comparison of HV to lower level loads

fiver

Well-Known Member
#22
how deep do you wanna go.
we could go down pretty dang far and discuss overlapping burn speeds and why they ain't exactly overlapping when the base components or the ending powder type [ball/flake/stick] will react different or burn at a different upper temperature.

I don't think most people understand why H-4895 will blow groups into patterns with the same charge as you were using with IMR-4895.
 
#23
Since I sold off or traded numerous arms in an effort to scale down to what I want and will use, I'm redoing a lot of my own development in new guns, so this thread is especially useful to me. I'm glad it wasn't deleted.

I've also reduced the number of powders (not the quantity) I keep on hand and am seeing a lot of those which I've had my eye on.
 
#24
5R i think your last post would be a FANTASTIC idea. Another idea would be the general differences of the three powder types of powders (other than there shapes LOL) When deciding on what powder to use. If i knew 2 powders peaked at the same pressure, but powder B took longer to get there. That would be a great leap forward for me.
From all you guyes have taught me so far. I can open a loading manual and understand what i am seeing in the differences in powders and the velocities. Before coming here all i saw was a list of powders. And used a dart to decide which one to use.
 

fiver

Well-Known Member
#25
we'll start simple and go with surface area and burn deterrents.
some powders are the exact same recipe [700-X and 800-X] but are vastly different in their burn speeds simply because of the flake size [diameter], the thickness, and the burn deterrent coating used for the second speed.
all of those methods are employed to control or change the burn rate of other powders too.
it helps if you think of a piece of powder not so much burning but more like it converting into a gas at a specific rate.
like different shaped pieces of ice melting.

a cube has X amount of surface area, one of those circle pieces of ice has an outer and an inner surface and thinner walls, and your crushed ice is all about surface area.
only it's packed quite close together and tends to act more like one solid piece of cold with small air spaces in between.
powder is the same way.

except it isn't just made up of the same ingredients like Ice is.
you have different base stocks for the powders and different additions.
a powder made with cellulose has a slightly different weight and internal structure to it than one made with a fibrous long thin strand base.
a powder washed in solvents as a finish step is different than one washed in water.
and adding a nitro content changes the whole picture for both of them.

so lets take the 4895 we all know and make a slight change to it.
lets take a stick of it and extrude it so it is twice as long.
we didn't change the formula or any of the base stock or any of the deterrent.
so we should have 4895 right?
well no.
now we lost the surface area off the end of two sticks of powder, but how is that going to affect our burn speed??
right we just slowed it down.
add another amount of burn deterrent to those longer sticks and suddenly you now have a long grained 4350 burn speed powder. [with a flame temp abut 150-F lower than the original powder]

which we are going to ruin in our powder dump.. LOL.
 

Ian

Well-Known Member
#28
One other thing to realize, aside from all the things that affect ignition pressure rise before the bullet moves, and while it moves the first 1/8", is how far down the barrel the pressure peak occurs. Some powders will peak before the bullet base is out of the case neck, while others will peak after the bullet has moved two or three inches down the barrel. Alloy, alloy temper, bullet shape, size, lube quality, jump, neck tension, crimp, all affect when and where that peak occurs, and how consistently in the same place is that peak.

The best way to approach this may be to pick ONE cartridge and bullet, and discuss all the things we can do to optimize the launch.
 
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Rick

Moderator
Staff member
#29
One other thing to realize, aside from all the things that affect ignition pressure rise before the bullet moves, and while it moves the first 1/8", is how far down the barrel the pressure peak occurs. Some powders will peak before the bullet base is out of the case neck, while others will peak after the bullet has moved two or three inches down the barrel. Alloy, alloy temper, bullet shape, size, lube quality, jump, neck tension, crimp, all affect when and where that peak occurs, and how consistently in the same place is that peak.

The best way to approach this may be to pick ONE cartridge and bullet, and discuss all the things we can do to optimize the launch.
Yep and groove dimensions also.
 

fiver

Well-Known Member
#30
the case shape will also affect the burn rate of a powder.
sharp shouldered cases like a completely blown out Ackley will speed up the burn rate a notch.

it took me some thinking to figure out why large cases like the 45-70 was using fast rifle powders like 4198 or H-322 to launch a heavy projectile to some pretty serious speeds and not using something like 4831 or the like.
there is plenty of room there for gas expansion and all kinds of bore space for it to fill.
so why didn't they use a case just crammed full of a slow burning ball powder.
the sharp shouldered case thing made the light go on for me, the big straight lower pressure round wasn't speeding up the powders burn and probably was actually struggling to completely burn all of the fast powder as it was.

the other thing that can affect burn speed is the length of the neck after the shoulder angle.
there is kind of a funnel thing going on there directing the gas forward and not into itself or straight onto the steel in the throat area.
case shape and the neck length IMO does influence accuracy and longevity of the barrel.
minimally of course and there are exceptions on a case by case basis but I believe the longer neck helps for more than one reason.
 

fiver

Well-Known Member
#33
I'm going to suppose you have a 30-06 and something like a 170 gr bullet and want to shoot it at 1900 fps.
you also don't want to use a filler [most guy's don't for one reason or another]
this is a stone cold deer killing combination out to about 150 yards if you have a good flat meplat and an alloy that isn't much over 10 BHN when air cooled and about 17 or so when water dropped.
yeah 10 and 17,,, it doesn't matter much which way you choose to get there they are pretty much the same alloy when it hits the animal [that's a different subject]

so where to start thinking about the correct powder?
lets explore some options and some of the pro's and con's of each choice.
we already talked about 4895 and it's ups and downs and the whole thing with it comes down to position and ignition.
so lets see what else we can come up with to get there.
 

Brad

Administrator
Staff member
#37
No, they are much faster than 4895.
RE7 and 4198 are faster burning rifle powders while 4895 is a medium burn rate.

Don't get caught up on stick or grain shape/size as it equates to burn rate because it really doesn't. Domt forget what fiver said about deterrent coatings and how they can be used to manipulate burn rate.

Think of a deterrent coating like this. I have two piece of identical firewood. I soak one if water overnight. Although they are identical they will not burn the same. Not an exact analogy but it gets a point across, right?

I don't recall where it was but in the past I borrowed a book from Khornet that went into some good detail on powder manufacturing and associated details. It was quite enlightening.
 

fiver

Well-Known Member
#38
they are faster.
they are right on that edge of being just slow enough to need a filler to hold the powder against the primer for positive consistent ignition, but fast enough you are more likely to get away with just a rifle primer and avoid velocity variations without one.
them not having a heavy burn deterrent helps immensely.

other ones in this area are 4227 and AA's 1680 both do well around 22 grains.
what I personally would like to see is a big fluffy flake powder in the rl-7 burn speed.
something that fills a 308 case to around 60% with 22-24grs of powder and doesn't run pressures up into the 50-K area.
 

Brad

Administrator
Staff member
#39
For 1900-2000 fps the 308 has an advantage in my opinion. The 06 has too much case capacity.

Yes, a big fluffy flake powder in that burn range would be nice. Sort of a rifle Trail Boss.
 

fiver

Well-Known Member
#40
yep something like the old lafflin and rand infallible, which was a smokeless powder that replaced black powder by bulk measurement.
3 drams would be something like 80 grains and replaces 18-20 of todays smokeless.
you could back it down to 65grs and fill a 30-06 case for 16-1700 fps shooting all day long at around 30K without worrying about fouling or heat issues.
then we could discuss powder compression and duplexing for the most efficient and accurate loads.