Oh dear another choke question !

[jwpzx9r]

I know , I know a subject hated and brought up quite frequently by me! ... but here goes

Do some manufacturers have different measurements for what constitutes a certain choke ? The reason I as is that last week when shooting a great and heated debate erupted at the shooting ground between some of the better shooters about choke measurements. This lead to one of them fetching his bore measurer and he went round the guns on the rack and measured the choke of each make. The up shot of this was that the Browning guns and the Kemmen's measured at the expected choke diameter measurement for say 3/4 and full whereas the Perazzi's were incredibly tight when measured. Both my gun and another measured at 17.325 mm for 3/4 on a 18.4 mm barrel and 16.845mm for full ! Is there any way that Perazzi have tested their barrels in the past and used that to get an observed choke size then bore their barrels accordingly or are they really just very tight ? I have never patterned my gun but I am going to next week as there is a patterning board at that shoot.

 

[Dibs]

.

 

[Skeet UK]

I know , I know a subject hated and brought up quite frequently by me! ... but here goes

Do some manufacturers have different measurements for what constitutes a certain choke ? The reason I as is that last week when shooting a great and heated debate erupted at the shooting ground between some of the better shooters about choke measurements. This lead to one of them fetching his bore measurer and he went round the guns on the rack and measured the choke of each make. The up shot of this was that the Browning guns and the Kemmen's measured at the expected choke diameter measurement for say 3/4 and full whereas the Perazzi's were incredibly tight when measured. Both my gun and another measured at 17.325 mm for 3/4 on a 18.4 mm barrel and 16.845mm for full ! Is there any way that Perazzi have tested their barrels in the past and used that to get an observed choke size then bore their barrels accordingly or are they really just very tight ? I have never patterned my gun but I am going to next week as there is a patterning board at that shoot.

Yes, they differ a fair bit.

As you know, choke is relative to the bore diameter.

Traditionally, full choke was 30 th/inch of constriction from cylinder.

So your gun, with an 18.4mm Bore and choke measurement of 17.325 mm is VERY tight for a 3/4.

25.4 / 1000 = 0.0254mm

3/4 choke should be around 25 thousandths of constriction so should measure around 17.765mm

The difference between bore and choke on your gun is 1.075mm and 1.555, which when divided into thousandths of an inch is

1.075 / 0.0254 = 42.3

1.555 / 0.0254 = 61.2

So your gun, has slightly over Extra Full and EXTRA EXTRA EXTRA FULL as a designation.

That is without considering your cartridge, and how loose or tight a pattern it throws. 

But it is all academic really.  What matters is what pattern you get at the range that you want, which you can check and tweak on a pattern plate

I wouldn't put any steel through it though!!  Maybe some nice Fibre carts, will give you a more open pattern.

 

[jwpzx9r]

Of course there is no saying his device for measurement was giving the correct reading... but it seemed to be right for the choking on the Browning and Kemmen guns both the Perrazi's were very tight when you just base the choke on barrel restriction. I have read somewhere that if a gun is over choked then the effect of choke is lost and the pattern disintegrates but the other gun that was measured the guy shoots 25 at UT and OT 75 - 80% of the time he has no problem and I have some great breaks with my gun and am not complaining!

 

[Finners]

I think I need a drink :crazy:

 

[ips]

Makes you wonder weather "proper" trap guns from Italian stables have designed there barrels to shoot 24G specifically therefore "generally regarded" choke designation is somewhat pointless as far as comparison ??

 

[no.1topdog]

As you know, choke is relative to the bore diameter.

Traditionally, full choke was 30 th/inch of constriction from cylinder.

When I was a lad, full choke was a 40"thou. variation from cylinder?  :biggrin:

Has it changed since we converted to metric?  

 

[ips]

Agree 40 thou is what i consider it to be but in these days of weird barell configuration with over bore and forcing cones and the like the old measurements don't prob mean much. Perhaps ?

 

[no.1topdog]

Agree 40 thou is what i consider it to be but in these days of weird barell configuration with over bore and forcing cones and the like the old measurements don't prob mean much. Perhaps ?

Funny you should mention that Ips.

On the new DT11 with it's extra, extra long forcing cones, I wonder where you would measure the bore size to compare the choke constriction with, as its virtually constricting almost to the area the chokes sit?

The normal bore micrometer has a mark on it denoting the point from the muzzle to take the measurement, (can't remember this measurement but 13" in, rings a bell. A Gunsmithing type will know this) but if you did this on the DT11 I think you would still be in a tapering part of the forcing cone, and therefore not the thinnest part of the barrel wall?

In the future that may make it a bit ambiguous checking one is still in proof. I would be interested to see if anyone knows how this would be done by The Proof House, and where you would stand with one that was a little shot out. Probably not something I need to worry about in my lifetime though?    :biggrin:

 

[jwpzx9r]

To be honest I wonder if his measurements were correct.. but both Perazzi's measured up the same, the Browning's were much more open as was his own Kemmen. I find it very strange that my gun is marked by Perazzi as being half choke ... three dots yet it measured almost exactly the same as one marked 3/4 two dots ? And also on the action of my gun under the ejector it is marked 1 and .9 ?? So many conflicting things. I wondered about the 1 and .9 on the action but did not think anybody would have a gun choked at  9/10 and 10/10 but is this possible ?

 

[Wonko the Sane]

Were the barrels clean?  

I've measured a number of barrels, Perazzi and others and I've never seen a 12ga choke that tight.  The tightest Perazzi choke I've come across was a 0.682 and that was marked " * ". 

The 0.663 "/16.845 is maybe close to impossible.  I would certainly suspect the measuring device.  I have two ways of checking mine and do it often enough to know it's on the money.

Mostly I would caution you to pay little attention to the plate since without some rigorous analysis patterns are not very informative EXCEPT to tell you that the gun is shooting where you want it.

from Neil Winston recently  

Four feet by four feet tells you everything you need to know about patterns

*tell you everything you need too know about patterns, that is, if you count all the pellets and shoot several (traditionally 10) patterns. If, however, you don't count pellets then really even a 48x48 target tells you essentially nothing about your patterns since you cannot judge patterns "by eye" except where the pattern is relative to the aiming mark and at 40 yards even that is far from certain.

Thirteen yards (or other close distance if you prefer and shoot enough at that distance to know what you are looking at) does a better job considering the fact that no one is going to do the hard stuff and shooters just want to play-test their guns "at the plate' which you can only say wearing Harris tweeds and a deerstalker.

The opening pages of this booklet

http://www.mn-trap.org/tech_corner/n_winston/Point_of_Impact_and_Pattern_Testing_at_13_Yards.pdf

describe a pattern-board which works great not only for the imaginary testing so popular here and in gun-club discussions but also for real testing, really finding out what's going on. If the spirit should ever move either you or someone at your club, this paper-based setup, paired with Andrew Jones' Shotgun Insight pellet-reading program, will allow you to find out how your gun actually shoots. There's no other way.

But really, 13 yards, using paper, will tell you if there is anything to worry about and in a few minutes, not weeks of achingly dull work.

Neil

One if the interesting things about patterns is that once you have seen a few, you really have have seen them all. But you have to do all that work just to find that out. Another other interesting thing is that almost all of what you have read and heard about patterns is total bull but no one is ever going to know since who, realistically, is going to do the work to find out?

There is a section on the friendliest site so packed with patterning nonsense it takes your breath away, but only Rastoff points any of it out and they just ignore him.

There really is nothing new under the sun. Except new hope, new ways for us to avoid the hard work of trapshooting practice by just buying something instead.

Neil

the whole thread at http://www.trapshooters.com/threads/99-pattern-board-at-40-yards.221169/

 

[jwpzx9r]

To be honest I doubt the actual measurement Charlie... but what about those figures stamped on the action of my gun under the ejector on the left hand side marked 1 and .9 although wait a minute I may have read that as upside down if you will may be it is .6 and 1 which would be correct for my gun which is stamped with three dots for the first and one for the second that makes much more sense! you would have to hold the barrels upside down to read it that way but hey it is an Italian gun

 

[ips]

I really don't care about pattern plate or choke measurement the only thing that tells you anything is kill quality on the shot as many things come into play on the actual shot

 

[Wonko the Sane]

I believe that the #'s under the ejector are date codes.  If you compare them to the proof code date I think you will find a correspondence.

"I really don't care about pattern plate or choke measurement the only thing that tells you anything is kill quality on the shot as many things come into play on the actual shot "

Mr. ips is certainly correct.  My only comment would be that the markings give me some convenient notice of expectations, not resullts.

 

[jwpzx9r]

Correct again Charlie my gun is indeed proofed for 1991 !

 

[Hotshot100]

I know , I know a subject hated and brought up quite frequently by me! ... but here goes

Do some manufacturers have different measurements for what constitutes a certain choke ? The reason I as is that last week when shooting a great and heated debate erupted at the shooting ground between some of the better shooters about choke measurements. This lead to one of them fetching his bore measurer and he went round the guns on the rack and measured the choke of each make. The up shot of this was that the Browning guns and the Kemmen's measured at the expected choke diameter measurement for say 3/4 and full whereas the Perazzi's were incredibly tight when measured. Both my gun and another measured at 17.325 mm for 3/4 on a 18.4 mm barrel and 16.845mm for full ! Is there any way that Perazzi have tested their barrels in the past and used that to get an observed choke size then bore their barrels accordingly or are they really just very tight ? I have never patterned my gun but I am going to next week as there is a patterning board at that shoot.

If he used a 'carrot' choke gauge it would be inaccurate as the bore sizes would vary. Some Perazzi's are 18.4 and others are 18.7. Brownings and Miroku's vary depending on whether or not they're back bored. 

 

[** Pending Removal **]

And....older Perazzis were made / tuned for 36grms as that was the OT load at the time.

Now they are tuned for 24grm.

I have examples of both and know the difference when we are shooting 36grm competitions or 28 and below competition.

Took sometime to realise the reason for the difference in results.....then discussion with an expert...then 'bingo'.......the light came on...!!

When we cannot fly guns anymore....I know which ones will be living abroad :wink:

 

[Skeet UK]

When I was a lad, full choke was a 40"thou. variation from cylinder? :biggrin:

Has it changed since we converted to metric?

This is what I thought when I first wrote it, but I thought I should check, and I found something similar to this

http://www.pakguns.com/attachment.php?attachmentid=8260&d=1328719095

Having checked again, it seems I was on the right track. Various sources claim full choke to be anywhere between 30 and 40 thou. So I guess this is where the problem comes from!

 

[jwpzx9r]

The guy was using some sort of digital calliper type thingy that to be fair read to three places but what ever both the P guns were way tighter then the others and both have 18.4 bores. I have been using 24g cartridges through mine and some of the breaks are incredible, mine is a 91 gun don't know when they changed to 24g. I would say it shoots the 24g carts better than the 28g to be honest but that could be a crock
Its funny because it would appear that the debate actually centred around cartridges. The man with the measuring device was using Clever RVS carts that use carbon /quartz treated shot ??? He reckoned that the choke was crucial in the way the skirt opened after leaving the barrel too tight and you are goosed, guy with the P gun who had just plastered a 25 straight told him he was talking crap, he was using Clever T4 ! All in French with a country dialect, try to imagine two yokels .... it was like the start of WWIII :fie:  Great to watch and listen in

Is it really necessary to use such expensive carts for practice ??