In breaking in the Stevens Mod. 200, .270, my cousin made up a couple of batches of 150gr. bullets driven by Data powder 86. We shot the ammo at the same time from the same boxes.He was using his Ruger circa 1970.A sweet rifle I might add.

55gr. 86,

Stevens 22in. barrel, 2775 fps avg. velocity.

Ruger 24in. barrel, 2650fps., avg. velocity.

56.5gr.86

Stevens, 2880fps. avg., soot ring partially around primer and primer started to extrude into fireing pin hole.

Ruger, 2760fps.avg.velocity, absolutely no over pressure signs.

A couple things; first we at last reached an upper limit in one rifle at least with Datapowder 86, and we show how two rifles of the same chambering react diferently to identical loads as has been stated a hundred times on this form. Here is some objective evidence. roger

Old age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone..

Hey Roger, No telling how many times we all see the statement come up about a rifle is making X,000fps with a specific Load, so the Pressure must be YY,000psi - WRONG.

Your example shows that it really doesn't work that way at all.

It's amazing what the difference in chamber & throat tolerances will do.
In a 30-06, using the same lot of ammo, I gained 270fps by shortening the barrel 1".
At 26", with a sloppy throat (IIRC it was .3125) and a loose (max diameter) chamber I was getting 2725fps. Cut the threads off, and rechambered with a Min spec chamber/throat (IIRC the new throat is at .3085), now the same ammo runs 2995fps.

Jam it into the lands, that is as good as a couple more grains.

quote:

Originally posted by Hot Core:
Hey Roger, No telling how many times we all see the statement come up about a rifle is making X,000fps with a specific Load, so the Pressure must be YY,000psi - WRONG.

Your example shows that it really doesn't work that way at all.

????

I think the data indicates that the higher pressure load resulted in a higher velocity, which is generally (but not always) the case.
So I don't think Hot Core's statement, although not necessarily totally wrong, is supported by the data.

What the data does show is that individual rifles vary significantly in how they behave with a given load. In this instance they vary so much that a shorter barrel produces a significantly higher velocity and exhibits proportionally higher pressures.

quote:

Originally posted by Jim White:
...HC thats usually the first out of your mouth whenever the talk turns to anything Ackley. "You can't get that kind of velocity without running extreme pressure"

Hey Jim, I think you have me confused with someone else. I realize the AI cartridges "normally" have a bit more Volume than their parent case and "typically" that allows a bit more Velocity, not much but a bit more.

And I realize there are some that do quite well, like the 257RobAI. Of course, a regular old 25-06 will work even better.

I believe where we differ is whether the aggravation of Forming the AI Cases and the extra expense associated with the "Special Dies" is worth it. To me, it just isn't worth the extra effort or cost.

Just one example, rather than taking a 30-06 and converting it to a 30-06AI, " I " would prefer to just go on and get a 300Win Mag or a 300WbyMag. Everything about those two Mags can be purchased at normal costs and no special Forming is required.

Plus, I can always "down-load" either of the Mags to the 30-06AI velocity level if there is some specific reason that I would want to.

P.O. Ackley is one of the people from days gone by that I hold in high regard. A lot of the wonderful regular cartridges in existance today are because of the Testing he and his friends did.

And I have no problem at all if "you" choose to waste your time and money on AI cartridges when there are better regular cartridges available in the same caliber.

quote:

And I have no problem at all if "you" choose to waste your time and money on AI cartridges when there are better regular cartridges available in the same caliber.

quote:

Originally posted by Jim White:
[QUOTE]Originally posted by Hot Core:
Damn HC thats usually the first out of your mouth whenever the talk turns to anything Ackley. "You can't get that kind of velocity without running extreme pressure"

Pressing HC's buttons ,Jim? Dog gone it . And here I was getting ready to buy land just out side Prescott. roger

quote:

Originally posted by Jim White:
Roger, If you are looking to get away from the Kalifornia liberals don't come here! We are over-run with the sons-a-bitches. I am considering a move back to Wyoming where I belong! Jim

Dog gone, Jim; I'd move back to Grand Junction but it's being over run by son's of bitches from Prescott. Dug up all my apricot and peach trees and put in pig tight fences. No respect roger

Roger, I've seen the same thing happen.

I currently have 2 7RMs one w/ a 24" tube and one w/ a 26" tube. The 24" tube is a good bit faster than the 26" tube when using the same loads I'd have to say around 75-80 fps faster. Yet, the 26" tube will show no pressure signs w/ loads that flatten primers in the other rifle.

Like someone else stated, it's amazing how much the dimensions can effect the pressures.

Reloader

Bartsche, maybe I missed something but, the increases in velocity look virtually identical.
For the apparent pressure difference, I think I would look at the case (if only one). The flash hole diameter is what comes to mind.
Regards, Curley

quote:

Originally posted by curley:
Bartsche, maybe I missed something but, the increases in velocity look virtually identical. You You are correct. The differential fps seems to fallow the different powder charges!
For the apparent pressure difference, I think I would look at the case (if only one). The flash hole diameter is what comes to mind. Accurately determining the cause just might lead to a whole lot of conjecture and is beyond my interest at this point. The fact that this shows that it does happen was and is my only intent.
Regards, Curley

Now about sizes of flash holes; I've tried to get people to respond to a couple threads requesting if they have any hard data on hole size variations and what affect they have or effects they cause. Nothing concrete yet. Now if anyone has this information will they please PM me and avoid refocusing this thread. Thanks, roger

quote:

Originally posted by tnekkcc:
Jam it into the lands, that is as good as a couple more grains.

brillient