Pressure

Nighthawk

Well-Known Member
Joined
Mar 2, 2002
Messages
429
Location
Central Minnesota
It is my understanding that when the bullet is seated farther in the case more pressure and velocity is produced, could someone clarify this please? My mag legnth limits the COL so I was wondering what would exactly happen if the bullet was seated farther in.
Thank You
 

Ian M

Well-Known Member
Joined
May 3, 2001
Messages
2,410
Location
Sask. Canada
Nighthawk,
You have brought up one of the dilemas that we face when we are making hunting ammo. I have always understood that setting the bullet into the lands will spike pressures and probably increase velocity, have never heard that seating deep will do that also. I would expect that seating deeper will give an almost Weatherby-like free-bore where the bullet has a little travel before being engraved in the rifling. There are guys who have much more understanding of internal ballistics and I would leave this discussion to them.
You also must remember that there seems to be some allowable lattitude in just how long each individual bullet can be. They just don't seem to be as uniform as we would expect so that makes uniform overall length a slightly tricky objective.
What you do bring up is the dilema of having a relatively short magazine well relative to how long you could or would like to seat your bullets. We can use the nifty Stoney Point OAL guages or whatever to get the bullets out to just "kiss the lands" but nine times out of ten that will result in the cartridge not fitting into the magazine. If we want to shoot single shots that is not a problem, but if we feel the need for fast repeats we usually have to shorten up our overall length.
I tend to load to the mag well length nowadays, just don't see the sense in not having ammo in the mags of my hunting rifles. We even do that with our steel clanging .308 Win. ammo - seems that 2.830" will fit in most mag wells.
Good question, I am looking forward to reading what some of the other fellows have to say.
 

Brent

Well-Known Member
Joined
Jun 12, 2001
Messages
2,537
Location
Palmer, Alaska
Seating depth changes should be treated just like switching a load component IMHO.

You have less "effective" case capacity when seating bullets deaper, and consequently more pressure is produced with the same amount of powder... in most all my experience with testing pressure thus far... FWIW.

You "can" experience higher pressures if they are seated out to the point they come in contact with the rifling, almost come in contact, or are into them. It's been my experience that pressure usually falls though, don't take that as a free advice to EXPECT it though. I have found a couple loads that HAVE jumped up in PSI as they approached the rifling. "Some" loads never change notably. Treat it as a change if you do it, and watch for pressure signs. A good Chronograph helps here too.
 

Nighthawk

Well-Known Member
Joined
Mar 2, 2002
Messages
429
Location
Central Minnesota
Thanks for the reply, guys. I like bringing up something technical because it is interesting. My bullets are long so I was just wondering what the better decision was.
 

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