Seating depth and pressure.

[GetReel]

Scenario: My brothers 6.5 PRC, 147ELD-M, IMR4955

We powder charge tested to find max charge weight at .02 off lands and yielded a good group for a quick hunt this fall. But velocities are lower than expected. We have case capacity left being the powder is slightly faster than maybe we should have.
Anyway. If we seat the bullet deeper in the case, we should be able to run another pressure test and get less pressure by seating deeper and allow to be able to increase charge weight shouldn't we?

Normally I would just test and figure it out but it's stupid cold right now (-40 wind chill) and so I'm just researching on my next steps.

 

[cajun]

Unless you were jammed in the lands which doesnt seem to be the case I would think the max load would be the same. As you jump more you increase the freebore which lowers pressure and velocity some. So you will have to increase the powder charge to get where you were initially. I'm not sure you would be able to seat the bullet deep enough to make a huge difference. I would use another powder rather than trying what you are talking about.

 

[RegionRat]

Agree with @cajun

Seating a little deeper is a mild effect on pressure/velocity when the starting point is already a jump of 0.020".
You can expect a small decrease in pressure/speed if you start seating deeper. If your case fill was less than 100% before, you won't see a dramatic difference in speed. Eventually if you seat deep enough, you will run into compressed load issues.

To really swing the situation for a significant increase in speed, you would want to try an altogether different recipe. YMMV

 

[GetReel]

Unless you were jammed in the lands which doesnt seem to be the case I would think the max load would be the same. As you jump more you increase the freebore which lowers pressure and velocity some. So you will have to increase the powder charge to get where you were initially. I'm not sure you would be able to seat the bullet deep enough to make a huge difference. I would use another powder rather than trying what you are talking about.

As I agree with the powder choice is wrong and want to use something else. Sometimes easier said than done right now with supply issues. Sometimes gotta use what you have.

 

[cajun]

As I agree with the powder choice is wrong and want to use something else. Sometimes easier said than done right now with supply issues. Sometimes gotta use what you have.

https://press.hornady.com/assets/site/hornady/files/load-data/6.5-prc-v2.pdf

Not sure of you have any of these powders but thats where I would start.

 

[GetReel]

https://press.hornady.com/assets/site/hornady/files/load-data/6.5-prc-v2.pdf

Not sure of you have any of these powders but thats where I would start.

I have 4 reloading books and one is the most recent Hornady version so I reviewed that and the only powder my brother had was H1000 and he wants to save that for his 7RM. I had an #8 jug of the 4955 and based on the burn rate charity's right in there with the popular choices. Probably better suited for a lighter weight bullet.
But as I said earlier, gotta work with what's available

 

[Varmint Hunter]

Scenario: My brothers 6.5 PRC, 147ELD-M, IMR4955

We powder charge tested to find max charge weight at .02 off lands and yielded a good group for a quick hunt this fall. But velocities are lower than expected. We have case capacity left being the powder is slightly faster than maybe we should have.
Anyway. If we seat the bullet deeper in the case, we should be able to run another pressure test and get less pressure by seating deeper and allow to be able to increase charge weight shouldn't we?

Normally I would just test and figure it out but it's stupid cold right now (-40 wind chill) and so I'm just researching on my next steps.

If you are at max charge weight, seating the bullet a little deeper will not help you to further increase the charge weight. Seating bullets deeper "can" cause pressure increases because you are reducing case capacity. Moving the bullet .010-.020-.030" won't change anything except accuracy IMO.

 

[Darkker]

Honestly, if you're going to start playing with random powders that you wouldn't otherwise; then maybe it's time you start to measure things.
Measuring and recording pressures, is how I found a couple powders we're actually outside in certain cartridges.

Here's an example of the burning curve recordings from that particular system.