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Post by Richard on Jan 16, 2017 20:19:19 GMT -5
Bushing set screw failure…. A member, who apparently frequents both boards, sent me a PM regarding the set screw that holds the bushing on his breech plug…………cracking? He was wondering if it had anything to do with his duplex of 5 gr. Clays International and 60 gr. of 4198? I could not say one way or the other? What I did tell him was that my present HIS breech plug with the SS set screw I got from Hank now has 334 duplex shots on it and is still in one piece. I take it out every week and wire brush the threads (all two of them) then re-anti-seize it and replace. Now what I will note is that Sunday night when I was going to remove the set screw, it did not want to come out?  ?-----------------This never happens!............But, I had left the gun dirty from a week before and thought that might be what was causing the problem so I applied a little heat and it came out. I did notice the bottom of the screw was a little rough but thought nothing of it. So today, when I got home from the range I wanted to immediately take out the plug and remove the set screw; it came out but almost NOT? I again wire brushed it and ran a file over the bottom and could see a couple of shallow groves crosswise on the bottom. So, I put it in the lathe and made a facing cut to smooth it out and have it back in place for next week. So here are my thoughts: When we put that set screw in, we have created a little “tunnel” to the hole in the bushing………right? So, what do you think used to happen to our beloved “vent liners?” They were burning out. Why?....................Man, we were going from shooting saboted 250 gr. bullets with low amounts of single powders and most were getting probably 50 to 100 shots on a vent liner which was only about 40 Rockwell C hardness. Gradually, we started upping the loads, duplexing, going sabot less, shooting 300 gr. + bullets which increased the pressures; low and behold we were eating up vent liners in 25 shots or less? Well NOW, we have carbide bushing which hold up very well to these hot loads but, there is the little mild steel or stainless steel tunnel that the flame has to go thru and where combustion is actually taking place in? It is NOT carbide? So, can it burn or erode?............I think so! What I also think is that the screw should be fairly tight when you install it (I was not doing that). If you tighten it but against the bushing face along with the pressure on the threads, there is less chance of pressure slipping by the threads? We put a lot of fine thread on the breech plug itself but we put a ¼ x 20 set screw with only two threads ? It is cheap insurance to call Hank and get a few extra set screws and replace them every once in a while. I guess another alternative would be to just leave them in place and let them “carbon-weld” themselves in place. I have changed bushings several times and like to be able to remove that screw. Any thoughts? ?? |
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Post by Deleted on Jan 16, 2017 20:57:42 GMT -5
I found out really quick on my first 5/85 duplex, clays/3031 under a 300gr Accumax, that the recessed nose of the HIS plug acts as a booster on a booster powder. I had a 40 bushing and the module was swollen so much that I had to remove it from the bolt face with pliers. WGK was there and saw it too.The chronographed velocity was not any higher than a single load of 3031. I believe the clays made an enormous amount of pressure in the small cavity of the plug nose (holds 5gr) until the 3031 lit. Jeff gave me some of the new aluminum/bronze modules so I will revisit this when I begin pressure tracing. I foresee chamber pressure NOT really reflecting the pressure of clays in the plug nose.
I think the difference in flame cutting the lock ring comes down to antiseize vs bearing retainer compound. Most use bearing retainer compound to install bushings and the associated lock ring. Antiseize tends to be "blown around", opening spaces where flame cutting begins. In order to flame cut, there has to be empty space for the pressure to try to access. With bearing retainer, pretty much all voids are filled around the bushing and lock ring.
Beware, that stainless lock rings are pretty much non-removeable after a while. They are soft and will round out pretty easily. I have a fixture that I screw grade 8 set screws into and surface grind the nose off. They are more foregiving than the stainless which will round out upon removal attempt even when heated. Richard, I think Jeff uses a 5/16-24 lock ring and most of the modified savage plugs and other plugs use 5/16-18 lock rings.
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Post by 12ptdroptine on Jan 16, 2017 21:21:13 GMT -5
I had a bushing break in to 3 pcs and the ring cracked 3 years back. Now I put Loctite bearnig retaining compound. 60o series in the bushig orifice and neversieze on the lock ring. I dont remove the bushing but do remove and clean and relube the lock ring. To this date I havent seen any problem. BUT I will inspect more closely next time inside it.
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Post by elkman1310 on Jan 16, 2017 22:45:01 GMT -5
I use a 5/16x18 lock screw in my breech plugs. But I have seen while experimenting if you have a pocket between the locking screw and the bushing it will hold a small amount of powder in that area. I didn't see any actually brake but I had one that actually got cocked it looked like it was cross threaded but it wasn't when I installed it. So yes that can be a weak link I make sure my lock screw actual bottoms on the top of the bushing now.
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Post by Richard on Jan 16, 2017 22:59:13 GMT -5
I was probably mistaken when I said 1/4 x 20. I didn't check, just blurted it out  But you can see from the number of shots I have on my plug that I don't really have a problem. This has been a NO issue for me? That IS a stainless retainer screw in my plug. I will be keeping it locked tight and will see how it goes in the future. |
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Post by Deleted on Jan 16, 2017 23:47:17 GMT -5
I am simultaneously on both boards, at the same time, apparently....  I do what scat does, apply bearing retaining compound to the bushing and blue loctite liberally to the retaining ring. I plan on getting some of the 2422 blue loctite which is supposed to be able to handle temps up to 650. |
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Post by elkman1310 on Jan 17, 2017 14:40:11 GMT -5
There is no way you should need Loctite to hold a bushing in place. Or the retaining screw. The bushing should be a simple snug tap in fit and once you fire a few shots the carbon will lock it tightly I'm place. I find this kind of stuff troubling to me because it clearly tells me who ever made your breech plug didn't use the proper reamer for the bushing.
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Post by buckdoehunter on Jan 17, 2017 15:36:09 GMT -5
Beware, that stainless lock rings are pretty much non-removeable after a while. They are soft and will round out pretty easily. I have a fixture that I screw grade 8 set screws into and surface grind the nose off. They are more foregiving than the stainless which will round out upon removal attempt even when heated. Richard, I think Jeff uses a 5/16-24 lock ring and most of the modified savage plugs and other plugs use 5/16-18 lock rings. Is this similar to what you use? www.mansiontools.com/5-16-18-socket-set-screw-kerrsss5-16-18x5-8-hardware-accessories-hardware-fas.html?channelid=GoogleAdwords&gclid=CP6r9uiDytECFQSoaQodgycFYQI am the one who messaged Richard about Clays and lock ring/breech plug damage. I am a jack of all trades but a master of none. I love to tinker but safety is my utmost concern. I enjoy hours of research before I tackle my muzzleloader projects. My daughter's 700ML is getting a Pac-Nor barrel put on soon. I am going to shoot some single powder loads in a few weeks to see if I still get cracked rings. It's hard to move away from my duplex load 'cause it shoots so darn nice with my 250/290gr Barnes TEZs. But, I get to go to range and test some more loads so that's a big plus. Many have given me some good suggestions to do, thank you all very much. Here are my pics of my troubles     |
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Post by redmule on Jan 17, 2017 15:44:29 GMT -5
I have two cracked bushings this end of season cleaning. One rifle has 75-80 shots with a load of 36 grs. of 4759. The other is has bout 25-30 shots at most with a duplex load of 10/52 4759/H4198. They are both .030 bushings. both rifles using 195 gr. Barnes and hsb's. kinda weird that two entirely different loads do this. The heavier load had the bushing loctited in with a bearing retainer sealant. The lighter load was just pressed in and seized with lock ring. Also both are savage type plugs. One plug was asg bushing plug other is PR plug. So what's up with that?
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Post by hillbill on Jan 17, 2017 15:47:51 GMT -5
to date I have had no problems, mind you I don't shoot any where near as much as Richard does but I normally shoot a few hundred shots a year, also I don't touch my bushing after it's installed, I will shoot it til it dies and than replace the plug if I need to.
Do boosters accelerate any potential wear? I am convinced they do just by what I have seen over the years but if all is sealed well there should not be a problem. Like Scat says though, that little dose of powder in the nose of the plug makes a lot of pressure very quickly, keep that in mind..
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Post by Deleted on Jan 17, 2017 15:49:40 GMT -5
Where are you guys getting your bushings and locking rings?
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Post by Deleted on Jan 17, 2017 18:00:14 GMT -5
There is no way you should need Loctite to hold a bushing in place. Or the retaining screw. The bushing should be a simple snug tap in fit and once you fire a few shots the carbon will lock it tightly I'm place. I find this kind of stuff troubling to me because it clearly tells me who ever made your breech plug didn't use the proper reamer for the bushing. Who makes your breech plugs? |
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Post by Deleted on Jan 17, 2017 18:38:31 GMT -5
Where are you guys getting your bushings and locking rings? I got mine from Luke and airborneike. |
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Post by linebaugh on Jan 17, 2017 19:55:36 GMT -5
Scat and I touched on this when we spoke a week or two ago and I think we kind of agree that if you have any recess in the plug that amounts to much capacity you are initiating a booster scenario even with single powder loads. Now if you take said recessed plug and use a booster or the faster powders you are actually boosting the booster. Who really knows what is happeneing but when you have guys getting over pressure scenarios with a 5gr recess and boosted loads there is something unhappy hapening.
To be 100% honest this probably has little to nothing to do with cracked retainers and cracked bushings but you never know I guess. It seems strange to me that a retainer would crack when it is in a static position and pressure should be acting on it in equalibrium around the retainer. Of course it seems strange to me that a slight interferance fit bushing would crack for the same reason but I just ordered two replacement bushings so I am certainly not getting the full picture.
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Post by Hank on Jan 17, 2017 20:01:22 GMT -5
Two things here can be the problem..... First the bushings are made from pure tungsten and if they are they will crack. It's only a matter of time. The second problem is the bushing pocket is oversize and allows room for the bushing to swell and that of coarse will cause it to crack. Elkman makes his breech plus one at a time paying close attention to detail and tolerances. This allow him to make a plug to properly fit the bushing. I make my breech plugs using CNC equipment and once I have it set up to bore the pocket I will run 100 or so plugs, therefore making them all the same. If you open up an existing plug with a boring bar or a reamer it is very hard to get it exactly to the size you need. Even a .250 reamer can bore oversize if your tail stock is off center of your head stock. With a single point boring bar if you are off .0005 that will make your hole .001 large and that is enough to let your bushing crack.
The plug in the picture above with the missing piece of thread,,,, needs to be thrown in the trash. This is only going to keep causing troubles. And that little 2 thread set screw ain't worth much in my book.. The set screw should (in my opinion) be made from a 5/16-24 X 1/4" set screw, not a 5/16-18 set screw ground down to 1/8 inch. Coarse threads were made for farm machinery, not gun manufacturing....
My bushings are made from a proprietary blend of Tungsten, Carbide and ?. I have yet to see one split. I have seen one chip off at the end but none have split down the middle like a pure tungsten bushing will do.
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Post by Deleted on Jan 17, 2017 20:01:28 GMT -5
There is no way you should need Loctite to hold a bushing in place. Or the retaining screw. The bushing should be a simple snug tap in fit and once you fire a few shots the carbon will lock it tightly I'm place. I find this kind of stuff troubling to me because it clearly tells me who ever made your breech plug didn't use the proper reamer for the bushing. The plugs I get from Jeff are a slight press fit and I recently debated even using a lock ring. I just hate to eject a $30 bushing downrange. Plugs that I have purchased in the past elsewhere did not have a press fit and required a lock ring. The bearing retainer compound was first used when bushings were cracking, thought being that it would add support to the bushing. Turns out the problem was a material one. Too Hard and brittle. Prior to that, only blue loctite was used. If a lock ring is installed without loctite, carbon penetrates the threads which makes it difficult to remove. The loctite/bearing retainer compound does act to fill voids that would be attractants to high pressure gas cutting. At any rate, the bearing retainer compound is very easily removed with a little heat to loosen it up. I realize that you don't shoot duplexes, therefore you would not have seen problems that we have with them. |
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Post by Hank on Jan 17, 2017 20:06:43 GMT -5
There is no way you should need Loctite to hold a bushing in place. Or the retaining screw. The bushing should be a simple snug tap in fit and once you fire a few shots the carbon will lock it tightly I'm place. I find this kind of stuff troubling to me because it clearly tells me who ever made your breech plug didn't use the proper reamer for the bushing. The plugs I get from Jeff are a slight press fit and I recently debated even using a lock ring. I just hate to eject a $30 bushing downrange. Plugs that I have purchased in the past elsewhere did not have a press fit and required a lock ring. The bearing retainer compound was first used when bushings were cracking, thought being that it would add support to the bushing. Turns out the problem was a material one. Too Hard and brittle. Prior to that, only blue loctite was used. If a lock ring is installed without loctite, carbon penetrates the threads which makes it difficult to remove. The loctite/bearing retainer compound does act to fill voids that would be attractants to high pressure gas cutting. At any rate, the bearing retainer compound is very easily removed with a little heat to loosen it up. I realize that you don't shoot duplexes, therefore you would not have seen problems that we have with them. Use the lock ring.... I doubt the press fit will hold the bushing in place against the blast of the LRMP.... |
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Post by Deleted on Jan 17, 2017 20:14:23 GMT -5
Two things here can be the problem..... First the bushings are made from pure tungsten and if they are they will crack. It's only a matter of time. The second problem is the bushing pocket is oversize and allows room for the bushing to swell and that of coarse will cause it to crack. Elkman makes his breech plus one at a time paying close attention to detail and tolerances. This allow him to make a plug to properly fit the bushing. I make my breech plugs using CNC equipment and once I have it set up to bore the pocket I will run 100 or so plugs, therefore making them all the same. If you open up an existing plug with a boring bar or a reamer it is very hard to get it exactly to the size you need. Even a .250 reamer can bore oversize if your tail stock is off center of your head stock. With a single point boring bar if you are off .0005 that will make your hole .001 large and that is enough to let your bushing crack. The plug in the picture above with the missing piece of thread,,,, needs to be thrown in the trash. This is only going to keep causing troubles. And that little 2 thread set screw ain't worth much in my book.. The set screw should (in my opinion) be made from a 5/16-24 X 1/4" set screw, not a 5/16-18 set screw ground down to 1/8 inch. Coarse threads were made for farm machinery, not gun manufacturing.... My bushings are made from a proprietary blend of Tungsten, Carbide and ?. I have yet to see one split. I have seen one chip off at the end but none have split down the middle like a pure tungsten bushing will do. My problems with bushings splitting was isolated to pure tungsten versions. I put a pure carbide in my BP and shot 95gr of I3031 plus several loads of 7/62 red dot/I4198 and it asked for more with no sign of wear. However when I went to clean it up and tried getting the retainer out it stripped the insides and wouldn't come out. So for now it's stuck like that. Moral of story: it's a carbide/tungsten blend for my bushings going forward and singles for now. Even if it's not necessary putting a coating of 609 ain't gonna hurt a thing on the bushing. If one gets messed up now and again I guess that the cost to play. |
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Post by schunter on Jan 18, 2017 8:22:34 GMT -5
Inspected my breech plugs earlier this week and found this. .030 tungsten carbide bushing maybe 25 shots with a load of 35 grs. of N110 and a 200ftx sabotless  |
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Post by elkman1310 on Jan 18, 2017 8:37:42 GMT -5
Hank is right that I make my breech plugs one at of a time from 17-4 S/S I have had no problems using the standard 5/6x18 black locking screw I don't use S/S for that application. And I don't use the pure tungsten bushings I never had any crack but the t/c ones hold up real well with straight loads I buy those from Luke I priced out having a bunch made and for the amount I use its more cost effective to simply buy from him. I also like the .250x.375 .030 bushing. Some I have gotten where actually .028 but they worked equally well.
Chucking reamers are good at reaming the correct hole size but you can get a over sized hole pretty quickly. I run into that problem sometimes when I do the primer pockets on my breech plugs I use a two step setup up and then polish the pocket you need to be careful with run out because it will make the pocket oversize and if that happens that breech plug goes in the scrap pile.
Making breech plugs for high pressure loads is not something a novice should tackle. If you have a decent lathe and a milling machine and have machining experience then knock yourself out and see how long it would take you to make a S/S shoulder breech plug with a 3/8 socket head using a bushing and lock screw
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?-----------------This never happens!............But, I had left the gun dirty from a week before and thought that might be what was causing the problem so I applied a little heat and it came out. I did notice the bottom of the screw was a little rough but thought nothing of it. So today, when I got home from the range I wanted to immediately take out the plug and remove the set screw; it came out but almost NOT? I again wire brushed it and ran a file over the bottom and could see a couple of shallow groves crosswise on the bottom. So, I put it in the lathe and made a facing cut to smooth it out and have it back in place for next week.
But you can see from the number of shots I have on my plug that I don't really have a problem. This has been a NO issue for me?
