Seating depth/new powder

[Jay Harrison]

Just a quick question. I know everything always needs to be tested, checked, then retested and rechecked. However just a general question, when changing powders for whatever reason from an established load, will the ideal bullet seating depth change?

Thanks,

Jay

 

[Beiruty]

If you keep the MV the same between loads while keep the jump for the same the same, there should be not be another seating depth.
Modern VLD Bullets llike to jump more than 0.040" even more than 0.060"

 

[Jay Harrison]

If you keep the MV the same between loads while keep the jump for the same the same, there should be not be another seating depth.
Modern VLD Bullets llike to jump more than 0.040" even more than 0.060"

Thank you for your reply, in my head it makes sense that it should not change but I didn't know. Just picked up some N555 to try and was just curious what to expect.

 

[Straightshooter1]

Just a quick question. I know everything always needs to be tested, checked, then retested and rechecked. However just a general question, when changing powders for whatever reason from an established load, will the ideal bullet seating depth change?

Thanks,

Jay

The answer to that question as you've phrased it is, yes. Even when you get a new lot of the same powder, its burn rate can be very different and your internal ballistics will be a little different, but starting at the same seating depth to find where you'll want to be is a good idea.

 

[Jay Harrison]

The answer to that question as you've phrased it is, yes. Even when you get a new lot of the same powder, it's burn rate can be very different and your internal ballistics will be a little different, but starting at the same seating depth to find where you'll want to be is a good idea.

Thank you for your help. I have so much info to absorb!

 

[David Christian]

Powder burn rate and the shape of the pressure curve will definitely affect your seating depth. If changing powders, I would always do a fine tuning of powder charges followed by a seating depth test. I even do this when changing jugs of the same powder lot.

 

[JMayo]

I bought a chronograph just for this reason. I'm chasing speed.
I'm beliving that if you get to the same speed then you need the same jam or jump. So far so good. But I'm not a big powder change guy. I like things to say the same.

 

[K22]

In my experience, changing seating depth become a significant issue when you change bullets rather than powder.

If I'm just changing powder, I use the existing seating depth I used with the other powder. I can't remember a case where I just changed powder and had to change the seating depth to obtain the desired precision. That is NOT the case when I have changed bullets which will often require a change in seating depth - see explanation that follows.

Different bullets often have different ogives which can significantly impact optimum seating depth for precision. In addition, the new bullet should always be checked in your rifle chamber to determine the distance to the lands. This is not only a precision issue but can be a safety issue to avoid jamming the bullet into the lands.

 

[22BRGUY]

ANYTHING that changes barrel harmonics (vibrations) will require a change.
JMHO

 

[Jay Harrison]

Thank you everyone for the help. I have a decent load worked up but just about out of my powder. So I was just wondering what to expect.

 

[Beiruty]

ANYTHING that changes barrel harmonics (vibrations) will require a change.
JMHO

Start from a base load, test and verify