Choke Tube Fouling

Dear Technoid,

During a recent trip to Central America I shot just over a case of White Rhino trap loads through the improved cylinder tube of a Beretta A303 without cleaning the barrel. When I did remove the choke tube it was quite snug due to some residue between the barrel and the outside of the choke.

This was not surprising to me…however I was rather shocked to find considerable buildup of a black hard material in the bore of the choke itself…this was rather difficult to scrub out…definitely not plastic. I have never seen anything quite like this in a gun with solid chokes. A couple of questions arise about which the Technoid might wish to pontificate.

1) Is this fouling is caused by the significant difference in size between the bore and the skirt of the choke tube?

2) Does it influence the degree of choke? It seems as tho it certainly reduced the diameter of the IC tube…tho perhaps mostly in the forcing area.Has any testing been done on this subject?

Enjoy reading your column…


Dear Dennis,

I always note a fair amount of hard black build up on the outside rear of my Beretta choke tubes. This is burnt-on carbon and is very difficult to remove. It usually takes some soaking in Shooters Choice and then a fair amount of scrubbing. I have not found that solvent alone will clean it.

It might be noted that the Briley aftermarket chokes (both extended and flush) do NOT accumulate this carbon in my guns. They have a tighter fit at the skirt end of the choke and seal better. The Beretta chokes have more slop at the rear and permit gas build up to accumulate between the bore and choke.

As to building up of deposits reducing the choke area and thus increasing the choke- it depends. Two things happen when you junk up the inside of a choke

1) the diameter gets smaller (not always concentrically) and

2) friction in the choke is increased.

Smaller choke ID may affect pattern, but you never know how much until you put it on paper.

Increasing the friction on the wad also may affect pattern by retarding the wad. Some choke makers (Ljutic, for example) do this intentionally by scribing the core of their chokes. There are also various “wad stripper” chokes on the market. The belief is that retarding the wad keeps it from knocking into the shot cloud and disrupting the pattern as it exits the muzzle. Dunno about that, but that is what they are selling. I never though “stripping” the wad made the slightest difference.

The only way to measure the effect of the build up in your choke is to go out and do a before and after pattern. I am afraid that there is no way around it. Some homework is required to be a Junior Technoid. Leave the “write without testing” to the writers.

By the way, I once shot four cases (not flats, cases) of Indumil Colombian ammo in one day in the Cauca Valley and had an acquaintance who did that every single day of the trip. We had a bird boy clean our guns each evening, but I didn’t notice an abnormal amount of build-up in the choke area at the end of the day. You may want to take another look at those White Rhinos.

Best regards,

Bruce Buck
Shotgun Report’s Technoid

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2 Responses to Choke Tube Fouling

  1. James C Jones says:

    Not a comment, but a question: you write that you “shot four cases (not flats, cases)”. I’ve always used the terms interchangeably. What is the difference? Thanks.


    • A full case was traditionally considered 500 rounds, or 2 boxes (flats) of 250 rounds. I can’t remember seeing shotgun ammunition in full 500 round cases. They may have been standard a long time ago, but not in the past 30+ years. Currently, when shotgunner speak of “cases” they refer to boxes of 250 rounds. The Technoid may be dating himself.

      Franklin Pierce


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