JP Enterprises website description of "Soft Seating" - what does this mean?

[ReaperDriver]

I was reading JP's website on their 6mm CM barrels and they give a technique for "soft seating" bullets to headspace off the bullet rather than the shoulder for min or under min spec new cases.

6mm Creedmoor Cartridge Compatibility​

From our hand-loading experience, most 6.5 Creedmoor cases can be resized to 6mm Creedmoor and work without issue. As a general rule, it is important to run the head space set back of the shoulder on the resized cases close to maximum while still allowing for a "drop fit" in the chamber on a self-loader. If you purchase new brass, gauge to see where it falls on the headspace spectrum.

If you have new cases that are at minimum spec. or below on a headspace gauge, you can use the Hornady 105gr. BTHP loaded to 2.740" or a bit longer to give a soft seat and force the case head to the bolt face. In other words, you will head space off the bullet, not the shoulder. This will allow the case to fire form and set the shoulder forward on the first fire. This minimizes case stretch in front of the web that could result in a premature case failure. https://www.jprifles.com/buy.php?item=JPSM6C-22M8XL9

So my question is not necessarily related to just the 6mm Creedmore but to all similar situations with new brass that is at or under min headspace spec. How exactly do you "soft seat"? Is this just another way to say jam the bullet into the lands? Or is there something more involved. I'm asking because I have a similar situation with some .260 Rem Virgin PRIME headstamped brass that is waaay under my match chamber HS specs. Like 10-12 thousandths under. The couple times I shot them as Virgin brass at my regular "warmish" loads seemed to really trash the primer pockets in 1-2 firings. Short of loading up some really weak loads to fire form them to the chamber, is this technique above worth trying and if so, how exactly do you do it?

TIA.

 

[oldiephrt]

My understanding of what was posted,
1. do not crimp bullet,
2. do not fill case to compression,
3. make sure bullet can move in case just with enough resistance to move case rear ward on bolt close but, not so stiff as to jam/stick bullet in rifling.
Seems to me that bench rest shooters used to do this regularly. My memory may be off. By the way you will know if bullet tension is too high when bullet remains in the rifling spilling powder all over, or low when bullet pushes inside case. I may have experienced one of these.
P.S. I have not done a soft seat for headspace on purpose.

 

[2aBaC̶a̶]

sounds like jamming to force the case head into the bolt and create the gap for shoulder to form into . Soft seat to me would be minimal amount of neck tension as to not jam too much.

 

[smoothy8500]

" use the Hornady 105gr. BTHP loaded to 2.740" or a bit longer"
As 2aBaCa points out, they are suggesting the longer length to do what F-class shooters call a "soft jam". The ogive is not hard in the rifling. There is a slight resistance, that if the case was pulled out the projectile is not jammed or stuck in the rifling. You can use a normal neck tension if minimal tension is not available. It just takes a little trial and error to get the right length. If you use a loose neck, the ejector can push the case away from the bolt face creating the gap you wanted to avoid.

 

[ReaperDriver]

" use the Hornady 105gr. BTHP loaded to 2.740" or a bit longer"
As 2aBaCa points out, they are suggesting the longer length to do what F-class shooters call a "soft jam". The ogive is not hard in the rifling. There is a slight resistance, that if the case was pulled out the projectile is not jammed or stuck in the rifling. You can use a normal neck tension, it just takes a little trial and error to get the right length. If you use a loose neck, the ejector can push the case away from the bolt face creating the gap you wanted to avoid.

That makes more sense now, thank you. Just to be clear, I want the bullet actually barely into the lands. I've loaded bullets in the past where they are just barely touching the lands and leaves small little square indents in the bullet jacket. I'm assuming I want to go in a bit more to ensure that there is a firm contact with the lands, correct?

Is this method the best way to fireform new min spec virgin brass? Or is it just one method?

 

[smoothy8500]

Yes, you're on the right track, just not too firm.