Does a choked barrel really improve accuracy ????

[rkr]

I can clearly see where a clean taper from the breech to the muzzle is the key.

& this would basically make the entire length of the barrel into  a choke, a long low degree choke.

I am also curious to know if any barrel manufactures provide an internal dimensional report for their barrels as I have not seen or found one yet.

iirc a few older barrel manufacturers used to, but I can't recall which ones. Most check to make sure their bores are within certain tolerances along the length but dont publish that info. It's more for their own internal use to let them know when there are issues with materials, tooling wear etc

The BSA SuperSport barrels are hammer forged with a taper from breech to muzzle................

https://www.pyramydair.com/product/bsa-supersport-tactical-air-rifle?m=3209

http://www.airgunmagazine.co.uk/tests/gun-test-bsa-supersport-se/
From the above.........
 "it does boast BSA’s world-famous cold-hammer-forged barrel – a carefully crafted spout that’s renowned for its accuracy."

If you slug a BSA barrel you will notice that there's no taper, just a choke. They are exceptionally accurate though unless you get a bad one.

[nced]

Here is an airgun discussion concerning "tapered bores" and "choked bores"...........
https://www.pyramydair.com/blog/2011/12/choked-bores-and-tapered-bores/
I do take exception with a couple statement from above.........
"But spring guns don’t need a choke, since the act of firing swells the pellet skirts. However, some spring guns do have the same resistance near the muzzle that is felt in better pneumatics. This is an accident of swaging-in the dovetails for the front sight attachment. Weihrauch guns that have front dovetails all have this and we have called it a choked bore. It’s really just an accident of the manufacturing process and is as random as can be. But it’s there and some shooters feel it helps accuracy. Even though the choke doesn’t wrap all the way around the bore, they feel that it still provides the same stability that an intentionally-choked bore does."
1. "spring guns don't need a choke".
After pushing several CPLs through both of my .177 HW95 bores I found that the "fit to the bore" became very loose once the pellet traveled 3 1/2" from the breech (just past the area the barrel was pressed into the breech block). The pellet fit only became "snug again" when being pushed through the choke. Seems to me that if the choke and last 4" of the barrel were removed the loose pellet fit to the bore wouldn't help stabilize the pellet at the muzzle. I guess that if the bore were "perfect" with no internal variations the choke wouldn't be needed but no HW barrel I've owned had a perfect bore but the factory choked .177 HW barrels are noted for being accurate (I've read this isn't so for the HW .22 bores)! 

2. "This is an accident of swaging-in the dovetails for the front sight attachment."
Hummmm...really? Perhaps this whole "accidental choke" is true, however I have worked a HW98 break barrel that had no "front sight dovetails" and I don't think the barrels was "accidentally choked".  The gun was very accurate as this 50 yard group shot sitting on a bucket resting the gun on cross sticks shows .........


I found this to be an interesting hammer forging video.................
https://duckduckgo.com/?q=bsa+hammer+forged+barrel+taper&t=canonical&atb=v129-5_j&ia=videos&iax=videos&iai=oALJDh43K3I

https://www.ar15.com/forums/ar-15/Do-All-CHF-Barrels-Have-a-Tapered-Bore-/118-707524/
From the above..........
"Originally Posted By col_hapablap:
As the title reads, is a tapered bore (or rather a tapered mandrel) a necessity for removal of the mandrel after the forging process? I've read a bit on the CHF process, but I have never found and answer to this particular aspect.

1) As stated above, steel is elastic it springs back.
2) Even if the mandrel is tapered, the largest diameter of the mandrel will be the diameter of the bore, remember, the mandrel is only about 6 inches long and the barrel is pulled over the mandrel and beaten to shape. The barrel is complete when the mandrel comes out the other end.
3) Barrels are allowed some taper, usually one tenth of a thousandths of an inch (0.0001") over the entire length, but only tapering from breech (largest) to muzzle (smallest)."

and

Question........."So for clarity, the CHF bbls that are advertised as taper bore are designed to have a taper bore and that feature is not merely an artifact of the production process? Can a bore taper more than a few ten thousandths over its length?"

Answer........"Yes, they can, but not a whole lot of taper is needed."

Concerning BSA "tapered mandrels"........
https://www.solware.co.uk/air-rifle-pellet-gun/bsa-rifles
From the above.........
"The tapered mandrels are made from specially formulated tool steel"

Very interesting thread that prompted some entertaining research on my part even though the "final ruling" won't affect my accuracy shooting from "bucket and sticks"!

[triggertreat]

I could be wrong, but I believe those tapered barrels are referred to as a "full choke" barrel.

No Sir, full choke is a shotgun term. These taper bore barrels have been used in competition for decades and are called Taper bore. Quite common in high end bench guns. They were also used in old black powder barrels such as some Sharps used in long range competition. It isnt' a new concept.


Speaking of this, another variation of a hammer forged bbl, is the FX system. However, rather than using a mechanical driven set of anvals, (hammers in rotation), it instead used hydraulics to press the outer dia into the bore. Which is a smooth bbl until the last part of the barrel which is now somewhat rifled. But very shallow marks. Imparting much less disturbance to the projectile.


the new X Barrels are an extension of this process. What was old, is new again. 


Knife


While a Taper bore can be obtained by skilled hand lapping, it is more commonly done usually done as a result of using a tapered mandrel in the hammer forging process.


Knife.


Knife

Thanks for the clarification Knife.  I didn't know tapered barrels had different names.  My shotgun does have a full bore and is tapered down all the way to the muzzle.  Just has no rifling.

[Motorhead]

Lets all step back and take a fresh perspective ....

Lead dust, we see it in our LDC's most because that's what they do    Where does it come from ? ... we did not load the pellet with lead dust all over it that's a fact !
IT COMES from the pellet eroding / wearing away lead as it travels the length of bore. Which tells us the pellet when loaded EXITS at muzzle SMALLER 

Yes indeed it does ... so while going down the bore the pellet fit to bore is getting looser and said pellet can start to gently side to side rock / tilt and become YAW destabilized.
Rougher the bores surface finish, greater is the abrasion on the soft lead pellet, Smoother less so.  Depth & width of land / groove also come into play.

CHOKES simply are nothing more than a short section of barrel that tightens up the bore to COUNTER the lead loss and looser fit of the pellet when it gets to muzzle end.
By snugging up the bore to 'Worn" pellet fit you get a YAW stabilization right as pellet is exiting.


So, have a nice smooth barrel with shallow land & groove rifling And / Or shoot harder alloy lead the down sizing issue of the pellet may indeed be fine having pellet exit without YAW wobble & shoot accurate without a choke.

Start out with under size pellets ( Common problem ) Just have a mass production so so quality barrel ( VERY common ) you'll be near guaranteed pellets going to get at the muzzle end of bore and NOT be in firm contact with bore any longer !!!     CHOKE ME PLEASE   

[Bob Pratl]

Scott, thanks, that is a great explanation.

[nced]

Lets all step back and take a fresh perspective ....

Lead dust, we see it in our LDC's most because that's what they do    Where does it come from ? ... we did not load the pellet with lead dust all over it that's a fact !
IT COMES from the pellet eroding / wearing away lead as it travels the length of bore. Which tells us the pellet when loaded EXITS at muzzle SMALLER 

Yes indeed it does ... so while going down the bore the pellet fit to bore is getting looser and said pellet can start to gently side to side rock / tilt and become YAW destabilized.
Rougher the bores surface finish, greater is the abrasion on the soft lead pellet, Smoother less so.  Depth & width of land / groove also come into play.

CHOKES simply are nothing more than a short section of barrel that tightens up the bore to COUNTER the lead loss and looser fit of the pellet when it gets to muzzle end.
By snugging up the bore to 'Worn" pellet fit you get a YAW stabilization right as pellet is exiting.


So, have a nice smooth barrel with shallow land & groove rifling And / Or shoot harder alloy lead the down sizing issue of the pellet may indeed be fine having pellet exit without YAW wobble & shoot accurate without a choke.

Start out with under size pellets ( Common problem ) Just have a mass production so so quality barrel ( VERY common ) you'll be near guaranteed pellets going to get at the muzzle end of bore and NOT be in firm contact with bore any longer !!!     CHOKE ME PLEASE   

LOL, I also want a choked barrel on my .177 springers, however I also think that shooting undersized unlubed pellets will contribute to bore fouling along with general gunge and "dust created by the sliding pellet" you mentioned!  When I shot  supposedly 4.52mm JSB Exacts most were loose fitting to begin with, but MANY were exceptionally loose fitting. Using 4.52mm exacts (marked on the tin) I had two dry fires with my .177 Beeman R9 at a field target match, and I would have had three dry fires if I didn't notice the Exact flipping out of the leade when relatching the barrel. I'm thinking that the edges of shallow rifling engraved on an undersized pellet can "strip off" in the bore (as well as dust & crud if the pellet is dirty), then residue gets packed tightly into the rifling after shooting "normal size pellets".

In the past I've posted this "sordid tale of woe" sniff sniff 
My brother's .177 Beeman R9 fouling packed so tight that no amount of pulled patches would remove it. He was shooting unlubed hard lead 7.9 grain Crosman Premier lights at 910fps and the Die #7 CPLs included a lot of "pee-wees and swarf" in the box. Whenever a CPL felt loose when loading it was simply shot into the ground which exaggerated the fouling. Using a "bore light" and seeing the rifling at the choke was buried under a layer of polished lead the issue was solved using Hoppes #9 and a bronze brush. This also started a search for a suitable pellet lube that would keep the "dust" from packing in the rifling and resisted plus the loose fitting pellets were tossed instead of shot. Using lubed and "proper fitting" CPLs (tossing the loose fitters rather than shooting them) only a few patches were needed to restore accuracy, plus the time between required bore cleanings was increased.

[Fred J]

My Marauder has a stock choked barrel that shoots JSB 10.3gr pellets like a laser at 891 fps. Any slower (below 875) and the groups are not great.

Attached is a 50 yard target that I shot last week. This rifle can shoot dimes anytime at 50 yards if the wind is light (below 5 mph).

[K.O.]

One method of choking for .22 long button rifled Match Barrels... I think it would work well for combo (pellet/boolit) barrels...  If you used ~.22 pellets
https://www.anschutznorthamerica.com/store/p36/1907_Target.html


wonder if they are stress relived  before boring/honing and then after buttoning before profiling... also wonder about bore growth of differing  steels used for barrels...

I wonder how green mountain chokes the .25 mrod barrels... mine show no sign of being swaged like the Lothar Walther barrels...

[skorec]

Scott, thanks, that is a great explanation.

+1.
Tapered barrel may the best ?

I am  thinking   that the much longer pellets/bullets/slugs  need much less YAW stabilization at the end of barrel .

I also read that they not like any choke at all.
Why

[Motorhead]

Scott, thanks, that is a great explanation.

+1.
Tapered barrel may the best ?

I am  thinking   that the much longer pellets/bullets/slugs  need much less YAW stabilization at the end of barrel .

I also read that they not like any choke at all.
Why

Pellets are supported within the bore on TWO narrow bands of contact ( pellet head and skirt tail ) which not only wears away quickly but also offers little resistance in crushing smaller via the choke.
Bullets & even those with bands have far greater contact area to the bore and while they too slough off lead via rifling contact there generally not loosing enough to become yaw destabilized.
With so much more contact area with the bore, forcing a bullet threw a choke slows it down far to much and can cause massive lead smear ( leading ) within the choked portion of the barrel ... not good.

[skorec]

Scott, thanks, that is a great explanation.

+1.
Tapered barrel may the best ?

I am  thinking   that the much longer pellets/bullets/slugs  need much less YAW stabilization at the end of barrel .

I also read that they not like any choke at all.
Why

Pellets are supported within the bore on TWO narrow bands of contact ( pellet head and skirt tail ) which not only wears away quickly but also offers little resistance in crushing smaller via the choke.
Bullets & even those with bands have far greater contact area to the bore and while they too slough off lead via rifling contact there generally not loosing enough to become yaw destabilized.
With so much more contact area with the bore, forcing a bullet threw a choke slows it down far to much and can cause massive lead smear ( leading ) within the choked portion of the barrel ... not good.

Also very believable/logical    explanation - THANKS

[Ribbonstone]

Neither yes nor no.

If you get a choked barrel that shoots great, then you belive in chokes.

If you get a non-choked barrel that shoots great,then you belive in no-choke.

Darn few of us will take a great shooting choked barrel and "unchoke it" on a hunt for greater-greatness (or choke a non-choked great barrel in the same search).

Generally, we'll try adding or reducing/removing the choke in barrels that don't shoot as well as we hoped.  Are hoping to salvage a less than great barrelby changing it rther than risking an already great barrel in hopes of improving what already works.

So 99% of the choke work is done (adding or removing) with a barrel that didn't work out as well as we hoped...a kind of salvage operation with no real down-side (worst would be crappy gets crappier).

Right about here, am going to call "NOT IT".

Just how many of us would seer at a 1MOA barrel and decide to choke it (or un-choke it) in hopes of a magical 1/2MOA barrel? If you FIRMLY belived in chokes, you'd choke that non-choked MOA barrel (or unchoke it if you firmly belived in no-choke)....but darned few of us (which is why the "not it") are willing to do that kind of thing to an already amazing barrel...so evidently we are not "true belivers"  in one system over another.

[rayw]

Personally I put all of mine through a 'sizer' of a size which suits after a the barrel test with all available head sizes, then wash and dry them after which they get a light lube. All the crown does is to resize them on the way out and is the get around for manufacturers to hide their not so accurate ammo production. Even the most expensive 'match' types are not 100% immune to the differentials in head size.

[nced]

Personally I put all of mine through a 'sizer' of a size which suits after a the barrel test with all available head sizes, then wash and dry them after which they get a light lube. All the crown does is to resize them on the way out and is the get around for manufacturers to hide their not so accurate ammo production. Even the most expensive 'match' types are not 100% immune to the differentials in head size.

"not 100% immune to the differentials in head size"
Hummm.... my three HW barrel bores have tight spots along it's length which will "size down" a pellet so it "kinda rattles" down the looser portions before being "stabilized" by the choke. My HW barrels are still very accurate as long as I don't shoot "loose fitters.

Regardless of the pellet head size from the tin, as long as the pellet head is large enough to be "sized" when loaded into the "first tight spot"....the leade all pellets exiting the choke will be similar. The issue comes when the pellet tins have excessively small heads. This situation happened when I was try in to use 8.4 grain JSB Exacts for a field target match using my .177 R9 which has a slightly larger bore than my newer .177 HW95. Here is a .177 HW95 barrel where I noted the "tight and loose sections" by pushing through a new pellet. My other HW95 barrel and my "looser leade" Beeman R9 barrel had "tight and looser sections" similar to this.............


LOL.......IMHO, as long as the pellet head is large enough to be "sized" when loading into the leade, a couple "silly little 1/100th mm of head dimension" doesn't matter...........every pellet when shot will be the same size after exiting the choke! Without a choke the pellet can "rattle it's way" down the loose sections of the bore and perhaps be a bit skewed when exiting the crown.

I have no experience with PCPs at all, and it doesn't seem to me that a couple 1/100th of mm in pellet size, or slight skewing at the crown from a PCP wouldn't matter very much and perhaps a "perfect bore" or a choke isn't necessary to maintain accuracy,  I really don't know.
 
IMHO, with the smaller .177 cal pellets I use it's either a "perfect .177 cal bore" (doesn't happen at my price point) or a simple choke that does work with less than perfect .177 cal bore as long as the pellet head isn't undersized to begin with.. The main reason I buy .177 cal 7.9 grain boxed Crosman Premiers is that they have relatively large 4.53mm-4.55mm heads so they all get "sized simply by loading into the leade". Even though they are "sore finger tight" when loaded into my HW95 the die lot marked and dated boxed CPLs are extremely accurate (when seated properly) I did go the extra step to make a pellet head sizer/skirt expander that eases the loading of a 4.52mm hard lead CPL as opposed to a 4.55mm unsized CPL head.......
Random unsized CPLs from the 1250 count box.........



 

[K.O.]

nced there is a problem with measuring pellets with electronic vernier calipers... at best they are only accurate to +/- .001... the resolution may be .0005 but all that means is it will display to 5 tens not that it is accurate to .0005...

here is an old vid about fixing some accuracy probs caused by under-size heads in 2014 when the Mrod .22 barrels(and my disco barrels) among having other probs could be as large as ~.219"... my different .22 crosman barrels in that time varied in size from about .217 to .2185+ with faint to decent rifling... not to sure about his measuring technique with the mic; seems to measure a bit small but...

the 7/32(.21875") ball seat is what did the work in my opinion... it let the head be bumped up in size enough that the choke gave some accuracy...do not think it was the skirt size... but do think consistent skirts can matter...

So I do think yes because of manufacturing tolerances a choke can do a lot at times to even things out giving more consistency to groups with pellets and give more consistency across differing pellet types/brands... still think that a taper lapped barrel with very consistent pellets is best tho...

[shorty]

I am glad this turned out to be a good discussion.

Been giving this a lot of thought still and I keep hearing (repeatedly) loose and tight spot with in the barrel PLUS leaving the barrel with a uniform squeeze.

So, what about the rifling. If the rifling is a .002" to .005" deep, and the bore fluctuates +/-.001", then the projectile is still riding the barrel without slop (right?). It should just feel tighter or looser but still be in contact.

[nced]

nced there is a problem with measuring pellets with electronic vernier calipers... at best they are only accurate to +/- .001... the resolution may be .0005 but all that means is it will display to 5 tens not that it is accurate to .0005...

here is an old vid about fixing some accuracy probs caused by under-size heads in 2014 when the Mrod .22 barrels(and my disco barrels) among having other probs could be as large as ~.219"... my different .22 crosman barrels in that time varied in size from about .217 to .2185+ with faint to decent rifling... not to sure about his measuring technique with the mic; seems to measure a bit small but...

the 7/32(.21875") ball seat is what did the work in my opinion... it let the head be bumped up in size enough that the choke gave some accuracy...do not think it was the skirt size... but do think consistent skirts can matter...

So I do think yes because of manufacturing tolerances a choke can do a lot at times to even things out giving more consistency to groups with pellets and give more consistency across differing pellet types/brands... still think that a taper lapped barrel with very consistent pellets is best tho...

A couple comments.........
Hummm.....I agree that a perfectly tapered airgun bore MIGHT be a better way of "choking the pellet", however I really don't care what the final "choke diameter" when the pellet leaves the barrel. The tightest constriction in the bore my .177 cal HW springers is indeed at the muzzle and those barrels are accurate enough for my purposes............


Concerning using digital Calipers to measure due to tolerances and such...........
When using my iGaging caliper to measure my micrometer test bar I believe this accuracy is close enough for measuring lead pellet heads with enough accuracy to sort pellets!


There is a "method to measuring", however I'm really not concerned if a pellet head is EXACTLY 4.52mm (or whatever), only that the pellet head diameter is consistent from one pellet to the other. I choose to start with boxed CPLs because the heads are indeed larger than most (4.53ish mm - 4.55ish mm) and after a trip through the sizer all have the same pellet head without "ovality". Here is an example of pellets that were head sized with my 4.48mm die and the pile on the right heads small enough to drop through the sizing ring of the die without pushing with the "ram"..........

Whatever the actual size of the pellet heads before and after sizing, there were quite a few in the 750 count tin with undersized heads. Here is the measuring method I use since it's accurate enough. Matter of fact, I can get repeated readings on the same pellet and the accuracy is good enough to determine if a pellet head is "oval" and many are indeed oval before sizing.........


Back when I used a digital caliper with less resolution than my current caliper I got these pellet head measurements of supposedly 4.52mm H&N FTS straight from the tin.........

I think that we could both agree that even the ole caliper was accurate enough to sort within a .005INCH accuracy (smallest .174, largest .179) regardless of the "unit round off".

Before I started sizing pellet heads I was sorting pellets into "size lots" and then shooting the larger size lots. Without sorting the H&N FTTs and JSB Exacts there was always a large variation of "pellet fit in the leade" and I knew from experience that a much looser fitting pellet wouldn't fly to the same point of impact as a properly fitting pellet. After sorting pellets into groups I learned that even the rather crude measuring you mentioned (tolerances & such) that the sorted pellet heads fit the leade consistently. The smaller head size sorts could be distinguished simply by the pressure needed to seat the pellet and I found that the "smaller size groups" that were a "real easy push" also weren't as accurate as the larger size groups that needed some resistance to seat the pellet in the leade.

LOL.....there wasn't much I could do to "adjust" the head size of the CPL on the left straight from the box..........


What I find interesting is that there are shooters that go through the hassles of sorting pellets using "precision holes in a plate" and reporting good accuracy gains doing so. Well....knowing that many pellet heads are a bit oval (due to the die parting line?) it does seem to me that the ACTUAL pellet head size isn't as important as the fit in the leade because I've measured pellet head "ovality" as much as .02mm.

Anywhoo......I'm still of the opinion that as long as a pellet head is "re-sized a bit" when loaded into the leade it will be the same size when shot regardless of the "silly little 1/100th mm difference" before loading. The problem comes when the pellet head is too small to be sized when loading. 

[Mod90]

Anywhoo......I'm still of the opinion that as long as a pellet head is "re-sized a bit" when loaded into the leade it will be the same size when shot regardless of the "silly little 1/100th mm difference" before loading. The problem comes when the pellet head is too small to be sized when loading.

correct.

[tor47]

I noticed "Ted`s holdover" in his vlog channel said when he was testing the wildcat mk2, he did not sort pellets anymore, as the effort was not worth the gain, in that gun. The reason being the barrel was choked.
But he also said it absolutely make a difference in other kind of barrels. So if what he say is true, a choke should be a benefit as I see it, as it makes the barrel less picky about the actual size of the pellet.

[Mod90]

Correct Aslak
A choke makes every pellet that exits the muzzle the exact same diameter as the one before it & after it. That is, once the pellet that is discharged has a head & skirt diameter that were larger than the choke.