Mk60 Fixed Chokes

[Straso]

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 

 

[Salopian]

Check your patterns using your cartridge of choice. 

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

 

[Westward]

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

 

[GeordieTrapper]

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

 

[Straso]

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

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

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

 

[MJJ]

Out of interest, what is the actual bore size?

 

[Jonny English]

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.

 

[Straso]

Out of interest, what is the actual bore size?

.739 mate

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.

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

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.

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

 

[vmax1010]

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 

 

[sich1]

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

 

[KRW]

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)