=e1954c7f-ebdf-4a92-ae5b-e3663ee70689&config_id=2&parent_item_id=17173783&guid=0b6117da-6e7c-4d46-ba5e-b654b5f10e6f&bucket_id=irsbucketdefault&findingMethod=p13n

 


I would for measuring a few of the Air arms pellets and see if it matters. I would then if getting groups try your  heavy-ish shopmade LDC again it just might shrink them ... ( I think some harmonics still just not as bad)

 that is if it  was not a fluke (yesterday) and it is trying to group now,  I would be tempted to do a quick 3-5 shots again today just to make sure.


Ted and sorting vid and this is a choked barrel so it will be a touch less picky until the to large pellets

[K.O.]

If not a fluke group(and I do not think it was) there were three factors that changed

The bolt

the barrel band

and maybe three right pellets...

it could have been just the bolt... but the only way to know would be to put the barrel band back on...

[nervoustrigger]

Quick update.  I'm in the middle of a barrel band / no barrel band experiment.  I just finished a round of groups using the pellets Andy sent, using a tight barrel band like I normally do (has given good results with every other QB I've worked on).  I just emptied the tank and pulled the barrel band so I can test again without the band.   However, two pellets did decently with the band in place.  The boxed CPUMs (die J) produced a 0.59" group and H&N FTT 4.52 produced a 0.68" group.  Everything else was over 1" and most over 1.5".

Kriby, I totally drink the head size matters Kool Aid.  For example, in my thread &quot;Crosman boxed pellets - first impressions&quot;, I sorted out some CPUMs by head size and shot them with my son's QB79.  Groups at 25 yards were 0.5" on average with unsorted pellets and those with matched heads grouped more like 0.15" - 0.20".  No joke.  But again, that rifle is not pellet picky...it's the one I mentioned earlier that gave groups under 1/2" at 25 yards with 5 of the 10 pellets I tested.  No fouling shots in between, no sorting, no special anything.  Just grab a tin and shoot 5 pellets at the target, then grab the next tin and shoot 5 more. 

Aaaand...drum roll...the two that just grouped well in Andy's rifle were indeed on the upper end of the spectrum.  The CPUMs are measuring 0.178-0.179" and the H&N FTT are measuring 0.177-0.178".

[K.O.]

I remember that thread...

I just do not hold on to detail very well any more

so it looks like 4.52 and 4.53 is what this barrel likes and will do ok with 4.54 ..?

So .5" groups are  not to bad but trying  for a .177 hole is a good goal

eagerly awaiting the results of the band/ no band test...

[vigilandy]

I can't be of any help to troubleshoot this barrel problem,  but wowsers I'm learning alot from following along.   All of a sudden I realize how little I know about prepping a barrel!  Thanks for all the help guys. 

[vigilandy]

Jason, it just occurred to me to ask.  Did you do the most recent CPUM group with your pellets or mine? Both are Die J and made very recent to each other so you would think results should be similar. 

I also wonder how big of a role that wire probe plays.  It's soft and is easily bent.  I'm looking at the gun from BZ and the probe appears to be more solid. 

Just a FYI,  I would be very happy with the groups you are shooting now.  You saw what it was doing before... 

[K.O.]

"I also wonder how big of a role that wire probe plays."

the answer is it depends...

Imagine one side of the pellet getting very slightly or more ground away or slightly mangled and the imbalance that creates

[K.O.]

And like the 50+ year old kid he is  " Is it soup yet?!"

anticipation...   anticipation...  anticipation...

I wonder if it was tried with/without the heavy-ish ldc also...

"  Kriby, I totally drink the head size matters Kool Aid.  For example, in my thread "Crosman boxed pellets - first impressions", I sorted out some CPUMs by head size and shot them with my son's QB79.  Groups at 25 yards were 0.5" on average with unsorted pellets and those with matched heads grouped more like 0.15" - 0.20".  No joke.  But again, that rifle is not pellet picky...it's the one I mentioned earlier that gave groups under 1/2" at 25 yards with 5 of the 10 pellets I tested.  No fouling shots in between, no sorting, no special anything.  Just grab a tin and shoot 5 pellets at the target, then grab the next tin and shoot 5 more.  "

that one is a keeper for sure and I get the feeling your goal was to get this one to mature into close as possible of a sibling as possible...

you know it may(I feel some do) mature a bit after some lead thru the barrel  50-100-200 pells after lapping... ?