Forming 300 Blackout Brass

buddyb

After it is cut,formed and trimmed,does it need to be annealed?

toad67

From what I understand, annealing only hardens the brass from stretching and cracking, creating the same neck tension. Not sure if the 300 B/O puts enough stress on the brass to make it necessary, or if your gun shoots good enough to make it worth while...

nononsense

toad67 said:

From what I understand, annealing only hardens the brass from stretching and cracking, creating the same neck tension. Not sure if the 300 B/O puts enough stress on the brass to make it necessary, or if your gun shoots good enough to make it worth while...

"The word "anneal" means "soften". In the context of cartridge reloading, it means to take a case with a neck that - due to repeated use - has become hard and brittle and prone to failure, and make it (the neck) malleable again so that the case can be reloaded a number of additional times.

Cartridge brass is actually annealed several times during manufacturing. The final annealing occurs after the neck and shoulder are formed. The evidence of this annealing is sometimes apparent on military brass as a multi-hued discoloration on the neck and shoulder (see Figure 1 below). Commercial brass undergoes the same process; however the manufacturers usually polish the brass afterward to remove the discoloration. When we anneal our cases, we are trying to duplicate this final annealing, and return the case neck to its "as manufactured" level of hardness."

http://www.massreloading.com/annealing.html

buddyb said:

After it is cut,formed and trimmed,does it need to be annealed?

The actual case forming is very minimal so it shouldn't require annealing until after several firings. I cold formed 1,000 pieces in one sitting a few years ago and did not anneal. The brass is still performing after 4 firings each case. The performance pressure level is a moderate 55,000 psi.

Best.

buddyb

Thanks

bpost

after forming and trimming you will need to neck turn about 90% of the cases to keep the neck wall thickness within limits.  I learned the hard way after cutting and forming about 1,000 cases.  I loaded 10 for checking accuracy, most would not chamber, the neck was too big to fit the chamber.

nononsense

bpost said:

after forming and trimming you will need to neck turn about 90% of the cases to keep the neck wall thickness within limits.  I learned the hard way after cutting and forming about 1,000 cases.  I loaded 10 for checking accuracy, most would not chamber, the neck was too big to fit the chamber.

It is simply good, safe procedure to check the neck thickness of brass which has been modified. Common sense.

But you will not always find the need to turn all necks after the modification takes place. Why? Because not all cases are made the same internally by every manufacturer. Shooters are aware of the external dimensions of cases because that's what allows us to chamber a piece of brass in the first place. But very few take the time to assess the changes in the internal dimensions.

Ever wonder why some manufacturer cases weigh more or less than others? Simple, it's the internal shape and dimensions which account for the increase or decrease in the weight of each case. Manufacturers like Lapua, who led the way in extending case life by decreasing both the internal dimensions (making case walls thicker) and improving the formula for the basic brass sheets, has been followed by several new U.S. manufacturers along the same road. Peterson, Alpha and ADG have all adopted the ideals of giving up a tiny amount of case capacity for improved case life. These changes occur in the lower portion of the case head which is most important in containing pressure.

But the changes in the internal measurements do not usually extend into the top of the case and neck/shoulder area. There can be a slight thickening in this area when there is a significant reduction in neck diameter to accommodate a smaller caliber but this is not the situation for the .300 Blackout. The 1,000 pieces I modified did not require neck turning because of the cases I chose to use.

Always check the neck wall thickness and the outside diameter to be sure it conforms to the chamber dimensions.

Best.

bpost

nononsense said:

bpost said:

after forming and trimming you will need to neck turn about 90% of the cases to keep the neck wall thickness within limits.  I learned the hard way after cutting and forming about 1,000 cases.  I loaded 10 for checking accuracy, most would not chamber, the neck was too big to fit the chamber.

It is simply good, safe procedure to check the neck thickness of brass which has been modified. Common sense.

But you will not always find the need to turn all necks after the modification takes place. Why? Because not all cases are made the same internally by every manufacturer. Shooters are aware of the external dimensions of cases because that's what allows us to chamber a piece of brass in the first place. But very few take the time to assess the changes in the internal dimensions.

Ever wonder why some manufacturer cases weigh more or less than others? Simple, it's the internal shape and dimensions which account for the increase or decrease in the weight of each case. Manufacturers like Lapua, who led the way in extending case life by decreasing both the internal dimensions (making case walls thicker) and improving the formula for the basic brass sheets, has been followed by several new U.S. manufacturers along the same road. Peterson, Alpha and ADG have all adopted the ideals of giving up a tiny amount of case capacity for improved case life. These changes occur in the lower portion of the case head which is most important in containing pressure.

But the changes in the internal measurements do not usually extend into the top of the case and neck/shoulder area. There can be a slight thickening in this area when there is a significant reduction in neck diameter to accommodate a smaller caliber but this is not the situation for the .300 Blackout. The 1,000 pieces I modified did not require neck turning because of the cases I chose to use.

Always check the neck wall thickness and the outside diameter to be sure it conforms to the chamber dimensions.

Best.

Thanks for adding this.  I checked the ones I had to neck turn and most that show the tell tail neck shoulder junction  turning mark were military 5.56 brass.  Commercial .223 brass was less likely to need turned.  The pressures for .223 are less than 5.56 NATO specs so it would seem the commercial .223 brass can be, and most likely is thinner as it runs lower pressures from the factory.