Chamber of Benelli B76 9mm pistol

J

JiriK

Inactive
I bought this pistol a couple of months ago. Haven´t shot much with it, but some rounds have gone thru.

I noticed odd markings on the chamber. Hard to take a good picture, but some are attached.

Notice the cuts on the barrel, just where the chamber ends?
Is this normal for B76? If yes, why did they make those cuts..
 

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The cuts are there to "float" the case on a pad of high-pressure gases to aid in extraction. Similar function to the fluting in HK rifle chambers. So yes, they are normal.
 
Any time the gun design allows the breech to open with significant pressure still in the chamber, there has to be some means of "floating" the case or else the extractor will tear through the case head or even tear it off completely. That is not needed in designs like the 1911 or the M9 because they have breeches that are fully locked until the pressure drops to near-ambient levels, or in normal blowback pistols where breechblock mass keeps the action closed until the pressure drops..

Jim
 
James , good explaination ! They did ,in some of early HK developments prove that ,they actually tore off the head of the case ! :eek:
I love my HK P7 ! :)

Certainly here, the Benelli is a rare piece but it is a delayed blowback for sure .
 
Ok, thanks for explanation.

I guess this also explains, why the brass this pistol ejects is so dirty.

I thought my loads (cast bullet with close to min. charge of powder) were too light and not enough pressure to seal the shell in the chamber. But that´s not the case.
 
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