300 Norma Improved 35 degree

[schw15]

Donuts dont hurt anything unless your seating the bullet too deep which means your throated wrong or your pushing them out with a mandrel causing a pinch point in the chamber. If your throated right and your not using a madrel they are a non issue.

I played with mandrels but stopped and been only using the bushing but went back to a mandrel to try and push the donut from the inside. I load just above it but the donut grows higher in the case neck I figured a mandrel would keep them at bay. Good info.

Bulletcentral has a mandrel for the micron die goes inside for a all setwp sytem is that something we shouldn't use then?

 

[Alex Wheeler]

Everytime someone is telling me that they have to bump the shoulders back a whole bunch to get an easy bolt close the first thing I ask if they are using a mandral. On any cartridge. Many times they are and pushing that donut out creates a tight spot in the chamber. I don't recommend them most of the time, so my advice is to just keep the bullet above the donut and don't worry about it. A couple of the absolute worst cartridges for donuts are the 6 ppc, and the 30Br. They also happen to be two of the most accurate cartridges on earth and suffer no problems because of donuts

 

[schw15]

Everytime someone is telling me that they have to bump the shoulders back a whole bunch to get an easy bolt close the first thing I ask if they are using a mandral. On any cartridge. Many times they are and pushing that donut out creates a tight spot in the chamber. I don't recommend them most of the time, so my advice is to just keep the bullet above the donut and don't worry about it. A couple of the absolute worst cartridges for donuts are the 6 ppc, and the 30Br. They also happen to be two of the most accurate cartridges on earth and suffer no problems because of donuts

Thank you for that Info always learning something. Best to leave them alone seems like. Is it hit or miss with the donuts in this case? Or something that comes with improving the case?

Does the standard 300 Norma get them as well vs the improved?

 

[Alex Wheeler]

Thank you for that Info always learning something. Best to leave them alone seems like. Is it hit or miss with the donuts in this case? Or something that comes with improving the case?

Does the standard 300 Norma get them as well vs the improved?

The donut comes from thicker shoulder brass flowing into the neck. As you size and shoot brass it grows in length. Thats why you have to trim it. Improved cases help because when you form them the thin neck brass gets pulled down into the shoulder. Steeper shoulders also flow forward less. But you will still eventually get them.

 

[schw15]

The donut comes from thicker shoulder brass flowing into the neck. As you size and shoot brass it grows in length. Thats why you have to trim it. Improved cases help because when you form them the thin neck brass gets pulled down into the shoulder. Steeper shoulders also flow forward less. But you will still eventually get them.

First time I have ever delt with this issue at least from what I remember thank you for information. Seems like it's impossible to stop or fix just load outside of it and your fine. Thank you for the information sometimes these things can drive people crazy haha

 

[schw15]

The donut comes from thicker shoulder brass flowing into the neck. As you size and shoot brass it grows in length. Thats why you have to trim it. Improved cases help because when you form them the thin neck brass gets pulled down into the shoulder. Steeper shoulders also flow forward less. But you will still eventually get them.

Also mine has moved to the inside of the neck and doesn't allow a bullet to drop into a fired case. They stop hard and no give. I can visually see it inside the neck

 

[Alex Wheeler]

Thats what donuts do.

 

[schw15]

Thats what donuts do.

I appreciate the info. Great design pure accuracy with it

 

[Sgt. Brumbaugh]

To the above, that is why it is best to design everything so the boattail / bearing surface junction is well in front of the shoulder neck junction. That said I had very good luck inside neck reaming a 338 LAI that was throated too short for the 300 Berger I was using. OAL was 3.9ish. Shot the rifle successfully in ELR and it was a legit .25 ish MOA rifle.

 

[Ledd Slinger]

I haven’t had any donut issues with the 300 NMI. But I dont run the 245…only 220 and 230.

I personally do not like donuts because sometimes i like to use graduated expander balls in conjunction with specifically sized neck bushings to fine tune neck tension a bit. To prevent donuts, i turn the necks all the way down on to the shoulder of the case. I have verified the absence of donuts after multiple firings by running a micrometer dial indicator thru the case necks using my milling machine. So it definitely works to prevent donuts and is a very simple procedure with a good quality neck turning tool.

 

[schw15]

I finally got a bulletcentral bushing and those bushing size the neck more than the wilson but still leaves part of the neck untouched. I think that will be way better than the wilson bushing I was using.

 

[schw15]

I haven’t had any donut issues with the 300 NMI. But I dont run the 245…only 220 and 230.

I personally do not like donuts because sometimes i like to use graduated expander balls in conjunction with specifically sized neck bushings to fine tune neck tension a bit. To prevent donuts, i turn the necks all the way down on to the shoulder of the case. I have verified the absence of donuts after multiple firings by running a micrometer dial indicator thru the case necks using my milling machine. So it definitely works to prevent donuts and is a very simple procedure with a good quality neck turning tool.

Do you neck turn before or after you fireform?

 

[Ledd Slinger]

Do you neck turn before or after you fireform?

Both. I turn the virgin brass just enough to clean up the neck and get down onto the shoulder a bit, but because we are fire-forming the shoulder to a completely different angle, I usually do it again after 2 firings to get a good cut on the new shoulder position.

That’s pretty standard practice for me, even on cases that do not have a modified or improved shoulder design. Why have donuts if you want to use a neck turner to clean things up anyhow? Cut down onto the shoulder and help prevent them.

Im running a no-turn reamer design on this NMI, so on the neck walls themselves, im only touching them up enough for good concentricity.

All that said, i still would never design a reamer where short freebore caused the bullets i want to use to be seated down in the area where a donut “can” form. Thats just never a good design. No matter what, always seat the base of the bullet bearing surface far enough out in the neck to avoid that area

 

[schw15]

Both. I turn the virgin brass just enough to clean up the neck and get down onto the shoulder a bit, but because we are fire-forming the shoulder to a completely different angle, I usually do it again after 2 firings to get a good cut on the new shoulder position.

That’s pretty standard practice for me, even on cases that do not have a modified or improved shoulder design. Why have donuts if you want to use a neck turner to clean things up anyhow? Cut down onto the shoulder and help prevent them.

Now I’m not saying neck turning works on ever case, because i havent shot every case design out there, but with the 300 NMI and its steeper 35 deg shoulder angle and large diameter, the shoulder cut seems to prevent donuts.

Im running a no-turn reamer design on this NMI, so on the neck walls themselves, im only touching them up enough for good concentricity.

What neck turner tools do you use?

 

[Ledd Slinger]

What neck turner tools do you use?

I personally like the 21st Century tool

 

[schw15]

I usually only run fed 215 primers but grabbed 5000 cci 250 during the shortage just in case. Has anyone seen any difference in the 215 vs 250 in the 300 norma improved?

 

[LCazador]

There's a difference in cup height between CCI and Federal, .118" and .117" so there could be a difference in ignition.

 

[schw15]

I just measured my throat at 708 rds and had .053 that's with n568 berger 245 2915 avg for matches like krg and nightforce ect. What do you guys normally see and when do you call it good for the barrel?

Have the nightforce to shoot and on the fence to switch barrels

 

[Darkside]

If it's still shooting good I would keep shooting.

 

[moondog]

I just measured my throat at 708 rds and had .053 that's with n568 berger 245 2915 avg for matches like krg and nightforce ect. What do you guys normally see and when do you call it good for the barrel?

Have the nightforce to shoot and on the fence to switch barrels

Don't be like me! I shot my 300PRC at KRG with 1100 rounds on the barrel. It was still shooting really well. I knew it was close, but decided to run it. Day one went well, after the 2nd stage on day 2, not so much. Might have done better with a shotgun. Borescope confirmed little chunks missing on the lands. Although the throat didn't move much, the barrel is done! I just screwed a new one on yesterday and started the process over. 25 rounds on it today. Hopefully I'll get it settled and tuned for Nightforce.