I am about to send these barrels off to be opened a bit but got to thinking I may not be interpreting these marks correctly. They are on the 26" barrels of the B.C. Miroku 20ga I posted earlier.

Jerry,
I believe the Miroku choke marking would be consistant with the Browning ones, that would make it Modified. According to the Browning book by Schwing, the 20ga. should have a bore diameter of .611 and the Mod. choke would be .018.
Hope this helps.
Karl

It would make which barrel modified?

Jerry,
Yes it would. I have several fixed choked Brownings marked with the same designation for a Modified choke. Improved Cylinder would be marked as xx-.
Karl

I read those as Mod and I/C. As the chokes become more open, the markings get "longer", so that a gun could be opened up, and the designation can be changed without altering the appearance of the gun. (I know what I'm trying to say, but am doing a poor job of describing it)

Jerry,
The Browning/Miroku choke designations would be as follows:

*** Cylinder
**$ Skeet
**- Improved Cylinder
** Modified
*- Improved Modified
* Full
The lower barrel would be Improved Cylinder marked on the right side,
while the upper barrel would be Modified marked on the left side.
Hope this helps,
Karl

Edit: I was wrong. I have assumed for the past 40 years that Miroku and Browning chokes were the same. Owned several and never knew any different. Good to know, I guess...
JR

John,
I only saw one picture, showing the left side of the monoblock which I believed to be marked Mod.
Karl

Above the ++ marking there is a +- marking.

http://www.shotgunworld.com/bbs/viewtopic.php?t=117362#ixzz15xqtiEZM

It's modified lower and light full upper. Shoot it some and see how you like it. Also double check it with a bore gauge, which should give a good reading because I doubt the gun has been over bored..

It is IC bottom and Mod top

I thought so.
Karl

Miroku's of that era did NOT follow Browning's choke markings at all, though they do look similar, they do NOT have the same meaning.

Suggest that you simply shoot it on a grease plate w/the ammunition intended for a specific use first. Then you can decide whether or not you wish it opened further.. or simply go shoot some skeet w/it low gun. Are you hitting the targets? Are the breaks good or..? Back at the grease plate do both bbl.'s seem to shoot to the same POA [Point Of Aim]? If the answers are 'yes', you are home safe; don't make further ado of it.

I'd made a similar suggestion once to another person who'd inquired here and was promptly roasted by an individual in IL. Another member got a decent pheasant hunt out of it & they both had a grand time as I recall and it did not invalidate wot I'd suggested in spite of remarks made to the contrary.

Its a quick & dirty method to find out how the gun shoots for you. I'll stick to my guns [Ha!] on the suggestion.

I agree, to the extent that I built a 4' x 4' grease plate to do so.

All I will say is that shooting a patterning plate with your guns is eye opening. Some will be more open than you thought, and some will be tighter. Some will "cross shoot" at certain distances, some will be perfectly regulated. Some will shoot higher, or lower, than you thought they did.

But, at least you will know.

SRH

I am not new to shotgun chokes and patterning them. But lacking a bore guage I just wanted to confirm what the markings indicated as other interpretations made little sense. I will certainly pattern them on the grease plate the next trip to the gun club. The gun is for my youngest grand daughter to begin shotgun instruction and hopefully a few doves this next fall. She is already started with rifle and pistol.

Appreciate everyone's help in deciphering the Miroku code.

There's another issue with the Browning choke markings, going back to the Belgian guns: They tend to be choked tighter--in some cases, quite a bit tighter--than guns from other makers with the same degree of choke. Always good to measure . . . and pattern.

That should work for most things...

Yes it should and does for me as my fixed choke Brownings are IC/MOD. For close work in the IC barrel I use spreaders for woodcock and the like.
Karl

I could not agree more with tw.
Just to add that, let the grand daughter shoot the grease plate as she is the one to use the gun. From this you can see what is all really going on with both gun & shooter.
My bet is that she will surprise you & the chokes will be good to go as they are.
As a boy I learned to shoot a very tight Beretta 12 gauge gun. Any choke less than that was then easy peasy.
O.M

In regards to things "gun", people who take tw to task may not be actual fools but their actions could certainly be viewed as ill considered.

Tha's prolly not just a JMO IYKWIM

have another day
Dr.WtS

The majority of 20ga o/u are choked ic & mod. But I don't think this one is. I think it is marked otherwise. If it actually choked mod & light full it would make it an unusual gun and beg the question why.

This reference is found several places on the net as Skeetx provided. miroku choke marks 26" barrels here as well. ymmv

Thanks. I learned something today.

Was the gun purchased new? If not are you certain that no one has opened the chokes on the gun.

As far as needing a bore gauge, for years I've successfully used an inside caliper and a 1" micrometer to measure bores and chokes. Typically when I've compared my measurements with a bore gauge they've been within 0.002" or less. The inside caliper is also excellent for measuring chamber lengths. You open it up in the chamber, slide it in until it's stopped by the forcing cone and then mark the length on the caliper with a Sharpie pen, pull it out and measure the distance with a ruler, very easy!

Steve

Rockdoc the gun was purchased before 1976 by someone who put it away for a long time as it is absolutely in like new condition. All I lacks is the box. I doubt it has been messed with at all. The typical scratches seen on the bottom of barrels from disassembly/reassembly are not there, not even one. I feel very fortunate to have found one in this condition. I will shoot it this week on a greased pattern board and know more about it then. I am going to have a recoil pad installed which will require little shortening of the wood to fit the grand daughter. After that she will begin the scholastic shooting program at the gun club this fall.

Well I tried Rockdoc's suggestion to measure the constriction in the choke with inside calipers. After measuring the barrel before the constriction and getting a consistent .615" diameter I then felt around for the narrowest portion of the choke itself. Topo barrel measured .607 and bottom .611 this gives me 4 points of choke in the bottom barrel and 8 points in the upper. Pretty typical for skeet and improved cylinder in a .20ga so perhaps someone did open these chokes before. Have to see the pattern board results for sure now. Ideally I would have liked a skeet lower and light modified upper. Still won't be surprised if the gun throws an IC and Mod pattern with modern shells. These gun were produced before plastic wads became prevalent.

Jerry,
Don't forget that the points of constriction for each choke designation would normally be less for a 20 ga. than for a 12 ga.
Karl