MK-85/BH209 curiosity question

[firedawg60]

A close family member has a No.11 Mk-85 and is wondering about the safety and practicality of using a 5 or 10 grain booster of black or a sub to set off BH. He is wanting easier reloading in the field and less corrosion. The flame channel is fairly large and long. Any known issues?

 

[1874sharpsshooter]

I would consider it unsafe to use Blackhorn in a plunger gun unless you want to take a chance on picking primer pieces out of your face .

 

[firedawg60]

Ok thanks. I recall the warning on plunger types but just wasn't thinking. Maybe he could consider a 209 conversion kit and 777.

 

[sabotloader]

Ok thanks. I recall the warning on plunger types but just wasn't thinking. Maybe he could consider a 209 conversion kit and 777.

Heck just shoot T7 with a #11 mag cap works great - I shoot 110 grains with a 458x275 grain Bloodline... 209's can blow back out of the BP very easily also unless you are using a red plastic jacket with a 209. That is safer than a NFPJ, bare primer,

 

[firedawg60]

Thanks for the info Sabotloader. Neither of us have ever shot T7, only BH or various grades of Pyro. He likes using pellets in his orange disk Knight, and it shoots great with three pellets and Knight Redhots. So we had been looking at the Hodgdon pellets page https://www.hodgdon.com/tripleseven-pellets.html and saw 209s only. Loose T7 and RWS caps may be the ticket.

 

[WV Hunter]

I would stay away from pellets, personally. I use loose pyrodex in my mk's, with RWS #11's and it works great. Obviously T7 would be great too, its really personal preference.

 

[firedawg60]

We tried numerous combinations of powders, 2 pellets, sabots, and conicals in his DISC when he first acquired it, with nothing shooting respectable. He sent it back to Knight who promptly sent it back with a test target less than MOA. The enclosed documentation stated the rifle was designed for three pyrodex pellets and 250gr red hots. He purchased the red hots and it easily shoots like their test target.
I have never tried the pellets in my rifles, but I could see where they are appealing if they happen to shoot well with a good bullet.

 

[Bill]

My MK85 rifles shoot well with the caps and loose T7, and better with Swiss. The bare 209 conversion can be hard to prime and mine will eject a spent primer if the T7 load gets too warm. I tried BH209 with the FPJ conversion-not a good idea-gas leakage. T7 will leave a crud ring with 209 primers. T7 pellets are bad juju with any ignition system.

 

[tpcollins]

A close family member has a No.11 Mk-85 and is wondering about the safety and practicality of using a 5 or 10 grain booster of black or a sub to set off BH. He is wanting easier reloading in the field and less corrosion. The flame channel is fairly large and long. Any known issues?

I have the LK-II for my grandson and earlier this year I used about 8 grains of 3F Triple 7 as an ignition starter, which was just enough to fill the flash channel, and then put 50 grains of BH209 on top. The #11 cap fired it off every time, pushing a 155gr Barnes with a special polymer tip. This will be our load for the youth hunt this fall.

Years ago I tried it in my MK85 with the 209 conversion kit - 1st time fired with no problems, 2nd time was a hang fire, 3rd time wouldn't ignite. The issue as I understand it was the excessive blowback around the 209 primer opening. With the #11 cap, I believe both the threaded breech plug and the threaded nipple are a helluva lot stronger than the saboted bullet sitting on top of the charge - ymmv.

 

[rugerbh103]

I tried it with my LK-93 for two years. Never had any safety issues, but I accepted I was pushing the limits and kept charges on the light side. Despite my best efforts, I never did get 100% ignition and occasional hang fires. When the hang fires cost me a buck last year I went back to T7 powder. I really wanted it to work, even drilled the flash hole, but it never happened.

 

[firedawg60]

Thanks for the replies everyone.

I know the burning rate and pressure curve is different with BH209, but I guess it just doesn't register with me how it can be ok to shoot 110 grains (or more) of FFFG T7 but not 80-100 of BH- with like bullets and not have similar problems regarding blowback/flying primer pieces.

With everything taken in consideration regarding possible safety issues and lack of consistent ignition, we will forgo the idea and stick with the known.

 

[ShawnT]

Thanks for the replies everyone.

I know the burning rate and pressure curve is different with BH209, but I guess it just doesn't register with me how it can be ok to shoot 110 grains (or more) of FFFG T7 but not 80-100 of BH- with like bullets and not have similar problems regarding blowback/flying primer pieces.

With everything taken in consideration regarding possible safety issues and lack of consistent ignition, we will forgo the idea and stick with the known.

While both are "BP Subs" the powders are 2 different animals altogether. BH 209 is a progressive burning powder (think smokeless powder) that has a much longer burning rate while 777 has a sharper quicker burn rate. There are some others that can probably explain it better than me here so maybe some one will chime in. You can think of it like this. Once the charge of 777 has ignited the pressure develops quick and the dies off so the burn rate is shorter. When BH ignites it keeps burning and developing pressure while that bullet is moving down the bore so the rate of burn it much longer making the pressure last longer. This longer burn rate making the pressure last longer is what can cause the plunger guns to "Recock" during when fired.