Internal Donut on new brass?

[Steel head]

Get a bigger mandrel for initial sizing and let it dwell in the neck a bit.
ADG necks when new are tight and stout, that’s why I use a -.001 mandrel, could possibly do a -.0005 mandrel even.

 

[2aBaC̶a̶]

I check my 300PRC with pin guages and usually have to hit some with the mandrel a second time.

 

[Cascade Hemi]

Reset your seating die. I can seat .308 bullets in 6.5CM cases without crushing the brass. Your seating die is running into the mouth of the brass.

 

[SmokyJoe]

Get a bigger mandrel for initial sizing and let it dwell in the neck a bit.
ADG necks when new are tight and stout, that’s why I use a -.001 mandrel, could possibly do a -.0005 mandrel even.

Sounds good. I ordered a couple of mandrels from 21st Century - 0.2625 and 0.263. I already have an expander that is 0.2635. Also 10 pin gauges to check diameter after springback if any. I’ve not run into this issue with Lapua brass, so I also pre-ordered 100ct of their 6.5 PRC brass coming out this Spring. I would like to end up with 100 pieces of brass that are on the same page instead of 50 that need one process and 50 that need a different process.

 

[SmokyJoe]

Reset your seating die. I can seat .308 bullets in 6.5CM cases without crushing the brass. Your seating die is running into the mouth of the brass.

I wish it were that simple. This is the first thing I checked. I can set an empty case in the Forster press, rotate the ram through the full sequence, and the die does not contact the case mouth. I also thought the seating stem might be kicking the bullet off center enough to bind up and create chaos. However, this is a custom honed stem which matches the profile of the 156 EOL and it seems to be nicely centered. A buddy of mine has a Redding seater with a VLD stem which I am going to try just to see if there is any difference.

 

[Baer45]

My guess is if you are using a mandrel only to push all inconsistencies in the neck/shoulder area to the exterior (which is fine) you need to turn your neck up the should 1/16” or so to avoid donuts appearing. Also load as long as feasible to keep base of BULLET out of neck/shoulder junction...good luck..

 

[Dragoon300]

I just found this yesterday when neck sizing once fired ADG 6.5 PRC brass. I sized the neck down with a .290 bushing and up with a .262 mandrel. When pin gaging the neck I found it smaller where it meets the shoulder. I thought I didn't get the mandrel all the way through so I made sure it was going deep enough and that the .262 diameter made it past the shoulder juncture. Still a .261 gage pin slip fits in the neck to the shoulder junction then has some friction but does go through. I don't think it will cause me any trouble because I don't seat the 156 Berger to that point, my chamber is throated long, however I don't like knowing this brass is having this problem. I will keep track of this issue and report back. Thanks for the information, please report your findings.

 

[Dragoon300]

I just checked 155 new ADG 6 5 PRC cases. The neck ID's are .262 to .263 slip fit on pin gages. There are no restrictions or smaller ID at the shoulder junction on these. I ran 2 through my .290 bushing neck die, then my .262 mandrel. I get .261 ID easy slip fit and a .262 gage pin just kind of starts at the case mouth. There is no smaller ID at the shoulder junction like I noticed with the once fired ADG brass yesterday.

 

[1moaoff]

I just found this yesterday when neck sizing once fired ADG 6.5 PRC brass. I sized the neck down with a .290 bushing and up with a .262 mandrel. When pin gaging the neck I found it smaller where it meets the shoulder. I thought I didn't get the mandrel all the way through so I made sure it was going deep enough and that the .262 diameter made it past the shoulder juncture. Still a .261 gage pin slip fits in the neck to the shoulder junction then has some friction but does go through. I don't think it will cause me any trouble because I don't seat the 156 Berger to that point, my chamber is throated long, however I don't like knowing this brass is having this problem. I will keep track of this issue and report back. Thanks for the information, please report your findings.

That is spring back due to more material at that junction. Annealing may or may not help.

 

[918v]

You want that spring back at the neck/shoulder junction. If that gets too soft your accuracy goes to shit.

 

[SmokyJoe]

OK, here’s what is probably happening. First off, this here is Kentucky brass. This is not some namby pamby brass. It is strong in the shoulder. When I push the .262 mandrel through, the neck expands and stays at .262. The shoulder neck junction, which is stout and strong like Kentucky brass oughtta be, expands but then springs back as the mandrel retreats, leaving a burnished ring. The retreating mandrel leaves the balance of the neck at .262 making it look like a constricting donut has been built into this fine Kentucky brass. But no, it was created by the mandrel and the thicker brass inherent in this part of the case. Now the neck gages at .262, the neck/shoulder gages at .2605 - .261. This constriction, while not substantial, is abrupt enough to allow me to f*ck up some fine brass while seating the Berger 156 EOL boat tail below the shoulder. The solution for me is to hit it with a larger mandrel or a larger expander ball. I do regret not checking ID and case weight right out of the box to see if the two boxes I have were substantially different or not. On the brighter side, I now have pin gages .260 through .265 in .0005 increments which will be put to good use.

Anyhow, that’s my conclusion after digesting much of your fine advice, and checking with pin gages.

918V, you were right, it’s not a donut. Steel head, you were right, ADG brass can be stout.

I did send an email to ADG with pics and a detailed summary, asking for their thoughts, and will let you know what they have to say.

 

[918v]

What do I win?

 

[BuLLet]

here ya go

 

[918v]

Yey!

 

[SmokyJoe]

What do I win?

How about a !

 

[918v]

I’ll take that too

 

[Cascade Hemi]

OK, here’s what is probably happening. First off, this here is Kentucky brass. This is not some namby pamby brass. It is strong in the shoulder. When I push the .262 mandrel through, the neck expands and stays at .262. The shoulder neck junction, which is stout and strong like Kentucky brass oughtta be, expands but then springs back as the mandrel retreats, leaving a burnished ring. The retreating mandrel leaves the balance of the neck at .262 making it look like a constricting donut has been built into this fine Kentucky brass. But no, it was created by the mandrel and the thicker brass inherent in this part of the case. Now the neck gages at .262, the neck/shoulder gages at .2605 - .261. This constriction, while not substantial, is abrupt enough to allow me to f*ck up some fine brass while seating the Berger 156 EOL boat tail below the shoulder. The solution for me is to hit it with a larger mandrel or a larger expander ball. I do regret not checking ID and case weight right out of the box to see if the two boxes I have were substantially different or not. On the brighter side, I now have pin gages .260 through .265 in .0005 increments which will be put to good use.

Anyhow, that’s my conclusion after digesting much of your fine advice, and checking with pin gages.

918V, you were right, it’s not a donut. Steel head, you were right, ADG brass can be stout.

I did send an email to ADG with pics and a detailed summary, asking for their thoughts, and will let you know what they have to say.

I have the same brass and the same size mandrel. I'm skeptical to say the least. I turned 6CM brass into 6.5CM brass in a single pass with a .262 mandrel without collapsing the shoulders. I don't see how .001" additional interference is going to collapse the shoulders. There's guys running .007" of interference every single day.

 

[flyright]

I've found the donuts appear after just a couple of firings on any brass that gets the mandrel. Never an issue with the regular pull through neck expander. Just my .03...

 

[918v]

That don’t make no sense mechanically.

 

[whatsupdoc]

I've found the donuts appear after just a couple of firings on any brass that gets the mandrel. Never an issue with the regular pull through neck expander. Just my .03...

Exactly!

 

[whatsupdoc]

You think of the brass as a piece of metal that you are bending back into shape
but really its like play dough that you extrude back into shape, that is why it gets longer as you resize it.

There is a difference in how the brass flows between a mandrel and a expander button, not sure why
but it does.

 

[918v]

If you are suggesting that a mandrel causes doughnuts on unturned brass then you’re wrong.

 

[whatsupdoc]

Yet I have seen it happen many times over so of course you know everything.

Edit: with non bushing dies

 

[918v]

Yet I have seen it happen many times over so of course you know everything.

Edit: with non bushing dies

I do. Thanks for acknowledging it.

 

[SmokyJoe]

Finally got back to this with larger mandrels from 21st C. Using a 0.263“ mandrel, hitting it three times, slowly, I end up with 0.2625“ for the upper portion of the neck, and 0.262” where the neck joins the shoulder. Bullets seat without issue now.

Feedback from ADG was kindly, indicating that their neck shoulder area is stout. They offered to replace the brass that I crushed, same lot number, which is really above and beyond since I was the one who was running the press. I lost four cases and learned something so it’s all good.

 

[Deleted member 10043]

I'm glad you got it to work but regular dies should still work. If not, you still have finicky brass.

 

[pabrousseau]

My guess is if you are using a mandrel only to push all inconsistencies in the neck/shoulder area to the exterior (which is fine) you need to turn your neck up the should 1/16” or so to avoid donuts appearing. Also load as long as feasible to keep base of BULLET out of neck/shoulder junction...good luck..

 

[pabrousseau]

The extra brass is going somewhere. Pushed to the outside will become thicker at the neck shoulder juncture through sizing and firing causing tight case fit.turning as baer45 said is the proper solution.

 

[SmokyJoe]

Yep, we’ll see what evolves over time. These are to be dedicated to a hunting barrel so I’m not going to get to more than a few firings over time.