Does necking up brass stretch and weaken the neck shoulder junction?

[thefitter]

22-250 necked up to 6.5CM

Necked up in 2 stages using tapered mandrels. 22-6mm then 6mm-6.5mm

I bore scoped the cases and it looks like the neck shoulder junction is stretched. Can't tell if it's really thinner because the ball mic wont work.

Thanks

 

[Steve Blair]

Anneal after cold working and it will be fine. I do this with .270 WSM to .300 WSM and 6.5-284 to .284 frequently.

 

[thefitter]

Anneal after cold working and it will be fine. I do this with .270 WSM to .300 WSM and 6.5-284 to .284 frequently.

So anneal before I fire form?

thanks

 

[Steve Blair]

That's what I do.

 

[thefitter]

Okey dokey.

thanks

 

[lrgoodger]

You do realize that necking up leaves a ridge on the outside of the case where the old neck/shoulder junction was, right? That's because the neck wall is thinner than the shoulder wall. You have to neck turn the cases to get the new neck to be a uniform size down to your new shoulder.

In my experience, there is always a shallow groove left inside the case on the back side of that old neck/shoulder junction when necking up any caliber case. It looks kind of like the thin spot of an impending case head separation in cutaway photos I have seen, but that is an illusion. That is probably what you are looking at with the bore-scope. If you happen to be seating bullets at the exact depth that the bullet pressure ring lands in that groove, it can cause neck tension inconsistency.

 

[timeout]

I may have done something wrong, but necking 6.5X47's to 30 cal. left a donut inside at the neck shoulder junction. Probably doesn't hurt anything if seating the bullet above the donut. K&M carbide neck turn arbors have a built in reamer to remove these if you have that trouble. Another remedy to remove them is a reamer from MCMaster Carr. They have them available in .0005" increments so that you can order a size that will not touch the inside of the neck, but still remove the donut. If you go the reamer route, rotate it counter clockwise while inserting it to the depth of the donut.

 

[Larryh128]

That's good advice from timeout, just remember to never turn a reamer backwards while cutting, only inserting to depth before cutting. It probably won't do much in brass but harder material will dull them fast.

 

[stool]

do not turn reamers backwards.......

I may have done something wrong, but necking 6.5X47's to 30 cal. left a donut inside at the neck shoulder junction. Probably doesn't hurt anything if seating the bullet above the donut. K&M carbide neck turn arbors have a built in reamer to remove these if you have that trouble. Another remedy to remove them is a reamer from MCMaster Carr. They have them available in .0005" increments so that you can order a size that will not touch the inside of the neck, but still remove the donut. If you go the reamer route, rotate it counter clockwise while inserting it to the depth of the donut.

 

[artbosco]

I've been Necking-Up new Lapua 220 Russian brass for the 6PPC and 6BR Norma for the 30BR [in one pass] for years. Rarely a neck will split, from the top down, but I believe that's a function of that case's metallurgic metamorphosis gone astray.

I've never seen a case, in all that time, weaken at the neck/shoulder junction from necking-up. I have however seen them weaken and eventually separate, as a consequence of over-turning into the junction.

 

[thefitter]

Thanks for the replies. I annealed them after necking up and I'm going to fire form next followed by neck turning.

 

[lrgoodger]

If you fire form before turning, it will push the thick part of the new neck to the inside. You can't turn it off then.

I suggest you read this thread and look at the excellent photos of 6BR cases necked up to 30BR. The process is the same for necking up any caliber.

http://forum.accurateshooter.com/index.php?topic=3833604.0

 

[Steve Blair]

I also turn them before fire forming and before annealing. It seems the slightly harder material condition produces better surface finish.

 

[thefitter]

But the angle of the 22-250 shoulder is not correct to fit the angle of my 6.5C cutter until it's fire formed?

 

[Steve Blair]

I use a 40° cutter for all neck turning and I have no cartridges that are 40°. It works fine as long as the shoulder to case mouth dimension is consistent and careful attention is paid to the stop point. Only a small shoulder cut is needed.

 

[spclark]

If you fire form before turning, it will push the thick part of the new neck to the inside. You can't turn it off then.

True enough, unless you first re-size the brass making sure to size the entire neck length then run each case neck over an expander mandrel, pushing the thicker section back to the outside where neck turning can get at it.

I find this procedure to be more reliable than using a neck reamer to cut away the thicker stuff from the inside....

 

[timeout]

do not turn reamers backwards.......

There is no harm to turn a reamer backwards by hand, especially into brass. If you ever use a throater reamer in your barrel, I would suggest turning that counter clockwise while entering.

 

[hydrotherapy]

Buy a IDOD from F Class products work great

 

[BoydAllen]

Back when I first started expanding and turning to make 6PPC cases, I was worried about my turning weakening the shoulder where I had lightly cut into it so I sectioned the neck and shoulder area. It made me a lot more confident. There was plenty of brass, and I have never had a problem. One precaution that I would suggest is wearing a paper mask and goggles when sectioning. Due to the direction of rotation my cordless dremel's cutoff disk threw very fine particles of brass toward me as I made the cut. These would have been a big problem if I had inhaled any or they had gotten in my eyes.