How much powder over book max is unsafe?

[IDHUNTER]

I'm going to be loading 160gr Accubonds with H1000 in my 7mm Rem Mag. The Hodgdon data shows 66 gr as being the max charge but I see many people are loading 70+ grains with the same setup. I dont want to short myself on speed so I'm thinking of loading a few rounds at 65gr, 66g, 67g, and so on until I reach pressure signs but i wanted to know if 1 grain increments are too big? Should be going in 1/2 grain increments? I guess what I'm asking is how much powder does it take to go from no pressure to an unsafe or catastrophic event?

 

[fisherman983]

That all depends on your brass, your chamber and how long your bullets are seated. I would do 1/2 gr increments.
Also, reloading books are basic info at best. Only use them for starting points and some very basic measurements

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[Corvus Corax]

Dude I think you can go from okay to a bomb in next to nothing. Each chamber is going to be a little different. Some tight match chambers seem to not show traditional signs until they are on the ragged edge. As mentioned above there are a lot of variables. I had a load just recently that I developed in December/January that was blowing primers in the August heat yesterday. I get wanting to wring out potential from your cartridge, but as long as you are getting the appropriate velocity for bullet performance at the distance you expect to shoot then why risk it? The load I was using was from Vihtavouri and it was almost 6 grains more than the Nosler book. I wasn’t even at the max that Vihtavouri published. It was good, until it wasn’t.

 

[rayporter]

this may sound crude, but if you have to ask, dont go over book.

 

[JGRaider]

Use a chrono and you're good to go. Can't have excessive speed without excessive pressure. The chrono will tell you when to stop.

 

[Wrench]

H1000 in a 100gr case....10 grains isn't unheard of. 9mm with red dot.....a couple tenths can get wild.

 

[Bomberodevil]

I spend some time listening to the Hornady podcasts with their staff, including ballistic and mechanical engineers. They have covered this topic many times, and their position is to use extreme caution when loading over max book values. They strenuously disagree that the max values are set by lawyers or safety folks, but they are set by engineers and max pressures.

I used to try to develop hot loads with most of my cartridges, but I’d usually lose some accuracy. Before laser rangefinders, tactical turret scopes and ballistic calculators, maximizing speed would help with MPBR in flattening out the trajectory. But now, I can just compensate a higher arc and more drop with turns on the turret.

Anymore, I rarely exceed book and I never exceed signs of pressure. I’ll usually be around 0.5-1.0 grains below pressure signs or max book values, and I’ll find good accuracy nodes. Like the Hornady staff says, you’ll get away with exceeding maximum values right up to the point when you don’t, and it can be catastrophic.

 

[Bulldog&Moose]

I've only loaded over book max in one round. That's the 458 SOCOM, and only by 1.0 gr. I've had a 30-06 and a 300blk show serious pressure signs at or below book max.

Lots of things to consider when reloading! I've recently been convinced how important environmental conditions are.

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[Bubbadoyle]

this may sound crude, but if you have to ask, dont go over book.

This was my first thought when reading the post.


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[aachey]

If you have to ask, then just please dont. Each bullet/manufacturer has a different max. Some close, some not so much. If the manufacturer says the book max is 66, that could be over max already in your gun. Start low, work your way up. If we’re loading to pressure signs, 1 grain jumps are definitely a lot. .5 grain jumps are safer. .2/.3 jumps are even better. A couple dollars shooting a few more rounds or blown up rifle/your safety? To each their own, though.

 

[rayporter]

conditions definitely are a part of the equation.

a wildcat i had for prairie dogs shot fine in Arkansas. in Texas it blew up bullets and blanked primers. back in Arkansas it shot fine.

 

[Vern400]

The brass case is basically a container, and a gasket. It flows plastically every time you pressurize it. You can measure the growth. You can feel the primers seating with no force.

But the steel parts- there's a funny thing about steel. It has a fatigue life, and it's not infinite. Trouble is hardened steel doesn't flow like brass. You can't see fatigue.

I have a load with RL15 that shoots better and better as powder load is increased. I settled on a hot load, tested them, and made up a nice batch.
On a hot summer day a buddy came over and we set up 40 milk jugs from 100 to 400 yd. We had a contest to see who could shoot more of them before they were all gone. My rifle got really hot. Way too hot to touch. Then I left a live round in the chamber for a minute or two, and then checked my zero stop on paper target. The blast smacked me in the face, and Hot gas shot out the safety vent of the receiver. The bolt would not open by hand. Even banging it with my hand.

Fortunately, I wasn't hurt and after spending a bunch of money my rifle is okay too.

It's all fun and games until it's not a game, and it ain't fun. That was book maximum load, and a temperature sensitive powder in a Model 700.

 

[The_Whitetail_Kid]

I start about halfway through book max and work up til I see ejector marks. That’s usually my first pressure sign. Regardless of book max, that’s where you stop.

 

[Chris B]

I start about halfway through book max and work up til I see ejector marks. That’s usually my first pressure sign. Regardless of book max, that’s where you stop.

If your see ejector marks your already past YOUR max .
Without pressure measuring equipment you don't have any idea where you are . Book maximums are there for a reason. You want more speed get a bigger cased cartridge.

 

[SDHNTR]

this may sound crude, but if you have to ask, dont go over book.

Don’t even go 2/3 of the way to max!

 

[The_Whitetail_Kid]

If your see ejector marks your already past YOUR max .
Without pressure measuring equipment you don't have any idea where you are . Book maximums are there for a reason. You want more speed get a bigger cased cartridge.

In my experience ejector marks come before heavy bolt. At least on my rifles.

 

[Chris B]

In my experience ejector marks come before heavy bolt. At least on my rifles.

Ejector marks means brass is flowing into the ejector recess in the bolt face . If brass is flowing pressure is way high for the case .If you have a case or three that are softer you have a blown primer and or a ruptured case .

 

[jimh406]

Take a look at how much more speed you'll get with a bit more powder, and then compare with ballistic charts.

I think you'll find a bit of a gain of speed isn't worth it. It's more important to find a load that shoots very well. Also, not all powders produce the same amount of speed for more pressure.

 

[TaperPin]

I agree with everything fisherman983 said. I’d also add different barrels just produce more or less pressure.

Published data has to be conservative to account for variations in all the variables, so I don’t see a problem going over published max as long as you’re good at determining that max.

If your reloading practices produce 6 loads before case head thinning or primers loosening then I don’t see a problem shooting that same load for 3 reloads, then tossing cases.

Are you using a feeler inside the case to check for thinning ahead of the case head? Are you tracking case head expansion with a .0001” micrometer? Are you comparing primer flatness? Tracking flow into ejector plunger? Are you keeping track of temperatures of tests? Only using these max loads with the same lot of powder? Same lot of brass? Same lot of bullets? Regularly track velocities?

For a decade I shot a .338 quite a bit with fat sloppy chamber and tight bore - factory loads from any source produced pressures beyond what common sense reloading would produce. I pushed reloads as much as possible and occasionally had cases that didn‘t last as long as I had hoped, but there was no drama - pressures never affected any hunting trip or even trip to the range.

 

[Axlrod]

Take a look at how much more speed you'll get with a bit more powder, and then compare with ballistic charts.

I think you'll find a bit of a gain of speed isn't worth it. It's more important to find a load that shoots very well. Also, not all powders produce the same amount of speed for more pressure.

This ^^^^^^
Most likely your best shooting load will be somewhere before "over max" 100 fps isn't useful if the bullets aren't landing close to each other.