Educational Side of SML

As a continuation with interpreting PT’S I have an earlier and popular duplex PT where a recommended powder was used to ignite a slower burning powder. Here you can examine the Rise Time and Area.
Even though this actual duplex wasn’t tested till 2013 it has been used for a while. The gain in velocity over a recommended load here is 300fps with peak pressure still well under 40K psi. The one thing I can’t verify off hand is whether the old or new 4759 was used.

Attachment 28599


Now on another thread I see a scare tactic of trying to use something mentioned that was intended for CF cartridge reloading and tossing it into the muzzle loading category.
Here I’m going to simply state and ask if you have any doubts about duplex loads of smokeless powder in a muzzle loader then do not venture there. I for one have no doubts and with my equipment can monitor what is happening in the bore. With a proper approach loads can be tailored to accommodate different bullet weights and additional velocity if desired instead of being limited without exceeding a safe margin for peak pressure. When I find some good safe combinations I will share them. Also I’ll break down why they appeal to me and any benefits I feel they will provide.

Ed

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Now on another thread I see a scare tactic of trying to use something mentioned that was intended for CF cartridge reloading and tossing it into the muzzle loading category.

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The subject was/is "duplex loads using smokeless powder " which is used in muzzle loaders also .

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Originally Posted by jaycee

The subject was/is "duplex loads using smokeless powder " which is used in muzzle loaders also .

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Jaycee

Boy you are just looking for an argument even if you have to cross-over to another thread.

You take an article out of a reloading manual dealing with CF principles of operation and simply think you can apply them to muzzle loading to prove a point when in fact the conditions for ignition and acceleration of a powder burn are not exactly the same in both. If you understood the difference then you would know why such faster burning powders and quantities are used in smokeless muzzle loading. I suggest you do some homework before twisting statements to suit your purpose.


Ed

The 10ML-II ignition system incorporating a breech plug is an interesting design with multiple functions. Most shooters don’t give it a second thought other than it is an integral working component. Now if you take a closer look at what transpires in the BP you get a different perspective on its operation.

For the moment I need to reference what happens in CF cartridge. Here the powder basically sits on top of the primer and when the primer ignites all of its thermal energy is expelled into the powder.
With the 10-ML when a primer ignites the thermal energy is dumped into what is referred to as a flame channel and then bled off in a regulated fashion through an orifice into the powder charge. When the powder in the bore ignites pressure is built up and now the orifice regulates the returning pressure into the flame channel which now becomes a reservoir to limit the amount of pressure buildup. This is also why there are no locking lugs on the bolt because it isn’t exposed to full bore pressure.

Note: The thermal energy intensity released in a CF cartridge will never reach the powder in a 10ML-II using a breech plug.

You might ask what good is there to knowing any of this?
If you are seeking accuracy repetitive levels of ignition can play a role here. For example: when the flame channel carbons up the volumetric size is altered. By producing more pressure of thermal energy in this smaller chamber the output energy passed through the orifice is increased.
For my personal routine of BP maintenance I clean my BP after 25 fired primers and below you can see why.

Attachment 28642


To remove this carbon buildup I just use a #21 drill bit. I also address the carbon buildup on the shelf below the primer with a larger drill bit or you can use whatever tool that works for you. If you allow this carbon buildup to continue you might eventually find primers difficult to seat.

Ed

Just wanted to step back to the ignition system of the 10ML-II again as this was part of my learning curve on how it can be altered to help the burn with a slower or harder to ignite powder in colder temperatures.
Now this process does involve altering the original design of the breech plug so I’m not going recommend that anyone should just jump into this. But I do have to mention that any test results I share will be using a modified breech plug/s that I have been using now for 5-years. There will be a slight difference in the test results compared to using a standard BP. My peak pressure will be slightly higher and a small gain of velocity will be seen.

Two major considerations before even considering any modification or moving outside the manufacturer’s recommendation is as follows.
What are the risks involved?
What beneficial gain can I expect?
The biggest obstacle some people have knowing what RECOMMENDATION represents that does not mean SET IN STONE or is an ABSOLUTE.
But to move safely out side of recommendations you also have to have some reasonable amount of understanding of operational principles you are now altering.

Okay now back to the BP mod and why some chose this route. The idea here was how to increase the thermal energy delivered to the powder.
By recessing the vent liner in the BP the flame channel (volumetric spacing) is reduced creating a higher pressure and amount of thermal energy delivered to the powder. This also created less exposure to heat loss from the now smaller area of the walls in the flame channel.
What the recess also provided was a smaller chamber area to start the ignition of the powder charge.

Now let’s look at the risks.
We now have a wall reduction of the BP that is going to be exposed to full bore pressure.
The recess now passes the boundary behind the sealing point of the bore. Normally the recess remains above the outside threads of the BP.
There will be higher return pressure now found in the flame channel.

When you first read the possible risk factors you become very apprehensive of this working at all. Your gut should tell you to avoid going this route.
So what changed my mind about trying this also?

Not to be accused of pushing something unsafe I’m going to stop here for the moment and allow the focus on the risk factors to settle in before proceeding with this mod that I now employ.



Ed

The origin of recessing a BP did not originate from me but by a machinist and here was his initial approach. He went with a 3/8” dia. recess ¾” deep. A few others followed his lead and were happy with the results. With the recess mod being employed for about a year with no detrimental effect from it I decided to look a little deeper into this mod.
The first thing I measured was the remaining wall thickness on the BP when 3/8” dia. recess was employed. .115” doesn’t seem like a lot of metal to support such pressures we use without being expanded. But no diameter expansion was reported. Also keep in mind there is an outer wall of metal nearby that would limit any real expansion of the BP to a point for possible tearing.

For my own piece of mind I opted to use a 5/16" diameter recess that now left a wall of about .145” for additional strength. This now included reducing the dia. of the vent liner head to fit into the recess.
As for the original ¾” recess depth that seemed a little too deep for my comfort even though no primer bulging or excessive blow-back was reported. After doing some tests at different level of recess depths using 1/8” increments I found a ½” was a good depth. The reason I chose ½” because I saw no gain at 5/8” where I’m now at.


Again no blow-back or primer-bulging but an increase of 2,500PSI in a known load signifying an increase of the ignition property.

Had I just taken the stance that this was a dangerous mod from my first impression and closed my mind to this option I would have lost out on a beneficial mod IMO.

Again I can’t recommend this mod because it is altering the original design. I can give/share dimensional parameters and observed results. Also to let you know why my test results may differ slightly from yours with a given load. To make this mod is a personal choice as it was presented to me. The decision is now yours to make concerning recessing a BP.

Before considering this mod you may want to try a Magnum 209 primer to see what results it produces and if you are satisfied with the results. Some shooters have reported better ignition results over the standard 209 primers in an unaltered BP.


Ed

I have a question for you Ed....way back when, PR bullets developed a solution to the 209 primer for the SML. It's a hardware swap out that modifies the ignition system a Large Rifle primer.

https://www.prbullet.com/s-kit.htm

Is there a fault with that concept, have you ever had a chance to see how it affects the pressure curves ?

I bought their Vari Flame kit a long time back (before they were making ML specific 209 primers) and found it made a world of difference to my grouping and had a far cleaner gun with no blow backs. The concept was brilliant.

https://www.prbullet.com/vf.htm

Would it not make sense to move away from a shotgun primer to a rifle primer if your using smokeless and looking for better ignition ?

The problem with the 209 primers is that they are dirty. I just picked up the s-kit and I am just about to go down to the cave to tinker! I will post some pics of everything. I just hand lapped my barrel and I'm going to get everything reassembled. I plan on using magnum lr primers.

Mike Pal

No I have not used PR’s LRVF system nor have I considered it in SML application. I can say some members on another SML board where not happy when they tried it with their 10ML-II. Currently most SML shooters on another board have opted to remain with the 209 primer even in other calibers now appearing.
I have no knowledge how it would work with black powder application.

First off I have no current sticky 209 primer issue to begin with. When my 10ML-II was new at first I had a few that would stick and require a second strike from the firing pin to loosen them. It wasn’t long before any sticking just stopped.
I agree most of the carbon issue in the BP of the 10ML-II originates from the 209 primer and cleaning this is no issue for me after a range session firing 20-25 shots in 4-5hrs with the aid of a cooling rod.
With PR’s system using rifle primers in modules I would have to constantly de-prime and prime the modules instead of simply sliding a 209 primer onto the bolt head.
With the above mention I don’t want to drop $130 plus to possibly find out I may not like their system either. If anyone wants to go this route to try then be my guest.

Another debate ongoing is which primer produces the highest thermal energy release for powder ignition? Where this would make a difference IMO will be in freezing temperatures. What I convey has proven itself and works for me. There may be other options I’m not familiar with that may work well also but for now I will leave that to others to try and hopefully they share their results.

Ed

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Originally Posted by rippin_355

about to go down to the cave to tinker! I will post some pics of everything.

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Thanks I'd like to get some first hand feedback.....seems the whole 209 primer is an issue with the SML and would like to hear how guys have found PR's solution.

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Originally Posted by ET1

No I have not used PR’s LRVF system nor have I considered it in SML application.

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I'm a little surprised Ed, with all the efforts your going thru to maximize the performance of the powder your gun it's something I would have thought you would have jumped on to explore. Especially, since you have access to the tools to witness the pressure peaks and bell curve offsets that can be manipulated by the primer itself.

Those VF adapters aren't a big issue, takes just a moment to prep for a shoot, really not an issue....takes less time than it does to clean up after those dirty shotgun primers :)