burn rate question lets see who has the answer for this

[Zero.40]

ok so here a little back ground: i am looking to go to a new powder to push a 115gr .355 out of my OPEN gun.

i am looking for a FAST burning powder so that i do not use much powder in a .38 super case.
well i have tried IMR 7625 all the way up 10.8 grs which filled the case tot he brim. and that still did not even come close to making major power factor in my gun. Now a friend told me to try Winchester auto comp. so a friend lend me some powder... i load up some ammo to 9.4grs which only filled half of the case. this load made major. awesome right.

Here is my question:

So i am looking at these burn charts and i find that IMR 7625 is faster burning than Winchester auto comp.... how so when IMR did not powder factor but the autocomp did? what am i missing?

 

[audioshooter]

It all depends on the density and packing efficiency of the powder. Less dense powders take up more space for the same volume. It could also depend on the actual cut of the powder (ball, flake,rod,etc).


It could also be that the IMR burns too fast and the friction from the barrel is overcoming the acceleration from the explosion.

 

[The_Shadow]

Yes, some powders are fluffy and other very dense, although they share similar burn rates. Such as is in these two powders. AutoComp is dense and produces a larger gas volume per cubic centimeter. It is AutoComp's faster and higher expanding gas volume that pushes the bullet despite the powders burn rate being slower and acting on the bullet past the initial ignition in the cartridge case. Sort of like diesel-long stroke of a piston vs. gasoline short stroke of the piston.

 

[Zero.40]

i see where you are coming from with that. if that is the case then where can i find that info for all the powder's out there?

 

[Goatwhiskers]

A word of advice: forget trying to select powders by the burn rate charts, those things are only relevent to closed pressure bomb testing. Stick with the recommended, tested charges in the loading manuals. Your route has a high chance of leading to disaster. GW

 

[The_Shadow]

i see where you are coming from with that. if that is the case then where can i find that info for all the powder's out there?

You may need to study what others are using and working with, like over at Brian Enos website. Best regards and be safe!

Heck, we are lucky to have the powders list, if they are single base, double base, triple base in their make up! I wrote Hodgdon a while back, explaining that they were omitting this information, which would help with making better decisions for some applications.

Not having access to a pressure testing setup, everything is a guess. There are labs that do testing, but cost prohibitive for regular guys. Another thing is cartridges like those that are listed as +P and +P+, while there may be some pressures listed for +P loads, you will be hard pressed to find data working in the +P+ range.

I work with 10mm and the major manufactures don't load to the potential of this cartridge, therefore, I have to test, to search for those edges of what works and what does not!

 

[Zero.40]

@Goat---- there is nothing in any manual out there that will give me what i need for OPEN class. unless you call 1550 fps from a pistol is normal.

@Shadow---- not many people have plaied with 115gr bullets yet.... also not many people have a "shorty" OPEN gun like i do. i have have to push my bullet faster that most people since the presure is leaving the gun sooner that most guns. so i am trying to find out what auto comp is pushing faster than IMR 7625. if i know that then i can shop around better instead of guessing in the dark.

 

[scooterj]

Don, IMR 4756 and VV n105 are two powders that should work. I may have some 4756 left and I know that I have n105, if you want to try.
I'll be working up a load with the n105 for my new super real soon.


Sent from my iPhone using Tapatalk

 

[ENVPMBR Shooter]

Give it up Don and just use Auto Comp........

 

[scooterj]

I have about 1/2# of 4756 that you are welcome to

 

[sksshooter]

i don't have a manual handy but is there no load data for bullseye or win 231? seems like you would have no issue making major with either of those with plenty of space in the case. i load bullseye for 9mm and 45 and its a fairly small charge to get a max load.

 

[Hammar]

I used VV N105 for my shorty 38 super. Plenty of gas. No problem making power factor. Almost impossible to over pressure. It's just pricey.

 

[noylj]

If you have a comp, then a fast powder is not your goal.
Auto Comp was supposedly designed just for what you want.
Personally, I look to Silhouette, 3N37, 3N38, 800X, AA7, and AA9. Some are using Longshot or Enforcer.