Mk60 Fixed Chokes

Hi

I just purchased a Miroku Mk60 Fixed choked stamped 1/2 and 3/4.

we put a bore gauge in the bottom and top barrel the bottom had a constriction of 12thou and the top barrel 34 thou.

That is a tight IC and a Tight 3/4 going of Briley specs how could Miroku get the choking wrong I contacted the supplier and he is convinced that the Miroku spec for Mod is 12-15 thou that to me sounds like a lie.

Has anyone had this issue or have the Miroku specs for there barrels constrictions.

Thank You in advance 

Check your patterns using your cartridge of choice. 

Barrels could have been polished out by a previous owner if the gun is S/H

Most MK60s are 1/4 and 3/4 which is what yours measures. What are the stamps?

MK60 should be 1/4 and 3/4, markings on barrel should be *- and **-

Mine are stamped *~ and**
 

but bottom barrel bore measurement is 12 thou constriction 

and top barrel 34 thou constriction

The gun is 5 days old even ln the certificate it says Mod/IMOD

Westward said:

Most MK60s are 1/4 and 3/4 which is what yours measures. What are the stamps?

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My stsmps *~ 34 thou constriction and bottom barre ** 12 thou

Supplier is saying that are the measurements for MOD I call BS I just want to know if anyone else has experienced this and has the Miroku specs for MOD and IMOD

Out of interest, what is the actual bore size?

That seems an odd choke combination in the first place. Mk60 have usually been 1/4 3/4 on the standard guns or 3/4 full on the high pheasant versions. The 3/4 in yours is pretty close but the bottom barrel is a bit open for 1/2 really. Choke is technically measured in percentages of pellets in a 30" circle at a certain range so may be worth patterning it to ser what it prints.

MJJ said:

Out of interest, what is the actual bore size?

Click to expand...

.739 mate

Jonny English said:

That seems an odd choke combination in the first place. Mk60 have usually been 1/4 3/4 on the standard guns or 3/4 full on the high pheasant versions. The 3/4 in yours is pretty close but the bottom barrel is a bit open for 1/2 really. Choke is technically measured in percentages of pellets in a 30" circle at a certain range so may be worth patterning it to ser what it prints.

Click to expand...

That is correct it was s special order I waited for 9 months it hss s higher stock then original Mk60 and supposed to be 1/2 and 3/4

Jonny English said:

That seems an odd choke combination in the first place. Mk60 have usually been 1/4 3/4 on the standard guns or 3/4 full on the high pheasant versions. The 3/4 in yours is pretty close but the bottom barrel is a bit open for 1/2 really. Choke is technically measured in percentages of pellets in a 30" circle at a certain range so may be worth patterning it to ser what it prints.

Click to expand...

I didn’t count pellets but I compared a briley c300 Mod on the right as you can see it is a lot tighter

16 yards

My understanding of the mk60 is that it is nominally bored to throw a 1/4 3/4 pattern as in so many pellets in a 30" circle not bored to a specific size ie 10 30 thou unlike teague do with their chokes 

maybe someone put the wrong (std) barrels on your action ? are the barrels numbered ? cant say i noticed on my MK.

Just experiencing the same with my 6000 SP-1 whilst checking if OK for steel shot

Top barrel, stamped as being 3/4 choke, is .023" down on the .729" barrel bore with a measurement of .706" putting it closer to  being a 1/2 choke (.020" restriction) than the indicated 3/4 choke (.030" restriction) on that barrel.

Bottom barrel,stamped as being 1/4 choke, shows .014" constriction from the .729" barrel bore and which falls between 1/4 choke (.010" restriction) and 1/2 (.020 restriction)