Hey fellers,

Back in the "Accubond performance" post we discussed the velocity numbers I was claiming to get from a 140 gr. Accubond outta my 7-STW. (3605 fps). Well.......I ran another batch of the same load across the chrono today. Only shot a 5-shot string. Average velocity for the string was 3567 fps. I suppose the 1.1% difference could have been from temperature, humidity or whatnot. But, I'm guessing the numbers are valid. Still don't know why I'm able to get these speeds without excessive pressure. But it's happening.

Sorry it took me so long to run this load again.

Strut, Velocity is a Pressure Sign! You may not be seeing other pressure signs but if you are running 140gr Bullets out of a 7 STW at 3600fps you are running WAY over normal pressures.
There is not such thing as "magic" barrels that somehow allow you to run bullets at 200fps faster than anyone elses. Don't kid yourself. You are running way over max pressures with that load.........................DJ

In the past, I saw, on reloading manuals, several photos of spent cases, shot as test at 10-15% over the max pressure, with very little or no visible evidence; it seems to happen with very tight chambers.

I agree there is no free lunch... Too much vel=too much pressure... I would back down, this is the advantage of a Croney

O.K. I am loading one grain of IMR-7828 under what Layne Simpson calls max. Did he publish some "out-in-left-field" data at some point? Maybe there's something about these recipes I should know but don't. The velocity numbers I am getting are on par with the data I used.

When Layne Simpson finally got around to pressure testing some of his original loads they found it in the 70-80k psi range, well over normal max. You may have been working with some of his original data. It would be a very good idea to check some of the more recent manuals. If I have time, I'll check the more recent manuals max load of IMR-7828 and relay them to you.
I've seen several times the phenomenon of a well made tight chambered rifle not showing traditional pressure signs at way above normal pressures. A gun with less than perfect lug contact is going to show sticky bolt lift a lot quicker than a rifle whose lugs are perfectly lapped in, etc. You might have a nice tight rifle...................DJ

Strut, Heres some data from the most recent reloading manuals. The following is the maximum listed charge for IMR-7828 and 140gr bullets:

Nosler 5th....77.5 @3355fps
Barnes #3.....80.0 @3473fps
Hornady 6th...75.5 @3300fps
Swift #1......76.0 @3233fps

Quite a bit of variation. I beleive that 7mm barrels tend to vary in bore diameter more than some other caliber. I have a 7mm Dakota that reaches the normal Maximum velocities with more than 4grains less than any max load I've found listed. I can only conclude that I have one with a tighter bore than the pressure test rifles/barrels. I would think that the variation in the manual data is due to the same cause but that's just a hypothesis.
If I were loading for 7 STW I'd use the lower of the data points here, work up slowly and quit when I got near 3400 with good accuracy................DJ

DJ........

Thanks for the info/data.

I am loading 82.0 gr. IMR-7828 for the loads in question. The rifle is a Model 70 Clasic Stainless. Bolt lift is like butter. All signs point to acceptable levels of pressure except for the chrony readings. Don't suppose it'd hurt me any to ease up a few grains.

quote:

Originally posted by djpaintles:
Strut, Velocity is a Pressure Sign! You may not be seeing other pressure signs but if you are running 140gr Bullets out of a 7 STW at 3600fps you are running WAY over normal pressures.
DJ

Well, velocity is a pressure sign but it's not a Gauge. I fully agree with this in the sense that it's very likely over SAAMI max for this round.

That said, if you're able to get three reloads of the brass with this load and the primer pockets have not loosened, then I agree that this load is OK for that lot of brass with that load in that rifle.

But just ask yourself; is that little extra velocity really doing anything for you?

quote:

Originally posted by wildboar:
In the past, I saw, on reloading manuals, several photos of spent cases, shot as test at 10-15% over the max pressure, with very little or no visible evidence; it seems to happen with very tight chambers.

And with tight chambers you won't see a decrease in brass life.....

Gee, mabey why some customers of custom barrels specifically ask for a "tight" chamber from their gunsmith....

The only really relevant "pressure sign" is brass life.

If you don't lose primer pocket tension with
five firings it's a "who cares" type of issue...

AllanD

I've just made some virtual tests with QuickLOAD 3.2:

7 mm STW + 140 gr. Nosler Accubond + 82 gr of 7828 = 72000 psi of pressure.

Your load seems to be about 5200 psi over the max.

quote:

Originally posted by Allan DeGroot:

The only really relevant "pressure sign" is brass life.

If you don't lose primer pocket tension with
five firings it's a "who cares" type of issue...

AllanD

This is very dangerous thinking. Continuous shooting of overpressure rounds can eventually weaken a rifle to the point of failure. A load that seems to work fine for years and then boom a rifle blows up. I've seen it happen, fortunatey noone was hurt.
There's a good reason SAAMI limits pressures to 65,000 or so. Why risk overstressing and maybe even blowing up a nice rifle for a couple hundred fps......................DJ

quote:

Originally posted by Strut10:
O.K. I am loading one grain of IMR-7828 under what Layne Simpson calls max. Did he publish some "out-in-left-field" data at some point? Maybe there's something about these recipes I should know but don't. The velocity numbers I am getting are on par with the data I used.

What is that Layne Simpson load? Is it a secret?

I had a Pact Chrono that read low even with 5' calibrated screen spacings.