Hello all, I'm building a M4 style .223 Wylde barrel. Do I need to headspace the bolt with .223, or 5.56 gauges? Or can it be either?

This is my first time with this caliber. The barrel is a 1/8 twist (I like that).

Thanks!

Use a 5.56 to check headspace.
Colt spec 5.56 NATO
https://www.brownells.com/guns...aspx?sku=100-010-713

Not sure why the first post was deleted as it had good info.

223 Wylde is a hybrid chamber not the cartridge.
While .223 can be shot from a 5.56, .223 Wylde is supposed to shoot .223 more accurately.

I shoot .223 and 5.56 NATO (M855) through 5.56 NATO and .223 Wylde chambers.
I have 5.56 GO, .223 NOGO and 5.56 field gauges.

I deleted it, felt it came off a bit wrong where as you simply answered the OP's question.

Thanks folks! I have 5.56 go, no go, and field. I’ll check it with those.

IIRC the wylde chamber is more about the throat vs the datum line used to check headspace, correct?

I'm not sure how that works out.
Myself, if it closes on a 5.56 Go, then I consider it good if you plan on shooting 5.56 through it.

Mine is an 18" WC SS barrel and not something I would be shooting M855 with anyway but I still checked it.

The .223 Wylde was developed for one specific thing.
CMP/DCM matches using 69-75 gr at 200 and 300 yds and single loading an 80 gr SMK for 600.

So far I've had two 5.56 and two .223 Wylde.
I have the Colt spec 1.4646" that all closed on.
From what I've read of others using the 1.4646 and not closing it wouldn't close on a .223 1.4636" either.

If I had one that only closed on the 223 I wouldn't sweat it.
If it doesn't close on a 1.4636" then it's bolt swapping time.