Is there something undesirable about imr 4831?

[Calvin45]

Hey all, just a random thought to pick your brains. Is there some reason imr 4831 isn't half as popular as hodgdon h4831?

Temp sensitivity differences?

Also how do the burn rates compare IN YOUR EXPERIENCE (I'm fully capable of looking at a chart).

I just never see half as much data for imr 4831 as h4831 AND on the auction sites it never fetches quite as ludicrous prices (though it's all nuts).

 

[Wedgy]

IMR 4831 is listed as 1.10 fps per degree while H4831 is 0.36 but the increase isn't linear when you get to about the mid 80F range then powders can really spike fast. The Hodgdon extreme series don't spike like that for me in our desert heat.

 

[Calvin45]

IMR 4831 is listed as 1.10 fps per degree while H4831 is 0.36 but the increase isn't linear when you get to about the mid 80F range then powders can really spike fast. The Hodgdon extreme series don't spike like that for me in our desert heat.

Good to know. Makes sense. So weird how some powders behave so "non linear" as you say. Both temp and pressure. Most temp sensitive thing I've worked with is rl22. Worked up a load in Saskatchewan January and in June it'll sieze the bolt.

Most abrupt spiker I've worked with imr enduron 4955. It went from no signs, no primer cratering or even flattening, no sticky bolt, nothing, zip, nada, to a bolt I had strike open with a mallet over a difference of 1 grain powder in a .300 win mag. So weird. Never seen anything like that with any other powder ever. Usually you get some warning ahha.

BY FAR THE STRANGEST is that there are two different powders I've seen that seem to be REVERSE TEMP SENSITIVE. I cannot explain why or even how that could be but simply cannot deny my experience and observations. Both in my 300 win loads, one is imr 8133 and the other is hodgdon superformance. AND!!!! It is what I think it is, has to be, because the loads are full tilt but safely worked up to in the summer months which I figured was a guarantee I'd be fine in the winter. But for two years now I've observed that when it's below freezing, the colder it gets progressively the velocity GOES UP and the bolt gets a tad sticky. Not in a dangerous or failing way but it's just freaking weird and I can't get my head around it. And next summer it's back to normal again, so no cold welding or any other of the theories some advance about shelf life. This does not happen with any other loads except the 8133 and superformance ones. I know I'm not the only one to observe with 8133. So so odd.

 

[Weaver93]

I have used both in my 7 SAUM and prefer the IMR. However, I do not see temp swings like the desert guys. It does get hot here, but I'm a morning/evening guy in those situations.

Powder is a strange thing. If you compare a grain of IMR4831 and H4831 you will see a hole in the center of the IMR and not in the H. Newer powders (Hogdon Extreme) have burn inhibitor (deterrent) coatings that seal off these holes and slow the ignition times to prevent spikes. The hotter powder gets prior to ignition the quicker it ignites. Having to burn off the coating slows that whole process down by limiting the initial burn surface available.

And yes, when you reach my age looking at extruded powder under a microscope is considered entertaining!

 

[Calvin45]

I have used both in my 7 SAUM and prefer the IMR. However, I do not see temp swings like the desert guys. It does get hot here, but I'm a morning/evening guy in those situations.

Powder is a strange thing. If you compare a grain of IMR4831 and H4831 you will see a hole in the center of the IMR and not in the H. Newer powders (Hogdon Extreme) have burn inhibitor (deterrent) coatings that seal off these holes and slow the ignition times to prevent spikes. The hotter powder gets prior to ignition the quicker it ignites. Having to burn off the coating slows that whole process down by limiting the initial burn surface available.

And yes, when you reach my age looking at extruded powder under a microscope is considered entertaining!

Heck I'm 30 (for four more days) and I'd be inspecting it with a microscope if I had a microscope haha.

 

[Boss Hoss]

Kind of funny in that------have in many firearms over the years have always had better luck accuracy wise with the H-4831 and H4350 than the "IMR" versions.

 

[Weaver93]

BY FAR THE STRANGEST is that there are two different powders I've seen that seem to be REVERSE TEMP SENSITIVE. I cannot explain why or even how that could be but simply cannot deny my experience and observations. Both in my 300 win loads, one is imr 8133 and the other is hodgdon superformance.

Some ball powder is stressed (flattened out) to make them more stable, but if too flat they become unstable in extreme cold.

 

[Calvin45]

Some ball powder is stressed (flattened out) to make them more stable, but if too flat they become unstable in extreme cold.

Superformance is indeed flattened a touch. I've never heard this before. Interesting. I wouldn't call what shot it in extreme cold. About -17 celcius or right around 0 Fahrenheit. But still, I had worked up the load in +25-30 c (77-86 Fahrenheit) so that is a big difference. Velocity about 110 fps faster and had to tap the bolt open.

 

[Capt RB]

Retumbo in extreme cold can bridge to the point of blowing up the gun in what is a safe load in near freezing to summer temps. I've not experienced this but saw the results of a 7rum and a 300 rum that were fed retumbo.
I have some experience with 4955 going from nothing to bang the bolt open in 1 grain increase in the 6.5 creed. I have 7.5 #s for back up but I don't plan on using it unless I run out of preferred powders in the cases that utilize similar burn rates for that powder

 

[cape cove]

In my experience of using both powders I have always favored IMR 4831. This pertains to my 300 Win mag, 25/06 and 270 Win. Not that H4831 was bad, just that IMR 4831 was in some way better. I have also not experienced these temp/velocity/pressure changes. JME

 

[Weaver93]

Superformance is indeed flattened a touch. I've never heard this before. Interesting. I wouldn't call what shot it in extreme cold. About -17 celcius or right around 0 Fahrenheit. But still, I had worked up the load in +25-30 c (77-86 Fahrenheit) so that is a big difference. Velocity about 110 fps faster and had to tap the bolt open.

The "extreme" part may have been more my interpretation. I've never been to Saskatchewan in the winter, but I have had the pleasure of Ft. McMurray in Jan/Feb a couple times and I found that particularly traumatic!

 

[cape cove]

If you say pleasure of being in Ft McMurray in Jan/Feb you are one tough dude.

 

[Mark37082]

I was doing some initial loads for a new rifle today. Loading AB 160's in 280AI. I was using the Nosler manual to load pressure test loads in 1 grn. increments. Started with H4831SC and then loaded some IMR4831. Also finished up a pound of IMR4350 and will run H4350 once confirm the loads. We will see what the results are when I get to the range. No worries right now about pressure spikes due to high temps outside. The manual shows best velocity with IMR4831.

 

[Calvin45]

The "extreme" part may have been more my interpretation. I've never been to Saskatchewan in the winter, but I have had the pleasure of Ft. McMurray in Jan/Feb a couple times and I found that particularly traumatic!

Fair enough haha. Yeah if you're not used to it that'll traumatize ya. As for me I like the cold and honestly can't stand extreme heat (and same thing about the word extreme - what I think of as extreme folks from Texas would probably laugh at haha) - I honestly feel so disgusting and out of strength and breath in anything much over 27 c or 80 F. And it does get hotter than that here in the summer, two years ago we hit 39 c or 102 F. That's not for me.

But the biggest extreme swing I've heard of was from my dad. When he was young and single he went on a vacation to see australia and New Zealand. He left from uranium city, Saskatchewan, just under the border to the north west territories, in January, at -46 celcius/-50 F. The first place he ended up was called "Eden" in Australia and it was +44 c or 111 F there. Talk about a shock to the system! And then going back home too haha.

He recalls saying out loud

"this can't be Eden! This is HELL!!!!"