Spotted an interesting comment by Ken Oehler in this thread about the position of a small amount of a Fast Powder where he mentioned:

quote:

I use a very similar load in 38 Special case to demonstrate the effects of powder position in a half-filled case. It shows 18K psi with powder forward and 27K psi with powder back.

Ken O

I noticed a HUGE lack of comments concerning his astute first-hand observation. Anyone care to discuss what Dr. Oehler saw?

I have no doubt that what he saw was true. Does it have any significance to anyone besides Dr. Oehler and me?

quote:

Originally posted by Hot Core:
Spotted an interesting comment by Ken Oehler in this thread about the position of a small amount of a Fast Powder where he mentioned:

quote:

I use a very similar load in 38 Special case to demonstrate the effects of powder position in a half-filled case. It shows 18K psi with powder forward and 27K psi with powder back.

Ken O

I noticed a HUGE lack of comments concerning his astute first-hand observation. Anyone care to discuss what Dr. Oehler saw?

I have no doubt that what he saw was true. Does it have any significance to anyone besides Dr. Oehler and me?

I have had rifle loads shoot at reasonable pressures with the powder distributed horizontally. The same load would lock up a 788 if the rifle was tilted to vertical and carefully lowered before firing.

The good doctor has brought this up a time or two on different forums. I think the major point is load desity is more important then a lot of reloaders realize.

Then again I`ve "thinked" wrong a time or two...

Hot Bore..... 2.7 grains of Bullseye in the, (for that charge,) cavernous .38 Special case was the most consistant, most accurate, most position non-sensitive load for target shooters, for about 50 years. There might have been lots of difference in pressure according to powder position; but a good shooter could put them all in the same hole......And wild fluctuations in pressure didn't mean sh##. Millions, perhaps billions of this target loading, attest to this.........
That's my comment on his astute observation.
Grant.

In the same line of thought; The American Rifleman (back when they were shooters) did an
article on seating depth/pressure. Anyway the
effects were dramatic. Another thing to worry
about.
Good Luck!

HC,

The power of a primer is enough to push a bullet out of the case, all by itself. Now, put the small powder charge up near the base of the bullet, and I would contend that the bullet could start moving before the powder is able to start burning completely.

On the other hand, if the same powder charge is by the flash hole upon ignition, it does have enough time to burn more completely before the bullet begins to move out of the case.

Bullseye is probably the closest thing to black powder of any smokeless powder, in that it burns extremely quickly. Thus, position in the case at ignition is not as critical as other slower burning powders.

Admittedly, my thoughts are antidoctal, so there is plenty of room for more scientific explainations.

[quote]Posted 22 February 2009 17:09 Hide Post
HC,

The power of a primer is enough to push a bullet out of the case, all by itself. Now, put the small powder charge up near the base of the bullet, and I would contend that the bullet could start moving before the powder is able to start burning completely.

On the other hand, if the same powder charge is by the flash hole upon ignition, it does have enough time to burn more completely before the bullet begins to move out of the case.

Bullseye is probably the closest thing to black powder of any smokeless powder, in that it burns extremely quickly. Thus, position in the case at ignition is not as critical as other slower burning powders.

Admittedly, my thoughts are antidoctal, so there is plenty of room for more scientific explainations.
You are entirely correct. You must read a lot of my posts!

quote:

Originally posted by bfrshooter:
[quote]Posted 22 February 2009 17:09 Hide Post
HC,

The power of a primer is enough to push a bullet out of the case, all by itself. Now, put the small powder charge up near the base of the bullet, and I would contend that the bullet could start moving before the powder is able to start burning completely.

On the other hand, if the same powder charge is by the flash hole upon ignition, it does have enough time to burn more completely before the bullet begins to move out of the case.

Bullseye is probably the closest thing to black powder of any smokeless powder, in that it burns extremely quickly. Thus, position in the case at ignition is not as critical as other slower burning powders.

Admittedly, my thoughts are antidoctal, so there is plenty of room for more scientific explainations.
You are entirely correct. You must read a lot of my posts!

Let's just suffice it to say... I read a lot. I will check more of your posts!! Would you happen to be a fan of P.O. Ackley?

You guys have been talking about handgun loads here and very fast powders, but it can be an issue in rifles as well.

I messed around with cast bullet loads quite a lot in a 7-08 Remington. I found a huge difference on the chronograph with some powders depending on powder positioning. As I recall, one of the worst offenders was 748 powder. Positiiong the powder near the primer gave 200 fps faster speeds than when the powder was positioned near the bullet.

Just this morning I was experimenting with powder position sensitivity in 357 mag. My load was 8.5gr Unique with 125gr sp.

Barrel up before firing gave 1350fps. Barrel down before firing gave 1060 fps. Quickload showed 32kpsi for up and 17kpsi for down.

I always get amused when I see a reloader fretting about how a primer change may affect their load.

What's interesting is that Unique showed zero sensitivity in 45-70. (16gr 340 cast)

quote:

Originally posted by Oldmodel70:
2.7 grains of Bullseye in the, (for that charge,) cavernous .38 Special case ...

Not sure where Grant got the idea the thread was linked to that Load. Just looked and I saw no reference at all to 2.7gr Bullseye anywhere in the thread.

If Bullseye is mentioned within that thread, I'd appreciate it if someone would tell me who's post it is in - I might be overlooking it.
------

The link should go to a thread about

quote:

Piece is a .357 S&W 640 Centenial with a 2-1/8 barrel. Load is 7.4 grs. Unique behind a 125 jacketed HP.

Unique is a relatively Fast Powder, but not nearly as Fast as Bullseye.

Using Loads similar to the one in the Link(Unique), does anyone think the 50% difference in Pressure should concern anyone?

Does anyone(besides Dr. Oehler, SR4759, Ol' Joe, R Flowers, unique and me) believe the Pressure variation would affect Accuracy?

And for those of you I just mentioned, how do you think it would affect your Accuracy?

lee covered all of this decades ago....

HC,

I am certian that such variations in velocity would adversely affect accuracy. A couple of things that may be negating this problem in my loads are:

1. I use a cast 160gr. SWC
2. I use a roll crimp on these loads

The combination of the heavier bullet, plus the roll crimp, may be enough to hold the bullet in place long enough for the powder to burn more consistantly, regardless of it's position in the case.

Still, I would also believe that it may have some effect to the load. I will try some testing this spring with the chrono and see if can replicate the same variations addressed on the thread.

quote:

What's interesting is that Unique showed zero sensitivity in 45-70. (16gr 340 cast)

That is interesting! What is the accuracy in the 45-70 using that load?

I really did not suspect that fast powders like Unique would be position sensitive in small cases like the 357 Mag. I even thought they were not position sensitive in bigger cases. I did compare Unique (or equivalent) with and without a filler but suspect those results were skewed by an inaccurate bullet (two diameter bullet with the bore riding section too small). I never really tried the Unique equivalent in 44 mag because I did not believe it to be the best choice of powder for that cartridge. I did load a few 'reduced' loads for it but they had so little range I wouldn't have notice any accury difference.

You can really see what a powder does in a 10" barrel 45-70. I tried every powder listed for it from Unique to Varget. Very poor accuracy and velocity with most powders. I would say 4227 was the worst. 4198 gave me vast velocity and pressure excursions. 3031 gave good accuracy but was very slow with a lot of unburned powder. Varget was slow but was very accurate with less unburned powder then 3031. Unique did not thrill me at all.
The ONLY powder was bulky SR4759 that fills a case pretty good, however Dacron filler tightens groups a lot even though 4759 is easy to ignite.
The big case DOES present powder space problems.
I also cut groups in half using a large pistol magnum primer. Sub 1" groups at 100 yd's and I have clanged steel rams at 500 meters with this revolver. It will out shoot every 45-70 rifle that has passed over my bench.
I can only say powder choice and position is very important no matter what you shoot.
Even Bullseye in the small cases WILL show a little change with position but it is very small and will get worse as powder speed slows down. Only when the case is near or at 100% load density will it go away.
It never ceases to amaze my why guys buy a gun with a huge case, then need tweezers to load the powder! Each and every advance in brass size was done to use more powder for more velocity.
Why buy a 45-70 and load a pinch of powder? Why not make a 45-10? Or a .45 Colt sub special?
Hey, this is fun!

Oehler's observations stand to reason. Powder that's kept right next to the flash hole has to get a better kick than powder standing loose a 1/4 inch away. Kept in place near the flash hole, more powder will light up immediately, and the burn of that powder will get the main charge burning sooner. This effectively increases the speed of your powder. Confusing the issue is the effect of initial bullet motion. A jacketed bullet pushed weakly into the rifling can later require greater pressure to get it moving again, leading to higher pressures. It's effects such as these that internal ballistics software such as QuickLoad cannot predict.

quote:

Why buy a 45-70 and load a pinch of powder? Why not make a 45-10? Or a .45 Colt sub special?

Good question! But it is exactly what I would do!
Having said that, I have rifle - a 303-25 - which leaves a large air space in the case with my powder which seems to be the best powder for this cartridge. Therein lies the problem. But after this thread, I shall be using a dacron filler (until I can find a powder that fills the case and produces a little more velocity - why more velocity? Actually, it's to get the flattest trajectory I can for longer range shooting with heavier bullets. The heavier bullets are to make the rifle just that little bit more versatile).

asdf, what's that rifle action in your 'Logo'?

Hot Core questioned accuracy as a function of pressure variations. Along with 18K psi going to 27K psi I consistently see 1100 fps going to 1400 fps in a 10" Contender. I'm not good enough with a handgun to vouch for accuracy of this load, but would look for a different load based on seeing the velocity variations.

When I was much younger I read about effects of powder position, but laughed them off. When I heard an engineer at Remington mention that failing to maintain powder position by failing to do the "SAAMI Twist" before each shot could "sure screw up the SD" I thought in terms of a few percent variation. When I was able to see +50% increase in pressure with a 25% increase in velocity depending on my starting from muzzle down to my starting from muzzle up, I got real religion.

Rick Jamison once stated simply, "You are not finished with load development until you have a full case of powder." It is often easier to take his advice than to test each load for sensitivity to powder position.

Ken O

quote:

Ken O

As it was explained to me many years ago, "I feel sorry for those who think ballistics is an exact science. They just don't understand the problems."

Ken, your sig line says it all!!

quote:

Does anyone(besides Dr. Oehler, SR4759, Ol' Joe, R Flowers, unique and me) believe the Pressure variation would affect Accuracy?

I am sure it would affect vertical dispersion due to variations in velocity. However when I ran into that phenomena I abandoned that powder and bullet combination.

I agree with all of you that the Accuracy would most surely be affected. And perhaps change the geometry of the firearm into scrap.