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Post by linebaugh on Mar 12, 2016 9:58:39 GMT -5
I am currently (slowly) working on a new muzzy build and I have some thoughts on plug design I would like to hear the boards thoughts on.
My plug will have an internal volume of about 30-35gr of powder which in this case would be about 1/4 of the entire charge volume. The plug mouth is tapered and the length of my internal plug cavity is .835 which starts at .370dia and ends at .400 diameter.
In the above scenario I am contemplating this idea and would welcome thoughts. My thoughts are that the "pre-chamber" built into the plug will act as a duplex charge with straight loads. My thoughts on this are obviousy derived from the fact that my plug bore diameter will be about 25% less than my bore diameter on average. Slow powder in smaller bores makes the slow powder act as a much faster powder. I am hoping to see this scenario in real life as it will immediately add a primary pressure burst to help ignite the large (120-140) gr loads of slow powder I plan to use.
This is not a 209 system so no worries there. That said what do you guys think of my thinking? Does it make sense? Do you think it's a reasonable scenario to expect?
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Post by Deleted on Mar 12, 2016 17:21:30 GMT -5
I have thought the same thing for awhile now and have coined a name for what you are doing..I call it reverse chambering...In theory it should have a duplexing effect while using a single powder....Very interested in how it works out for you.....
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Post by Kyle on Mar 12, 2016 19:49:13 GMT -5
Would allowing that much powder in the plug possibly lead to a plug rupture or swell? 25% of the charge in the plug is a considerable amount. Never know till you try though I guess. Interesting.
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Post by typical171 on Mar 12, 2016 20:36:02 GMT -5
I like the idea, I think it has a honest chance of working. Keep us posted.
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Post by Deleted on Mar 12, 2016 21:53:34 GMT -5
Would allowing that much powder in the plug possibly lead to a plug rupture or swell? 25% of the charge in the plug is a considerable amount. Never know till you try though I guess. Interesting. I agree Kyle. For what my opinion is worth...here goes... Make sure the walls of your powder chamber (in the plug) are of sufficient thickness to withstand the pressure as I recently cracked the nose of a Savage plug that had a 1/4" bushing installed. The wall thickness was .120". The gun was very cold and the charge was 78gr of imr4198 and a 275 Accumax. That was a factory hardened Savage plug. If the plug is too soft it will swell, which I have seen happen too. IMO, a rear sealing plug with an 11/16-16 thread and a minor thread diameter of .616" would be needed. With a 1/4" bushing hole/powder chamber, there would be .183" thick walls. I would consider that the minimum wall thickness as it isn't quite 3/16" .
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Post by Richard on Mar 12, 2016 22:43:24 GMT -5
Are we forgetting that the walls of the plug will be supported in the barrel? The plug thread into the barrel.........if the fit of the threads is pretty tight, I doubt there would be much swelling of the plug? or am I missing something? Much the same as a CF cartridge having its sides supported by the chamber?
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Post by Deleted on Mar 13, 2016 2:35:14 GMT -5
Are we forgetting that the walls of the plug will be supported in the barrel? The plug thread into the barrel.........if the fit of the threads is pretty tight, I doubt there would be much swelling of the plug? or am I missing something? Much the same as a CF cartridge having its sides supported by the chamber? I was taught that threads must have clearance to function. Granted, it has been 31 years since then. For example, how could some people use teflon tape on their breech plug if there was zero clearance. If the plug were left soft and allowed to swell, it likely would gall upon removal...if it could be removed at all. As far as cracking is concerned, if the walls are too thin and the plug is hardened to that of a Savage plug, it would likely crack. Think of all of the supported bushings that have cracked as of late. Rifle brass is only ~.017" thick which allows it to be manipulated such as on ejection much easier than something made of steel that is 10 times as thick and threaded.
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Post by linebaugh on Mar 13, 2016 7:44:50 GMT -5
I can somewhat attest to the fact that a tapered plug does not swell or crack. I am presently running a stock savage plug with about .100 wall thickness at the mouth. My present plug holds about 20gr of 4198.
To date I have about 300 rounds on this plug with no issues whatsoever. Most of these loads have admittently been in the 40,000 psi range but some of them have been substantial.
Somebody mentioned rear sealing plugs. By design if you believe in this concept your plug area sees full pressure on the barrel shank every time the trigger is pulled. I realize some of the rear seal plugs are .5625 diameter (over this actually to keep thread clearance. Now depending on threaded shank size you have many guns with very minor barrel diameters. Keep in mind if you believe in the rear seal design there is no advantage to running a long plug out into the 1.200 of the barrel which is the concept behind some plugs being safe.
Like the comments, lets keep talking through it. I am mostly concerned with what the powder does when the hammer falls.
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Post by Deleted on Mar 13, 2016 9:30:46 GMT -5
What about leaving the cup straight walled at .380 all the way out...? You can taper it later and see if the theory is working... What powder are you wanting to shoot with this plug...? Could you press a sleeve in the barrel in front of the plug to act as the chamber...It would be fully supported and different volume sleeves could be evaluated for performance....
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Post by linebaugh on Mar 13, 2016 9:53:08 GMT -5
Sml,
Good idea on both counts. THANKS for the input, brilliant!! I am not going to add a sleeve personally BUT that would work very well with 209 systems provided it was a reasonable solution to a problem. I may be making a problem that does not even exist as this is all theoretical.
I wanted as much volume in the plug as I could BUT I actually really like your idea of leaving it straight walled after reaming. I will just brake the edge on one and leave it at .370 all the way to the bushing. As you said I can taper it later BUT more importantly I can build a couple different versions and actually compare notes. The second plug I will taper out as I already have. I would think that if the booster effect works I should see a rise in velocity due to better burn.
Right now I am looking at H4350 or RL17 as starters for powder. 29 or 30 inch barrel, perhaps 29.5"
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Post by Deleted on Mar 13, 2016 9:53:35 GMT -5
Powder wise...Imo h4198 is a good candidate as it in a .40cal is like 4759 in a .45....Maybe since you are at .370 it might be too hot....Glad you are exploring this idea.....
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Post by 150class on Mar 13, 2016 15:53:53 GMT -5
The comments about taper frighten me a bit due to the extra surface area facing the high pressure, unless the taper mentioned is somewhere different from what I am picturing.
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Post by elkman1310 on Mar 13, 2016 18:18:31 GMT -5
For what I am reading you what to make a breech plug with a powder chamber! Unless your planning on going to a smaller caliber than a 45Cal stay with the proven designs and you will be very happy.
I strictly use a Shoulder plug for my M/L's you get a great seal and no worries about flame cutting on the front sealing ring like on a Savage breech plug.
If this is your personal gun you can take the chance and experiment. But for a customer there is no way I would stray from the proven breech plugs'
I had a pretty serious talk with Bobby Hart last month about muzzleloaders. I told him he was behind the times because he wasn't building a 45 Cal muzzleloader. He said that he will never build a 45 Cal M/L because they all blow up. He tried to convince me that the sabot was going to protect the shooter I told him he should think that over. Also any muzzleloader they sell comes with a Liability contract that the customer must sign off on or they don't sell that person a M/L.
The guns I build go to people in my local area. (1) They must have good reloading experience and equipment and (2) They must have a lot of regular muzzleloader experience. (3) I do not take any down payment when I build a gun when the gun is finished I go shoot it. Then I take the time to mount their rings and scope and then we go over sizing bullets and weighing out powder charges. Then we go to the rifle range. If that customer can't show me he can load and handle the rifle the scope comes off and he doesn't get the gun period I don't need any headaches. This maybe a tough approach but it gives me a little piece of mind.
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Post by Deleted on Mar 13, 2016 18:58:13 GMT -5
Linebaugh, what ever you do be safe.
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Post by jims on Mar 13, 2016 19:15:22 GMT -5
linebaugh: Keep us posted on the results. Elkman: A good approach on the sale of an ML, I often wonder what happens when the original buyer sells to another and is not so careful. Does he go back against the seller or the original builder or both? Always a concern of mine, maybe over thinking it.
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Post by linebaugh on Mar 14, 2016 9:16:15 GMT -5
Thanks for the input guys. To answer a couple questions.
I don't build guns for profit and don't build guns for anyone other than family and close friends. I have built one .40 cal muzzy for my father but that is it on the muzzys for others. This is my third muzzy project and likely my last so no worries about the general public.
No idea who Bobby is but I bet you I can blow a gun up using a sabot just as quickly as I can without a sabot. I don't personally believe in the safety valve theory. In addition I don't know of any gun specifically that has blown with a single charge.... I think they have all been double loads. Could be wrong here. As far as liability goes I am no lawyer but I can venture a guess that in todays environment if you build and sell a "smokeless muzzy" to anyone and it blows up you can damn sure bet on being liable if it goes to court. There is no leg to stand on there as I see it. Just my opinion and each is welcome to his own.
As far as proven designs on breech plugs I'm not even sure what that means. Lots of different designs of plugs out there, we all focus on a couple designs here. Does that mean only the three basic designs we see here are "proven"? One of the most dangerous plugs I have been whitness to (from what I think is bad) came from precision rifle and used cut down .308 brass. I assume because that design was on the market you could call it proven but I would suggest to you it was the most unsafe I have seen.
I should point out that the above is in no way an attack on Elkman. I have much respect from what I see of his (your) work as well as you design and problem solving (thinking outside the box). In a word... skills
As far as powder choice and caliber. I am not building a .45 caliber gun or a sub caliber. I am going to be going in the opposite direction and building a .510 caliber gun. Because of the caliber and heavier projectiles I plan to shoot I am modeling my design more towards the .510 wells and 50 A-square. With this model in mind I will be running a bunch of slower burning powder and want tomake sure my ignition is all it can be. This is why I am thinking a pre-chamber of smaller diameter in the plug may be advantageous... mostly my point in this discussion. I will probably end up buying a copy of quickloads when this project is complete as a tool to help with my powder and projectile choices. As for now I am using the information available for the .510 wells and 50 A-square as a starting point and it looks like 4350 is one of the main choices in the above calibers.
Someone mentioned bolt thrust with the tapered plug. I have no way of proving or disproving what effect this has on bolt thrust. Pressure is not directional so my conclusion would be simply to rate the bolt thrust on the major diameter of the threads. From a pure pressure standpoint if you believe in the rear seal plug design then pressure should be equal on the inside of the plug and the outside on the threads. I believe this to be true to a point but my personal belief is the threads do seal far prior to the rear sealing ring.
As far as the tapered plug goes. That idea may be scrapped. I originally wanted to kill 2 birds with one stone by adding powder volume and a pre-chamber. I am now certain, in my mind anyway, that SML has the better idea and I intend to run a straight .370 reamed hole right down to my bushing.
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Post by linebaugh on Mar 14, 2016 9:37:20 GMT -5
I want to get back on topic and finish my thoughts on the last cpl sentences of my last post.
Considering I run a .370 diameter pre-chamber in my plug at .865 deep (can't remember off top of head if depth is correct but it's close) what are your thoughts on the following:
I feel like this idea will cause the powder in the pre-chamber to initially act as a booster by confining the powder in a smaller space. In addition I think it should also make ignition better. By confining the powder and additionally giving the primer a smaller space to act upon and for primer pressure and heat to dissapate into would it not also make ignition much better?
Thoughts?
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Post by elkman1310 on Mar 14, 2016 10:08:46 GMT -5
Linebaugh since your working with a 50Cal or .510 bore I really don't see the need to make a elaborate plug. Your bore diameter puts you in a 300 Ultra mag case diameter already. Your breech plug design what ever you use needs to be removable so that means it will be .695 or less or it won't come out of the action. I know your trying to ignite a large amount of H4350 you could recess your plug so that it holds several grains of powder and go with a .040 bushing. This might be a simpler and safer approach. I believe Bad Bull M/L ignites 140gr of H4350 with a LRMP in a 45 Cal M/L with no powder chamber. So just be careful!
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Post by Deleted on Mar 14, 2016 10:12:27 GMT -5
Caliber manipulation better describes whats going on here imo...The heavier class weight bullets are going to help pressure wise on the total burn and by igniting in the smaller chamber the burn rate should speed up from the increased pressure which should migrate into the main charge....The theory makes sense,the right powder candidate is the big question.
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Post by Deleted on Mar 14, 2016 10:19:30 GMT -5
But doesn't 4350 burn faster/more pressure in a .45 than it would in a .510....? He would have a shorter powder column but the charge would have to produce more pressure since it would be in a larger bore.....
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