Bulged .223 cases fired from AR

[wwillson]

All,

My Bushmaster Varminter leaves a bulge in every case that comes out of its chamber. The bulge is on one side of the case, while the other side is left unbulged. Maybe the chamber is reamed non-concentric to improve feeding?

[BarryinIN]

It is so far forward I don't think it's from a feeding mod. That would be farther back I would think.

I have a theory if you want to hear it.

My guess is the chamber is uniformly oversize.

And the ejector is pushing the case over to one side.

And the bulge is forming on the opposite side.

Rifles with plunger type electors will give constant pressure against the case, forcing it toward one side of the chamber. Usually chambers are tight enough the case won't really be moved over. It would be more like the case being held in place but with a twisting pressure against it.

With an oversize chamber, the ejector will be able to move it farther, and will have enough unsupported space on the other side to let it bulge.

Can you tell if the bulge is always opposite the ejector and more or less on the extra for side?

If you can tell, try chambering a few cartridges the same orientation (makers name at 12:00 for example) and firing them. If the bulge is always on the same side, and that side is opposite the ejector, I'd say that was it.

(I've seen this in Garands. Plunger ejector there too.)

[jjjxlr8]

Does this barrel have on of the .223 Wylde chambers?

[wwillson]

Does this barrel have on of the .223 Wylde chambers?

From Bushmaster's site:

Quote:

This non-chrome lined barrel is button rifled 1 x 9"; has a hybrid SAAMI Spec. chamber with longer throat or "Leade" to accommodate 5.56mm ammunition