Duplex Post by RB
Jan 29, 2009 12:13:56 GMT -5
Post by edge on Jan 29, 2009 12:13:56 GMT -5
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Duplex loads have to be broken down by caliber. The caliber most in need of a duplex is the standard 50 caliber rifle. The reason for that has been repeated time and again but let’s consider the fact that NO 50 caliber rifle regularly shoots a 250 grain bullet. It is unheard of because of it’s slight weight. Most 50 caliber rifles never shoot a 300 grain bullet. The average weight bullet is between 435 and 600 grains.
The common duplex is 14/61 with the booster powder being N110 and the primary powder H322. Many shoot this load because it’s fast (2600 to 2700fps) and accurate. You are allowed to move up a grain or two to 15/60, 16/59 and down to 13/62, 12/61 in search of best accuracy but I suggest you stay in this area unless you consult with some one who can develop a custom load.
In the above load using Imr-4759 or Xmr-5744 as a booster is permitted if you can’t find N110. However go easy, it might be best to start with less and work up if you substitute.
All I have to say extra about duplexes with a 250 grain bullet is that loads of less powder are possible. If you're recoil adverse but still would like some extra speed loads of 70, 65, or 60 grains would work. If 2500fps was your perfect speed a 65 grain duplex would shoot a 250 grain there with little temperature sensitivity and safe pressure. I’m not suggesting a load just a concept. I will help you with the load if you need it.
Lately I’ve heard of 300 grain bullets being used in duplex loads. In the past I’ve not recommended that, even now I have reservations but will accept this: the load I’ve seen suggested is a very good load. I’ve seen a 10/60 load suggested with 5744 and 4198. If the timed speed is correct (2450fps) it is very near the ideal pressure for this amount of powder.
What I don’t want to happen is a speed war started with 300 grain bullets. They kick and most can’t take near what is offered for a full single powder load. I help some shooters go to very fast speeds but it’s not with duplex, so why bother?
Still there is always the need for temperature stability and this new load would be just that. Add the fact it is immune to misfire and I can see the attraction. But still I believe one 300 grain duplex is enough if you have a speed you have to go let me know and I’ll tell you how to get a broke shoulder errr... safely.
I have more thoughts on duplex in 45 and 40 caliber but I will add those as the post progresses
8-)For some time I have been getting inquiries about duplex loading. Since so many of you have questions I thought I should try to answer them all at once. Or at least most of them at once.
Duplex loads have to be broken down by caliber. The caliber most in need of a duplex is the standard 50 caliber rifle. The reason for that has been repeated time and again but let’s consider the fact that NO 50 caliber rifle regularly shoots a 250 grain bullet. It is unheard of because of it’s slight weight. Most 50 caliber rifles never shoot a 300 grain bullet. The average weight bullet is between 435 and 600 grains.
The common duplex is 14/61 with the booster powder being N110 and the primary powder H322. Many shoot this load because it’s fast (2600 to 2700fps) and accurate. You are allowed to move up a grain or two to 15/60, 16/59 and down to 13/62, 12/61 in search of best accuracy but I suggest you stay in this area unless you consult with some one who can develop a custom load.
In the above load using Imr-4759 or Xmr-5744 as a booster is permitted if you can’t find N110. However go easy, it might be best to start with less and work up if you substitute.
All I have to say extra about duplexes with a 250 grain bullet is that loads of less powder are possible. If you're recoil adverse but still would like some extra speed loads of 70, 65, or 60 grains would work. If 2500fps was your perfect speed a 65 grain duplex would shoot a 250 grain there with little temperature sensitivity and safe pressure. I’m not suggesting a load just a concept. I will help you with the load if you need it.
Lately I’ve heard of 300 grain bullets being used in duplex loads. In the past I’ve not recommended that, even now I have reservations but will accept this: the load I’ve seen suggested is a very good load. I’ve seen a 10/60 load suggested with 5744 and 4198. If the timed speed is correct (2450fps) it is very near the ideal pressure for this amount of powder.
What I don’t want to happen is a speed war started with 300 grain bullets. They kick and most can’t take near what is offered for a full single powder load. I help some shooters go to very fast speeds but it’s not with duplex, so why bother?
Still there is always the need for temperature stability and this new load would be just that. Add the fact it is immune to misfire and I can see the attraction. But still I believe one 300 grain duplex is enough if you have a speed you have to go let me know and I’ll tell you how to get a broke shoulder errr... safely.
I have more thoughts on duplex in 45 and 40 caliber but I will add those as the post progresses