Compressed, (or not), loads

[Leo_B]

I have one of those minds that always thinks about many things concurrently. So while I'm focused on what is the best choice for a light recoil rifle to add I'm looking at various things. I really like the Hodgdon Reloading Data Center online. Based on my thimbleful of knowledge, I think of H4895 as a main player in powder choices. I'm looking at it in .223 loadings since .223 has a small lead in my rifle thoughts.

So in going through all the bullets it covers, from 35gr to 90gr, some are compressed and some are not. I find it interesting, based on my current ignorance (lack of information, not stupidity) that powder charges as low as 22.4gr can be a compressed load while at the same time as high as 26.1gr can be a non-compressed load. I'm sure it's how far into the case the bullet base extends when seated, but just interesting it can be that great a spread of the two.

But when there's a bucketful of knowledge available and you currently have a thimbleful at your disposal this is what you find. Ain't it great fun!

 

[NZ_Fclass]

You are on the right track - the overall length of the round is the issue. Hodgdon's does show the OAL for their loads - often in the case of the 223, to fit an AR magazine. My 2 FTR/300m 223's have longer freebore to accommodate more length and therefore more capacity., as I only use 75g+ projectiles
The brass capacity also varies - again Hodgdon's will show the brass and projectile for those loads.

If you are using a bolt gun, loads can be increased = carefully - and yes, H4895 is one of the great powders for the 223, particularly with heavier projectiles.

 

[243winxb]

Changing shape of some powders can change burn rate.
Read post 11

 

[ronemus]

Compressed loads also change the burn rate by fracturing the kernels. I've also found it increases ES/SD because it's next to impossible to do so reproducibly.

 

[ELR LVR]

Compressed loads also change the burn rate by fracturing the kernels. I've also found it increases ES/SD because it's next to impossible to do so reproducibly.

I would add, within compressed loads - I feel more comfortable using slower powders
since slow powders do not react as much as faster powders do when kernels fracture due to compressing

 

[jds holler]

I've noticed that quite a few of the "most accurate" loads listed in various data are also marked as compressed. jd

 

[NZ_Fclass]

I've noticed that quite a few of the "most accurate" loads listed in various data are also marked as compressed. jd

Arguably..the most accurate should be 100% loads...but life isn't like that, I guess. But it's a matter of reaching an acceptable accuracy node, with say 105%.

I suggest that the manuals - particularly Nosler - show "most accurate load tested", which could be very different from the most accurate load possible.

 

[Tommie]

All other variables being equal I prefer 100% or slightly compressed. It’s not the primary goal by any means but if a pet load ends up being compressed it’s icing on the cake.

 

[jds holler]

All other variables being equal I prefer 100% or slightly compressed. It’s not the primary goal by any means but if a pet load ends up being compressed it’s icing on the cake.

I pretty much agree. I finally got a chronograph (thirty years too late), and it gives another piece of the puzzle to use when working up. I've done pretty well over the years, and had no disasters, but this new tool gives me a lot of peace of mind if I have to go into the higher end to hit the sweet spot. And for me, the sweet spot usually happens about when the powder reaches the neck, jd

 

[243winxb]

Problem powders, that give poor results, because of low start pressure, may benefit from a lightly compressed charge, and/or a magnum primer.

A crimp has allowed some powders to work correctly, by delaying bullet movement. Higher start pressure.

Note that crimps are never good for Benchrest accuracy. (Bottle neck cartridges.)

https://apps.dtic.mil/sti/citations/ADA341390
Open PDF link on this page.