Fireforming help needed

[victor3ranger]

It's probably the same as a "false" shoulder. When I form 6.5 Sherman from 280 Rem brass, I neck the brass down through a bushing die. I start long and check the brass in my chamber. Basically, keep adjusting the die down to the point where you can chamber it with a decent amount of resistance. This "false" shoulder ensures correct headspace.

In the case of the 7 STW, you could run your brass through an expander to .308, then neck back down to .284 in increments like I mentioned above until you have that resistance on chambering.

View attachment 487370

Well crap, mine looked like that and I necked it down just enough to get rid of the bump

 

[Willys]

It's probably the same as a "false" shoulder. When I form 6.5 Sherman from 280 Rem brass, I neck the brass down through a bushing die. I start long and check the brass in my chamber. Basically, keep adjusting the die down to the point where you can chamber it with a decent amount of resistance. This "false" shoulder ensures correct headspace.

In the case of the 7 STW, you could run your brass through an expander to .308, then neck back down to .284 in increments like I mentioned above until you have that resistance on chambering.

View attachment 487370

This !!!!!

 

[Mike Matteson]

That works for me.

 

[Lefty7mmstw]

It's probably the same as a "false" shoulder. When I form 6.5 Sherman from 280 Rem brass, I neck the brass down through a bushing die. I start long and check the brass in my chamber. Basically, keep adjusting the die down to the point where you can chamber it with a decent amount of resistance. This "false" shoulder ensures correct headspace.

In the case of the 7 STW, you could run your brass through an expander to .308, then neck back down to .284 in increments like I mentioned above until you have that resistance on chambering.

View attachment 487370

yup, same thing...

 

[300 Driver]

It took me a while, but I seem to have figured it out. I couldn't isolate one issue so I basically did what everyone here suggested.

I broke the bolt down(not my first time, but WTH) and ultrasonic cleaned, then re-lubed. Pin protrusion was fine. I removed the ejector completely for Fireforming.

I then reloaded each case again, but with a .375 shoulder instead of .356. There was barely any difference between an easy bolt close and a hard closure. I went halfway between and then loaded each case with a primer only. I fired 3 primers in each case before I was confident I had solved this. I know I wasted components, but wasn't willing to have another range trip with misfires.

fireform load was a crush fit, no jam, 300gr sierra and 70gr W780 from long ago. WLRM primer and Peterson brass. All fired with zero issue today. As a bonus, the rifle is showing some promise. Left group is 50yds and right group is 100yds. I was shooting with my kid at our range and you'll see one of his pulled 22lr shots.

either way, I learned a bit along the way here and am ready to start load dev.

Thanks to all for the insight!

 

[victor3ranger]

I hope mine does that good.

Looks like you are on your way