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#574019 - 06/18/20 09:55 AM Browning Invector Plus Chokes query
wootang Offline
Boxlock

Registered: 07/13/19
Posts: 21
Loc: Suffolk, UK
Can anyone kindly advise on design dimensions of these chokes please?
I have a multichoke B525 sporter 1 and was thinking of obtaining some additional chokes for the skeet range. It was proofed at 18.7mm (0.736") both tubes, and still measures that. So some degree of over/back boring present. I have a standard set of Browning chokes at 1/4, 1/2, 3/4 and full UK sizing.
On inspection and with chokes installed, i note a distinct step at the junction of the breech end of the chokes and the muzzle end of the bores (pre-choke) All 4 chokes measure the same 0.750" bore at the breech end and taper according to the particular choke size. Please see attached NTS drawing.

So to my queries, the difference in bore diameter between each end of the chokes seem to conform approx to the expected constriction for each choke size ie 10, 20, 30 & 40 thou, however would the previously mentioned step not negate this? or does the conventional method of choke measuring not apply to invector plus chokes with over-bored tubes and the choke is determined purely on pellet count % in the circle at set yards?
I have not pattern tested any of the chokes, but would like to know if the step should be there by design?
I usually shoot antique muzzle loaders and early breech loading hammer guns, so removable chokes are new to me!
Many thanks.

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#574021 - 06/18/20 11:31 AM Re: Browning Invector Plus Chokes query [Re: wootang]
lagopus Offline
Sidelock
***

Registered: 06/22/08
Posts: 2476
Loc: Derbyshire, England
Sorry to come in on Wootang's interesting question but it is along the same lines; can Browning Invector Plus Chokes be used in Winchester SX4 semi autos too? Lagopus…..

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#574025 - 06/18/20 11:43 AM Re: Browning Invector Plus Chokes query [Re: wootang]
Shotgunjones Offline
Sidelock
**

Registered: 02/16/03
Posts: 3686
Loc: Michigan
The 'step' is required to some degree on all screw in choke systems. There's also a bevel there.

This is necessary for safety, to keep gas from getting behind the choke tube and blowing things up. It also keeps lead and wad material from shaving and accumulating at the junction and acting as an obstruction.

This results in some 'jug' effect and varies considerably by manufacturer.

In general, screw in chokes shoot tighter than marked.

That said, factory supplied Invector+ (flush length) have a poor reputation in constrictions of modified or tighter. The various extended aftermarket chokes for this system are a HUGE improvement. The 'Midas' chokes shoot way better than flush ones and are rumored to be made by Briley.

For skeet in my Invector+ guns I use Briley chokes marked 'Cylinder'. There is still some effective choke constriction in those chokes because of the 'jug' section that's just part of the design. They work very well for skeet.
_________________________
"The price of good shotgunnery is constant practice" - Fred Kimble

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#574026 - 06/18/20 11:52 AM Re: Browning Invector Plus Chokes query [Re: wootang]
Shotgunjones Offline
Sidelock
**

Registered: 02/16/03
Posts: 3686
Loc: Michigan
Winchester shows the SX4 as equipped with Invector+.

So, yes, Browning chokes will work too.

As will the various aftermarket chokes made for Invector Plus.
_________________________
"The price of good shotgunnery is constant practice" - Fred Kimble

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#574033 - 06/18/20 01:08 PM Re: Browning Invector Plus Chokes query [Re: wootang]
Drew Hause Offline
Sidelock
***

Registered: 01/18/06
Posts: 7904
Loc: AZ but dreaming of KS
Good illustration of the step



It appears the tube is not however fully seated, allowing burnt power debris to accumulate in the gap, and with enough build up, blow out the tube

This is more likely from a dropped tube with bent skirt


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#574040 - 06/18/20 01:49 PM Re: Browning Invector Plus Chokes query [Re: wootang]
wootang Offline
Boxlock

Registered: 07/13/19
Posts: 21
Loc: Suffolk, UK
Thanks guys, interesting explanations as to why the "step" is there. The greater the step i would guess the bigger the discepancy in actual to marked choke performance?
Sounds like some "jugging" is occuring with the design of these chokes, which is why the maths doesn't add up.
I would normally shoot UK 1/4 and 1/2 (US imp cyl and mod) on sporting clays, but from reading this would UK imp cyl and 3/8 (US skt and light mod) chokes equate more to this?
And for skeet, cylinder and cylinder seems the way to go?
Appreciating all you input.

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#574044 - 06/18/20 03:00 PM Re: Browning Invector Plus Chokes query [Re: wootang]
DmColonial Offline
Sidelock
**

Registered: 01/27/09
Posts: 338
Loc: Canada
Only the pattern board knows.....
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Dumb, but learning...

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#574050 - 06/18/20 05:01 PM Re: Browning Invector Plus Chokes query [Re: wootang]
Shotgunjones Offline
Sidelock
**

Registered: 02/16/03
Posts: 3686
Loc: Michigan
Originally Posted By: wootang
Thanks guys, interesting explanations as to why the "step" is there. The greater the step i would guess the bigger the discepancy in actual to marked choke performance?
Sounds like some "jugging" is occuring with the design of these chokes, which is why the maths doesn't add up.
I would normally shoot UK 1/4 and 1/2 (US imp cyl and mod) on sporting clays, but from reading this would UK imp cyl and 3/8 (US skt and light mod) chokes equate more to this?
And for skeet, cylinder and cylinder seems the way to go?
Appreciating all you input.


That's about right.

It depends on the length of the choke 'leade' (for lack of a better word) as to how much jug effect you might observe.

Invector+ is a good sturdy system, at least the threads are not under the choke constriction like Beretta did with the Mobil Choke.

Not every mistake results in a blown barrel either. I once changed out a Beretta Optima choke at a sporting clays station, got distracted, and forgot to tighten it down. I shot 8 targets with it held in the barrel of the 391 by about 2 threads. No damage. My lucky day I guess.

Another time my shooting partner did the same thing with the choke just inserted and not threaded at all. I watched the choke sail off, kept my eye on it, and we walked right out and picked it up.
_________________________
"The price of good shotgunnery is constant practice" - Fred Kimble

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#574075 - 06/19/20 09:37 AM Re: Browning Invector Plus Chokes query [Re: wootang]
lagopus Offline
Sidelock
***

Registered: 06/22/08
Posts: 2476
Loc: Derbyshire, England
Shotgunjones, thanks for the info. I fairly recently bought an SX4 for vermin at work and it only came with three choke tubes. I already had some Browning Invector Plus choke tubes that I bought in a box of bits at an auction. The SX4 lacks a full choke tube in the package so now I can tighten up when needed. It looked to fit and I couldn't see any join so suspected that would be the case. Thanks again and apologies to Wootang for coming in on his similar topic. Lagopus…..

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#574092 - 06/19/20 01:54 PM Re: Browning Invector Plus Chokes query [Re: wootang]
wootang Offline
Boxlock

Registered: 07/13/19
Posts: 21
Loc: Suffolk, UK
No problem Lagopus, glad my OP helped you out. If you have any invector + cylinder and skeet tubes you don't require, please PM me as i see you are also in the UK.

Thanks to Shotgunjones for the "leade" theory, ie the point up the choke taper that the shot column hits before being constricted (if it doesn't immediately expand upon passing the step?). Thinking about that and checking my choke dimensions, i see that the lighter chokes have a greater than expected total restriction, whereas the tighter ones do not. Could this explain why the tighter chokes perhaps do not perform so well?
Does anyone have a skeet and a cylinder invector + choke they could measure to add information to this?

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