Some help understanding short-cut powders

C

Charles E

curmudgeon
Hodgdon H4831-SC is suppose to be "the same" as plain old H4831. The claim is the SC has the same burn rate, but the grain size is smaller for easier use in a powder measure.

OK, these are single-base powders. If the grain is smaller but the burn rate the same, then either (1) they have to have a thicker grain, or (2) they have to use more of the deterrent coating -- or perhaps it is of a different type? Or, I suppose, they might use a bit of both 1 & 2.

Are there any downsides to using more of the deterrent coating? Now that many of us are on the Chargemaster bandwagon, "easy metering" is less an issue.

While I'm particularly interested in H4831-SC versus H4831, I'm generally interested in the whole topic. I see there is now an IMR 7828-SSC, too.

TIA
 
Charles

I'd bet that the formulae and the science behind the SC and SSC powders are a well guarded secret. Very likely more secret than the formula for Bush's Baked Beans or the Colonel's fried chicken.

Ray
 
Last edited by a moderator:
Charles,

SC is an Aussie powder, therefore you have the other variable that the cellulose is derived from different species to those of North America or Europe. I understand that has an impact on the outcome too.

John
 
John, my understanding is that "regular" as well as "SC" in the 4831 line is an extreme powder. Further, I understood that all the extreme powders were made in Australia. Is any of that wrong?

As for 7828 & it's SSC, both are IMR powders. Ever since DuPont sold the company, it's been hard to follow. Was owned by a Canadian firm for a while, but I never did hear who did the manufacturing. And of course, IMR was sold again, to Hodgdon. Probably still the same manufacturer, though.

Anyway, just now, it's the H-4831 I'm most interested in. Anybody have success/failure stories with the recent products, esp. the "regular Extreme"? I've been using the "short cut" & it shoots very well, but like everyone else, I'm always looking for that last little edge.

Charges are weighed, not thrown, so the metering aspect is not an issue. I also don't have an issue with loading density -- I have to go to Rel-25 to get 100% loading density.
 
Having used a good deal of H4831 and its SC version, I can find no difference in accuracy or velocity. Data really is interchangeable, at least with the lot numbers I have used to date. Been using the original version since '65. My recent experience with 7828 and the SSC version is very limited (one cartridge, .270 Win.) but it seems to follow along the same lines as H4831 / H4831SC.
 
Charles E said:
Are there any downsides to using more of the deterrent coating? Now that many of us are on the Chargemaster bandwagon, "easy metering" is less an issue.

While I'm particularly interested in H4831-SC versus H4831, I'm generally interested in the whole topic. I see there is now an IMR 7828-SSC, too.

TIA
Click to expand...
Charles, call Ron Reiber at Hodgdon. He is the Hodgdon Product manager and is a very knowledgeable powder chemist.
 
Charles E said:
The claim is the SC has the same burn rate, but the grain size is smaller for easier use in a powder measure.

OK, these are single-base powders. If the grain is smaller but the burn rate the same, then either (1) they have to have a thicker grain, or (2) they have to use more of the deterrent coating -- or perhaps it is of a different type? Or, I suppose, they might use a bit of both 1 & 2.
Click to expand...

Hi Charles

As you noted the grains are shorter and they may be thicker but there is also a small hole through the centre of the grain critical to controlling burn rate.

The burn rate and hence the rate at which propellant gas forms is largely influenced by the surface area to volume ratio of the grain - high surface area equals high burn rate and vice versa.

As the outside of the grain burns the surface area decreases, but as the hole through the grain burns the surface area there increases.

The balance between the two, when the shape of the "extruded donut" is manufactured correctly, produces nice even production of propellant gas until the entire grain is consumed.

Avoiding spikes in pressure that may be produced by ball powders as they burn from the outside in only and instead maintaining more of a plateau in peak pressure as the bullet accelerates down the barrel produces velocity by maximising the area under the pressure-time curve.

Deterrent coatings like dinitrotoluene certainly play a role, but the clean burning and even burn rates of ADI's extruded powders is very much influenced by their precisely manufactured shape.

Regards
Ben
 
And there is Google for those of us who do not know what we're talking about. ;) ;)
 
I have used near maximum loads in an old 25-06 AI that I have and I see no difference in pressure or accuracy between the two.

Concho Bill
 
You must log in or register to reply here.
Back
Top