Is this normal for all .25 LW barrels
Hi
If I push a .25 cal. H&N Barracuda (Beeman Kodiak) 31.02 grain pellet through the breech end of my stock AF LW 24 ” barrel with a cleaning rod I notice that the pellet encounters increased resistance immediately where the paper thin breech end of the barrel ends . This resistance then continues for quite a length of the barrel and then seems to disappear . When the pellet is at the last couple of inches of the barrel (the choke) it again encounters (much higher) resistance . Is this behavior NORMAL for stock Airforce barrels. I can understand that for the choke part but why should a barrel be choked TWICE is beyond me. Could it be that when the pellet is in the thin breech end, the flimsy wall slightly gives way and kind of stretches when the pellet is pushed through it and when the pellet enters the normal thickness zone of the barrel it encounters increased resistance as it cannot stretch the bore due to the thickened barrel .
P.S. – I am asking this because I am having accuracy issues with my Condor and need to eliminate the barrel as a probable cause . Any inputs from the veterans , fellow members would be a HUGE help . Just need to know if this is NORMAL for all stock barrels. Thanks in anticipation.
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When I first got this gun it grouped very well like .5″ or so at 50yd…since then it has been getting worse and worse…The other day I lapped the barrel according to Greg Davis’ instructions, using Mothers Aluminum Wheel Polish (on the Yellow forum). It seemed to help. But there is much inconsistency. Yesterday it was totally windless and 79F. Perfect conditions. My groups were all about 1.5″ then all of a sudden I get one group that was .5″ …maybe a tad tighter…I didn’t feel like I had suddenly acquired a Zen-like concentration for that group; I felt I had been consistent with my hold, breathing etc. for all.
I know that there are a lot of variables at stake. So it might be worth checking that seal.
Hi DG . To get at the delrin part you will first have to empty your tank ( just put in a few dimes in your fill adapter and screw in till it starts leaking ) , after making SURE that there is no pressure left you will need to pull out your valve stem ( insert two screwdrivers or spoon handles on both sides of the valve stem and pry it out ) then you would need a special tool for unscrewing the top brass insert , in case you don’t have the tool you may use needle nose pliers albeit a little carefully to screw out the brass insert , just behind the brass insert would be the delrin part and the spring.
I’d like to know how to remove the Delrin seal you are talking about…just to check it as my accuracy has been going downhill.
When I first got this gun it grouped very well like .5″ or so at 50yd…since then it has been getting worse and worse…The other day I lapped the barrel according to Greg Davis’ instructions, using Mothers Aluminum Wheel Polish (on the Yellow forum). It seemed to help. But there is much inconsistency. Yesterday it was totally windless and 79F. Perfect conditions. My groups were all about 1.5″ then all of a sudden I get one group that was .5″ …maybe a tad tighter…I didn’t feel like I had suddenly acquired a Zen-like concentration for that group; I felt I had been consistent with my hold, breathing etc. for all.
I know that there are a lot of variables at stake. So it might be worth checking that seal.
Yes, the bbl. or bore will be looser in a .25 at the breach end. As the machining releases some of the stress in the bbl. It is even worse in my .257. But OldGoat had already machined the bbl. for the standard breach. So there was nothing Dyotat could do about it.
The valve face where the del. plug rest may be too sharp, and causing it to sink further in. A mild radius might very well help here.
The reason several people here answered with what to you seemed not related to your question., is that we run into accuracy related questions often. And have found certain causes.
In your case, you found the answer your self, and it too was unrelated to what you thought might be the problem! Listen to advice without complaint. You my just benefit from the knowledge here. 😉
Knife
It may be Saturday before these guys have the time to look at this. But I am interested in the answer as well.
Finally nailed the culprit which was causing inaccuracy . The factory delrin seal had sunk too much inside the brass valve seat resulting in what I would call – ” A STICKY VALVE ” I had a partial valve lock at as low as 2500 p.s.i. even at PW6 with a heavy hammer (90 grams) and the pellet barely made it to the target at 50 yards and when the pressure came down to around 2300 -2400 p.s.i. it started barking and nothing would tame it down even at PW 0 . So either I had valve lock or too much velocity . Now I have put in a new delrin seal , a heavy hammer (90 grams) . To my delight – I filled her up to 3000 p.s.i. and even at PW 0 it didn’t lock up . I haven’t done much of accuracy testing but all of those 5 shots made a ragged one hole group at 50 yards. Question is how long do I have before this new delrin seal becomes sticky once again and would need replacement. Any idea anyone ?
I also tried pushing a pellet through a .22 and a .177 barrel . On the .22 this constriction at the beginning of the thicker part of the barrel could be felt but to a much lesser extent as compared to the .25 barrel . On the .177 barrel it is almost non existent . This leads me to conclude that the more material you remove at the breech end, the looser it get. Now this may be a whole new can of worms . In a .25 barrel the breech end of the barrel gets ridiculously skinny and with that breech sliding over it and getting hit with the hammer and the resulting jolt and chatter surely shouldn’t help accuracy ( remember the powderburner folks saying that “A bullet which doesn’t start straight doesn’t fly straight ) Though there are a lot of .25 condors doing just fine with the current design but maybe they can be made to shoot exceptionally brilliant with a beefier breech end of the barrel. Of course that would require a custom machined barrel , a breech with a larger bore and a matching top hat . Flex in frame as we all know is bad but flex in barrel may be worse.
Ah chief Thanks a TONNE . Exactly what I wanted to know 💡
The answer to your question is: Probably yes. These barrels are rifled and then later machined. The rifling process induces stresses in the barrel and the subsequent machining of the breech end relieves a portion of those stresses and appears to allow some shrinkage of the bore at the machined breech end. You are not the first to report what appears to be a double choke. Post machining bore polishing at the breech or additional passes with a rifling button could alleviate some of this but would be very expensive for a tuner/manufacturer.
I cannot answer your question directly as I do not have a .25 barrel at this time to compare results. What you may be encountering is they may have rifled the barrel after it was machined down. When the rifling button is drawn through the thin part, the barrel is allowed to expand a little more than the rest of the barrel. After a bit, the pellet has been shaped to the rifling in the thick part and can move through it with less resistance until you reach the choked end.
You may try giving it a good cleaning / polishing and see if that helps. Take a bronze or brass brush tip on your rod and coat it good with something like this.
http://www.pyramydair.com/s/a/J_B_Non_Embedding_Bore_Cleaning_Compound/1086
Starting from the breech end, slowly run it through the barrel back and forth about twenty times and then clean it out good. Try it out and see if that helps.
As I said before, that may not be THE pellet for that particular setup.
Thanks doc for the reply but as it is I have already checked everything and tried a shitload of stuff with this rifle . Even right down to the scope. The barrel is the last thing that I am considering now .
I once had an acuracy problem I couldn’t figure out with a new rifle I found the problem it ended up being the barrel bushings had came loose might wana check all ur fasteners first before u go chasing ghosts
Thanks edge but my question is very simple and very specific . All that I NEED to know is whether all .25 Cal 24″ LW barrels are as described below (in quotes)
” If I push a .25 cal. H&N Barracuda (Beeman Kodiak) 31.02 grain pellet through the breech end of my stock AF LW 24 ” barrel with a cleaning rod I notice that the pellet encounters increased resistance immediately where the paper thin breech end of the barrel ends . This resistance then continues for quite a length of the barrel and then seems to disappear . When the pellet is at the last couple of inches of the barrel (the choke) it again encounters (much higher) resistance . Is this behavior NORMAL for stock Airforce barrels. I can understand that for the choke part but why should a barrel be choked TWICE is beyond me. Could it be that when the pellet is in the thin breech end, the flimsy wall slightly gives way and kind of stretches when the pellet is pushed through it and when the pellet enters the normal thickness zone of the barrel it encounters increased resistance as it cannot stretch the bore due to the thickened barrel “
There are several things that could contribute to your accuracy issue. Almost every gun will like a particular pellet. The Baracuda may not be the pellet for yours. You may have to try several different pellets until you find The One that your air rifle prefers. I had an air rifle that only liked the H&N Field Target Trophy and only in the 4.52mm.
Also, the power level will have a direct affect upon accuracy. Diabolo pellets are designed for subsonic flight. If you are pushing it along at transonic or supersonic velocities, you are going to be lucky to hit what you are shooting at. Try dropping the power level to where the pellet is in the 800-900 FPS range and see if that helps.
It aint really a million dollar question but 76 views and no reply . Bump
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Hypothesis:
As everyone knows, some barrels like 5.53, some like 5.52 or 5.51 and pellets from same box vary in size.
When a pellet is inserted on breech end, the skirt presses hard on rifling, as you push it thru, marks are formed on skirt and resistance is lowered. The amount & length/distance of resistance should depend on size and material of pellet.