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Post by linebaugh on Jan 9, 2016 17:03:34 GMT -5
If we minimize the flame path to reduce backflow would that not mitigate the need for bushings and vent liners?
I am working on a new build and plan to forgo the traditional vent liner or tungsten bushing in favor of 15-5 stailess with a .035 EDM hole popped through. My plug will be more a kin to the Remmy ultimate muzzy plug and use cut down casings fully supported.
To my way of thinking if I reduce the flame path and the flame path size there should be hardly any back flow to cause deterioration.
On a very similar note. Why do we see flame cutting on the plug face, vent liners and such but not see it in the bore when you are shooting smooth formed. It seems to me there should be far more flame cutting in the barrel from bumping up the bullet as the pressure escapes around the bullet through the groves.
Deep thoughts from the deer blind. Anybody have any thoughts on this?
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Post by elkman1310 on Jan 10, 2016 18:21:04 GMT -5
Linebaugh Henry Ball was a pretty smart guy.He designed the Savage plug and replaceable vent screws. The 5/32 size flame channel and its length is the right diameter for the 209 Primer. The vent screws with a .030 orifice wear out pretty darn quick. That why the search for something better produces the tungsten bushing. 15-5 S/S will not last any longer than the grade #8 screws. I make my breech plugs out of 17-4 S/S but I still use the proven 5/32 flame channel with a tungsten bushing this system works flawlessly. Cartridge cases and LRMP are not the way to go. Stay with a 209 primer and you will be very happy.
Flame cutting will happen when you try to seal the front edge of the breech plug to the barrel. There is only a very thin contact area. No plug seals 100% so anywhere where the gas can exert force it will blow by that area. In the beginning it you won't see any cutting but over time it will flame cut. How fast it cuts is dependent on how well it seals. The best plug design is a shouldered style plug with this design you don't have to worry about sealing the front of the plug. Its also stronger.
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Post by eml9 on Jan 10, 2016 19:53:58 GMT -5
So pretty much with a Savage breech plug its not if gas cutting will occur it's when? Depending on how good a shoulder seal you have, every gun being different. I will definitely have a rear seal plug with my next build.
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Post by elkman1310 on Jan 10, 2016 20:07:56 GMT -5
When you use a Savage plug in a 45 caliber barrel you get a little more metal for the plug to seal up against. The plug is still the weakest link you get more barrel steel with the smaller the caliber barrel but the sealing area on the front of the Savage plug never changes. That said some Savage plugs have lasted a long time. Most people don't shot their M/L'S enough to really worry about flame cutting.
The shoulder style breech plug is the way to go on a custom build.
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Post by hillbill on Jan 10, 2016 20:08:45 GMT -5
Tungsten bushings came about when vent liners were burning out alarmingly fast, we were migrating toward shooting high pressure loads with full sized bullets and they would burn out in less than 20 shots. we are talking 209 primers here. the 209 primer needs a lengthened flame path to minimize pressure on the primer, the other purpose served is to keep powder from packing against the primer or rushing out of the plug when loading. the said flame path creates a pressure relief so to speak. as the powder burns and pressure goes up the gases rush toward the primer, this vent hole erodes from the flame/pressure combo. many different alloys were tried but with pretty much the same result.
I have to give credit where credit is due: Earnhardt on the other board started experimenting with tungsten and different hole sizes/ flame channels, 95% tungsten was originally used with good success and we were getting hundreds of shots instead of 20 with a vent liner. then the 99 % bushings were made and they pretty much last  ?, anyway I've never seen one burned out.
Now lets talk Jeffs HIS system;
since he uses a very short plug and a rifle primer, the powder is very close to the primer, the LMRP is designed for high pressure so over pressuring the primer is not the problem. he was using a fairly large flash hole opening so it did not erode much to speak of as the 209 style plug with the long flame path and the very small vent hole BUT I think Jeff also saw the benefit of the bushing in that the plug/ bushing will pretty much now last forever with no powder escaping through the vent hole when loading without a spent module in place. the tungsten bushing has benefited both camps.
Jeff might elaborate more but that is somewhat an overview of the whole tungsten bushing subject, I might need to be corrected to a degree but I think Im close.
Is there a down side to using tungsten bushings? I don't think so, either plug/any plug still needs routine maintenance from time to time but as far as the bushing goes, its here to stay...
as far as gas cutting goes; JUST SPEAKING FROM EXPERIENCE WITH THE SAVAGE PLUG
the Savage design will gas cut if shooting high pressure loads AND IF it does not seal well, two things accelerate the problem IMO, BUT most will never shoot enough or with hot enough loads to see gas cutting.
1. poor plug face seal; poor primer seal
2. substantial use of booster powders
the other designs will also cut if they don't seal completely.
I have never seen one of Jeff's plugs flame cut, why? 100% seal
in order for flame cutting to occur gas has to escape through a very narrow pathway..
again these things are just the way I see them, others might see things differently.
I WILL ADD; with the addition of tungsten bushings and rear seal plugs I think both designs are very good, it takes a little work to get proper headspace/ primer fit for the 209 system, Jeff's is plug and play. I USE BOTH AND ALWAYS WILL, ask me which is better ?? this is all you will get  
Bill |
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Post by linebaugh on Jan 10, 2016 20:26:32 GMT -5
Elkman,
A couple thoughts and please don't take them as against you. I do appreciate the response and hopefully we can both learn from each other.
I will not be going with 209, no way no how. I do think it is a fine system for most but there are just too many problems and weaknesses with a 209 system that I would rather not deal with. I don't want to clean carbon, don't wanna play with flame channel sizes, don't want to worry about sealing them or deal with the leakage between the inner and outer primer.
Enough on that, here is a thought on your 17-4 plug material. It just occured to me a few months back when I had a buddy show up with a new plug design. I believe airborne made them. At any rate it was stated that the plugs were not hardened and at first I kind of felt that was a bad idea. I had thought of going with 15-5 or 17-4 for the body of my plug but then it clicked that the threads in the barrel are still 416R so the weak link still exists with super stainless or not. The only way I see to increase the strength is to increase the thread count, thread length or thread class.
These are my thoughts and opinions, they may well be wrong to others and heck they may be wrong in real life.
Also why don't we see flame cutting in the bore when smooth forming. It seems to me that the flame cutting should be highest in the bore during obturation.
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Post by hillbill on Jan 10, 2016 20:35:21 GMT -5
no flame cutting in the bore because the bullet is in motion and pretty much completely sealed in milliseconds, the flame cutting occurs on a fixed object that has enough clearance for gas to escape around.
regardless of the plug design you use you Will need to clean carbon, its just part of the game.
hardened or not the plug has plenty of strength to hold the pressure, JMO
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Post by Hank on Jan 10, 2016 21:34:21 GMT -5
I make all my plugs from 416. No reason to use anything stronger., it just makes it harder to machine.. I went for years making my plugs without a bushing. I was able to shoot several hundred shots with these plugs without any noticeable vent hole wear. I started out with a .041. I think the vent didn't wear because I experienced no back flow from the powder gases. My primer is very close to the powder column with very little flame channel inbetween.
The only reason I started making my plugs available with bushings is because so many people wanted bushings... Now the breech plug went from costing $35.00 to costing $80.00.. The cost of the extra machine time and the added cost for the tungsten bushing drives up the cost of the plug.. But now you can rest assured that the plug will last practically a lifetime.
I don't want to get into a debate as to what primer is best.. It's all up to the individual to research the pros and cons of both and take the info they learn and make the best decision they can.. It also bepends on what action you start with.. If it's a ML action you don't have much choice but to go with a 209 if you're building off a center fire action the logical choice is a LRMP in some sort of priming module. The higher pressure guns will encounter less problems using a fully supported rifle primer that using an unsupported 209...
The tungsten bushings just add a since of security to the plug and gives the owner more confidence in their rig. All of my plugs now come standard with a bushing..
Adding thread count to a plug will not necessarily make it stronger.. 1 inch of threads will hold more pressure than the wall thickness of the barrel, so you could make the breech plug 3 inches long and you're not gaining any strength.. You're only using up valuable barrel length. When designing a plug use fine thread and no more than an inch is needed...
I hope this helps some. Tungsten bushings are your friends....
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Post by kbrezlin on Jan 11, 2016 4:29:10 GMT -5
7 shots through a vent liner with a 7/60 load of red dot/I4198 with 300 match hunters and it opened up from 0.030 to 0.050" all my plugs for sabot less have 0.040 tungsten bushing. I still shoot vents in a sabot gun using a recessed PA Pete savage plug.
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Post by GMB54-120 on Jan 11, 2016 11:19:38 GMT -5
You would not believe the number of shots that are through my NULA and the plug is still like new. No vent or bushing is in it. There are around 1000 shots through this plug. Granted its a 50cal and mostly N110 and SR4759. I know one of the few people with a NULA 45 and his shot count is even higher. He shoots mostly light loads of 4198 and sabots.   This style seals on the rim of the primer. When the action is close the gap in this photo is gone. The rim is tightly sandwiched between the bolt and plug. The result is virtually zero blowby and no primer bulging.  |
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Post by linebaugh on Jan 11, 2016 12:02:36 GMT -5
Thanks for the reply and pix GMB54.
I had never seen one of their plugs but that is how I planned to tackle the problem if I was going to use 209s. I wanted to seal on the rim and the sides of the 209 using a CF bolt to provide the crush fit. My only problems were if I used high pressure loads I would still get leakage around the inner primer and also probably primer sticking. To be honest I was thinking I could quell the inner primer leakage by camming the primer in with a tight slip fit on the primer shell.
Do you ever have hard extraction with that system?
Can I assume there is not a pre flame channel in that plug like there is in most 209 systems??? I would think this is why you see no wear on your plug.
That flame length looks great also, as in the flame path is short.
Thank you so much for posting that. I am going ahead with my plans as I have them in my head and that will be with no bushing. I plan to make a few plugs at the same time so even if I get some errosion at some point I will have replacements on hand.
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Post by Richard on Jan 11, 2016 12:24:22 GMT -5
Lots of good thought provoking stuff here! So far, for me, I have been using Luke's rear seal plug with a .028" bushing that is of the 99% pure tungsten variety? 1,050 shots so far in this rifle and the bushing had been in a regular Savage plug before for ? many shots. The closest gauge I have from .028 is .030 and it will not go in. I shoot duplex loads with fast boosters and mainly 250 to 300 gr. bullets. The plug has worked flawlessly with no perceivable leakage. Permatex anti sieze used exclusively on the threads. |
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Post by GMB54-120 on Jan 11, 2016 12:54:59 GMT -5
Thanks for the reply and pix GMB54. I had never seen one of their plugs but that is how I planned to tackle the problem if I was going to use 209s. I wanted to seal on the rim and the sides of the 209 using a CF bolt to provide the crush fit. My only problems were if I used high pressure loads I would still get leakage around the inner primer and also probably primer sticking. To be honest I was thinking I could quell the inner primer leakage by camming the primer in with a tight slip fit on the primer shell. Do you ever have hard extraction with that system? Can I assume there is not a pre flame channel in that plug like there is in most 209 systems??? I would think this is why you see no wear on your plug. That flame length looks great also, as in the flame path is short. Thank you so much for posting that. I am going ahead with my plans as I have them in my head and that will be with no bushing. I plan to make a few plugs at the same time so even if I get some errosion at some point I will have replacements on hand. The flame channel is 5/32 but short. I have never had any kind of hard primer extraction. The NULA action does cam forward. The lug is in the rear of the bolt and the bolt handle acts as an additional lug. This style has one drawback, its primer sensitive. Only CCIs fit in mine. The action wont close with other primers. The primer is totally supported including the rim. The bolt has a recess for the rim. There is no leaking between the anvil and primer cup.    Its my opinion that the relatively small flash channel volume and the near total seal of the primer GREATLY reduces flash hole erosion. The really odd part is i hardly get any carbon build up in the flash channel too. No where near the amount i get in a Savage plug. I don't think ive ever seen a 45cal shooting sabotless with this kind of plug so i have no idea if it would handle the higher pressures well. I imagine its possible to some extent. I chose the simple and well tested tungsten bushing plug for my MLII/Pacnor45. |
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Post by 12ptdroptine on Jan 11, 2016 15:27:37 GMT -5
Back to the original question " why do we need tungsten bushings'
It is simply a process of evoloution of the spml guns...as we achieve higher pressures to achieve higher velocities we have an erosion problem . The ventliners first help control the pressure going theough them to the flame channel. And at the pressures we were experiencing at that time they were sufficient. But as we progressed the erosion became more prominent. Causing an ill effect on the diameter of the orrifice of the ventliner. Ither materials were tried...but to no real acail. Then someone made a carbide bushing that.lasted dozens more shots....then a tungsten bushing. But the reason we need them is the fact that few of us have the skills or machinery to make a plug repeatedly to replace. But we can push a bushing out and replace them.....IF we ever need to. They help with one piece of the puzzle....and that.is.to maintain consistency....key player in the.game.of muzzeleloading
Drop
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Post by elkman1310 on Jan 11, 2016 17:39:00 GMT -5
As you can see the with the Nula design the 209 primer well supported. When you make a 209 plug the primer should be a nice press fit. The 209 is not perfectly round and that cause some problems also the lengths can vary a few thousands and that can cause some problems. The CCI Mag 209 primers usually measure .339 to 342 in size so I reamer the primer pocket in my breech plugs to .2405 and the polish the pocket. With my bolt nose and breech plug setup I get a great seal because I take the time to head space the primer to the bolt face and the breech plug. I use a .030 bushing and have shot 50 shots through the plug and get very little carbon build up. If you seal the primer tight enough you will get zero blow back and no primer bulge. If you don't setup it up properly you end up with bulges primers and blow bye. I will go with a 209 primer system every time.
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Post by linebaugh on Jan 11, 2016 17:58:07 GMT -5
Elkman & GMB45,
I like both the comments on lack of carbon. I have spoke with others and all seem to agree the carbon is wayyyyy lower when the systems are sealed tight.
My module plug had 120ish rounds through it without cleaning the first go round and there was basically no carbon. I cleaned the plug with a rag and aresol and put it back in the gun. I believe I am someplace close to 75 shots after that cleaning. I plan to do some more range work coming up directly and will pull my plug again after that for another look. That should put me in the 100-120 shots again.
Elkman,
I like the way you set your primer pocket up. Sounds like you are sealing on the nose in addition to some on the shoulder.
BTW, thanks to all for your responses!
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Post by hillbill on Jan 11, 2016 20:50:53 GMT -5
linebaugh,
keep in mind IF you plan to shoot full pressure loads you are dealing with a whole different animal, best of luck with the plug, let us all know how it works out..
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Post by GMB54-120 on Jan 12, 2016 11:27:55 GMT -5
That is my opinion based on my experience and a couple other NULA owners but the loads are a bit different than shooting higher end sabotless loads. Like anything else its a balancing act and not very forgiving under some conditions. Peak pressure is only part of the problem. Length/time of the pressure above "x" amount plays a role also. The slowest powder ive used in mine was 58gr N120 with a 275gr Parker BE in a sabot. It worked without any issues also. FPS was pretty impressive compared to my old Savage 50cal with the same load.
A friend has a LRMP module plug he uses in a smoker. Shooting really hot BH209 loads the LRMP module system had less problems and very soft carbon in the flash channel. His vents even wore much much slower.
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?, anyway I've never seen one burned out.
