How to choose a choke tube for Sport Shooting

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You have decided to use a choke tube for your sporting activities, but still can’t steer yourself towards a choice? You are in the right place, as this article aims to display the world of Gemini choke tubes, or rather, to try to guide you in choosing the choke tube that suits you best.

Flush, Ported or Extended?

Let’s start by saying that the choke tubes are mainly divided into three models; Flush (internal choke tubes), to be totally applied inside the barrel of the shotgun, Ported +20 mm and Extended +20 mm, to be applied inside the shotgun but sticking out 20 mm past the barrel.

The choice among these three models is really subjective, first of all it is essential to explain that the chief discriminating factor consists precisely in the positioning of the same. Are you looking for a choke tube entirely inserted into the barrel and with a lower weight? Then you should choose a Flush one (internal choke tube). You have no problem in terms of weight, you are looking for the utmost comfort and you take care of your equipment maniacally … including time to clean it frequently and thoroughly? Hence you should choose a Ported +20 mm one. You are aiming at a good performance, but you prefer an ordinary maintenance, without too many constraints? In that case we advise you to opt for an Extended +20 mm one. We would like to highlight that the weight is not a real discriminating factor, as at any time you can opt for a titanium choke tube instead a steel choke, suitable of reducing the weight by 40%.

Gemini boasts a wide range up to 14 constriction sizes for the Flush model (internal choke tubes) and up to 11 constriction sizes for the Ported +20 mm and the Extended +20 mm ones. As explained above, all of our choke tubes are made both of 42CrMo4 alloy steel, and Ti6Al4V (grade 5) Titanium Alloy. Steel is a super resistant and high-performance material, with different finishes (external grinding + internal lapping) and treatments (Nickel or Nickel + DLC). Titanium stands out for its strength, elasticity and lightness, shows-off the same finishes as steel and is exclusively available once it has undergone the DLC treatment.

How to orient yourself when choosing a choke tube for sport shooting.

In order to select the best suited model according to your shooting needs we have to mainly consider the type of discipline you practise and understand whether you are going to use the choke tube on the first barrel, the bottom one, which usually shoots closer and with a broader cone of fire, or the one on the second barrel, the top one, which shoots farther and with a tighter cone of fire.

What kind of sport shooting discipline do you practise? Trap, electrocibles, double trap, sporting or skeet? Once you have identified the model, i.e. whether you prefer a Flush choke tube (internal), a Ported +20 mm or an Extended +20 mm one – in compliance with the aforesaid indications – we shall focus on the type of constriction size.

What is the best suited choke tube for Trap shooting?

For Trap shooting with a Flush choke tube (internal) by way of example, we shall use choke tubes with an aperture ranging between 0.60 and 0.80 (also indicated with 6-7-8) on the first barrel and choke tubes ranging from 0,80 to 1,10 (also indicated with 8-9-10-11) on the second barrel, while if we opt for Ported +20 mm and Extended +20 mm models we shall chose a modified (M), improved modified (IM) or light full (LF) type on the first barrel and a full (F), extra full (XF) and extra full (XXF) one on the second barrel.

What is the best suited choke tube for Double Trap shooting?

Do you practise Double Trap shooting? We recommend you use the Flush (internal) model with choke tubes ranging from 0,30 to 0,50 (also indicated with 3-4-5) on the first barrel and with sizes ranging from 0,50 and 0,70 (also indicated 5-6-7) on the second barrel. On the other hand we suggest improved cylinder (IC), light modified (LM) and modified (M) in the first barrel while modified (M) and improved modified (IM) in the second barrel for Ported +20 mm and Extended +20 mm models.

For any type of shooting the suitable choke tubes.

To further simplify the explanation and guide you correctly for the best choice, we have drawn the table below showing the choke tube models and the relevant sport disciplines, so as to specifically identify the two, three models best suited to your "style".

  TrapDouble TrapElectrociblesSkeetSporting
First barrelFlush from 0,60 to 0,80 from 0,30 to 0,50 from 0,50 to 0,60 from -0,30 to 0,00 from 0,30 to 0,50
Second barrelFlush from 0,80 to 1,10 from 0,50 to 0,70 from 0,70 to 0,80 from 0,10 to 0,30 from 0,50 to 0,70
First barrelPorted M, IM, LF IC, LM, M M, IM SK2, C IC, LM, M
Second barrelPorted F, XF, XXF M, IM IM, LF SK1, IC M, IM
First barrelExtended M, IM, LF IC, LM, M M, IM SK2, C IC, LM, M
Second barrelExtended F, XF, XXF M, IM IM, LF SK1, IC M, IM

In order to understand the correspondence between the different systems of indicating the constriction size value (letters, *, decimals) refer to the following second table.

Flush (internal)
with 7 constriction sizes
Flush (internal)
with 14 constriction sizes
Ported and
In/Out +50
In/Out +100
XXFExtra Extra Full- - - 1,14 -
XFExtra Full- 1,20 1,10 1,02/1,20* 1,20
FFull* 1,00 1,00 0,89/1,00* 1,00
--- - 0,90 - -
--- - 0,80 - -
LFLight Full- - - 0,76 -
IMImproved Modified** 0,75 0,70 0,63/0,75* 0,75
--- - 0,60 - -
MModified*** 0,50 0,50 0,50 0,50
--- - 0,40 - -
LMLight Modified- - - 0,38 -
ICImproved Cylinder**** 0,25 0,30 0,25 0,25
--- - 0,20 - -
--- - 0,10 - -
SK1Skeet 1- - - 0,15/0,13* -
CCilinder***** 0,10 0,00 0,00/0,10* -
--- - -0,10 - -
SK2Skeet 2- -0,30 -0,30 -0,30 -

* the constriction size may vary depending on the model range, consult the catalogue for more details

Is that a bit clearer now? Well, keep in mind that these are general guidelines, moreover Gemini is always recommending that you purchase two or three models of choke tubes and spend some time performing ballistic tests in order to try out them empirically. There are additional variables that may affect the shooting performance, such as the type of cartridge chosen, which we prefer not to deepen at this stage to avoid creating too much confusion.

The present analysis refers to the 12- gauge shotguns, but there are Gemini choke tubes suitable for 20-, 28- and 36- gauge ones.