Bifurcated Lumps & Trunnions


                   Bifurcated Lumps                                                        


Bifurcated Lumps - A locking system for over & under guns whereby the barrels are fitted with semi-circular hooks that hinge around trunnions on either side of the lower barrel. A pair of bolts move forward into recesses on either side of the barrel-set when the gun is closed. This system makes it possible to build an over & under gun with a sleeker, lower profile than possible when mounting the lumps, hook, and locking bites to the underside of the bottom barrel. Boss, Woodward, Perazzi and most Beretta Over/Under guns are built with bifurcated lumps. (Bifurcated, means split in two.)


Inside the receiver of an A&S Over/Under. The bifurcated lumps engage trunnions on either side of the knuckle, just above the cocking rods.


  Trunnions on a cannon barrel



Browning Superposed and Merkel Over/Under guns, on the other hand, are built with lumps under the barrels and with the hook revolving around a traditional hingepin. While strong, this design results in a gun with a taller profile than does the bifurcated lump design.


The Hallowell & Co. Illustrated Firearms Dictionary is for informational purposes only. We do not necessarily offer the items described above for sale. Please click on any of the links below to see what we actually do have available for purchase.

American Shotguns      English Shotguns       European Shotguns      Double Rifles      Magazine Rifles        Single Shot Rifles      Combination Guns

Winchester      Colt      Smith & Wesson        Other Handguns          Antique Guns       New Arrivals             Custom Knives          Other Neat Stuff


Who We Are       How to Order      We want to buy your Gun(s)       Recommended Links     Historical Gallery         

Firearms Definitions, Abbreviations & Opinions     Store Photos     Magazine Articles          Home  

Hallowell & Co., Inc. PO Box 1445. Livingston, Montana  59047   USA   Tel: 406 222-4770    Fax: 406 222-4792     Email:

Hours: Tuesday - Saturday, 10 - 6.   (Mountain Time)   Our inventory is constantly changing. Please bookmark this site and return often.