Chamber Revisited

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RBinAR

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We had a discussion not long ago suggesting a smokeless muzzle loader with a powder chamber. I was foremost in denying the need for such a thing. As fate would have within a month of the debate I?m now in the process of designing and building a smokeless rifle with a chamber.

I have something like the following image in mind.
CHAMBER.GIF


I figured I?d have to face the question: what made you change your mind? Well I didn?t change my mind but as it is I don?t get to decide all these issues. It seems a customer (and good friend ) has decided he wants to stretch the limits of the smokeless muzzle loader and I?ll be compelled to try and make a 38 caliber rifle shooting a 35 caliber bullet work with smokeless.

When figuring what type of load to shoot in this rifle it occurred to me that the primary bullets to be shoot would be either the 200 or 225 grain in weight. Those are rather heavy compared to what been shot before if you take into the account the caliber and sectional density of a normal muzzle loader. In order for the speed to be achieved that is desired the rifle will have to either shoot enough powder or higher pressure. I?m not prepared to raise pressure greatly so that only leaves the possibility of shooting enough powder for the task at a moderate pressure.

When you decide you have to shoot more powder than from a case (but not a lot more) then you have to answer the question: where do you put it? I don?t think it?s in the best technical interest to plan for a powder column to be longer than 3 inches so I?m stuck with having to make it wider. Exactly how wide and long I haven?t decided yet but it seems certain to me the chamber should hold about 45 to 50 grains of most powders. The reason I choose that amount is because I can be sure the chamber will always be full. No one in his right mind would shoot less than 45 grains of power in this caliber rifle.

Still if you look at CHM in the image you will see that there still has to be room for a positive stop at the barrel, breech plug junction. So the chamber can?t be too wide. For this reason I?m leaning toward 7/16" as the best place. That about 43 caliber if you switch it to gun dimensions and the breech plug will be the same as I use for the 40 and 45 caliber rifles.

I didn?t (and still don?t) think this is the best method for a rifle caliber that accommodates a straight case sized bore. However I will have to divert from normal because this is an unusually different rifle.
 
It's funny Rick, I was just about to send you a question on an idea I'm working on, when I read what your up late working on...
Kinda scary really... :D
The chamber situation you illustrate is basically what I believe will happen if I were to install a BP into a 45-70 chamber. The only other way around the issue in my thinking would be to go with a BP similar to the Swinglock design, but making the BP length equal to the 45-70 case and adding a bushing to the flame hole.
SwinglockBreechPlug.jpg

Feasible?[/img]
 
I wish you the best of luck. I tried it 15 years ago, on a Mini-Mk X action, with switch barrels, both in in .45 cal. The major difference between our design and your's, is that I placed the chamber in the breech plug, where as yours looks to be part of the barrel. In our test over several hundred rounds out of each design, there was very little or no difference in performance (FPS), accuracy, or ignition reliability.

As you stated the actual chamber cannot be but so wide or so deep, or the projectile will seat into the chamber, and that will not be good. Our chamber was relatively small, as the powders we were shooting back then were very fast and charges were light, compared to the powders available today. Back then with the powders we were shooting, the charges were in the 30-40 grain range, of Win. 571, 2400, Herco, IMR 4756, and Blue Dot. The charge column was approximately 1"-1.75" long. As such we had to settle on getting the majority of the charge into the chamber, and ensure that even with a minimal charge there was still some of the charge in the barrel, so that when the projectile was seated it was still fully in the barrel.

15 years ago, I concluded that there was really no need for a "chamber" and have not change my mind since. However I haven't totally closed my mind to the idea either.
 
I find this Smokeless Alternative Muzzleloading site quite interesting and informative. Many of us are glad it is available.
 
1SHOT1KILL said:
I wish you the best of luck. I tried it 15 years ago, on a Mini-Mk X action, with switch barrels, both in in .45 cal. The major difference between our design and your's, is that I placed the chamber in the breech plug, where as yours looks to be part of the barrel. In our test over several hundred rounds out of each design, there was very little or no difference in performance (FPS), accuracy, or ignition reliability.

As you stated the actual chamber cannot be but so wide or so deep, or the projectile will seat into the chamber, and that will not be good. Our chamber was relatively small, as the powders we were shooting back then were very fast and charges were light, compared to the powders available today. Back then with the powders we were shooting, the charges were in the 30-40 grain range, of Win. 571, 2400, Herco, IMR 4756, and Blue Dot. The charge column was approximately 1"-1.75" long. As such we had to settle on getting the majority of the charge into the chamber, and ensure that even with a minimal charge there was still some of the charge in the barrel, so that when the projectile was seated it was still fully in the barrel.

15 years ago, I concluded that there was really no need for a "chamber" and have not change my mind since. However I haven't totally closed my mind to the idea either.

WOW there's nothing like getting the insight of a true veteran of the art. Thanks for your comments Bill.

I have built rifles to 40 caliber and found that a chamber is a waste of time as well. I don't really have any idea what might happen with this new rifle.

Truthfully I wouldn't have considered a 375 caliber muzzle loader at all. The laws in my state require at least 40 caliber or above and in many states the bullet requirement prohibits the use of this caliber. Today there seems to be so many different barrels available one can almost choose a bullet and find a barrel maker who has a land diameter to match the bullet.

I've also had inquires about what sabot this rifle will shoot and I've had to explain shooting without a sabot. That is something I'd like all to know was probably another of Bill Ball's inventions. All of the sub-45 caliber rifles I've built rely on sabot-less loading. No matter how many times I explain it I have so many who doubt it will shoot. But the two targets below are fairly typical of the 100 yard accuracy you can expect.

less-copy.jpg


This rifle is for a customer who has the nature to take a few risks. I don't mean that as a safety item I wouldn't build any rifle I couldn't make safe. However it will have a special caliber barrel for shooting the .358 bullets sabot-less and there is no way to predict if the project will work as planned (accuracy wise) until it's on the shooting bench.
 
RB,

When it comes to sabot-less muzzleloading, it is sometimes hard for people to grasp the concept of "sabot-less". I've had to explain it many a time myslef, so I feel your pain.

I have gone as small as .358 caliber. As you already barrel tolernaces are critical in sabotless rifles. I finally got tired of shipping barrels back and forth, and made bullet expander jigs and bullet swagers. In .458 cal. sabotless, I expand .452 and .4515 bulets out .454, so that they get a grip on the rifling during seating. In the .358 cal., I had to swage .358 cal bullets down to .354. Upon firing the obturation(?) of the bullet will take care of the rest. Accuray wise I got better consistent accuracy out of the .45 cal sabotless, than the .358 cal. I conlcuded that, it was possible that the swaging process, distorted the bullet to much ofr consistent accuracy.

With sabotless, the tighter the bullet fit the better. This means that it is going to hard to ram the bullet home. But it is a must for reliable ignition.
 
Any new activity on the .38 caliber/chamber project ?
 

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