Barrel consistency & chokes

[F. Baum]

I just wanted to post something about choked barrels, also I just read an article by Tom Gaylord about joke barrels on PYAIR as well.

Well when I first discovered the more higher end air rifles that I didn't even know they existed growing up I always had a Daisy 880 pumper but I didn't know that there was much higher quality spring/gas powered rifles out there. My first higher end rifle was actually gamo swarm magnum (About 3 yrs ago)  which I still have and actually shoots decent but not great(loose barrel towards the end) soon after that I caught the magnum bug and I started to purchase some hatsans and I went through quite a few of them then I spoke with a guy that has YouTube videos his name is Mike ellingworth I believe he's a member here too, and he told me how to push a pellet through the breach and feel for resistance. I soon learned the importance of a uniformed barrel,  I've also learned a lot from reading here too!!!  I don't post much and I never type I'm actually using dictation to write this. I remember reading something that hector Medina wrote about how almost all break barrels are tight in the breach from when they press the barrel into the breach and also tight near the muzzle where the barrel is choked.  I find that to be very true he also mentioned something about the importance of consistency in air rifle barrels.   

I'm actually making this post because I recently got a gamo hunter pro extreme.22 and I actually really like the gun from the Wood stock to the solid steel barrel and the metal breech!, not the plastic one's they also use. But the problem I see with almost every gamo I've had is they're very tight in the barrel while it's going through the breach block then they get very loose, some even falling out the last five inches of barrel!!! To be honest gamo gets a bad rap for having inconsistent accuracy and I find the problem is solely on the way they make their barrels I truly believe if they would incorporate a choke in their barrels their rifles would be way more accurate, I do like the direction they're going in now by using more metal breach blocks instead of the Poly ones.  But they need to start making better barrels and honestly I think they would appeal more to the true enthusiast like myself that demand quality and accuracy.  A lot of things they do well though,  their crowns for one always seem to be done well. But I'm definitely sending this one back because after 400 shots I could still not get it to group well enough.. And now I know why after pushing it through.   

Closing statement you can learn a lot about a airgun and its accuracy by pushing a pellet through the barrel with a brass rod with a piece of tape on the end and slowly feeling for inconsistency..

[gloob]

But how does it shoot?

Springers are unique, because of the way the pressure spike collapses.

In a firearm or a PCP, it's simple. You want the bore to be uniform all the way down. But due to realities of manufacturing, you'll get more good barrels if you choke the muzzle end a little.               

There have been experiments with firearms barrels that are conical, tapering down significantly at the muzzle. E.g., a 22LR that tapers down significantly, say to .177 by the muzzle. The bullet gets squished as it goes through, and they can shoot just fine.

A springer is different, because the pressure spike collapses rapidly (down to basically nothing useful), typically BEFORE the pellet leaves the muzzle.* So you don't want the fit to be too tight. That's why most good shooting springers have a significant choke at the breech end. This squeezes down the head of the pellet a bit, so that it doesn't drag too much once it gets past that point.

*There are exceptions to this. In say a TX200 HC, the barrel is so short (for the velocities that it shoots) that most lighter pellets are leaving the muzzle before the pressure collapses. This is good for locktime/accuracy. And in the UK, where 12 ft lbs is the max, this works out great. For instance, in 177, you can reach the max power with a 8.4 grain pellet out of this short 9" barrel, and let the moderator take care of the excessive muzzle blast. But when you shoot heavier pellets, you won't lose as much power, because the heavier pellet is shooting more efficiently. 

I have springers where the breech choke is tight, and then the pellet falls out after it passes this point. And they shoot great. As long as it's not TOO loose, it'll shoot fine. But on the other hand, I have had several springers without a breech choke, and a tight fitting pellet takes significant force to push the pellet all the way to the muzzle. These guns don't shoot well unless you shop around for a pellet that fits just right and is sized consistently. (Or you can shorten the barrel, so a given pellet leaves the muzzle before the pressure drops too low).

Gamo knows how to make springer barrels. Your findings give me confidence I should buy one. It's a compromise that allows that barrel to shoot a wide variety of pellet weights and head sizes accurately. The TX200 HC method is another compromise that does the same. But the latter means you're losing efficiency; you have more cocking force and recoil and muzzle blast and rifle weight for a given velocity.

[F. Baum]

It doesn't shoot that great,   the most I've been able to produce is 2-3 pellets in 3/8 inch group and then the next shoot is way off.    Every air rifle I've had that was loose at the end of the muzzle was never that accurate for me.

If you are saying it is good for a break barrel to be tight in the breach area as long as there is GOOD contact to the inner bore of the barrel before exiting the barrel then i get your point.

 What I'm talking about is having to forcefully(Like 10LBS of pressure)  push the pellet past the first 3-4 inches and then it just completely falls out! I just don't understand how an air rifle can be accurate if it has little to ZERO contact with the boar before exiting the muzzle.... personally I only have 2 springers that are what I consider very accurate my Diana 350.177 and my HW97K The Diana (choked barrel) has some good resistance going through the breech but once it passes the breach it still has some resistance although very little, you can still feel it touching the inner bore then the last like 2 inches of the barrel it gets tight again about as tight as it was going through the breech but not noticeably more. And that gun is very accurate can easily get .25 inch groups at 25 yards not always but if I don't it's on me not the gun.. The 97K is just as accurate and actually a lot easier to shoot Being is not a magnum and its weight. I would like to check the bore on it as well,   but it's always shot great so I never touched it. I just don't understand how inconsistency can produce consistency....
 
I do see some improvements in gamo and I really do like the power that they make I just think they could benefit a lot from slightly choking their barrels they definitely have some advantages over any other manufacturer of spring/gas powered air rifles, especially for hunting they're light, powerful, some are multi shoot , they're also made pretty well. And their gas pistons/struts  seem to last forever I've got about 8000 shots in my swarm magnum, And lately the quality control seems better than Diana it's just the consistency in their barrels,  if they could fix that the sky's the limit-  then they would be Light, Powerful and Accurate instead of just the first two .

[nced]

I just wanted to post something about choked barrels, also I just read an article by Tom Gaylord about joke barrels on PYAIR as well.

Well when I first discovered the more higher end air rifles that I didn't even know they existed growing up I always had a Daisy 880 pumper but I didn't know that there was much higher quality spring/gas powered rifles out there. My first higher end rifle was actually gamo swarm magnum (About 3 yrs ago)  which I still have and actually shoots decent but not great(loose barrel towards the end) soon after that I caught the magnum bug and I started to purchase some hatsans and I went through quite a few of them then I spoke with a guy that has YouTube videos his name is Mike ellingworth I believe he's a member here too, and he told me how to push a pellet through the breach and feel for resistance. I soon learned the importance of a uniformed barrel,  I've also learned a lot from reading here too!!!  I don't post much and I never type I'm actually using dictation to write this. I remember reading something that hector Medina wrote about how almost all break barrels are tight in the breach from when they press the barrel into the breach and also tight near the muzzle where the barrel is choked.  I find that to be very true he also mentioned something about the importance of consistency in air rifle barrels.   

I'm actually making this post because I recently got a gamo hunter pro extreme.22 and I actually really like the gun from the Wood stock to the solid steel barrel and the metal breech!, not the plastic one's they also use. But the problem I see with almost every gamo I've had is they're very tight in the barrel while it's going through the breach block then they get very loose, some even falling out the last five inches of barrel!!! To be honest gamo gets a bad rap for having inconsistent accuracy and I find the problem is solely on the way they make their barrels I truly believe if they would incorporate a choke in their barrels their rifles would be way more accurate, I do like the direction they're going in now by using more metal breach blocks instead of the Poly ones.  But they need to start making better barrels and honestly I think they would appeal more to the true enthusiast like myself that demand quality and accuracy.  A lot of things they do well though,  their crowns for one always seem to be done well. But I'm definitely sending this one back because after 400 shots I could still not get it to group well enough.. And now I know why after pushing it through.   

Closing statement you can learn a lot about a airgun and its accuracy by pushing a pellet through the barrel with a brass rod with a piece of tape on the end and slowly feeling for inconsistency..

The "they're very tight in the barrel while it's going through the breach block then they get very loose" is also common with the .177 HW95 and .177 R9s I've owned and here is a "map" of the bore for my .177 HW95..........

The main difference between what you described with the Gamo and my HW barrels is that ALL of the HW barrels I've owned had the greatest constriction at the muzzle called a choke........


I think the constrictions are due to the barrel being pressed into the "pivot block", then the unreduced bore, then the tighter constriction at the muzzle to guarantee that the pellets are "swaged" to a consistent size when it exits the choke. I've found that my HW springers have been very consistent and accurate with the proper pellet (loose fitting pellets no so much)..........

[F. Baum]

Thanks NCED !!  i appreciate the pictures and the insight very explanatory.    i've learned a lot from previous stuff you've posted in the last couple of years since iv'e been into air gunning thanks man.

 the problem with most of the gamos that I've experienced is they are like the R9/hw95 minus the choke,   pellets just falls out the last couple inches and I believe that's where the accuracy difference comes in.  Sure you can get a gamo that will shoot 1 inch group at 30 yards and even then you might get an occasional flyer.

 That new hunter extreme is a really nice rifle. But I truly believe if they just choked their barrels they would be so much more nice.

,Forrest

[gloob]

If the bore is smooth and consistent, a pellet can fall out under gravity but still be fully supported. The head only has to just touch the lands, not squeeze through the bore.

You could check that by trapping the pellet from falling out, using a piece of tape. Then push it back in, and see if the head is able to wiggle in the last quarter inch of the bore? Should be easy to check, using a hollowpoint pellet to stick a rod into.

Yes, I have a springer like this, where the pellet is tight in the breech block but then it falls out the rest of the way under gravity. Shoots great.

Someone on the forum has found many of his HW rifles still shot accurately, even after cutting off the muzzle choke. I want to say NCEd, but he would confirm that if he's still following the thread.

[gloob]

The lead alloy of the pellet has some compression or elasticity. It springs back out to a slightly larger diameter after passing the tight point at the breech block. The harder the alloy, the more spring back. This is why it's ok for the tightest point to be at the breech.

[Bayman]

Forrest, you may have better luck reposting this in the Spanish gate. They are more familiar with the Gamo barrels there.

[nced]

If the bore is smooth and consistent, a pellet can fall out under gravity but still be fully supported. The head only has to just touch the lands, not squeeze through the bore.

You could check that by trapping the pellet from falling out, using a piece of tape. Then push it back in, and see if the head is able to wiggle in the last quarter inch of the bore? Should be easy to check, using a hollowpoint pellet to stick a rod into.

Yes, I have a springer like this, where the pellet is tight in the breech block but then it falls out the rest of the way under gravity. Shoots great.

Someone on the forum has found many of his HW rifles still shot accurately, even after cutting off the muzzle choke. I want to say NCEd, but he would confirm that if he's still following the thread.

"If the bore is smooth and consistent,"
There's the rub.......the barrels of my HW break barrel springers AREN'T "consistent" due to the constriction at the leade caused by pressing the barrel into the barrel pivot block. The older HW95 barrels were both pressed and pinned into the pivot block.IF the bore is constricted at the leade (all my HW bores are) the pellet will get a "sizing" at the leade, then slide through the rest of the bore if there isn't another "sizing" at the muzzle. This may work well if the PELLET is a "perfect match" to a "perfect bore" without a constriction at the leade also making the barrel very "pellet fussy". For my "normal" bores however, the pellet gets "sized" when loaded, then slides down the looser bore till stabilized by the choke before being released. LOL....my experience has been that a "loose fitter" in the leade relative to a "normal fitter" will most likely be a flier which I learned when shooting supposedly 4.52mm JSB Exacts which varied considerably in head size.

Concerning my HW bores with "pivot block constrictions and chokes"
My newer HW95 barrels are actually splined and appear to be pulled into the pivot block with an odd looking lock nut.
Old design.......

Newer design......


To determine the constrictions in my HW springer bore I would push a new tight fitting pellet through the bore taking note of the constrictions. The now discontinued Crosman Premier from the 1250 count cardboard box were the perfect pellet for this due to the rather large 4.54-4.56mm heads and indeed the all the .177 HW barrels I've owned had a tighter leade than the bore but less tight than the choke. With the constriction at the leade a hard lead CPL would be "sized" when pusher through the barrel pivot block area, then the push through the remaining bore would be an "easy push" till the second "resizing" as the pellet was pushed through the choke.

As a side note, over the decades the large head hard alloy lead boxed Crosman Premiers were the most accurate pellet from my R9 and HW95. I never had issue with loading a CPL in the leade of my .177 R9, however I found the CPL to be "sore loading finger tight" in the leade of my HW95. I then realized that it seems HW had changed the barrel specification because I found that my newer HW95 bores were indeed tighter than the older Beeman R9 bore. Here is a pic showing the engraving of a new CPL after being pushed through both my HW95 and R9 bores. Notice that the rifling engraving from the newer HW95 bore is sharper and the pellet skirt more collapsed than the ones pushed through the R9 bore.........


"HW rifles still shot accurately, even after cutting off the muzzle choke"
LOL....that wasn't me! I did buy a used .177 cal R1 barrel to replace a .20 R9 barrel and didn't like the extra length so I "chopped and choked" the barrel to "R9 length using a minilathe, then swaged the muzzle  a bench vise using machined "choking block". The accuracy after the chop and choke was great..........

[Motorhead]

As one who tunes and preps a lot of Air Rifles, Shoots AR's competitively .... BARRELS, yea they are the last word in accuracy potential no matter how fantastic the rifle is around it !!  Sad truth.

When pushing pellets breech to muzzle, starts out snug and goes slack hardly being felt until at muzzle choke ... GARBAGE BARREL that will never shoot well.
Reason for .. YAW that of the pellet being spun by rifling yet wobbling never being held snugly enough to be kept spinning on true axis center line. It contacts choke slightly tilted it exits slightly tilted ... wobbler !!

Break barrel type rifles have the worst potential here. You could have a good barrel before it is pressed into the breech block, but a Too Tight press fit chokes the entire bore area within the block.
Result is you are pre-sizing the pellet as it passes threw the breech blocks now tighter bore into a bore that is larger once past it.
While choke may be tighter yet, it is the distance pellet travels between where the pellets lack of support with bore/rifling has it able to acquire YAW.

[only1harry]

Lots of good info here but I am moving this to the Airgun gate since it is not specific to German airguns, and I don't want to restrict it to the Gamo gate.

[gloob]

"If the bore is smooth and consistent,"
There's the rub.......the barrels of my HW break barrel springers AREN'T "consistent" due to the constriction at the leade caused by pressing the barrel into the barrel pivot block.

Yeah, I might have said that wrong. I meant that after it has passed the choke point at the breech, the pellet could slip/slide/fall through the rest of the barrel and it might still shoot accurately. I didn't mean consistent bore size, I meant that the bore or rifling or whatnot is consistent and smooth once past the breech constriction. A slip fit is good enough for accuracy. The only place the pellet should NEED to be squeezed is at the breech.

Interesting that HW chokes the muzzle tighter than the breech. There's not necessarily significant pressure by then. I would have imagined the muzzle choke should be not quite as tight as the breech, by a hair.

[Novagun]

I had a Diana barrel thar I suspected was allowing the pellet to yaw in the barrel. The shot holes looked rough on the target. The other thing that I guessed at was that the slack transit of the pellet through a good part of the barrel where there is no engagement with rifling must allow high pressure air to leak past thus reducing thrust and causing turbulence in front of the pellet that interferes with the smooth exit from the muzzle  That seems to me to be something that the best choke could not remedy.
I strive for perfection in my amateur way but just can't get there  Neither can I deal with wobbly Shooter syndrome especially out rabbiting.

[nced]

As one who tunes and preps a lot of Air Rifles, Shoots AR's competitively .... BARRELS, yea they are the last word in accuracy potential no matter how fantastic the rifle is around it !!  Sad truth.

When pushing pellets breech to muzzle, starts out snug and goes slack hardly being felt until at muzzle choke ... GARBAGE BARREL that will never shoot well.
Reason for .. YAW that of the pellet being spun by rifling yet wobbling never being held snugly enough to be kept spinning on true axis center line. It contacts choke slightly tilted it exits slightly tilted ... wobbler !!

Break barrel type rifles have the worst potential here. You could have a good barrel before it is pressed into the breech block, but a Too Tight press fit chokes the entire bore area within the block.
Result is you are pre-sizing the pellet as it passes threw the breech blocks now tighter bore into a bore that is larger once past it.
While choke may be tighter yet, it is the distance pellet travels between where the pellets lack of support with bore/rifling has it able to acquire YAW.

Hummm....I've never considered my HW barrel to be a "GARBAGE BARREL that will never shoot well" due to "choke induced wobbling".

I do all shooting from "bucket and sticks" so I always attributed "fliers" to be induced by the "sitter on the bucket", a dirty bore, or perhaps a pellet that was incompatible to my R9 or HW95 bore like the supposedly 4.52mm JSB Exacts I bought a few years back. I've been content with the accuracy of my choked HW barrels once the "proper" pellet was chosen but then I'm only started as "bucket and stick" squirrel hunter from West Virginia a couple decades ago.........
 

I never shot well from a bench however my brother could and he shot these two 3 shot "powder burner style groups" back to back (which I consider as good as a 5 shot airgun group) using his factory choked .177 R9 that i home tuned. LOL.....I don't consider his R9 barrel a "GARBAGE BARREL that will never shoot well" either........

[Motorhead]

Ed,
Can you ever post NEW information, Pictures or Content ?

It is a month after month after year REPOSTING of the same stuff ... Honestly

I'm not trolling you, just a observation being publicly noted.

[nced]

Ed,
Can you ever post NEW information, Pictures or Content ?

It is a month after month after year REPOSTING of the same stuff ... Honestly

I'm not trolling you, just a observation being publicly noted.

LOL......at 75 years old and not very active anymore ALL I have is "old stuff to re-post"!!!!

This thread was started by a new "GTAer" with only 40 posts so perhaps some other "new folks" might be interested in "old stuff" relevant to their threads! As a side note, I'm simply inferring that HW barrels aren't "garbage" due to the factory choke and barrel pivot block area constrictions. LOL, as they say, "a picture is worth a thousand words" so I tend to include pics to back up my old often stated opinions!

Here is a new pic of a couple groups (never posted before) I shot sitting on a bucket resting the gun on cross sticks from a HW98 that I tuned and it also had a choke. I always thought that a HW choke was created when the front sight dovetail was swaged however the HW98 muzzle was choked even without the front sight dovetails........
   

Anywhoo, with the reposting of "old stories and pics" but perhaps they may be useful to new members shooting springers! 

[Novagun]

I have noticed the reposting by NCED. It has never bothered me but I thought he was an 18 yd shooter off a bucket  today I noticed for the first time a couple of groups at 50 yds not too shabby at all even off a bucket.. Let's just keep doing what we can do. 75 is not old. I know that as a fact.

[subscriber]

The only place the pellet should NEED to be squeezed is at the breech.

Interesting that HW chokes the muzzle tighter than the breech. There's not necessarily significant pressure by then. I would have imagined the muzzle choke should be not quite as tight as the breech, by a hair.

The pellet has a lot of momentum at the muzzle.  It does not need air pressure to push it through the choke.  Yes, that slows the pellet down; compared to no choke.

The pellet being sized by the breech is a side effect of pressing the barrel into the breech block.  German engineers do not work on getting the breech choke perfect.  They work in minimizing it or eliminating it, without blowing the budget for a low cost airgun.  The breech choke is what make the muzzle choke a requirement, or the barrel won't shoot as well as it otherwise might.   If there were no breech choke, a parallel bore could shoot well without a muzzle choke.

In other words, a breech choke is not required to make a barrel shoot accurately.  It is what happens when you make cheap barrel assemblies.  Then to compensate, a cheap muzzle choke is added.

You might argue that the breech choke reduces pellet friction down the bulk of the barrel length, increasing power potential.  I will argue that the act of swaging the pellet down at the breech block, stole power, and that a breech choke does not gain as much power as you think.

To shoot well, the pellet must not rattle down the barrel.  It most certainly must not rattle or yaw as it leaves the muzzle.  The way to increase the odds of the barrel shooting acceptably is to choke the muzzle to a smaller size than the breech.  If you always choke the muzzle, you can get away with a bore that varies in diameter, or that tapers "open" towards the muzzle.  Rather than improving barrel making, or throwing away the barrels with too much variation, most airgun manufactures just choke all their barrels at the muzzle.

The original poster's experience is an example of why cheap barrels need a choked muzzle.  It is more apparent when a given barrel has a tighter "choke" at the breech block.  If a pellet falls down the barrel after passing the breech block, that is an indication that it won't shoot well.  Of course, "shooting well" means different things to different people.  For some, that might mean occasional one inch 5 shot groups at 25 yards.   For others it might mean consistent 1/2" ten shot groups at 50 yards.

As for pellets springing "open" to prevent ratting down the barrel; you should research Young's Modulus.  It is a measure of the springiness of a material.  Pure lead has a YM of only 16 GPa.  While pure iron (not steel) has a YM of 211 GPa.  Compared to copper at 120 GPA.  And pure gold has a YM of 79 GPa.

My point is that lead pellets have very little "spring-back" to keep them in intimate contact with the bore of an airgun, after the breech "choke" has sized them down by a few thousands of an inch.  The extent of that springback is so small as to be considered zero, for all practical purposes.  For this reason lead is known as a "dead" material.  It does not ring.  It won't bounce on an anvil, like a steel ball bearing. 

You might argue that Crosman high antimony pellets have more springback than JSB pure lead pellets, and are better able to deal with heavy breech choking.  I would argue that pure lead pellets have softer skirts, and thus size down easier, wasting less power; and that the air pressure 3" down the barrel is still high enough to size soft pellet skirts back up to contact the looser section of barrel.  As for pellet heads; those are not springing back up in diameter, nor blowing open after passing a tight breech, no matter what. 

Tight airgun breeches are not only not required; they are an abomination, wrought by avarice.  If you are stuck with a tight breech choke, and expert airgun tuner may be able to lap it out, or substantially reduce it.  If the job is well done, the airgun should shoot better.  When this is combined with a skilled overall polishing of the bore, velocity should increase, rather than reduce.  Such lapping is not something for the novice to attempt, without accepting that the process is fully capable of taking a bad barrel and turning it into scrap.  Whereas experts improve most barrels so lapped.  Some by a lot; other by a little.

[subscriber]

This thread was started by a new "GTAer" with only 40 posts so perhaps some other "new folks" might be interested in "old stuff" relevant to their threads!

Bingo!   Until Weihrauch change their barrel manufacturing again, Ed's info remains relevant and illustrates the point perfectly.  Even if it was captured some time ago.

[Motorhead]

Ed,
Reactive .. I'm getting older too.
No intent of insult or otherwise.

We're too small a family to bicker and for that I'm sorry.

Scott S