Home Forums Hunting & Shooting Hunter's Campfire Reloading... Reading pressure signs

All the experts say, check your pressure with a chronograph. Flattened primers, don’t tell the story.

But I would say, when a Federal brass leaves a Hornady imprint in your bolt face, you may want to test those loads with a string and stand behind a wall…

LMAO, saw that but you beat me to it….

Mule Deer wrote an article i Handloader a few years ago on pressure and various ways we laymen interpret it. His studies have caused me to be more cautious about loading top end loads in my rifles ever since. I don’t own a chronograph and if I did it would be a huge aggravation setting it up to use without an actual bench to shoot off of for me. If I were ever to get a case extracted looking anything like what’s in those pics I’d be pulling bullets as soon as I got back to my loading bench.

I'd save that load and feel confident shooting it in 90° weather...

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Multiple occurrences? If at first you don't succeed, try, try again?

A few grains of Bullseye left over in a powder trickler shaft will radically alter the pressure curve of IMR 4350. Like a "hammer the bolt open" pressure spike, for instance! The primer fell out of the pocket when we finally got the bolt open! Neither the old Mauser action nor the new stainless steel barrel sustained any damage, but I had set the headspace very close on assembly. Won't make that mistake again!

A few grains of bullseye wouldn't alter it, it would render it no longer the pressure curve of IMR 4350.

"You might be a redneck is you've ever tied a string to your trigger and......"

Didn't Steelhead do that with a Savage then use it as a tomato stake?

BTDT, Jap 7.7 between straw bales fired with a string

I've never understood how you're supposed to check pressure with a chronograph.

To use an exaggerated example, a typical velocity for a 150 grain bullet in the .308 is 2650 fps. But if you're getting 2650 fps with a 150 in the .308 using Bullseye powder, pressure is going to be through the roof. So are pieces of the rifle.

Chronographs measure velocity. They don't tell you anything about pressure.

Correct, they do not measure pressure, but they can help indicate pressure. Just as the OP's photos did not measure pressure, but they did indeed indicate pressure.

Just lap the barrel a bit to open it up…

Prepare to be skewered. I see your point (your Bullseye analogy is unreasonable), but velocity IS a great indicator for perssure.

When a rifle cartridge goes off, the primer is pushed backward, due to powder gas pushing through the flash-hole, so it would seem to make sense that a really flat primer indicates high pressure. Not necessarily. A really flat primer can also be caused by slightly excessive headspace.

When the firing pin hits the primer, it drives the case forward. If there’s a little slop between case and chamber, the expanding powder gas first pushes the primer backward in the primer pocket. If the pressure is low enough, as with the .30-30 Winchester, the primers will remain slightly backed out of the fired brass. This is common in ancient and well-worn .30-30 lever actions.
If the pressure is higher, however, as with the .30-06, the rear of the primer itself expands a little as it backs out, since it’s no longer supported by the primer pocket. In another micro-second the case itself is thrust back over the slightly expanded primer.

At the same time, the case stretches a little bit, so the handloader also finds a shiny ring a half-inch in front of the case head. Our innocent handloader now sees what he thinks are two signs of high pressure, when in reality the only problem is oversizing the case.

https://www.handloadermagazine.com/mistakes-and-misconceptions

Of course the OP's photos are most certainly not a Headspace issue.

Ever seen any data giving the 308 and a 150 grain bullet 2650 fps and Bullseye being the shown powder?

Use the chronograph in conjunction with the load manuals given data.

Bullet type has to be accounted for when loading for rifles. One example I ran into was with the 6mm 100 grain Hornady round nose. The 100 grain 6mm round nose was almost like a wadcutter with a round nose. That's to say, almost the entire length of the bullet was bearing surface.

I loaded up a batch with 40 grains of H4350 in the .243. 40 grains of H4350 with a 100 grain bullet isn't a maximum load in the .243. But using those long bearing surface 100 grain RN bullets with 40 grains of H4350 would hammer the primers flat and expand the primer pockets so much that the cases couldn't be used again.

Hornady stopped producing those bullets shortly after I tried them. I suspect that others found out what I did,...that so much of the bullet was in contact with the rifling that 100 grain .243 load data was too hot for them.

No. But the principal remains. All else being equal, faster powders will generate more pressure at a given velocity.

Velocity can't be used to gauge pressure.