Home Forums Hunting & Shooting Single Shots Purpose of the slit on a B78's falling block....?

Could someone please clarify the purpose or function of the thin quarter inch long horizontal slit which is just visible on the upper left side of the B78's falling block ? I�ve never disassembled the action of mine so I don�t have a practical explanation - possibly a gas vent for a faulty cartridge!? Cheers,Ross.

Nearly 70 views and nobody knows the purpose of this rather mysterious slit in the actual falling block mechanism - as clearly observed when in it's in the upper most position (lever fully closed). I'm simply curious by nature, hence my reason for asking.

I have one of these and I never recall seeing any slit on the breechblock either when it's together or when I've had it apart. A picture would really help. Short of that, it's only conjecture on my, or others', part. Take care.

Don't own a B78, but I do have a High Wall 45-90 and a sharps Rfile. The sliding wege block bleeds off gases from a pierced primer or ruptured case through the firing pin hole and downwards to a gas relief hole or slot that directs hot gases down and away from the shooter's eyes and hands. Back in the olden days when the design first hit the fields, pierced primers and blown cases were very common and the fix was both simple and effective AND (a rare occurence) retained because it wuz such a good idea in the first place.

Gewehrfreund, unfortunately I don�t currently own a digital camera so I can�t post a relevant photo of the thin offending slit on the upper left hand side of the breechblock.
I�ve actually slipped the end of a narrow strip of paper into the hollow breechblock !

EvilTwin�s notion of possible gases diffusing through the firing pin hole and downwards to a gas relief hole or slot that then directs the hot gases down and away from the shooter's eyes and hands certainly sounds feasible � rather than almost directly into the shooter�s face via this mysterious slit.

Note, after unsuccessfully studying Browning�s schematic drawings of their similar 1885 High Wall model for a possible answer I elected to seek an explanation from a Gunsmith sourced from Browning's Authorised Service Centre Listing � I�m still waiting for their email response.

My B78 High Power single shot is a 1978 model, .243 Win, with a 26� round barrel � bought second-hand 3 years ago. Heaven knows why but I�m beginning to wonder if the previous owner�s responsible for this very odd slit.
Thanks for your input. Ross.

I took a look at a B78 this morning and I think I see what you mean. With the action closed, the breech block barely exposes a cut in the left side.


I think this is normal and yours has not been modified. The schematic shows a fairly large notch in the left side.



If this is for gas control as Eviltwin suggests, then I think the notch should not extend above the sidewall. This may have been a manufacturing error.

You are very fortunate to have a .243 as these are quite rare in B78's. If you feel it is unsafe, feel free to send it to me for proper disposal

Jerry

Jerry, your blood�s worth bottling ! Thanks ever so much for visually clarifying the �common� existence of this odd notch/slot/slit on the upper left side of the B78�s breechblock � I�m certainly relieved. As you inferred it might be a manufacturing and/or design error � particularly if it�s an exposed gas vent. How unsafe it is I�m not sure but as to sending my apparently rare .243 to you for proper disposal � sorry, I absolutely love this very unique and otherwise beautifully constructed rifle !! I�m most grateful for your time and effort in solving this issue. Cheers from �downunder�, Ross.

I have a B-78 in 45-70, I have never noticed this notch on mine. I will look at it tomorrow and see if mine has the notch that your .243 has.
Good shooting!
Marcus.

Guys,

I pried open my vault to check my B-76's.
It seems to be a manufacturing variation! My hornet with 22" octogonal bbl. does not have this slot. However my 244 rem. 26"
round bbl. does. Perhaps this is because rimmed vs rimless??