OAL verses FPS

[martyj]

I was wondering if you use the same powder and load but make the OAL .060 longer do you loose alot of velocity.
I read this morning on good ole internet some guy saying .01 longer equals 25 fps and not buying that but could be wrong.
thanks

 

[918v]

On some rounds it doesn't do much. On other rounds it has a huge impact, even in standard factory chambers. But it's usually an increase in velocity, not a decrease. The longer you seat the bullet the closer it is to the rifling the shorter the jump.

 

[J E Custom]

I was wondering if you use the same powder and load but make the OAL .060 longer do you loose alot of velocity.
I read this morning on good ole internet some guy saying .01 longer equals 25 fps and not buying that but could be wrong.
thanks

I don't know where he got the numbers, but .025 ft/sec every one thousandths has got to be wrong.

Normally, the reason you loose or gain velocity with seating depth is because of pressure. With more free bore you can add more powder and get more velocity without more pressure.

Seating the bullet against the lands will limit the velocity potential of the cartridge, but in many cases the desired velocity can be reached safely anyway.

Once you get off the lands, velocity change is very little unless you shoot a large over bored cartridge, and then it can vary depending on the amount of free bore.

If there is a general rule, the more free bore the more powder. the less free bore the less powder is used to reach SAMME Pressures.

Don't believe everything you read on the internet. think about his claims. If every thousandth gained or lost you 25 ft/sec going from touching the lands to .200 thousandths free bore would give you 500 ft/sec.

There is no doubt that there is a velocity change with different seating depths as long as the same pressure is maintained but no where near that much. and there are no accurate predictions.

Just my opinion

J E CUSTOM

 

[Mikecr]

MV could go up, or could go down.

 

[HNDLDR]

Actually .01 would be ten thousands but that still seems extreme.

 

[woods]

In this caliber with this powder and this bullet

.001 reduction in OAL decreased velocity by an average of .7 fps

Other combinations may have a slightly different outcome, but not much

IMO

 

[Canadian Bushman]

I think this is a scenario where two variables are being focused on but several are at play.