Replicating accuracy relating to velocity

[constructor]

I'll probably have to add to this,need to get to the shop soon.

Most of us here talk about charge weights when discussing accurate loads, IMO it is the velocity that is important. Changing primers or to a new lb of powder will change the velocity so I think for those that can shoot through a chrono keep accurate records of what velocity the good group was shot at. Powder dries over a period of time and velocity will increase because at the same charge weight you actually get more powder granules in the load. For most shooting 100 yards and looking for 1" groups it may not be so important but it all helps.
I have been working on the 6BRX for a few months now and have found a great accuracy node at 3070fps, loading the same charge with a different primer dropped me out of the accuracy node and groups opened to 7/8 just because of a 50fps variance. I opened a new can of powder and the same thing happened I had to increse my charge a whole grain just to get back to the 3070 and my accuracy came back. For the last year I have been drying RE7 and 10x by leaving the container open to let the acetone evaporate in order to increase velocity of the 6.8 loads but I believe it may be best to do this with all powder because the evaporaton rate is highest when the powder is new and velocities could change at every loading even though the charge wt is the same.
Now I check the velocity of a charge wt and increase or decrease that charge to get to the velocity I want before I load 50 rounds and head to the range. I have even resorted to mounting a press on a 2x10 so I can load at the range. I know it sounds extreme but I think I would rather go through the trouble to get it right than to go to the range and shoot bad groups.

[Ratdog68]

Ok... previous discussion of "drying your powder" had a totally different meaning to me. I thought you were talking about getting WATER content out of the powder. Living in the Pacific North Wet... I wondered how that would be doable for me.

With that being said... is the smokeless powder we use "hygroscopic" by nature? Will leaving it open "to dry" cause it so take IN moisture in a more humid climate? Or... is this purely to allow the acetone to evaporate?

[DDriller]

Good points H. I built a portable stand for my press and powder dispenser. I load my preliminary loads at the house and take my press with me also. I use an inverter to power my scale and just load in the back seat of my truck. Too much trouble to run back and forth home working on loads.

[joshuades]

Ok... previous discussion of "drying your powder" had a totally different meaning to me. I thought you were talking about getting WATER content out of the powder. Living in the Pacific North Wet... I wondered how that would be doable for me.

With that being said... is the smokeless powder we use "hygroscopic" by nature? Will leaving it open "to dry" cause it so take IN moisture in a more humid climate? Or... is this purely to allow the acetone to evaporate?

Given you open it to dry in an inside, climate controlled area, it should not pick up moisture (most air conditioned homes should have less than about 35% humidity just due to the way air conditioners work). I also tend to save and reuse dessicant from other containers and put one in my bottles when I open one.

[Ratdog68]

Given you open it to dry in an inside, climate controlled area, it should not pick up moisture (most air conditioned homes should have less than about 35% humidity just due to the way air conditioners work). I also tend to save and reuse dessicant from other containers and put one in my bottles when I open one.

Home air conditioning? Wassat? My house is pre-1900... and hi-tech means I have "un-stuck" my painted shut windows and plug a fan in when summer ramps up. So, relative humidity is what it is... inside or outside (for me).

[joshuades]

Louisiana and pre WWI house. Know what you mean. I actually had to insulate the floor underneath because it's on two foot stilts. If you could manage a window unit in a smallish room that would do the trick on dehumidifying the room.

[constructor]

The main thing is to let the acetone evaporate for 3 reasons, first the powder weighs less so you get more granules in the same weight charge, I believe the wet powder does not release as much energy and after the inital high rate of evaporation I do not have to adjust my charges as much to stay at the vel I want to hit. The only way I can get 3200fps from an 85 Barnes out of a 16" barrel is by drying the powder for weeks and using about 30.6 gr.
If it is humid you may want to try the dessicant packs.

[Ratdog68]

Louisiana and pre WWI house. Know what you mean. I actually had to insulate the floor underneath because it's on two foot stilts. If you could manage a window unit in a smallish room that would do the trick on dehumidifying the room.

Yup... had one at one point... let the folks have it at their place... dad needed it more than I did.

[Ratdog68]

The main thing is to let the acetone evaporate for 3 reasons, first the powder weighs less so you get more granules in the same weight charge, I believe the wet powder does not release as much energy and after the inital high rate of evaporation I do not have to adjust my charges as much to stay at the vel I want to hit. The only way I can get 3200fps from an 85 Barnes out of a 16" barrel is by drying the powder for weeks and using about 30.6 gr.
If it is humid you may want to try the dessicant packs.

Otay... thanks H... keeping it "open" to dry under these definitions makes a bit more sense to me now.

[Drifter]

I'm in agreement. When I switch to a different powder lot, the same charge used before often has to be adjusted slightly to match the same velocity and accuracy as before. I record velocity, accuracy, and temperature in a spreadsheet after testing loads, as even seemingly unsuccessful loads can help me to understand what's happening.