Purpose of Duplex Powder Load

First off I’m not promoting for anyone to try or use a duplex powder load in a SML. As stated in another post I personally have been using a single powder load for my 10ML-II for years because it sufficiently provided what I needed for a given load. But now I find myself at a cross road where more than likely I will need to duplex for my new load parameters.

I imagine there are some that wonder what a duplex provides or does that is so beneficial. I will try not to be long winded but there is more that needs to be understood than just this short explanation. The simplest analogy is that the duplex when properly used provides the burn response you would get as in a CF where the bullet is engraved into the lands. When the bullet is engraving into the lands that delay of chamber expansion allows pressure to build that in turn accelerates the powder burn to a given jump point for continuation when the bullet begins progressing down the bore.

With SML’ing we don’t have that stage of bullet engraving for initial pressure build up for the burn. This in turn is IMO the reason for utilizing a faster single powder to develop a stable burn for required pressure to launch the bullet. Now if we try to use a powder with a slower burn rate we run into ignition problems and unreliable or erratic burn cycle. By adding a booster powder with a faster burn rate to the start of the burn this aids the burn start to accelerate to a jump point for more stable continuation burn of the slower powder. Where one has to be careful is the amount of booster being employed.
The gain of using a slower burn rate powder for the main powder charge is the extension of the burn that produces higher velocities. Also if properly employed the actual peak pressure developed can be lower than what a faster single powder produces.

This is the shortest possible explanation I can provide without going into long details. To anyone even giving a thought about experimenting with duplex powder loads I suggest doing some serious homework or you will get into trouble quickly. Because duplex has been mentioned this thread is intended only to describe what a duplex powder load does and why it may be used.


Ed

Good Job explaining - I understood it well.

MC

In other muzzle loaders, say a flintlock, duplexing allows the use of powders that would not normally be used due to their ignition properties.

i.e. 10 gr 2f Goex under T7 or another harder to light powder like BH209.

The GOEX is there to provide the positive ignition of the T7 or BH209 which otherwise might not ignite reliably in a flintlock.

I have done this with T7 but generally found it not worth my time as I saw no appreciable gains in accuracy.

Now the Savage is a totally different ball game.

HA

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Originally Posted by ET1

First off I’m not promoting for anyone to try or use a duplex powder load in a SML. As stated in another post I personally have been using a single powder load for my 10ML-II for years because it sufficiently provided what I needed for a given load. But now I find myself at a cross road where more than likely I will need to duplex for my new load parameters.

I imagine there are some that wonder what a duplex provides or does that is so beneficial. I will try not to be long winded but there is more that needs to be understood than just this short explanation. The simplest analogy is that the duplex when properly used provides the burn response you would get as in a CF where the bullet is engraved into the lands. When the bullet is engraving into the lands that delay of chamber expansion allows pressure to build that in turn accelerates the powder burn to a given jump point for continuation when the bullet begins progressing down the bore.

With SML’ing we don’t have that stage of bullet engraving for initial pressure build up for the burn. This in turn is IMO the reason for utilizing a faster single powder to develop a stable burn for required pressure to launch the bullet. Now if we try to use a powder with a slower burn rate we run into ignition problems and unreliable or erratic burn cycle. By adding a booster powder with a faster burn rate to the start of the burn this aids the burn start to accelerate to a jump point for more stable continuation burn of the slower powder. Where one has to be careful is the amount of booster being employed.
The gain of using a slower burn rate powder for the main powder charge is the extension of the burn that produces higher velocities. Also if properly employed the actual peak pressure developed can be lower than what a faster single powder produces.

This is the shortest possible explanation I can provide without going into long details. To anyone even giving a thought about experimenting with duplex powder loads I suggest doing some serious homework or you will get into trouble quickly. Because duplex has been mentioned this thread is intended only to describe what a duplex powder load does and why it may be used.


Ed

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Where one has to be careful is the amount of booster being employed.
[and this is where problems develop in most cases of guns blowing up]

Also if properly employed the actual peak pressure developed can be lower than what a faster single powder produces.
[ can lower pressures but not necessarily , depending on what combinations of powder are used ]


There are many posts on smokeless ML sites and others where guns were damaged by fellows that as they said " I just deviated a little from the norm and damaged my rifle , had to install a new barrel" , they were lucky that that is all that happened.

Unless you are very experienced and familiar with what you are doing , it is best to stay with standard published loads that are known to be safe and produce constant results .
Why experiment to try and get that extra 100 to 200 fps and possibly at the least , only damage you firearm or seriously injure yourself or an innocent bystander. It's Not Worth It .

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Originally Posted by huntaway

In other muzzle loaders, say a flintlock, duplexing allows the use of powders that would not normally be used due to their ignition properties.

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Flinters have been doing duplex loads for years...FFF on the pan and FF in the bore.. :)

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Originally Posted by jaycee

Why experiment to try and get that extra 100 to 200 fps and possibly at the least , only damage you firearm or seriously injure yourself or an innocent bystander. It's Not Worth It .

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Especially, since the accuracy can be compensated for by altering the reticle in the scope to achieve the trajectory required.

I have to say, this duplex load idea is not new and has been tested and re tested by brave souls since the ML10 rolled off the assy line. There are numerous sites that have pre-tested loads combinations with of a variety of powders etc that can be used safely now. A tweak here and there for your acceptable 'ouch factor' and your good to go. There really isn't much uncharted territory left anymore.

Jaycee

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Where one has to be careful is the amount of booster being employed.
[and this is where problems develop in most cases of guns blowing up]

That is a misleading statement and no proof can be provided. In most cases the reference of a double load is considered the cause of rupturing barrels. Even that is questionable especially when the President of Savage has purposely fired a double load in front of witnesses to demonstrate the strength of the 10ML-II.

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"I just deviated a little from the norm and damaged my rifle, had to install a new barrel", they were lucky that that is all that happened.

Another misleading statement by OTHERS because even with a 10% increase in recommended loads you can’t come close to the yield strength of the barrel. That I do know and have shot such a load with 4759. In order to damage a 10ML-II it has to be a major deviation from a recommended load.

Ed

Need more beer to read these....lol..just point and shoot my hawkens (circa 1980 BP). I do cast my own bullets though. 250gr R.E.A.L. Lee bullets.

Line052

To each their own to satisfy a desire and I respect that.
For some of us it’s exploring further to unlock more potential that also provides a deeper understanding from what we learn.
At least you get to enjoy a beer that is a migraine trigger for me, chuckle.

Ed

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Originally Posted by ET1

Jaycee

Quote
Where one has to be careful is the amount of booster being employed.
[and this is where problems develop in most cases of guns blowing up]

That is a misleading statement and no proof can be provided. In most cases the reference of a double load is considered the cause of rupturing barrels. Even that is questionable especially when the President of Savage has purposely fired a double load in front of witnesses to demonstrate the strength of the 10ML-II.

Quote
"I just deviated a little from the norm and damaged my rifle, had to install a new barrel", they were lucky that that is all that happened.

Another misleading statement by OTHERS because even with a 10% increase in recommended loads you can’t come close to the yield strength of the barrel. That I do know and have shot such a load with 4759. In order to damage a 10ML-II it has to be a major deviation from a recommended load.

Ed

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Agreed.

Even in the owners manual it states clearly that you can increase recommended load by two grains. That is a lawyer friendly statement.

Quote:

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Quote
"I just deviated a little from the norm and damaged my rifle,

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"Deviated a little " for some , is a lot to others , it still stands that this guy that said it , did damage his rifle .

Who knows how little his deviation was. ????

No where was it mentioned that this person used a "Savage " smokeless ML .
The topic was "duplex loads " and the inherent dangers to the inexperienced.