Newb Question

[Static030]

Hey Guys - I'm pretty new to shooting and have read some posts on this topic but want some opinions of those who know, and there are a lot Nutz that know their stuff.
I don't want to spark the age old debate about 223 vs 5.56 buttttt I purchased 1000 rounds of advertised .223 REM Sellier & Bellot from one of the advertisers here. When it showed up the box says .223 REM / 5.56x45. There is nothing noted about it on the website to say anything about 5.56. I have a Remington 700 VTR, and contacted remington about this topic.....their response was as expected - "Don't shoot anything in the rifle that doesn't have a headstamp that matches your rifle". I just get a little worried, and like I said am pretty new to this. I went to Sellier and Bellot's website, found the spec for this ammo and again nothing mention about 5.56 just 223-Rem. FMJ but doesn't give any load spec's. BTW the headstamp on the ammo is 5.56x45.
I called the store and they assured me that these will be fine and that there is some discrepancy between North America and Europe. S&B say this debate is a North American phenomenon.

What do you guys think? And sorry for opening this door again. If I missed any critical information - let me know.
Thanks

 

[Tinman204]

While I'm no expert in either of these calibers some quick research told me this.

Bothe .223 and 5.56x45 are BERY similar in dimension. The main difference is the 5.56x45 has a longer throat and runs at a higher pressure.

Generally it is said that it is ok to shoot .223 in a 5.56x45 chambered gun but it shouldn't go the other way around. 5.56x45 shouldn't be fired in a .223 from what I've read.

Now that being said others probably will chime in and give specifics about the ammo you bought and wether it should be fired or not.

Hope this shed a little light on the situation.

 

[Static030]

I understand that there could or is a pressure difference but how can a store advertise .223 then send 5.56x45?
Ok I have done some physical measurements:
Commercial round has a bit of a hollow point and the 5.56 has a rounded tip
Overall length
.223 = 56.35mm
5.56 = 56.21mm
Throat to "head"
.223 = 44.53mm
5.56 = 44.61mm
Bullet @ throat
.223 = 5.66mm
5.56 = 5.66mm
Casing at the "head"
.223 = 9.47mm
5.56 = 9.46mm
Now I was planning on firing the 5.56 tomorrow and then doing a water volume test on both.
Any thoughts on this?

 

[jonnyc]

They are the same thing. If military "5.56" won't fit into your commercial ".223" chamber it is simply because military chambers are usually cut a bit more generous to accommodate different manufacturers and a bit of dirt....commercial chambers not so much.
And you are bound to find dimensional differences between the different manufacturers of the same cartridge.