I started typing this in response to my other thread. First I'm not a gunsmith or a tuner that's worked on all different types of airguns. I'm just a car guy and retired machinist who has worked on a fair amount of Weihrauchs. In the process I've slugged quite a few Weihrauch barrels and had fairly similar results across the board. Slugging a barrel is pushing a pellet manually from the breech out the muzzle. It's a good way to understand what might be going on with a gun's accuracy or output. There's a guy on here that has an excellent video on doing it. I'm just gonna explain what I've found and learned over the years.
Weihrauch barrels are rifled before the the muzzle end is either crimped for sights or threaded for moderators. A muzzle choke is created by the crimp or threading.
I'm not sure if the knurling is done prior to rifling or not. Either way there's typically some sort of constriction inside the breech block especially the knurled areas from either the knurling process and or pressing it into the breech block.
The leade where the pellet is loaded is crowned for loading and sometimes reamed for fit. Pellet fit in the leade isn't necessarily an indication of a loose or tight bore. Reaming can sometimes result in a noticeable step into the tighter breech area just a past the opening. The step is so noticeable on some guns it's visible with a flashlight. I took a picture of it on my first Weihrauch (Hw95) thinking it was a defect causing my accuracy issues. I sent the rifle back to AOA where they explained that was normal and there was nothing wrong with the barrel or rifle. It was a string of bad UTG scopes that had me chasing my tail. A newbie mistake. Now the rifle is my most accurate break barrel. Except the muzzle choke the bore is usually tighter inside breech block than the rest of the barrel. For simplicity I call that tight area inside the breech block the breech choke. Perhaps not technically correct by the definition and manufacture of a traditional choke.
Although the tight area or areas inside the breech block's length is a byproduct of manufacturing, I'm sure it's existence is deliberate and part of the design. After 11 years a BMW master mechanic I'm plenty familiar with German engineers and their philosophy and practices. They are very good and well aware of their work. They won't admit mistakes but they don't let them go unfixed for decades either. Let me explain some of the positive effects this breech "choke" has when working correctly. Then you'll understand why it's been left in production that way.
The first benefit of the breech constriction or choke is it sizes down all pellets to a consistent size to fit that barrel. The rifle automatically does something competition shooters painstakingly do. If Weihrauchs size all the pellets in this breech choke why does head size still make a difference in accuracy? First it can't size down already undersized pellets. Second and this is really getting in the weeds but even lead has a certain amount of elasticity or rebound after forming. Larger heads will still rebound to a slightly larger size after the passing through a tight spot like the breech area. Larger head sizes will also smear to a longer rifling engagement area which might change it's accuracy.
When the breech choke or constriction is too tight, it can shrink the pellet too much. Then the pellet may not engage the rifling properly and air pressure can bypass the pellet. This can negatively affect accuracy and or power. I've experienced this twice now. Once with a brand new 20 caliber barrel and now with a 22 caliber barrel. The accuracy on both was acceptable but the power was well below normal or advertised.
Another possible benefit of a breech restiction is it may create a spike in pressure to pop the pellet out at a faster velocity than it might if the bore was straight. Think pop gun. In the typically desired low drag, perfectly straight bore the pellet would likely accelerate in a more linear fashion and consume the swept volume before reaching the same velocity as the pop gun effect breech.
Past this breech constriction, restiction, choke or whatever you want to call it, the barrels usually open up. The barrels typically have only light drag from the rifling engagement between the breech and muzzle. That's partly why there's no real difference in power outputs between long and short barrels on these guns. Almost every Weihrauch barrel I've slugged has this basic profile. Some barrels are tighter in areas than others. Some have inconsistent engagement drag. When slugging barrels some will have such light engagement the pellet will gravity fall through some sections. This is most commonly found around an inch or so before the sight crimp. Any bore size inconsistency can cause the pellet to chatter down the bore and have bad accuracy. This is why you have a muzzle choke.
The muzzle choke basically grabs the pellet and straightens it out before it leaves the barrel. Weihrauch muzzle chokes vary in resistance. Most are only noticeably tight and some are ridiculously tight. I almost have to pound the pellet through the muzzle choke of the threaded 22 barrel I've been messing with recently. This obviously would consume energy. Especially since there's no significant air pressure left behind the pellet by time it gets to the muzzle.
You'd think it might make sense to use pellets that run small in a gun with a tight choke at either end to reduce resistance and increase power. The problem is not that other pellets are too big but the choke is too tight. I've run smaller and softer pellets through tight choke guns hoping to gain energy. There's typically little to no gain in velocity because the driving air pressure bypasses the undersized pellet. Plus the accuracy tanks because it doesn't engage the rifling throughout most of the barrel.
I'd be remiss if I didn't mention that some people have reported cutting off the choke and recrowning Weihrauch barrels without losing accuracy. I personally wouldn't do it without slugging the barrel first to make sure there's adequate rifling engagement through the full length of the barrel. Even with adequate engagement I'd still look to cut it at a tighter spot.
Also I slugged all my rifles today before posting this to ensure my accuracy after other people's differing experiences. I did find that my 177 Hw50 wasn't particularly tighter in most of the breech than most of the bore. There was a slightly tighter spot just inside the breech towards the front of the breech block otherwise the drag was fairly consistent throughout most of it's length. It did have what I'd call the typical loose spot before the muzzle crimp and of course the associated muzzle choke. Don't ask me what causes that loose spot. F'd if I know.
In a perfect world Weihrauch's chokes wouldn't be necessary. We don't live in a perfect world and pellets aren't always consistently sized so Weihrauch sizes them for you. Unfortunately (albeit rarely) their tolerances are sometimes off and we wind up with a dud. Like I said, I've had two now that were under powered. Thats only two out of dozens of guns I've worked on that were produced from the 80s to this year. I did have two brand new 177 77SEs with consecutive serial numbers that had atrocious accuracy. The guns were returned for a refund. The exact barrel defect is still unknown to me. So I guess that's four defective barrels. I imagine no caliber or model is exempt from an occasional defect. IMO nothing mass produced is. Overall Weihrauch produces good quality barrels and rifles as a whole.
If you ever have accuracy or low power issues I highly recommend slugging a barrel. I normally use bamboo BBQ skewers. They're usually strong enough to push a pellet through without the possibility of damaging the bore. If they're not strong enough the barrels probably bad and you can use a brazing rod. Also slugging has to be done with a good fitting pellet from the breech out to get accurate feedback. This requires complete disassembly of 77s and 97s. I'm not sure if it can be done at all with a 57. Its the only current Weihrauch I haven't worked on.
I hope this helps some people understand what's normal and what to look for. Even knowing this myself I still have to prove a barrel faulty by swapping it out. I'm not happy to have to have done this twice now, but it does help me learn what to look for. I guess I'll eventually get a feel for how tight it's too tight and what's too loose.
Be well all.
Ron
Weihrauch barrels are rifled before the the muzzle end is either crimped for sights or threaded for moderators. A muzzle choke is created by the crimp or threading.
I'm not sure if the knurling is done prior to rifling or not. Either way there's typically some sort of constriction inside the breech block especially the knurled areas from either the knurling process and or pressing it into the breech block.
The leade where the pellet is loaded is crowned for loading and sometimes reamed for fit. Pellet fit in the leade isn't necessarily an indication of a loose or tight bore. Reaming can sometimes result in a noticeable step into the tighter breech area just a past the opening. The step is so noticeable on some guns it's visible with a flashlight. I took a picture of it on my first Weihrauch (Hw95) thinking it was a defect causing my accuracy issues. I sent the rifle back to AOA where they explained that was normal and there was nothing wrong with the barrel or rifle. It was a string of bad UTG scopes that had me chasing my tail. A newbie mistake. Now the rifle is my most accurate break barrel. Except the muzzle choke the bore is usually tighter inside breech block than the rest of the barrel. For simplicity I call that tight area inside the breech block the breech choke. Perhaps not technically correct by the definition and manufacture of a traditional choke.
Although the tight area or areas inside the breech block's length is a byproduct of manufacturing, I'm sure it's existence is deliberate and part of the design. After 11 years a BMW master mechanic I'm plenty familiar with German engineers and their philosophy and practices. They are very good and well aware of their work. They won't admit mistakes but they don't let them go unfixed for decades either. Let me explain some of the positive effects this breech "choke" has when working correctly. Then you'll understand why it's been left in production that way.
The first benefit of the breech constriction or choke is it sizes down all pellets to a consistent size to fit that barrel. The rifle automatically does something competition shooters painstakingly do. If Weihrauchs size all the pellets in this breech choke why does head size still make a difference in accuracy? First it can't size down already undersized pellets. Second and this is really getting in the weeds but even lead has a certain amount of elasticity or rebound after forming. Larger heads will still rebound to a slightly larger size after the passing through a tight spot like the breech area. Larger head sizes will also smear to a longer rifling engagement area which might change it's accuracy.
When the breech choke or constriction is too tight, it can shrink the pellet too much. Then the pellet may not engage the rifling properly and air pressure can bypass the pellet. This can negatively affect accuracy and or power. I've experienced this twice now. Once with a brand new 20 caliber barrel and now with a 22 caliber barrel. The accuracy on both was acceptable but the power was well below normal or advertised.
Another possible benefit of a breech restiction is it may create a spike in pressure to pop the pellet out at a faster velocity than it might if the bore was straight. Think pop gun. In the typically desired low drag, perfectly straight bore the pellet would likely accelerate in a more linear fashion and consume the swept volume before reaching the same velocity as the pop gun effect breech.
Past this breech constriction, restiction, choke or whatever you want to call it, the barrels usually open up. The barrels typically have only light drag from the rifling engagement between the breech and muzzle. That's partly why there's no real difference in power outputs between long and short barrels on these guns. Almost every Weihrauch barrel I've slugged has this basic profile. Some barrels are tighter in areas than others. Some have inconsistent engagement drag. When slugging barrels some will have such light engagement the pellet will gravity fall through some sections. This is most commonly found around an inch or so before the sight crimp. Any bore size inconsistency can cause the pellet to chatter down the bore and have bad accuracy. This is why you have a muzzle choke.
The muzzle choke basically grabs the pellet and straightens it out before it leaves the barrel. Weihrauch muzzle chokes vary in resistance. Most are only noticeably tight and some are ridiculously tight. I almost have to pound the pellet through the muzzle choke of the threaded 22 barrel I've been messing with recently. This obviously would consume energy. Especially since there's no significant air pressure left behind the pellet by time it gets to the muzzle.
You'd think it might make sense to use pellets that run small in a gun with a tight choke at either end to reduce resistance and increase power. The problem is not that other pellets are too big but the choke is too tight. I've run smaller and softer pellets through tight choke guns hoping to gain energy. There's typically little to no gain in velocity because the driving air pressure bypasses the undersized pellet. Plus the accuracy tanks because it doesn't engage the rifling throughout most of the barrel.
I'd be remiss if I didn't mention that some people have reported cutting off the choke and recrowning Weihrauch barrels without losing accuracy. I personally wouldn't do it without slugging the barrel first to make sure there's adequate rifling engagement through the full length of the barrel. Even with adequate engagement I'd still look to cut it at a tighter spot.
Also I slugged all my rifles today before posting this to ensure my accuracy after other people's differing experiences. I did find that my 177 Hw50 wasn't particularly tighter in most of the breech than most of the bore. There was a slightly tighter spot just inside the breech towards the front of the breech block otherwise the drag was fairly consistent throughout most of it's length. It did have what I'd call the typical loose spot before the muzzle crimp and of course the associated muzzle choke. Don't ask me what causes that loose spot. F'd if I know.
In a perfect world Weihrauch's chokes wouldn't be necessary. We don't live in a perfect world and pellets aren't always consistently sized so Weihrauch sizes them for you. Unfortunately (albeit rarely) their tolerances are sometimes off and we wind up with a dud. Like I said, I've had two now that were under powered. Thats only two out of dozens of guns I've worked on that were produced from the 80s to this year. I did have two brand new 177 77SEs with consecutive serial numbers that had atrocious accuracy. The guns were returned for a refund. The exact barrel defect is still unknown to me. So I guess that's four defective barrels. I imagine no caliber or model is exempt from an occasional defect. IMO nothing mass produced is. Overall Weihrauch produces good quality barrels and rifles as a whole.
If you ever have accuracy or low power issues I highly recommend slugging a barrel. I normally use bamboo BBQ skewers. They're usually strong enough to push a pellet through without the possibility of damaging the bore. If they're not strong enough the barrels probably bad and you can use a brazing rod. Also slugging has to be done with a good fitting pellet from the breech out to get accurate feedback. This requires complete disassembly of 77s and 97s. I'm not sure if it can be done at all with a 57. Its the only current Weihrauch I haven't worked on.
I hope this helps some people understand what's normal and what to look for. Even knowing this myself I still have to prove a barrel faulty by swapping it out. I'm not happy to have to have done this twice now, but it does help me learn what to look for. I guess I'll eventually get a feel for how tight it's too tight and what's too loose.
Be well all.
Ron
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