Actually, H.C., the correlation between pressure and velocity is quite good. The old Powley Computer gives a decent estimate of the fps a cartridge might obtain at a given peak pressure. That may be what ALF referred to.

The published data I've been able to find does, though, suggest that in general, you can't work the problem the other way (fps to pressure). Component substitutions (esp. primers) seem to have an effect on pressure and velocity which doesn't follow the basic trends dictated by mass ratio and pressure and expansion ratio.

quote:

Originally posted by Steve:
H.C., Easier for you...

I'd be glad to go through the experiment, as I was thinking about doing it anyway. I have to find the article first though.

I just went through usual spots where I 'drop' magazines and haven't been able to find it. I suspect that my wife might have mistaken my filing system with the recycling pile, however.

If I find article I'll play with things and let you know my results. In the mean time If you could paraphrase the passage for the manual we could get started on the conversation. -Steve

Hey Steve, Sounds like a plan to me.

If you will pick a "Cartridge", I can go ahead and store the info I'm going to get on a Word Document and have it ready to cut/paste into the discussion.

By the way, there are two "Traps" built into the previous 4 questions - 1. The Powder the Factory used. - I know this is an Unknown. Without knowing what Powder the Factory actually used in the Cartridge seems(to me) to negate all the resulting data. For any Cartridge, there may be 2-20 suitable Canister Grade Powders the Factorys could use that "we" have access to. But, the Factories typically "blend" Non-Canister Grade Powders that "we" do not have access to, and make a Lot of Powder specifically for a run of Cartridges. This puts an Unknown Powder into the situation that I do not understand how Mr. Shoemaker will be able to address.

The next Trap - 2. The Pressure the chronograph is indicated. - Is totally impossible to dervive Pressure from a chronograph. It has no way at all of determining Pressure. Nor can it account for Lot-to-Lot variations in all the components, nor the variations in the Chamber/Bore dimensions. All it does is let a person know what Velocity it detected.

That is totally different from "guessing, speculating or using a mathmatical model(Internal Ballistics Program)".

So, I'm really interested in Mr. Shoemakers thoughts as well as yours on how well this Method is thought out and just how he believes it works. I can't say it doesn't work, cause I don't as yet understand what Mr. Shoemaker believes is going on.

I would also recommend we start a separate thread so as not to hose this one up any more. Just let me know the Cartridge and I'll PM you now so you can let me know when you are ready with the article. Hopefully asdf will join the new thread and provide us with some amusement as he cheers for the chronograph.

quote:

Originally posted by asdf:
Actually, H.C., the correlation between pressure and velocity is quite good. The old Powley Computer gives a decent estimate of the fps a cartridge might obtain at a given peak pressure. That may be what ALF referred to.

Hey asdf, Glad to see you mention the word "estimate". That is very significant because it indicates the resulting data is not as exact as some folks lead people to believe.

Glad to see you "believe" you can understand ALF. I tried to discuss Bullets with ALF a few weeks ago and found he is a better at Politics(saying stuff that is non-relevant to the actual discussion) than at being able to communicate a useful response. Total waste of time when I tried to talk with him.

quote:

The published data I've been able to find does, though, suggest that in general, you can't work the problem the other way (fps to pressure). Component substitutions (esp. primers) seem to have an effect on pressure and velocity which doesn't follow the basic trends dictated by mass ratio and pressure and expansion ratio.

Yes, lots of "Variables" to make the data questionable. And you didn't even include the Variables in the Chamber/Bore dimensions.

.

Hey ALF, Once again you are totally wrong. I'm certainly not sniping at you, simply stating facts - in the open. When I engaged you to explain your thoughts in the other post concerning Bullets, you went into a song and dance routine that had ZERO to do with the question - at least three separate times.

It was quite obvious to me then you had gotten in WAY over your head, because you simply were unable to answer a simple question.

Also not taking any "back shots" at you, the post is right in the OPEN for anyone to read. Apparently your desire to "skew the visible facts" is as good as your song and dance ability.

It is also apparent your knowledge of this discussion concerning what chronographs are actually good for is lacking. Creating posts that mislead the Beginners is something I just don't allow to go unchallenged once I spot them.

But, I don't see any real need for me to "attempt" to discuss anything with you in the future. I realize it is nothing but a total waste of my time.

Best of luck with your "song and dance" routine.