Retumbo and temps

[LRShooter7mm]

I am somewhat new still to reloading so I thought I would ask a question on here. So anyway I was under the impression that Retumbo is a pretty stable powder for temp variations? I was working on a load for my 7mm rm I worked up from 70 gr to 72 gr in .5 gr increments. I found a load that was shooting .75 at 100 at 25°C. After that testing i went back home to try loading a few more rounds with .2 gr increase and .2 gr decrease and the exact same but at 8°C. All 3 groups were more then 1.5 inches nothing tighter. So I thought maybe Retumbo isn't as stable as I thought it was when compressed anyone have any thoughts or experiences similar with Retumbo? Thanks for any and all help

 

[AZShooter]

I would suggest you need to shoot the load that seemed to shoot so well again. Sometimes you think you have a load and you don't. Happens to me from time to time too.


I would also expect the velocity wouldn't change with such a small difference in temperature of 30 degrees F.

Are you chronographing the load?

 

[LRShooter7mm]

I didn't chronograph these loads. I did try the loads that shot decent but I wasn't able to repeat it. I was able to repeat one load which shot .9 inch group. I may end up just sticking with that load. The load that shot .75 or under don't remember for sure but I wasn't able to repeat that one after loading again to same measurements. I will keep playing around with them see what I can get thanks

 

[Darkker]

So anyway I was under the impression that Retumbo is a pretty stable powder for temp variations?

Don't take Hodgy's marketing garbage for face value.
Whether or not any powder is "extreme", temp sensitivity is primary about the cartridge it's being used in.
There is no such thing as a universally stable powder.

 

[LRShooter7mm]

Don't take Hodgy's marketing garbage for face value.
Whether or not any powder is "extreme", temp sensitivity is primary about the cartridge it's being used in.
There is no such thing as a universally stable powder.

Thanks will keep that in mind.

 

[FEENIX]

Every time powder temp sensitivity issue is discussed it always takes be back to GG's #2 post http://www.longrangehunting.com/forums/f28/powder-temperature-sensitivity-31096/

Cheers!

 

[Greyfox]

I have been using Retumbo extensively for several years in my 6.5x284's, 300WM, and 338Lapua. No issues with temperature sensitivity. I shoot/hunt temps that can range in a season from 85F down to 0F.

 

[Darkker]

Every time powder temp sensitivity issue is discussed it always takes be back to GG's #2 post http://www.longrangehunting.com/forums/f28/powder-temperature-sensitivity-31096/

Cheers!

His post is exactly the reason why people don't know chit about powder...
He thinks ball powders are sensitive by their own virtue, apparently he hasn't looked at any of the work done by the Naval Warfare Testing Center in many decades. Or that 95+-some percentage of all American armed forces ammo is ball powder....

If you want science, and not some schmoe who thinks there is a difference between Bl-c(2) and H335, read Dr. Denton Bramwell's testing. He used to write for the note defunct Varmint Hunter magazine, but she of his articles on temp are still up at RSI. But yourself a Pressure Trace while your there and learn that no, no you can't "read signs" of pressure in brass.

 

[FEENIX]

His post is exactly the reason why people don't know chit about powder...
He thinks ball powders are sensitive by their own virtue, apparently he hasn't looked at any of the work done by the Naval Warfare Testing Center in many decades. Or that 95+-some percentage of all American armed forces ammo is ball powder....

If you want science, and not some schmoe who thinks there is a difference between Bl-c(2) and H335, read Dr. Denton Bramwell's testing. He used to write for the note defunct Varmint Hunter magazine, but she of his articles on temp are still up at RSI. But yourself a Pressure Trace while your there and learn that no, no you can't "read signs" of pressure in brass.

Perhaps you missed his caveat ...

There have been many tests on this subject. Many have been published and some data is contradictive but I'll give you my own personal results.

 

[Darkker]

I caught that, and Is well said. The problem is, lack of understanding furthers the misconceptions out there.

We the reloader, are and always have been, a waste market.
WC846 & WC 844 are the same powder, they only differ on an "as-built" basis; and the distinction happened near 1970. Hodgdon says one was built for the 308 & one for the 5.56. Except that powder was actually designed in the mid 1930's....

Hodgdon says CFE was developed with the same tech designed for the US military, except that "tech" came from the French, for the French, around 1900.

Win 760/H414/AA2700 are all identical from General Dynamics, simply a question of what label Hodgdon ordered.

Go read some of the articles done by Denton, where he has good and repeatable measurement equipment. In the 223/5.56 with 55gr bullets, H335 is notably less "sensitive" than Varget. So is Varget temp sensitive?? Well, compared to a couple powders, including ball powders in that application, somewhat. Doesn't mean it's a poor choice for that application, just that all things are relative.
Varget was designed for ball ammo in the 7.62 NATO. In that setting, it excels. Take it out of its design parameters, and it's a different story.

A camel can go a long distance in extreme heat without drinking water, but can't climb a tree for chit. Does that mean a camel is a "bad" choice? Not necessarily, Just depends on what you are trying to accomplish.

 

[FEENIX]

I caught that, and Is well said. The problem is, lack of understanding furthers the misconceptions out there.

We the reloader, are and always have been, a waste market.
WC846 & WC 844 are the same powder, they only differ on an "as-built" basis; and the distinction happened near 1970. Hodgdon says one was built for the 308 & one for the 5.56. Except that powder was actually designed in the mid 1930's....

Hodgdon says CFE was developed with the same tech designed for the US military, except that "tech" came from the French, for the French, around 1900.

Win 760/H414/AA2700 are all identical from General Dynamics, simply a question of what label Hodgdon ordered.

Go read some of the articles done by Denton, where he has good and repeatable measurement equipment. In the 223/5.56 with 55gr bullets, H335 is notably less "sensitive" than Varget. So is Varget temp sensitive?? Well, compared to a couple powders, including ball powders in that application, somewhat. Doesn't mean it's a poor choice for that application, just that all things are relative.
Varget was designed for ball ammo in the 7.62 NATO. In that setting, it excels. Take it out of its design parameters, and it's a different story.

A camel can go a long distance in extreme heat without drinking water, but can't climb a tree for chit. Does that mean a camel is a "bad" choice? Not necessarily, Just depends on what you are trying to accomplish.

You're welcome to share those personal experiences as he did and let the end users decide and benefit from it. Everything is indeed relative and as always YMMV ... there's no need to complicate it unnecessarily esp when we all have varying experiences, knowledge, applications, etc ...

He also noted ...

A guy could spend a lifetime with a hundred powders and a thousand calibers and never figure all this stuff out!

Again, by all means do share those personal experiences ...

Cheers!

 

[Darkker]

I would ask which is more complicating to the point of knowledge:
A) telling someone all ball powders stink, and powders that are identical, give different results, from"personal experience".
B) Saying that it is application specific.

For extruded, read #7
http://www.accuratepowder.com/faq/

Where you can read some of Denton's work:
https://www.shootingsoftware.com/tech.htm

A little testing from GD, larger temps than Hodgy uses btw:
http://www.dtic.mil/ndia/2010armament/WednesdayCumberlandSteveFaintich.pdf

My own:
This was part of a chamber soak test we did in a Hawkeye, chambered in Creedmoor a couple years back. As you know, cooking in a chamber is about the worst thing you can do for affecting the pressures/burn rate. We used a calibrated Pressure Trace II strain gauge, on the same rifle, for all of these.

Devil ball powder, Vs. Extreme Hotness

Now you will note, we had some ignition timing issues with that lot of Superformance. That particular lot was @ 12% different than the lot tested by Hornady. Subsequent lots which were faster and more in line with expectations, didn't have that issue. they are "cleaner" looking, but the same outcome, and these were handier to post. Since Hodgy refuses to list nominal specs for anything, don't know if that is "normal", but was different than the other 16#.
In any case, note the ES in both velocity and pressure, between the two powders.

The Extreme darling, is a good powder in the Creedmoor. So is Superformance with that wild progressive burning curve. Is ball powder temp sensitive? It depends, like I said all along. In the Creedmoor, shooting 140gr bullets, Superformance is "better" than H4350.

We also tested the hype around the FlatLine bullets and getting pushed faster, "with no extra pressure".... Yeah, it's bogus too.

 

[FEENIX]

I would ask which is more complicating to the point of knowledge:
A) telling someone all ball powders stink, and powders that are identical, give different results, from"personal experience".
B) Saying that it is application specific.

lightbulbPerhaps he's simply not as knowledgeable as you.lightbulb

But now that you have shared your personal experience, members can now decipher what can possible work for their particular application(s).

 

[MagnumManiac]

Temp sensitivity is blamed on so many events in shooting that quite possibly are caused by other factors, such as AIR DENSITY. I have a pressure trace also, it appears to me that air density will change a known load without there being any change in temperature. I can go from my house in the city, to my rural property, and have a gain in velocity, simply due to the higher altitude and lower air density. Air density changes throughout the day, it generally thins as they day goes, but, will thicken in the afternoon within an hour before sunset, this changes how your rifle drops, simple fact.

Darrker,
Your example of a powder cooking off in a hot chamber is not what temp stable powders are DESIGNED to withstand. They are designed to be stable in varying ambient temps, this includes being exposed to sunlight and freezing conditions. A flash over event in a cartridge is not the same as a cartridge firing at a normal temperature. There are limits to what temps a powder can withstand.
Also, lately you keep reporting that powder burn rates can vary by 10%, this is simply misleading and untrue.
By law, canister powder MUST stay within 3% of the very first batch of whatever powder was first sold as. If it doesn't meet this criteria, is blended and sold as a commercial powder. Canister powders are not blended, this has also been reported, not by you, but, needs to be cleared up.
The reason that it is recommended to start 10% below a listed max is due to the fact that a simple change in COMPONENTS, cases, bullets or primer, can change pressures by 5%, or thereabouts, which means a 10% reduction will still be safe with a load that raised pressure by that amount which can be compounded by all those changes. Also why it is suggested to ONLY change ONE thing at a time.
I have seen 8,000psi difference with just a brand change with a primer, not a type change either.

Temp sensitivity is a subject too many worry about. My best loads for my 1000yrd rifle use RE25, it is meant to be 'touchy', but, I have never seen it, even over the chrony or on the pressure trace. I've seen bigger swings from primer changes than any other factor.
I also run H1000 and Retumbo, they appear to swing with elevation and air density just as much as other non temp sensitive powders.
I have had problems in high temps with both ball and double base powders going overboard and popping primers, I learned, if you up your loads in hot temps, you won't get surprised when you switch from cold temps to hot temps, I know I no longer have to worry.
I just don't think that the temp stable thing is what is occurring in most of the so called troubles people blame it on.

Cheers.
gun)