Does the compression change velocity in a given load ? My mind starts to wonder during this time year . The temp got down to 33 below zero the other night so I got time to wonder on the little things.

Perhaps the question should been worded some what different. Will compression levels change velocity in a given load with compression being the only change made? For instance a change from .150 to .200 compression..

I have read that to a point, more compression = more velocity but have never measured it myself. It is Cold here too so ponder is all I want to do. That is why I am writing this instead of in basement casting bullets for next season.

As near as I can tell compression by it's self only serves to make for more uniform velocity. But adding more powder and compressing to the same depth will add velocity.

Many times more velocity is not the cure-all to getting a rifle to group well. Different bullet shapes and lengths and lubricating methods, along with a PROPER chg, the said chg. may be less than what the shooter wishes to try. A small amount of compression can work well with one bullet, where a moderate to hvy amount will group much better with a different one.
The joys of finding what works well in your rifle!
Jim

I shoot year round and during the winter shooting the old Goex powder that needed some heavy compression I saw a lot of unburned powder on top of the snow that made me wonder what the gain in velocity was per compression. The velocity increased with every .100" of compression but at a point as the compression increased the velocity increase started to drop but the bore had more shine, but the velocity never stopped increasing.
This took me to another thought what is the increase of unburned powder from light compression to heavy compression.
I went to a carpet installer and picked up a 12' cardboard tube the carpet roll is on and I split that tube and taped it back together and taped several layers of cloth over the far end and shot into that tube to collect the unburned powder. I was amazed just how much unburned powder in chunks I found. It was mot bad powder because when I was done weighing it I set a match to it and it flashed up.
This also made me think that the unburned compressed powder chunk up front is what whipped the fouling out and made it look like a clean burn.
If you look at the picture below, that powder is compressed .300" and it is solid up front.

Kurt


I shoot during cold weather also and have seen lots of unburnt powder in snow but a switch in primers solved this problem and accuracy returned.

(12-18-2016, 09:40 PM)Kurt Wrote: I shoot year round and during the winter shooting the old Goex powder that needed some heavy compression I saw a lot of unburned powder on top of the snow that made me wonder what the gain in velocity was per compression. The velocity increased with every .100" of compression but at a point as the compression increased the velocity increase started to drop but the bore had more shine, but the velocity never stopped increasing.
This took me to another thought what is the increase of unburned powder from light compression to heavy compression.
I went to a carpet installer and picked up a 12' cardboard tube the carpet roll is on and I split that tube and taped it back together and taped several layers of cloth over the far end and shot into that tube to collect the unburned powder. I was amazed just how much unburned powder in chunks I found. It was mot bad powder because when I was done weighing it I set a match to it and it flashed up.
This also made me think that the unburned compressed powder chunk up front is what whipped the fouling out and made it look like a clean burn.
If you look at the picture below, that powder is compressed .300" and it is solid up front.

I have also noticed the colder the weather the more unburnt powder seen.

Allot has to do with powder granulation too.
Also why I use a paper coffee filter 'wad' over the primer, at the bottom of the case.
Gary

Ok, I have a question, I compress my powder column .400 if it is compressed into a solid mass why does granulation size have any affect? I know it gets compressed more at the top than the bottom, but it is pretty solid all the way down. Just wondering.
Trapper