300 Norma Mag Improved. Follow along!!!

[Huntnful]

I hear this all the time. I'll have to measure shoulder datum to see how much merit there is to that.

It wasn't the growth in the shoulder necessarily. It was in the case body at the datum line. It took a lot of pressure to force that area out to the walls. Sizing die wouldn't even touch it after the first firing in my old chamber. This chamber could be different.

I used 75gr. of N570 with a 225 ELDM in my old chamber. I could have just been very light on the first fire forming shot. But it also didn't didn't hold at the shoulder for fire forming. I had to Jam the bullet into the lands because the neck also shortened up.

 

[Mike D Texas]

It wasn't the growth in the shoulder necessarily. It was in the case body at the datum line. It took a lot of pressure to force that area out to the walls. Sizing die wouldn't even touch it after the first firing in my old chamber. This chamber could be different.

I used 75gr. of N570 with a 225 ELDM in my old chamber. I could have just been very light on the first fire forming shot. But it also didn't didn't hold at the shoulder for fire forming. I had to Jam the bullet into the lands because the neck also shortened up.

Yeah that was definitely a light load. I was fireforming with 85 grains of N570 with a 230 Berger.

 

[COBrad]

Yeah that was definitely a light load. I was fireforming with 85 grains of N570 with a 230 Berger.

I've been shooting full power loads to form, 88 grains N570 and 245 Berger EOL's.

 

[Elk Hunter 338]

I run a max 300 Norma/230 load for forming Peterson/ Lapua brass @83 gr h1000 jammed hard on close.

 

[Huntnful]

Apparently I was just WAY underforming mine hahaha. I was also hesitant because my old 300 NMI chamber wasnt a crush fit for forming. It was only held by the bullet in the lands. I don't know if that matters at all, but i didn't like it lol. Harder to get super consistently formed cases from what I found.

 

[Elk Hunter 338]

Apparently I was just WAY underforming mine hahaha. I was also hesitant because my old 300 NMI chamber wasnt a crush fit for forming. It was only held by the bullet in the lands. I don't know if that matters at all, but i didn't like it lol. Harder to get super consistently formed cases from what I found.

part of the reason you were not getting consistent cases formed was the low charge weight of that dense powder .. to much volume made of air space..

even with a shoulder crush on close i still run bullet into the lands some

 

[Huntnful]

part of the reason you were not getting consistent cases formed was the low charge weight of that dense powder .. to much volume made of air space..

even with a shoulder crush on close i still run bullet into the lands some

Makes sense! My shoulders would be different heights as well as the necks not being consistent lengths. Only on a few cases, but it was noticeable for sure.

 

[QuietTexan]

Apparently I was just WAY underforming mine hahaha. I was also hesitant because my old 300 NMI chamber wasnt a crush fit for forming. It was only held by the bullet in the lands. I don't know if that matters at all, but i didn't like it lol. Harder to get super consistently formed cases from what I found.

That's part of why I used the false shoulder on my 243 AI. Smaller bullet, not as much benefit from jamming the bullet because less grip in the neck to start with, I felt it was worthwhile to put in the extra few steps and run full-house forming loads. Brass life has been excellent.

 

[Mike D Texas]

P

Apparently I was just WAY underforming mine hahaha. I was also hesitant because my old 300 NMI chamber wasnt a crush fit for forming. It was only held by the bullet in the lands. I don't know if that matters at all, but i didn't like it lol. Harder to get super consistently formed cases from what I found.

Interesting. I wonder whyMike doesn't set his reamer up for a crush fit?

 

[Huntnful]

P

Interesting. I wonder whyMike doesn't set his reamer up for a crush fit?

Just more powder capacity and thought the original neck didn't need to be as long. I just never needed the extra case capacity of the entire shoulder moving .100 forward. So I'd rather use the crush fit style and just reshape the shoulder angle like Ty's reamer does.

 

[7.62 Gunner]

Just more powder capacity and thought the original neck didn't need to be as long. I just never needed the extra case capacity of the entire shoulder moving .100 forward. So I'd rather use the crush fit style and just reshape the shoulder angle like Ty's reamer does.

What's your case capacity fully fire formed?
Mine is a 40 degree improved with .004 crush fit, I'm around 106.5 grains H20

 

[QuietTexan]

I just never needed the extra case capacity of the entire shoulder moving .100 forward.

So his reamer is set up with the shoulder a full .100" forward but the total case length is still the same, so the neck shortens some?

 

[Mike D Texas]

So his reamer is set up with the shoulder a full .100" forward but the total case length is still the same, so the neck shortens some?

Mike at HCA does. But I thought he told me he only moved the shoulder .050.

That's one reason I went with Alex Wheeler's reamer design instead of Mike's. I wanted to keep the neck length.

 

[Huntnful]

So his reamer is set up with the shoulder a full .100" forward but the total case length is still the same, so the neck shortens some?

Mike at HCA does. But I thought he told me he only moved the shoulder .050.

That's one reason I went with Alex Wheeler's reamer design instead of Mike's. I wanted to keep the neck length.

Yeah the whole shoulder moves forward.

Yep I was mistaken. It moved forward .050". Thanks Mike!