GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: Taso1000 on May 04, 2016, 02:03:39 PM
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I was interested in putting a choke on a B51 barrel and in my research I found this post:
http://www.gatewaytoairguns.org/GTA/index.php?topic=43105.40 (http://www.gatewaytoairguns.org/GTA/index.php?topic=43105.40)
In reply #40, Whitefang mentions a cable crimp tool that can be tightened with a torque wrench. I have not been able to find something that matches his description but I found a hydraulic cable crimp tool. Can this be used to choke barrels?
They are right around $40 but all the changeable dies I have seen are hex shaped. Do any dies exist that are round? I guess you could drill out and split a nut to use inside one of the existing hex dies.
Would something like this work or are there better diy options out there?
Thank you all in advance. :D
Taso
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The best setup I have seen is a large pipe cutter with the cutting disc replaced by a third ball bearing.... As you tighten the tool, the three bearings press harder on the barrel, and you rotate the tool around the muzzle to collapse it.... You can check the bore with pin gauges and stop when you get the right amount of choke.... I haven't done it, but I understand it is pretty easy to control the amount of choke, and the fact you are rotating the "die" (bearings) around the barrel makes it even....
Bob
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Bob,
Thank you for your input, I appreciate it. :D
I was trying to figure out how to apply the force on the hydraulic ram consistently and repeatedly. I haven't yet. Maybe a hydraulic fluid pressure gauge could be installed somehow depending on the unit.
I was thinking rotating the barrel 120 degrees, or less, each time and compressing to make it even all the way around but that is still not as even as the rollers on the pipe cutter.
I was hesitant on a pipe cutter because in reply #33 Whitefang said the rollers were digging into the barrel versus rolling and I would still need to buy a heavy duty pipe cutter and figure out how to replace the cutter.
I have a light duty pipe cutter but I don't think it would be strong enough to choke the barrel even if I could figure out how to replace the cutter with a roller or ball bearing.
I don't have a problem farming out the choke labor but I figured if I was going to choke 6 or more 1/2" barrels shipping will start to add up.
I enjoy learning how to do stuff by myself. Most of my posts are about me tinkering with new things lol If I can't do it, then I can't do it. ;)
Taso
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Bob,
You were right. After more research, thinking it through and my lack of tools I looked into the big pipe cutters on Ebay. I found a Ridgid 202 in great condition for $42 shipped.
When you said ball bearing I only though like a bb not an actual bearing. Sorry. Once I get the cutter could you help me find a bearing or maybe a third roller?
Then Taso's barrel choking business will be open! Just kidding Administrators. :D
Thanks,
Taso
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Hey Bob,
Do you think putting the barrel end (1") in a lathe chuck and tightening it very hard could work too?
Kirk
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I don't think so.... more likely to break the chuck, IMO....
Bob
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Bob,
So I would use the pin gauges like "go" and "no go" gauges? Can you recommend what sizes to start with for .177 as I don't have any pin gauges.
How much choke do you recommend? .001" from what the grooves currently are or choke down to a certain size to be kinda pellet universal lol?
Thank you,
Taso
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I was interested in putting a choke on a B51 barrel and in my research I found this post:
http://www.gatewaytoairguns.org/GTA/index.php?topic=43105.40 (http://www.gatewaytoairguns.org/GTA/index.php?topic=43105.40)
In reply #40, Whitefang mentions a cable crimp tool that can be tightened with a torque wrench. I have not been able to find something that matches his description but I found a hydraulic cable crimp tool. Can this be used to choke barrels?
They are right around $40 but all the changeable dies I have seen are hex shaped. Do any dies exist that are round? I guess you could drill out and split a nut to use inside one of the existing hex dies.
Would something like this work or are there better diy options out there?
Thank you all in advance. :D
Taso
I've choked a R1 barrels that was chopped for use with my R9 and it was successful. I used two methods when testing the choking procedures and I first used a heavy pipe cutter bought from a Cummins Truckload sale truck and replaced the cutter wheel with a home turned steel roller to swage the muzzle after cutting off the factory sight grooves and choke. While it did create a choke it also messed up the bluing on the muzzle.........
(http://www.snapagogo.com/uploads/source/442015/1423920509_404712264_PipeChoke1.jpg) (http://www.snapagogo.com/photo.php?id=66813)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
(http://www.snapagogo.com/uploads/source/502015/1424450253_1584645116_pelletmuzzle.jpg) (http://www.snapagogo.com/photo.php?id=67089)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
After cutting off the messed up choke, facing and re-crowning the barrel, I used a home made "clamp block" from the head of a 1"-8 hex bolt (has a head 1 1/2" across the flats). After cutting off the bolt shank I chucked the head in my lathe and faced both front and then back. Next step was to bore the bolt head and lap the hole so it was .005 larger than the od of the R1 muzzle. Next step was to radius the lapped hole edges and then split the bolt head across the corners with a hack saw, then smooth up and sharp edges from the hack saw cut. The muzzle of the barrel was then placed in the bored hole in the "clamp block" and tightened in my HEAVY 5" vise! The way I gaged the progress of the choking procedure for each method was to push new pellets through the bore till the smallest restriction was at the muzzle. Using the clamp block and vise method required EXTREME PRESSURE on the vise handle and, toward the end of the swaging I had to add a piece of pipe to the handle to get the restriction. After noticing a slight restriction at the muzzle I rotated the barrel 90 degrees in the clamp block and constricted the muzzle till I felt just a tad more restriction to the new pellet being pushed through the bore.......then I called it quits. There was indeed a noticeable choke at the muzzle when I finished but it wasn't as tight as the factory HW choke. A couple pics......
(http://www.snapagogo.com/uploads/source/2842014/1413150033_1735908122_halves.jpg) (http://www.snapagogo.com/photo.php?id=59226)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
(http://www.snapagogo.com/uploads/source/2842014/1413150035_1329087059_halves1.jpg) (http://www.snapagogo.com/photo.php?id=59228)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
(http://www.snapagogo.com/uploads/source/2842014/1413150034_1445852816_halves2.jpg) (http://www.snapagogo.com/photo.php?id=59227)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
Here is a target I shot at 50 yards "from bucket and sticks" using that home chopped and choked R1 barrel on my R9..........
(http://www.snapagogo.com/uploads/source/2352014/1408919774_1744796446_fts50yds2.jpg) (http://www.snapagogo.com/photo.php?id=56425)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
I shot group #1 aiming at the bull where I shot group #2 and was so pleased with the group that I took the time to zero the gun at 50 yards and proceeded to shoot the second group.
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Ed,
I had considered using your bolt die idea in the hydraulic cable crimper. Unfortunately I don't have the tools to make a die like yours. I do have a vise but it's a "warehouse" special so I doubt it's very strong.
With the pipe cutter all I need is another roller and I should be good to go. I hope. ;)
I am lucky that all my guns' muzzled are cover by breaks, ldc's and sights. So any marring from the rollers will be hidden. I'm just hoping I don't have a soft barrel where the rollers will dig in. Hopefully I can go slow enough not to create a speedbump.
Thank you,
Taso
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Hi All,
So I received my Ridgid pipe cutter. It is model 202 with the wide rollers. I have attached pictures. Can anyone help me with a roller to replace the cutting wheel? The width of the cutting wheel axle? is .7435 inches. And the axle diameter is .346. I am not sure what the max roller diameter can be? Does any one have any suggestions or know if a narrow model roller will fit in the cutter position?
Thank you,
Taso
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"I am not sure what the max roller diameter can be?"
When I made my "roller swager" from a Cummins Truckload Sale pipe cutter set I simply machined a roller to replace the cutting wheel to fit. In my case a piece of O1 tool steel was machined to the same width as the "cutter roller" and the diameter was the same as the cutter diameter.
IMHO, simply match the cutting wheel if possible and keep in mind that the wider the flat surface of the fabricated roller the more pressure will be needed to effect the constriction. Actually, only about 1/2" of the muzzle needs to be constricted to affect a choke.
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Ed,
Thanks for the help. I don't have access to machine tools or have any friends that do. Unfortunately. If I did I would be dangerous. :P In a good way.
There is a version of my pipe cutter that has narrower rollers opposite the cutter. These "seem" to be the same width as the cutter. The cutter is the same on the regular and wide pipe cutter.
I was looking online for dimensions of replacement rollers but no dimensions are listed. I guess I could order them and trim or shim them.
Thanks,
Taso
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Taso, I saw your response to my post on this subject, thanks for directing me here.
Is it possible that one of your rollers would fit in the position of the cutter ? If it will then you just need a replacement roller.
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No. My cutter is the wide roller model. The cutter side seems to be the same as the regular roller cutter. There are two different part numbers for regular and wide roller. I was curious if the regular roller would fit on the cutter side. I can't find any dimensions for the rollers. Either the regular roller fits or it doesn't. I could trim or shim the width. But if it's too big in diameter it may not fit and roll.
I am new to huge pipe cutters. I guess I can order the narrower rollers and find out. If they can't be made to work I cn return them. I was wondering if also getting new wide rollers for the other side to minimize the barrel marring.
Taso
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I ordered and just received the narrower roller for the regular width pipe cutter. While it fits perfect width wise it's diameter is too large.
So now I have a dilemma. I think I may be able to get the roller fixed in my drill press with a bolt and nut with rubber washers for friction to keep it from spinning.
I think this way I can bevel the edges so that it will clear the pipe cutter head? Or I would need someone to turn the whole diameter down to fit.
If I bevel the edge the three roller ends will be more offset. If I turn down the diameter I will have the smallest offset but I may not have the reach.
Or I can try to clearance the cutter head with a rotary tool and some sand drums to clear the roller as is? This would be the easiest for me to do and maybe the best solution. Do you think the tool will weaken or because the force is in the opposite direction it will not make any difference?
What do you guys suggest?
Thank you,
Taso
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I think I would grind or turn a bevel on the edges of the roller until it drops into the casting and you can get the pin in place.... ASSUMING of course you know that there is clearance at the back of the hole for that diameter, in enough width to do the job intended....
Bob
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So I tried to clearance the edges of the roller to fit in the cutter head. All I accomplished was to make it shinier lol. I guess it's too hard for my tools to cut.
I didn't put those dings in the roller. I uncovered them lol
Taso
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I just remembered I have an old bench grinder. I'm going to see if that will work on the edges.
Taso
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Just grind a bevel on the edges.... keeping it 100 straight isn't critical, just eyeballing it will do.... as long as it fits in the hole....The working surface will simply be a bit narrower....
Bob
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Bevel grinding was a success with the bench grinder and a drill going the opposite direction. I'll post some pictures when I get the pipe cutter back together.
Now my question what should I lubricate the rollers with? I have Super Lube, Ultimox and Loctite moly paste. I think I read moly is for high pressure applications.
Thanks,
Taso
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Definitely NOT Silicone based (eg SuperLube).... I would use a Moly grease, for sure....
Bob
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Bob,
I think you got what I meant but just to be clear. I'm talking about lubricating the pins the rollers rotate on.
Also should I use a lubricant between the rollers and the barrel? Or will I then have trouble turning the barrel because it's too slick?
Bob, you had mentioned pin gauges. Can you explain and guide me what size to order?
I am afraid I may over choke. Lol I over do almost everything.
Taso
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I agree with Bob.... Moly based lube for sure....
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I was referring to the pins that the roller rotates on as well, I don't think you need to (or want to) lube the barrel, the roller might skid on it.... Pin gauges are generally a "go / no-go" style of two different diameters, and you probably don't need to choke more than 0.001"-0.002", and ideally you should be able to measure to 0.0002", so you may have fun getting the gauges you need without spending quite a bit of money.... I don't have any, I just know that is the proper way to do it.... I have never choked a barrel....
Bob
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Bevel grinding was a success with the bench grinder and a drill going the opposite direction. I'll post some pictures when I get the pipe cutter back together.
Now my question what should I lubricate the rollers with? I have Super Lube, Ultimox and Loctite moly paste. I think I read moly is for high pressure applications.
Thanks,
Taso
When I modified my pipe cutter for swaging my muzzle I used molly paste to lube the axle. Even with the molly lube the pressure on the axle when rolling was great enough that I could feel the heat generated by friction when touching the roller after the swage. To determine the amount of choke I would frequently use a coated cleaning rod to push through new CPLs to detect when there was a "felt constriction" at the muzzle before the pellet exited which is the same "gage" used with the "clamp blocks". Once the tightest constriction through the bore was at the rolled choke the swaging was stopped. IMHO, the only purpose of a choke is to guarantee that the tightest portion of the bore is the last 1/2" before the pellet exits. My chokes weren't as tight as a factory HW choke but certainly worked well as this 50 yard target shot years ago will show...........
(http://www.snapagogo.com/uploads/source/2352014/1408919774_1744796446_fts50yds2.jpg) (http://www.snapagogo.com/photo.php?id=56425)Uploaded at Snapagogo.com (http://"http://www.snapagogo.com")
While the choke for this target was done with my "clamp blocks" and vice, I see no reason why a rolled choke wouldn't be at least as good.
That's two 50 yard "bucket and sticks" groups a bit under 1/2" ctc. I was so pleased with the first group using holdover that I zero'd the R9 at 50 yards and shot group #2 so it seems that my choke at least didn't hurt my accuracy.
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Number drill bits
15=.180
16=.177
17=.173
Best I can suggest without buying pin gauges
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Thank you all,
What is the standard .177 air rifle bore dimensions? Lothar Walther lists on their site .176 for the lands and .182 for the grooves.
I was curious should I "standardize" the barrel to some dimension?
Ed,
I was going to try your pellet test fit method till I read where you found some pellets were oval. Then I thought about resizing the pellets like you mentioned.
But I guess the choke will ultimately resize the pellet on exit.
Obviously choking down the barrel till the pellet heads touch the grooves would be a bad thing because of drag.
I know some pellets will either be skinnier or fatter than spec or somewhere in between.
Taso
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Number drill bits
15=.180
16=.177
17=.173
Best I can suggest without buying pin gauges
IMHO....pin gages only indicate the diameter at the choke, not the choke diameter relative to the tightest constriction in the rest of the bore. A lot of the old style R9 barrels I've had were constricted at the breech end where the barrel was pressed and pinned into the barrel pivot block. IMHO (again) there is a possibility of choking the bore more than necessary (not necessarily a good thing) without testing the progress of the choke by pushing new pellets.
Granted.....if you make the choke tight enough it will be smaller than the tightest constriction, however that is an unknown without pushing through a new pellet.
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Ed, your comment about some R9 barrels being tightest at the breech inrigues me.... I wonder if the concept of choking pellet barrels is merely a fix for the fact that many Springer barrels may be choked at the wrong end when pressed into the breech.... ie the choking was to fix a problem, and once discovered (or advertised) became the "thing to do" with all airgun barrels.... even ones that weren't pressed into a breech block....
Bob
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Intriguing!
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Ed, your comment about some R9 barrels being tightest at the breech inrigues me.... I wonder if the concept of choking pellet barrels is merely a fix for the fact that many Springer barrels may be choked at the wrong end when pressed into the breech.... ie the choking was to fix a problem, and once discovered (or advertised) became the "thing to do" with all airgun barrels.... even ones that weren't pressed into a breech block....
Bob
Don't know for sure but I suspect the choke is simply to guarantee that the muzzle stabilizes the pellet if it was swaged down previously in the bore. As you know, airgun rifling is very fine and bores are very precise so it takes very little variation in the barrel boring and rifling to create a tight spot "early on" which causes the pellet to rattle down the rest of the bore and exit at various amounts of alignment. Just a personal opinion that makes sense to me because there is some reason some airgun manufacturers add the barrel choking step. I've often wondered if HW chokes their muzzles by pressing in the front sight dovetails, however my fixed barrel HW77k had a choked barrel and the front sight dovetail was on the cocking lever retaining bracket rather than dovetails pressed onto the barrel itself (hummm, I don't think that there were dovetails pressed in the muzzle under the retaining bracket but I could be wrong!
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Yeah, I've seen muzzles with dovetails pressed in, and figured that was adding a choke as well, all in one step....
Bob
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The black ox replacement pins are $2.50 each. do not know about shipping...
http://www.meyergage.com/products/individual-gage-pins/ (http://www.meyergage.com/products/individual-gage-pins/)
I bet about a .002 choke is enough on a .177
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Crosman barrels are .1755.
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Bob,
Thank you for your input, I appreciate it. :D
I was trying to figure out how to apply the force on the hydraulic ram consistently and repeatedly. I haven't yet. Maybe a hydraulic fluid pressure gauge could be installed somehow depending on the unit.
I was thinking rotating the barrel 120 degrees, or less, each time and compressing to make it even all the way around but that is still not as even as the rollers on the pipe cutter.
I was hesitant on a pipe cutter because in reply #33 Whitefang said the rollers were digging into the barrel versus rolling and I would still need to buy a heavy duty pipe cutter and figure out how to replace the cutter.
I have a light duty pipe cutter but I don't think it would be strong enough to choke the barrel even if I could figure out how to replace the cutter with a roller or ball bearing.
I don't have a problem farming out the choke labor but I figured if I was going to choke 6 or more 1/2" barrels shipping will start to add up.
I enjoy learning how to do stuff by myself. Most of my posts are about me tinkering with new things lol If I can't do it, then I can't do it. ;)
Taso
The key to the pipe cutter is go slow with the tightening process the ham handed approach will dig the rollers into the barrel in and not allow the rollers to move freely to much pressure will cause binding so small incremental tightening of the handle is necessary
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The black ox replacement pins are $2.50 each. do not know about shipping...
http://www.meyergage.com/products/individual-gage-pins/ (http://www.meyergage.com/products/individual-gage-pins/)
I bet about a .002 choke is enough on a .177
"I bet about a .002 choke is enough on a .177"
As long as the choke is the smallest fart of the bore I'm thinking that less than .001 is more than enough. When I was choking my own cut off HW barrels I would choke just enough that a pushed pellet would have a bit of added resistance at the muzzle. The pressure needed to push a new pellet through the bore from breech through the choke was about 1/2 of a standard HW factory choke at that time (over a decade ago). I did notice that the pellet fit to leade of my newer .177 HW95 was considerably tighter than the older .177 R9. I just finished working up a newer HW95 for a fellow that was having accuracy issues and noticed that the choke was considerably tighter than any other HW piston gun I've messed with so perhaps HW has tightened up their .177 bores.
Anywhoo........here are two 50 yard 5 shot groups shot from my .177 R9 fitted with a .177 R1 barrel that was home "chopped and choked" when living in West Virginia.........
(http://img.photobucket.com/albums/v734/wved/Targets/fts50yds2.jpg) (http://smg.photobucket.com/user/wved/media/Targets/fts50yds2.jpg.html)
Both groups were shot "bucket and sticks" and the 1st group was shot aiming at the bull where the secong group was shot after re-zeroing the R9 for 50 yards and aiming "dead on".
LOL.....this is the only R9 that ever shot the Beeman FTS pellets well and choking the muzzle till there was just a tad of extra "squish" at the muzzle worked real well.
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Thank you Don. Yeah I had imagined if I tightened too much too fast I'd create like a speed bump that I'd never get straightened out aside from cutting off more of the barrel and starting over.
But it seems that very little choking is necessary. I haven't choked any barrels since I don't have a range close by do see the results of my experimentation. ;D
Taso
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Hi All,
I recently realized I never posted pictures of the finished "choker". So I just took some pictures to post. So all totaled it cost me $75 for a used pipe cutter off ebay, a pair of replacement rollers from amazon and shipping on both items.
Unfortunately I have not been able to test the effects of choking because I don't have a long range to do testing on.
Thanks,
Taso