Powder and pressure question

[Pheroze]

I am looking at options to develop loads for a 308 Norma Mag that is currently being built (something to do while waiting for lunch). I noted that for 180 gr Hodgdon H1000 and H4350 produce similar velocity (+- 50 fps) but the H1000 operates at a lower pressure. The difference seems slight with H1000 at 51,900 cup vs 52,800 for H4350, but I really don't know the significance of this variance. My question is when developing a load is there any reason to consider using one powder over the other based on pressure, assuming it is within a safe operating range?

 

[Graham Hunter]

As long as the load is under the maximum allowable pressure limits just find the load that is more accurate with good velocity.

 

[Pheroze]

As long as the load is under the maximum allowable pressure limits just find the load that is more accurate with good velocity.

That was my assumption but then I was curious whether lower pressure equates to less recoil, brass or barrel life or some other variable I hadn't thought of.

 

[Ridgewalker]

IME, if you run lower pressures, your brass will not get worked quite as much, i.e., work-hardened, stretched, etc. so you get more reloads. Don't ask for a number of "more reloads" because there are other variables as well.
Slower Powders tend to give lower initial spikes of pressure spreading it out for longer durations in the barrel. Results would/could include less perceived recoil, (slower impulse) and less barrel erosion (heat spread over a larger area of the bore).
The critical parameter is whether it is accurate or not in a given rifle with a given bullet weight and design (length, shape, bearing surface, balance).

So after all the blah blah blah, the only things IMO that count are accuracy and velocity. Try one and see how it does.

Sorry for the long drawn out info. I've been retired for 18 years and I still miss working on occasion.

 

[gillettehunter]

The H-1000 is generally considered to not be sensitive to temperature extremes. Both are powders that have been around for a while and have beeen used a lot. Given the choice I'd go with the H-1000. Bruce

 

[Pheroze]

Ok thanks guys. I was just curious about that so appreciate the feedback. I don't know what I don't know if you know what I mean

 

[PHOENIX PHIL]

@Pheroze, I'd always go the lower pressure route if all other things are held equal. Particularly accuracy and velocity being equal. But the pressure difference here is less than 2%, so I would tend to think whatever gains are to be had you'll likely never notice.

I'd concentrate on accuracy first. If either powder gives you the accuracy you want, then use it. If both give you good accuracy, then I'd be inclined to use the load that has better velocity.

 

[rookhawk]

I'm a reluctant hamdloader. When absolutely necessary only.

That being said, 4350 is awesome because it works really well in almost everything worth owning from a 500 nitro for black, a 375hh, a 318 Westley and your .308. One powder to rule them all!

 

[Pheroze]

I'm a reluctant hamdloader. When absolutely necessary only.

That being said, 4350 is awesome because it works really well in almost everything worth owning from a 500 nitro for black, a 375hh, a 318 Westley and your .308. One powder to rule them all!

That has been my approach to life too! 6.5, 06 and 375. But new cartridge may require a fresh approach ...Maybe...

 

[rookhawk]

That has been my approach to life too! 6.5, 06 and 375. But new cartridge may require a fresh approach ...Maybe...

When sick of 4350 you can do 3031. Then RL19.

Those three powders should cover the 1000 most popular calibers for Africa.

 

[Ray B]

The unmeasurable differences in the interior of barrels will cause the pressure in your barrel to differ from those measured in the test barrels. If you are really interested in getting the most for the least you'll need to measure the pressures and velocities of various loads in your barrel. this means you'll at least have to borrow a chronograph with strain gauge for pressure. then keeping track of everything and only changing one variable at a time work your way up the pressure/velocity ladder while also checking the accuracy of the loads. This can lead to the firing of many hundred rounds- which is great fun and very interesting to some of us- or you can pick out a load from a loading manual, get the components, start at the start, work-up to signs of pressure, back off some, see if it's accurate, if so, call it good.

 

[KMG Hunting Safaris]

.308 Norma Mag. Woooohooooo!!!!

 

[Pheroze]

The unmeasurable differences in the interior of barrels will cause the pressure in your barrel to differ from those measured in the test barrels. If you are really interested in getting the most for the least you'll need to measure the pressures and velocities of various loads in your barrel. this means you'll at least have to borrow a chronograph with strain gauge for pressure. then keeping track of everything and only changing one variable at a time work your way up the pressure/velocity ladder while also checking the accuracy of the loads. This can lead to the firing of many hundred rounds- which is great fun and very interesting to some of us- or you can pick out a load from a loading manual, get the components, start at the start, work-up to signs of pressure, back off some, see if it's accurate, if so, call it good.

I do enjoy working up loads. I find you really get to know your rifle and it is fun figuring out the puzzle. Maybe I will have to futz around as you described - sounds like a first summer of retirement kinda thing

 

[Pheroze]

.308 Norma Mag. Woooohooooo!!!!

Better believe it buddy! The brass and dies I ordered arrived this week...This train is moving!

But...No rifle yet

 

[Shootist43]

Out of curiosity how many Grs. of the respective powders generate the pressures stated? A follow up question is what is the expected muzzle velocities of the respective loads?

 

[Pheroze]

Out of curiosity how many Grs. of the respective powders generate the pressures stated? A follow up question is what is the expected muzzle velocities of the respective loads?

The pressure as seen with Hodgdon loads that I got off of Loaddata.com:

H1000 at 51,900 cup vs 52,800 for H4350

The velocity is H1000 2940fps & H4350 2999 fps

Grains 76 vs 69

Also, the H1000 is a compressed load and H4350 is not. I thought that interesting because I understand from the Lee Manual that you typically get better accuracy with a fuller case.

 

[lwaters]

I've used H4831 in everything from 270 to 338 win. It work well in a 300 winchester should be good In the Norma. I remember buying it surplus for buck a pound.

 

[KMG Hunting Safaris]

Also, the H1000 is a compressed load and H4350 is not. I thought that interesting because I understand from the Lee Manual that you typically get better accuracy with a fuller case.

This is true, but just keep an eye on pressure. I run some compressed loads, but that is with bullets that have drive-bands and are known for having no pressure problems at all.

 

[PHOENIX PHIL]

@Pheroze, FWIW I haven't seen a rifle in 7mm Rem Mag that didn't like IMR4350 behind both 140gr and 160gr projectiles. This includes at least 5 separate rifles ranging in manufacturer by the same amount. Remington, Winchester, Browning, Tikka and Savage.

 

[Mekaniks]

@Pheroze I was looking through my Speer 13 manual and noticed that they have 308 Norma loads published. You might check it out for what it's worth