300BO 223 Reclaim Brass Neck Thickness
- Thread starter H2OBUG
- Start date
The converted 300BO (made from .223 / 5.56 donor brass) have thick necks because it is formed from the case wall of .223 body. Whereas, factory new 300BO has a neck thickness set my the manufacturer.
There is a list of favorite headstamps for conversion into 300BO. The determining factor is neck wall thickness on the converted cases. Do a search and it should be easy enough to find.
There is a list of favorite headstamps for conversion into 300BO. The determining factor is neck wall thickness on the converted cases. Do a search and it should be easy enough to find.
I don’t know about the specific thickness, but I know that Lake City 5.56 brass works just fine, so there’s that.
FYI: Don't get too caught up on neck thickness unless you are loading for accuracy from a bolt gun. I have converted (probably) every different brand of brass imaginable from 5.56/223 into 300BO. All of my 300bo is range pickup. I always use a case gauge to verify that they are correct after loading. My experience has taught me not to break down the ones that don't fit in my gauge. After loading hundreds and hundreds of "plinking" rounds I will end up with a half dozen or more that will not fit the gauge. I took those rounds with me to the range and it turns out, they chambered and fired just fine in my weapons.
dellet
Gold $$ Contributor
As with all things Blackout, it gets complicated.
What are you using for a bullet?
What does the chamber measure?
How thick is the brass?
The SAAMI specs have max loaded neck diameter of .334”, and a minimum chamber of .335” tapering to .337” at the shoulder.
If you Shoot cast or plated bullets, which is popular with the cartridge, with a bullet diameter do .309-11”, .012” can get sticky in a minimum chamber. With a high pressure load, possibly dangerous.
The next overlooked problem is most converted brass comes with a built in doughnut. The body of most brass is tapered. Depending on the brass, you can have a taper of .003-4” in the neck. You need to check at the neck to shoulder junction, preferably with a bullet seated.
Varying thickness is a huge problem with converted brass. Until you true some up, you don’t no how poor some of it is.
I’ve seen brass as thick as .016”, measure everything. When you look at charts that show the variations of 223/5.56 case capacity, all of that variation ends up in the neck of converted brass.
Neck turning thick brass to fit your chamber can go a long way to improving accuracy instead of having more than .010” of neck clearance in the chamber using brass with .008” thickness. Cuts down on split necks from firing/sizing cycles also.
What are you using for a bullet?
What does the chamber measure?
How thick is the brass?
The SAAMI specs have max loaded neck diameter of .334”, and a minimum chamber of .335” tapering to .337” at the shoulder.
If you Shoot cast or plated bullets, which is popular with the cartridge, with a bullet diameter do .309-11”, .012” can get sticky in a minimum chamber. With a high pressure load, possibly dangerous.
The next overlooked problem is most converted brass comes with a built in doughnut. The body of most brass is tapered. Depending on the brass, you can have a taper of .003-4” in the neck. You need to check at the neck to shoulder junction, preferably with a bullet seated.
Varying thickness is a huge problem with converted brass. Until you true some up, you don’t no how poor some of it is.
I’ve seen brass as thick as .016”, measure everything. When you look at charts that show the variations of 223/5.56 case capacity, all of that variation ends up in the neck of converted brass.
Neck turning thick brass to fit your chamber can go a long way to improving accuracy instead of having more than .010” of neck clearance in the chamber using brass with .008” thickness. Cuts down on split necks from firing/sizing cycles also.
Hoser
Gold $$ Contributor
I convert a lot of brass for people. Anymore I just tell them US headstamped brass only. With PMC and lapua being the only off shore brass that I will work with.
Some will work and some wont. Just sticking to LC makes things about a million times easier.
For boltgun accuracy ammo, look for Lapua 300 BLK brass. My little DTA bullpup holds MOA accuracy out past 300 yards, very quietly.
Some will work and some wont. Just sticking to LC makes things about a million times easier.
For boltgun accuracy ammo, look for Lapua 300 BLK brass. My little DTA bullpup holds MOA accuracy out past 300 yards, very quietly.
drop_point
Silver $$ Contributor
I've used several handstamps to covert for my ARs. I prefer LC, but almost everything made in the US I've tried has worked.
Here's a clip I found on it:
Here's a clip I found on it:
I have a list somewhere posted on the stock diameter of 223 brass for making 300 BO. Basically any 223 brass with a neck thickness of .012" will work.
jsn
Gold $$ Contributor
One or more of the 300blk forums will probably have a list of "good" brass for conversion, but those lists are several years old. Also, some people experienced different results with various brands of FC headstamps, speculating that some lots were subcontracts or other manufacturers.
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