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 Post subject: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Mon Dec 16, 2019 7:20 pm 
Field Grade

Joined: Mon Mar 26, 2012 8:15 pm
Posts: 92
Location: Pittsburgh, PA
So I assume any of you that have bought newer B Rizzinis have noticed the choke markings.
Maybe it is only 12ga models, I dont know.

I recently bought a new leftover BR320. (2015/16)
The chokes had me confused with their markings.
Cylinder choke says "IC on 18.6 Overbored Barrels".
All chokes are marked as .010" tighter on overbored barrels.

https://photos.app.goo.gl/X1VY6mabRDMe4Qyt8
(I cant figure out image hosting anymore)

I did not understand this completely especially because I used a micrometer to measure the entrance of the factory chokes and they measure 18.6 or .732".
( edit: these measurements are incorrect. Proper bore gauge results at bottom)

Trulocks cylinder choke exit diameter is .725 according to their site.

Long story short Rizzini said that there is .010" constriction built into the barrels. ( if yours is overbored)
Trulock informed me that the reason I measured the entrance at 18.6 is because all chokes are larger than bore diameter to be absolutely sure they do not protrude.

I am somewhat disappointed that with a cylinder choke and an IC in the gun for skeet I have been shooting an IC and M pattern.
So 2 cylinder Trulocks are on the way.

I thought this may help someone since B Rizzini info is scarce.

Is this how all overbored/backbored barrels are? Do they all have constriction built into the barrels?
I was under the impression that they were larger all the way to the chokes.

***Edit with bore gauge info.....***
So I got a skeets bore gauge.
Top barrel measures .733
Bottom barrel measures .735
There is no constriction in the bore.
Chokes open to .740 at the skirt, then taper to .725 (CYL), .715 (IC), .705 (M) ect...
I have no idea why the chokes are based off a .725 barrel and not a .735




Last edited by saddlerocker on Thu Jan 23, 2020 9:08 pm, edited 2 times in total.

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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Tue Dec 17, 2019 7:48 am 
Crown Grade

Joined: Thu Jul 31, 2008 11:12 am
Posts: 4980
Your barrels (.735 bore) like mine are for the newer Rizzini Plus chokes. I sold off the factory chokes. I got Trulocks. The Trulocks will also be tighter than marked.IC in both barrels for Sporting. IC is more like M. I have LM and M in Trulocks. My Trulock Mod is like a LF. LM more like IM. All my info was confirmed with a bore gauge and on paper.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Tue Dec 17, 2019 8:40 am 
Field Grade

Joined: Mon Mar 26, 2012 8:15 pm
Posts: 92
Location: Pittsburgh, PA
lt0026 wrote:
Your barrels (.735 bore) like mine are for the newer Rizzini Plus chokes. I sold off the factory chokes. I got Trulocks. The Trulocks will also be tighter than marked.IC in both barrels for Sporting. IC is more like M. I have LM and M in Trulocks. My Trulock Mod is like a LF. LM more like IM. All my info was confirmed with a bore gauge and on paper.


Do you understand it to mean that the bore has built in conctriction or a "fixed" .010 within the barrel?

Thats what I gathered from talking with Rizzini.

Im not familiar with how and where you measure with a bore gauge.
Does your bore show .735 or .725 just before or at the choke shelf?


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Tue Dec 17, 2019 3:53 pm 
Crown Grade

Joined: Thu Jul 31, 2008 11:12 am
Posts: 4980
.735 The choke designations (IM,IC,SKT, LM or M) marked on the choke don't mean anything, even with Trulocks. Do the math between .735 and the bore diameters numbers on the choke. Then shoot some patterns. See what you get. This explains it better. https://trulockchokes.com/basic_choke_information.html


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Tue Dec 17, 2019 4:51 pm 
Field Grade

Joined: Mon Mar 26, 2012 8:15 pm
Posts: 92
Location: Pittsburgh, PA
lt0026 wrote:
.735 The choke designations (IM,IC,SKT, LM or M) marked on the choke don't mean anything, even with Trulocks. Do the math between .735 and the bore diameters numbers on the choke. Then shoot some patterns. See what you get. This explains it better. https://trulockchokes.com/basic_choke_information.html


I have read that info from trulock and understand it, but what im trying to understand is how Rizzini factory chokes can be used in their "standard" bore and "overbored" barrels producing different patterns.

It is either that the bore is .735 and constricts to .725 before the choke.
OR
The choke skirt (entrance) is flush with the .735 bore at the shelf, and on a "standard" .725 barrel there will be a small ledge where the choke skirt is wider than the barrel. (Trulock said this is normally how chokes are made. Their CYL choke exit diameter is .725, but the skirt will be larger even though it is .000" constriction.)
I measured my factory choke skirts at 18.6mm ID. So if they fit flush I think that is the answer.

I am working out of town, but will be checking for a ledge with choke installed and looking for the barrel diameter proof marking as soon as I am home.
The manual I received with my BR320 was for the S2000, S790, and Premier so cant trust much in it.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Tue Dec 17, 2019 5:46 pm 
Crown Grade

Joined: Thu Jul 31, 2008 11:12 am
Posts: 4980
I have the BR 320. Very simple. It's the difference between the .735 bore barrel and the diameter marked on the choke or what the gauge says the choke is. The specs online and my bore measurements confirm .735. These guns have been out of production for about 4 years. The BR320 uses the same action and barrel as the 2000. Just less bells and cosmetic differences. I have ordered parts based on the schematic provided with the BR320.. The older Rizzini guns with a smaller bore used a different choke system. Not the Rizzini Plus used in the BR320.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Tue Dec 24, 2019 8:46 am 
Field Grade

Joined: Mon Mar 26, 2012 8:15 pm
Posts: 92
Location: Pittsburgh, PA
lt0026 wrote:
I have the BR 320. Very simple. It's the difference between the .735 bore barrel and the diameter marked on the choke or what the gauge says the choke is. The specs online and my bore measurements confirm .735. These guns have been out of production for about 4 years. The BR320 uses the same action and barrel as the 2000. Just less bells and cosmetic differences. I have ordered parts based on the schematic provided with the BR320.. The older Rizzini guns with a smaller bore used a different choke system. Not the Rizzini Plus used in the BR320.


Why are chokes marked 2 different ways then?
It's like they are used in 2 different bore sizes.

I checked my gun and see proof Mark's, but no bore size. (Unless the 1860 in the bottom left is meaning 18.60?)
https://photos.app.goo.gl/TXrjWHN3RZfSQr4q8


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Wed Dec 25, 2019 8:35 am 
Crown Grade

Joined: Thu Jul 31, 2008 11:12 am
Posts: 4980
1. My bore size was checked with a gauge. .735 verified.
2. The catalog for Rizzini listed the bores at .735 for that gun when it was made. Rizzini made a change to newer Rizzini Plus chokes in that gun and a .735 bore.
3. Put the gun on paper and see what you have. I had one size tighter, even with Trulock.
4. IC breaks targets fine on the usual Sporting course.
5. Rizzini must have made a decision with those chokes, or they were made before they went to a .735 barrel. Either way mine is a keeper. All the aftermarket chokes will have the same results. One size tighter. Briley will make custom chokes if you wish.
6. No harm will come to your gun. Guns get overbored/backbored aftermarket all the time without changing chokes. The difference your concerned about is tiny.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Fri Jan 17, 2020 8:30 pm 
Field Grade

Joined: Mon Mar 26, 2012 8:15 pm
Posts: 92
Location: Pittsburgh, PA
I updated the original post with some bore gauge results.
There is no constriction built into the barrels like Rizzini told me.

That .010 constriction is all from in chokes.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Sat Jan 18, 2020 8:29 am 
Crown Grade

Joined: Thu Jul 31, 2008 11:12 am
Posts: 4980
saddlerocker wrote:
I updated the original post with some bore gauge results.
There is no constriction built into the barrels like Rizzini told me.

That .010 constriction is all from in chokes.


And that is no problem. Your chokes will shoot one size tighter. Simple math. The bores are overbored.
FYI I got my 10th punch in a year last week with the BR320.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Sat Jan 18, 2020 12:35 pm 
Field Grade

Joined: Mon Mar 26, 2012 8:15 pm
Posts: 92
Location: Pittsburgh, PA
lt0026 wrote:
saddlerocker wrote:
I updated the original post with some bore gauge results.
There is no constriction built into the barrels like Rizzini told me.

That .010 constriction is all from in chokes.


And that is no problem. Your chokes will shoot one size tighter. Simple math. The bores are overbored.
FYI I got my 10th punch in a year last week with the BR320.


Forgive me ignorance, but what's a punch?

And yes it's not a big issue, but when using factory chokes for skeet you are limited to an IC and M pattern with a C and IC factory choke.

I just wanted to figure out exactly what was going on since info is so scarce.


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 Post subject: Re: Rizzini Overbored Barrels. 18.6mm / Choke Info
PostPosted: Sat Jan 18, 2020 1:03 pm 
Crown Grade

Joined: Thu Jul 31, 2008 11:12 am
Posts: 4980
"Forgive me ignorance, but what's a punch"? Wins in Sporting Clays.




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