Compressing powder

[rammac]

Google- https://forum.snipershide.com/threads/7-62-vs-308-brass.6822996/

True or False?

Like most things in life - it depends.

Not all military brass has less volume,

 

[ChitownCopper]

They are really long longer than the 155 lapua secnars

 

[Jackal2016]

41.3 grs is Hornady maximum.View attachment 1135784

Hornady's generic Reloading Data not a good thing.

Hornady's data is also based on using Hornady/Frontier brass (for many of their cartridge data) too. So therefore, I would be cautious if using a different brand of brass especially if it had less case volume.

 

[riflewoman]

2.800 hornady match 178

Ok... Hornady lists 41.3 or so as MAXIMUM for these bullets. This was probably in Hornady brass.

As told by others, military cases are generally thicker than commercial. LC cases average near 180 grains where commercial cases average around 170 grains. Is this significant? Well, when I shot Highpower using an M1A rifle I used a lot of military cases. I also used commercial, but I never mixed the cases. BUT my loads for each WERE DIFFERENT. For military cases my load was 41.5 grains IMR4895 whereas in CMMERCIAL cases it was 42.5 grains. Same 168 grain match bullet, same OAL, same primer. Velocities were within 50 fps. Pressures were nearly identical.

in your cases, you are probably near maximum. If you want to load hotter, you’ll need to load in thinner cases.

 

[VaniB]

As a general rule, don't compressed loads normally also work better with hotter primers too? Reloading books list one primer which can't possibly perform great across the spectrum of light loads to heavy compressed loads.

 

[Webster]

I'm using imr 4064 in 308 mil brass. The powder is already compressing at 40.6 . I want to work up to 42.6. Is this going to be a problem compressing powder like this.

https://www.accurateshooter.com/cartridge-guides/308win/

 

[DirtySteve]

I don't like compressed charges. After reading some of Litz's writings on the subject I will share what he stated. Compressed charges will give higher velocity, but higher extreme spreads. But loads not compressed yield better accuracy (a long with lower SD's). If you're after speed, get a different cartridge. If you can not get the job done with a 175 at 2650 fps you really need to consider if your endeavor is worth while.

 

[Straightshooter1]

2.800 hornady match 178

Running some numbers through QuickLoad the 40.6 gr of IMR 4064 shows the case is filled to 103.7% of capacity (assuming a smaller case capacity at 55.0 gr of H2O). Then, if you put 42.6 grs in, QL shows the case filled to 108% of capacity and pressure goes way up to around 64,000 psi (compared to a SAAMI max listed at 62,000 psi).

Assuming a more normal case with a capacity of 55.5 gr of H2O, the 42.6 grs of 4064, QL shows case to be filled at 107.6% of capacity and pressure still over SAAMI max. And with 40.6 grs of 4064 the case is filled to 102.5% of capacity and well below SAAMI max pressure (about 54,000 psi). . . which shouldn't be a problem, but testing is essential.

So, at 108% of capacity, it doesn't surprise me you'd hear some crunching as it's definitely being compressed at that COAL.

PS: I've use 43.8 grs of 4064 in Lapua brass having 55.9 grs of H2O capacity with 175 SMK's set at 2.869 COAL, but 43.9 grs did just OK. In both cases I had significant pressure signs and these loads just really didn't do well for me.