Powder Burn Rate and Case Life?

[Syncrowave]

I was reading a thread here on 6.5/284 handloads where one user reported that although he got decent accuracy, etc., from H4350 and H4831SC, they both opened up the primer pockets fairly fast, and that he switched to a load using H1000 – the slowest powder of the three – and got both excellent accuracy, and longer case life before the primer pockets opened up.

My question to the board is, is this a fairly reliable "rule of thumb"?

In other words, all other things being equal, and assuming that you can get an efficient burn and accurate loads out of several different powders, wiil a slower-burning powder typically give a longer case life than a faster-burning powder?

Thanks in advance for any insights.

 

[dkhunt14]

I believe pressure is what opens the pockets. The H1000 should be able to get more velocity with less pressure. If that is the case the cases should last longer. I believe most slower powders would work that way. I think for accuracy the powder has to burn fairly clean and you can go to slow. Matt

 

[BradY]

I like powders on the faster side for a case/bullet combo. Shoot for accuracy not velocity and enjoy clean burning and less barrel wear. I would rather less carbon as it has the potential to damage a barrel earlier than it will wear out!

 

[swampshooter]

IMHE. when referring to a very overbore cartridge such as the 6.5x284 that there is some validity in what your friend stated. With H1000 producing a longer more gradual pressure curve it should be able to match the velocity of the other two while producing less peak pressure. IMHO the differences would be mostly theoretical, I just seriously doubt if the difference would be noticeable in actual shooting and reloading. I tried all three powders in my 6.5x284, 7828 also, I found H-4350sc to be the most accurate powder in my rifle.

 

[L.Sherm]

Over pressuring is over pressuring no matter what powder you use you are going to stretch the cases and open up the primer pockets. Now barrel life using a slower powder I don't know about that one personally I use the most accurate powder, I have a 6.5-300wsm and can not get it to shoot slow powders loves RL-17 so I don't worry about it accuracy is more important IMHO

 

[mikecr]

Missing from baseline in your comparison is barrel length.
Results are going to stem from powder actually burning inside the bore, or not.

With a 6.5x284 capacity, I seriously doubt H1000 will work out as better(for accuracy or velocity) in a ~26" barrel.
But faster powder -vs- slow would turn out different in a ~30" barrel.

 

[LCazador]

Given the same bullet weight and powder volume, a slower powder most of the time (every situation and rifle is different) is going to produce less pressure at the same charge weight. Less pressure(burn rate can change this) is going to produce less velocity and of course longer case life, as higher pressure is what creates expansion of the web area and in turn loose primer pockets. The slower powder will now require several more grains to achieve the same pressure and velocity as the faster powder. Most cases like the 6.5/284 or 284 will not have the powder capacity for the slower powder to equal the pressure and velocity of the faster powder. In my case I went to the Shehane version of these two calibers and the added case capacity allowed me to use the faster powder without enlarging the primer pockets, and still produce the velocity I wanted out of the case. Sometimes just lowering the amount of your powder charge is all you need to do to achieve the case life and down range goals you have set for your rifle 8) !!

 

[ShootDots]

I think your friend is right on the money... I shot, for 2 years, a 6.5 X 284... The first barrel I shot VV N560... I was getting awesome accuracy and velocity. But my case life was 2-3 shots before the primer pockets opened.. I turned to H4350, same results, then on to H4831, getting somewhat better (about 3-4 shots) BUT on my 2nd barrel, when I went to H1000, I was getting 3030f.p.s. 6-9f.t. e.s.'s, awesome accuracy and it burned very clean! Primer pocket life? They never went bad! I was getting with H4350 and H4831 right at 3015f.p.s.>>>exactly where it liked to shoot. No "pressure signs" as we know them>>sticky bolt, flattened primers etc...Just primer pockets opening up. I went to H1000 and all that went away and my velocity increased somewhat, by 15-20f.p.s. I told 2 of my friends about it, they tried it and they went in the same direction I did! I and one of the friends I have, use 30" barrels. He needed 55.5grs of H1000 to get to "about" 3030f.p.s, I used 54.7grs and got that velocity and my other friend shot the same 54.7 BUT he has a 28" tube and he is getting 2980f.p.s. NOBODY wants to go back to any of those other powders.

 

[mikecr]

You'll get better barrel life w/H1000 to.
Just need the capacity(which you have) and enough barrel length for it.
With too short of a barrel & H1000, muzzle pressures shoot up (toward dominant to chamber peaks), and you get a big ole fireball slapping the back-sides of unrestrained 26cal boat tails. Makes no sense to go here with anything less than a pristine crown.

The underbores(like a 6.5x47L) running faster powders in shorter stiffer barrels, hold more consistent chamber peaks and lower muzzle pressures. A 6.5x284 is overbore, and you can never get these advantages from overbore. You've traded them for higher BC per velocity,, which makes sense at 1kyd.

 

[stacy]

H-1000 good stuff I switched my 243ackley from H-4350 to h-1000 for the same reason

 

[Syncrowave]

Thanks, fellas. I appreciate the replies.

 

[Erik Cortina]

Pressure opens primer pockets, not powder burn rate.

 

[swampshooter]

IMHO, if you are not getting at least 10 loadings out of your brass before primer pockets are too loose then you are loading too hot. I loaded H-4350sc in my 6.5x284 and I'm still using that same brass in my 284. An extra 50 or even 100 fps is not worth loading to 65,000 psi.

 

[ShootDots]

Pressure opens primer pockets, not powder burn rate.

You are exactly right Erik... However, if I can achieve 2900 (or so) with IMR 7828 in my Shehane and never hurt the primer pockets, why would I want to run 2840 (or so) with H4350? In order to get to 2900 with H4350, I will have to UP THE PRESSURE considerably and that loosens primer pockets.

So far, on my "load development" brass, I have about 8 firings with nary a problem, yet I am getting 2900f.p.s. It is done with slower powders.. The same went for my 6.5 x 284, only with H1000..

 

[swampshooter]

Damn the torpedos, full speed ahead.