when does a compressed load become dangerous?

[willymc]

I'm working up loads for my 300 AAC blackout. I'm using 125gr. Nosler ballistic tip over Lil Gun. Their data says that 17gr. has a load density of 102% and 18gr. is 108%. That is with brass that is trimmed to, I would assume, 1.363-1.368. They say their 18gr. load is the most accurate. I bought some 300 blackout brass and it turned out to be trimmed to an average length of 1.355. Loading 17gr. Lil Gun into a 1.355 case should give me a load density of more that 102%. As long as I start low and work up slow, checking for over pressure signs as I go, I should be ok, right?

 

[rcmodel]

Right.

Case length has no bearing at all on OAL or internal case volume.
You just don't have as much case neck outside the bullet.

If the load data says a compressed Max load is safe, it is.
As long as you work up the load in steps to get there.

rc

 

[willymc]

Thanks rc.

 

[CLP]

It won't matter as much to you since you're using actual 300BLK cases, but there's less volume in the 300BLK cases formed from 5.56 (compared to brass originally made as 300BLK), though that shouldn't surprise anyone. I anticipated that and started my load accordingly, but my velocities were still about 5% higher consistently as I worked up my load. I'm pretty sure the CCI #41 primers I was using were the culprit. I've read there's more brisance with them vs. other standard SR primers. However, I didn't have any pressure issues and it's a great load for the AR build I use it in (converted LC 5.56 brass, CCI 41, 18.8gr of AA 5744, and 125gr SMK). Not the first choice of powder I wanted to try, but there's not a wide selection of offerings if you haven't noticed.

 

[bluetopper]

When does a compressed load become dangerous? It won't if you follow data correctly.

 

[gamestalker]

I'll add my .02, as this is an area in which I often work.

So when does a compressed charge present a concern of over pressure?

If a compressed charge is published as such, there is no concern, unless;

The data doesn't reflect, or isn't designated compressed charge with said cartridge or powder.

The reloader fails to perform a proper load work up.

Other wise, just perform your load work up as you would with any other powder.

GS

 

[brickeyee]

Around that much.

Or maybe THAT much.

Or if you load a rifle case with many pistol powders, that much.

There is no answer.

 

[larry syverson]

Brisance? C'mon... really?

 

[rcmodel]

Hey!
Cut some slack!

How many chances does anyone get to use the word Brisance in a sentence?
In a lifetime!

I would use it more often myself if I could remember how to spell it!

rc

 

[Andrew Leigh]

Yeah, but when you get the one chance to use the word then at least spell it correctly .... brisciance. .

I am all for the correct terminology when discussing technical matters, it clarifies exactly what we are referring to and can leave no doubt.

 

[Ridgerunner665]

When you use the wrong (faster) powder...

Compression doesn't necessarily equal over pressure...

For example....you cannot cram enough Retumbo powder in a 280 Remington or Ackley to even reach normal operating pressures....

As has been said...follow the load data, from a reputable source...and you'll be fine.

 

[witchhunter]

Start low and work up, looking for pressure signs. Especially when using brass made from something else. There are several variances here to include chamber size, throat length, bullet construction, bore size, etc. If you always start low and work up, you will know what is max for that rifle and you get to shoot more too.

 

[larry syverson]

OK, use it if you spell it correctly.. Though someone should really explain what it means. Don't know if anyone has seen the new Hodgdon reloading webpage. Pretty nice! Notice how many "C" loads they specify i.e. compressed. They are pretty common.

 

[Captcurt]

Many loads in the manuals show compressed loads, even 106% loads. A slow powder for caliber usually isn't a problem. That is unless someone doesn't seat the bullet deep enough. A safe load that is seated off the lands can develop a lot more pressure when seated out farther where it is jammed into the lands. This is another reason to double check overall cartridge length any time you change bullet brands or weights.

 

[Sunray]

There is no compressed load using Lil'gun and a 125 on Hodgdon's site. Nosler doesn't show compressed Lil'gun 125 grain loads either.
Your Trim-to is too short too. Should be 1.363". However, a compressed load is nothing to worry about.

 

[rogn]

The correct combination of powder case and bullet weight is always safe. "Correct" as spec'ed by one of the powder or bullet companies. I have run into one problem with a wildcat type cartridge, 22BR Norma. Ive been using a discontinued powder and 80 gr bullets. The powder is a very slow one for the case and getting enough in the case requires a lng drop tube. Occasionally the powder may not settle just right and the compression makes the case very mary to chamber, the case walls are slightly bulged by the compression. Well over 100% density, unsafe ,, not really.