Screw Choke Profiles

Dear Technoid,

Browning Maxus choke inlets 19.2 mm. but the inside of the barrel is 18.80 mm . Why don’t choke entries start from 18.80? I sent a sample photo.

Thank you so much

Best regards



Good question. But there is a very good reason why the rear, or skirt, of the choke should always be larger than the bore of the gun. If the rear of the choke were smaller than the bore, the shot and wad would eventually push out the choke after hitting that skirt ridge a number of times. That doesn’t happen in the normal choke constriction as that is a smoother transition and gives the shot time to squeeze down. Ideally, the rear of the choke should be exactly the same size as the bore for a smooth transition from bore to choke. But in the real world, due to variances in bores and chokes of mass-produced guns, manufacturers like to build in a little bit of safety and make sure that the rear of the choke is larger than the bore. Custom gun makers and choke makers can tailor the choke skirts for exact fits if they take the time, but mass production needs a little more leeway.

A small difference between the bore and choke skirt probably doesn’t matter. A large difference would mean a bit of an expansion when the shot column makes the jump and that probably isn’t good for the pattern. Of course, the ideal chokes are fixed chokes as there is no variance or jump in those. Fixed chokes can also be more efficient as they can vary the length of the choke with its constriction. Tighter chokes need more constriction, hence more length, than open chokes. Screw chokes are all the same length, regardless of the constriction. Then again, you can’t swap fixed chokes in and out, so that’s the trade-off.

Best regards,
Bruce Buck
Shotgun Report’s Technoid

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1 Response to Screw Choke Profiles

  1. Gerald Elwood says:

    Just my opinion. When the wad makes the jump from barrel to choke you have plastic build up on contact. The wad slows down the lead continues down the choke. You can see marks on the choke inner surface similar to marks in the barrel as in the old days of fixed chokes and fiber wads.


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