Home Forums Hunting & Shooting Ask The Gunwriters I'd Like Some Proof....

How about adding a second strain gage to the system, to cross check against one another, like the "Proof Channel" of a 35P Chronograph? Seems that it would help rule out instrument errors and/or confirm real events?

Jeff

5sdad...

LOL!... Bet you do too follow it!

Condensed version:

MD said that the 7 Mag doesn't have "pressure excursions", it just has less consistent peak pressures than some other rounds.

I chimed in with a minor side note, that MD was right, and posted what pressure excursions look like.

Herr Broemmel thought that my post looked like equipment problems, not a real effect.

Ken said he agreed with Broemmel.

I said, Naaaah... three different guys saw the same thing using different equipment. There is also a good physical reason why it might happen. Besides, it blows up guns. Maybe the effect is so fast your equipment can't see it?

Ken says his equipment is fast enough. It follows that if this effect is really there, we should be able to see it on his equipment (but maybe not on mine).

Now I think Ken is going to try to reproduce the experiment that was done by one of the guys I cited. It sounds like a lot of fun, but I'm worried about his health.

I'm also thinking Broemmel and I are cousins or something... very similar last names. Maybe a common ancestor 200 years back?

I tend to agree because I can reliably reproduce a 50% increase in pressure in a handgun with absolutely no change in load, just change powder position in a 60% density load.

On the other hand, I'm aware of similar problems in the 105mm tank gun with a full charge.

That might explain why I want a full-case load at moderate (less than factory) pressure, but then I don't understand it all.

KenO

That's a possibility.

Don't worry about Ken's health.

I'm not going to start shooting until someone can assure me that the ammo is practically guaranteed to develop the pressure excursions. When I do fire suspect ammo, it will be from a universal receiver behind the wall and triggered with a long lanyard.

Jeff can be assured that my test barrel will have multiple pressure sensors attached. Pressure testing is no challenge until you try to make two or more systems agree on each shot.

KenO

Ken This is a scary thought, can you expand on this? I offen load starting level/very light loads in my pistols as plinking ammo. 4gr or so of powder in a 45 cal case isn`t much fill.
I`ve heard of velocity changes from powder position but, never thought it also varied pressure as much as you state.

Joe,
I can't remember the exact load because I haven't loaded it in several years. We still have a couple of boxes in the drawer I use for a demo. We'll let two guys each select five rounds from the same box. We then designate one guy the hot-rodder and the other guy the plooper. I'll fire the loads in a 357 Mag Contender equipped with a strain gage. During a little BS and clumsy gun handling, I'll manage to fire the plooper's load with powder positioned forward. They will typically average 1100 fps and 18K psi. Continuing with the same gun and test, I'll fire the hot-rodder's rounds with the powder deliberately positioned to the rear. They will typically average 1400 fps and 27K psi. We are continually amazed [entertained] at the alibi's and explanations offered by the observers when they see the differences in pressures and velocities without noticing my clumsy gun handling.

As I recall, the load is 6.5 grains Unique behind a 125 grain bullet in a 38 Special case. It meets 38 Special pressure spec if fired with powder forward, and exceeds +P specs when fired powder back.

It does give you religion.

KenO

You just gave me something to think about. I don't remember the charges, but I used to burn a bunch of Unique in mid-speed 158 grain cast bullet loads in 38 Special and 357 Magnum.

Mark: That 7 mag that likes the RL25 also does just fine with 7828 for just about the same velocity. The charge is 68-RL25-160 Partition. Some data shows 70 gr with 160 gr bullets, but after seeing the chronograph click off about 3060, I decided "good enough" and let it go at that...

Barrel is a Douglas,24". My Kreigers have taken heavier charges for the same velocity. Just another example as we've discussed, that every barrel is different.I have never had a "problem" with the cartridge, just watch what I'm doing one rifle to another.

But for sure, I have seen this characteristic manifest itself with other cartridges as well.I've noticed that my charges for the 264 Win Mag have run lighter than some I've seen posted here for about the same velocity. Maybe I have a "fast" chronograph?

Thread has been very interesting to follow.Thanks to all for the input. After careful review, I am not selling my 7 rem mags!

That would be impossible for me also. I've had (6), all but one had stellar accuracy for a factory, non-beded rifle. My personal best 100 yd and 300 yard (5) shot groups were with a Remington 700 and M70 in 7 mag, Hornady 162 SPBT. My rifles were built in 63,67... to present.

Now, my safe currently also includes two 308's, two 06's, two 270's, a 223,243,25-06,300 RUM and a 338 WM. Just an example of "one" fluke? I only use level one reloading techniques. Ignorance has been bliss.

My favorite load was 6.6 grains of Unique with a 150 grain cast bullet.