Reaming open muzzle choke?

[Mycapt65]

I have a threaded 22 cal Weihrauch barrel that the muzzle is choked too tightly. When slugged the pellet stops dead about 3/8" from the end. Im looking for suggestions how to open the choke without removing metal from the rest of the bore.

Thanks
Ron

 

[Firewalker]

I have a threaded 22 cal Weihrauch barrel that the muzzle is choked too tightly. When slugged the pellet stops dead about 3/8" from the end. Im looking for suggestions how to open the choke without removing metal from the rest of the bore.

Thanks
Ron

Just speaking for myself here, I'd cut it off.

Otherwise you would have to use something like valve grinding compound and lapp it open.

 

[Bedrock Bob]

Six suggestions...

1- Borescope the muzzle so you know exactly what you are dealing with. Have a gunsmith measure the bore with an inside micrometer.

2- using a tight patch estimate how far you need to polish.

3- Slug the bore using cerrosafe or linotype to get an exact profile of the barrel.

4- A hard rubber rod sized correctly and abrasive paste. Adjust the viscosity of the paste to match the tolerance of the rubber rod with the bore.

5- Cut and recrown if the above dosent work. Your barrel will be unchoked and your piston may slam. It will change the dynamics of the shot cycle.

6- Buy a replacement barrel.

Good luck!

 

[GeneT]

Cut and recrown. Any sort of abrasive is going to first attack the lands of your rifling. It is very likely that there would be an attendant reduction in accuracy. What you want is intact rifling with a crisp and even end, which you will only attain by removing the offending section entirely.

GsT

 

[Mycapt65]

I'll have to recheck if they'll be enough thread left to attach the muzzle weight after cutting off the tightest part of the choke. If so it'll make it easy to decide. Plus I won't have to worry about the cosmetics of the cut.

 

[RM.510bigbore]

You can yes hand lead lap the choke out of the barrel..All premium benchrest barrels are hand lead lapped with various grits of lapping compound after reaming the bore and again after rifeling..You have to pour a lead lap to the bore...its not complicated..been doing it since we were shooting muzzzle bombs..I worked at ER Shaw in bridgville pa.. I drilled thousands of barrels , ran the reamers, chambered barrels, polished barrels huge 6 ft belt sander, stainless barrels dont make any sparks you can see,,must wear fire rated shirt or stainless sparks will catch shirt on fire... I lapped the choke out of a factory lother walther pellet barrel and it look like a perfect uniform smooth bore..

 

[Mycapt65]

You can yes hand lead lap the choke out of the barrel..All premium benchrest barrels are hand lead lapped with various grits of lapping compound after reaming the bore and again after rifeling..You have to pour a lead lap to the bore...its not complicated..been doing it since we were shooting muzzzle bombs..I worked at ER Shaw in bridgville pa.. I drilled thousands of barrels , ran the reamers, chambered barrels, polished barrels huge 6 ft belt sander, stainless barrels dont make any sparks you can see,,must wear fire rated shirt or stainless sparks will catch shirt on fire... I lapped the choke out of a factory lother walther pellet barrel and it look like a perfect uniform smooth bore..

Thank you for that information. I shoot PBs too and know that the almost all the competitive Bench Rest guys where I shot had hand lapped custom barrels that cost more than my guns. I didn't know how they were lapped. I've since moved to the sticks and don't have access to their knowledge. I dont even have a real gunsmith within hours of me. I'll have to look at whats involved in pouring a lead lap to the bore.

Thanks
Be well
Ron

 

[nervoustrig]

I'll just say from my limited experience lapping barrels, the idea of removing a ~1 thousandth choke typical of a LW barrel...it's a punishment I would not wish upon anyone. I'd much prefer to chop and recrown.

 

[Firewalker]

I'll just say from my limited experience lapping barrels, the idea of removing a ~1 thousandth choke typical of a LW barrel...it's a punishment I would not wish upon anyone. I'd much prefer to chop and recrown.

I won't do it either, I'd cut new 1/2*20 UNF threads on the barrel after chopping the end off and recrowning it.

 

[Mycapt65]

Thanks. All, I've since come up with a plan to avoid lapping or cutting off the threads. I'll update with results. Good or bad.
Be well
Ron

 

[Mycapt65]

Just checked out my idea and it's nots going to work without a machine shop. At that point cutting and rethreading is just as well. I'll have to make a call back north. Here's a drawing to help conceptualize. There's a too loose spot just before it gets too tight. It has to be cut back before the loose spot.

I could also leave the 20 cal barrel on there and say F it.

 

[nervoustrig]

FWIW it looks like the classic symptom of the bore opening up from having removed material from the OD to produce the threaded muzzle, combined with an overly aggressive choke.

I'm really perplexed by the choke being only 3/8" long. I don't recall ever encountering one that short. Makes me think something was off when the choke was applied. I don't know how Weihrauch does it but I can imagine a scenario where the end of the barrel was not fully inserted into the machine fixture. If the instrumentation is set up to apply pressure until it reaches a particular value, that would explain why the choke is so excessive in that short region.

 

[subscriber]

This may be a poor suggestion, because it is anathema to a short shallow crisp crown; but it is done in cases where the original muzzle needs to be retained. Essentially it is a deep tubular crown. It looks a bit like what CZ was applying to its Slavia spring airgun muzzles image below. I believe it is also known as counter boring a muzzle.

If you think about it, counter boring the muzzle back to just past the stud shoulder probably won't shoot worse than what it does with the meandering choke. If it is unacceptable, then you are back to cutting off 3/4" of barrel at the muzzle, re-threading and re-crowning :

The video below is about collectors items that have a worn out or abused muzzle, but where they do not want to cut the barrel shorter, as that alters the appearance, but they do want to be able to shoot the guns:

 

[Mycapt65]

This may be a poor suggestion, because it is anathema to a short shallow crisp crown; but it is done in cases where the original muzzle needs to be retained. Essentially it is a deep tubular crown. It looks a bit like what CZ was applying to its Slavia spring airgun muzzles image below. I believe it is also known as counter boring a muzzle.

If you think about it, counter boring the muzzle back to just past the stud shoulder probably won't shoot worse than what it does with the meandering choke. If it is unacceptable, then you are back to cutting off 3/4" of barrel at the muzzle, re-threading and re-crowning :


View attachment 502276

View attachment 502277


The video below is about collectors items that have a worn out or abused muzzle, but where they do not want to cut the barrel shorter, as that alters the appearance, but they do want to be able to shoot the guns:

Thanks that's exactly what I did this morning. After calling a machinist friend that works at a serious gunshop. They build custom guns right down to the actions. He told me it'd cost more than a new barrel cost to have them cut, crown and thread this barrel.

I asked him about reaming it by hand as was considering. He said to drill it in steps, then ream it. That's what I did. I chucked a 7/32" drill bit in a tap holder and hand drilled it past the choke and loose spot. Then I stepped up to 15/64". Then lapped the internal crown with the drill bit flipped over and 600 grit compound.

I Reinstalled it on my R1 for a net gain of zero fpe. I haven't figured out why but this barrel makes a full 2 fpe less than another 22 barrel on the same rifle. The muzzle choke was ridiculously tight so I was sure that was it. Tomorrow I'll slug both barrels and look again for differences. I'm done for today.

Not that it matters but the accuracy is excellent on the drilled barrel. Perhaps even better than before. At least I didn't ruin the barrels's accuracy.

 

[Mycapt65]

This may be a poor suggestion, because it is anathema to a short shallow crisp crown; but it is done in cases where the original muzzle needs to be retained. Essentially it is a deep tubular crown. It looks a bit like what CZ was applying to its Slavia spring airgun muzzles image below. I believe it is also known as counter boring a muzzle.

If you think about it, counter boring the muzzle back to just past the stud shoulder probably won't shoot worse than what it does with the meandering choke. If it is unacceptable, then you are back to cutting off 3/4" of barrel at the muzzle, re-threading and re-crowning :


View attachment 502276

View attachment 502277


The video below is about collectors items that have a worn out or abused muzzle, but where they do not want to cut the barrel shorter, as that alters the appearance, but they do want to be able to shoot the guns:

Good to hear from you again Subs. Hope you've been well.
Ron

 

[subscriber]

Ron,

I try to keep such a low profile that I am virtually two-dimensional.
Still working on lots of projects; just not showing them here.

 

[subscriber]

One potential reason for a power variance between barrels could be the shape and smoothness of the breech cone. That sets the release pressure before the pellet pops loose at the start of its travel.

Another reason could be the degree of "breech choke" that results from press fitting the barrel into the breech block. That rear choke reduces pellet to bore friction down the rest of the barrel. It is also why the muzzle choke helps to straighten out the pellet before it is sent on its way. Now, considering your R1's bad choke, cutting it of has probably improved the system, rather than hurt it.

If you push a pellet down the barrel with a cleaning rod, you should be able to feel the breech cone resistance (needs to be significant), followed by some friction. After the end of the breech block, the friction may drop off substantially. If it drops to zero that could mean the pellet's travel axis is not controlled, and it may yaw in the bore. Some friction to the muzzle means the pellet is likely to be more stable in the bore.

Of course, the general smoothness of the bore is also likely to affect the average friction; and that can affect the pellet velocity. Different pellets may shoot more efficiently than others. So, a "fast" barrel may not always beat a "slow" barrel by the same degree.

Ultimately, what matters is that it shoots well enough. Especially in terms of consistent grouping ability. Something that sometimes seems elusive with springers.

 

[Mycapt65]

One potential reason for a power variance between barrels could be the shape and smoothness of the breech cone. That sets the release pressure before the pellet pops loose at the start of its travel.

Another reason could be the degree of "breech choke" that results from press fitting the barrel into the breech block. That rear choke reduces pellet to bore friction down the rest of the barrel. It is also why the muzzle choke helps to straighten out the pellet before it is sent on its way. Now, considering your R1's bad choke, cutting it of has probably improved the system, rather than hurt it.

If you push a pellet down the barrel with a cleaning rod, you should be able to feel the breech cone resistance (needs to be significant), followed by some friction. After the end of the breech block, the friction may drop off substantially. If it drops to zero that could mean the pellet's travel axis is not controlled, and it may yaw in the bore. Some friction to the muzzle means the pellet is likely to be more stable in the bore.

Of course, the general smoothness of the bore is also likely to affect the average friction; and that can affect the pellet velocity. Different pellets may shoot more efficiently than others. So, a "fast" barrel may not always beat a "slow" barrel by the same degree.

Ultimately, what matters is that it shoots well enough. Especially in terms of consistent grouping ability. Something that sometimes seems elusive with springers.

Thanks I'll look more carefully at the leade area now. I know it's been written about but I've never experienced power differences between many loose and tighter leades. Then again most of my experience is with smaller calibers. Perhaps it makes a bigger difference in 22. I know that 22 Weihrauchs typically make considerably more power with tighter fitting pellets or at least pellets with stiffer skirts.
I wrote this a few days ago and you'll see we have similar ideas.
Thread 'Weihrauch barrel idioscyncrosies explained'
https://www.airgunnation.com/threads/weihrauch-barrel-idioscyncrosies-explained.1320320/

Be well Subs
Ron

 

[subscriber]

Thanks Ron,

That link suggest you already know Weihrauch springer barrels very well.

 

[Mycapt65]

Thanks Ron,

That link suggest you already know Weihrauch springer barrels very well.

Only quoted this to get your input.
I've been busting my butt getting the homestead ready for winter so I only just got back to comparing these barrels today.

The higher powered 22 barrel that normally resides on the R1 has the typical Weihrauch bore profile. Pellets fits with a snug spot at 3/4" some drag through next almost couple inches until a couple of tighter spots where the knurl bands are. Once out of the breech there's nearly no drag until the choke. The muzzle choke is almost or possibly as tight as the one I cut off the "problem" barrel.

Now the "Problem" barrel. After pushing dozens of pellets through both barrels, the best I can tell is that the resistance profile through the breech area is the same. Besides the missing muzzle choke the only notable difference is this barrel has much more drag after the breech block and all the way out the barrel. That additional drag is probably responsible for most if not all of my missing power.

I didn't forget to check the leade. Both are the same in there's not much pressure to pop the pellet past them. Both look to be machined with the same small crown.

At this point in time I'm not sure what to do with this barrel. Its accurate as hell without the choke but it doesn't make the power I need to shoot the longer distances I shoot. I don't see a way to open the bore without hogging out the breech to the same diameter. With a looser breech I might not reach peak pressure and lose even more velocity. I guess I could sell it or trade it with a disclaimer to someone who doesn't need full power.

You got any suggestions?