Pressure difference

[cornkolb]

Hello everyone,trying to figure out if seating a bullet longer than the standard c.o.l would affect case pressure and or velocity.i realize shorter c.o.l does but cant find much info on the longer c.o.l any help or guidance is appreciated.thanks

[74A95]

For most handgun cartridges, yes, seating longer will decrease pressure and velocity.

If the bullet is seated so long that it touches, the riflings (true for rifle and handgun cartridges), pressure can go up.

[cornkolb]

Thanks i was trying to work up a 223 load and wasnt sure if my fps with a longer c.o.l than the listed standard c.o.l would be different.

[Dufus]

It depends on how close to the lands you are.

If you have a short chambered rifle, then longer COL will create higher pressures.

That is the basis that Roy Weatherby designed all his calibers on....a long jump to the lands.

Of course you can go wrong in both directions.

If you are shooting a magazine fed gun and you load to fit the magazine, then most of the time it is nothing to worry about.

If it is a Savage bolt gun, then check your bolt face to lands dimension. I have seen a lot of short chambered Savage rifles.

[gwpercle]

Longer lessens pressures...but in reality not by very much at all and not enough to worry about. You will NOT need to add extra powder to compensate for the pressure.
In theory some would make it seem like this is a big deal but in practice with the normal deviations in velocities , it will be hard to notice .
The standard COL is not something written in stone , it is what was used to work up the data you are looking at and a place to start. You can ease it out or seat deeper, just do not start with maximum loads when seating deeper. Back off and work up for that .
Gary

[cornkolb]

Thanks for the help. I havent got a cronograph yet and kinda playing with groups and trajectory charts.the rifle is a remy 700 sps tactical 223.vortex 4-16 scope.3/8 3 shot groups at 100 yards is best for me.

[F. Guffey]

To avoid confusing other reloads and for the purpose of avoiding giving them more than they can keep up with I make it clear I am the fan of 'the jump start'; I want my bullets to hit the lands 'a running', I want my bullet pass the lands before the bullet knows they are there. As opposed to setting against the lands wondering if the pressure behind the bullet is sufficient to force the bullet past the lands.

And then there are factors, distance is a factor, time is a factor, if my case is full length sized to minimum length pressure is reduced because pressure can not get serious until the case fits the chamber. I was accused of being involved in some very risky stuff. I was using a very heavy bullet with a lot of powder but using time and distance to reduce pressure. It had nothing to do with taking other reloaders advise, I called Hodgdon, I explained to them what I was doing and why I thought it word work, they agreed and then we talked about what would happen if I changed distance and time.

F. Guffey

[Unclenick]

This plot shows pretty long distances off the lands for a pressure minimum that only applies to the round nose bullet used because of its very gradual side taper. IME, where this plot is at 0.25" off the lands, a spitzer nose bullet may get there in as little as just 0.030" off the lands, and I've also seen as much as 20% difference and not just 10% as the plot shows. But at least it is measured data and gives you a sense of the shape of the relationship.