Bolt with vent holes modification??

[TactAdv]

Okay, so first time I've seen a BREN bolt so modified-
http://www.brpguns.com/mk-1-bren-lot-w-cut-receiver/

Anyone want to speculate, beyond the obvious??
Origins?? Who/when/where??
Any possible reason beyond gas venting??
Ever seen another so modified?

-TomH

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Brit plumber]

If it’s what i think it is, it’s the early bolt used on the early Mk1 guns.

And yes I reckon I have a few dozen or so, but deactivated.

[TactAdv]

Okay, good to know! BTW, there is a face-on picture of said bolt at the link I provided.

So then, thinking all things BRNO-ish/Czech-ish at the time there, WHY the extra holes in the bolt face?? Obvious answer to me is same as vent hole in side of Mauser bolt action rings- catastrophic overboard gas vent in case of case rupture.

But it's been said over and over...."no deviation was permitted" from the signed-off BRNO drawings, at least early on??

And yet my period, live-never altered, Zb-30 doesn't have those extra bolt face holes?? I'd've thought both guns might share that.
-TomH

[Peter Laidler]

They are simply gas vent holes to draw away any gas leeching from the primer or in the case of a burst cap - which plagued the early .303 trials. I was found to be an unnecessary frill and quietly dropped from production. The part number of the block remained the same after it was deleted. The only mention I ever found about it was to the effect that while they were to be deleted from further production existing stocks (of the vented blocks?) were to be utilised in the normal way. In real life, so I was informed, the gas leeching and blown-out caps problems ceased once the big dumpy oval firing pin was introduced, which spread the cap into the primer pocket immediately on fitting and reinforced by the ejector which added a firm stake mark. End of problem

[CINDERS]

As usual Peter the hands on experience shines through with the explanation.