Barrel twists

Barrel twists

Postby marshninja » June 12th, 2013, 2:27 pm

I have a Knight Mk85 and a Knight Disc Rifle. I am having trouble shooting anything over 110 grains of American Pioneer Powder or the Pyrodex equivalent to black powder. I have been reading about magnum charge sticks of 150 grains and shooting 200 yards. Somebody told me that my guns are old technology with a twist rate that is for large slugs and round balls - that the modern guns have a different twist rate for longer shooting. I looked up a modern Encore which has a 1/28 twist but can not find information on my guns. I bought them second hand and do not have a owners manual. Can anybody shed any light on my guns ? Is anybody maxing out their guns to a satisfactory shot group at any considerable distance ? My guns are great from close range (up to 100 yards). I am kind of anal and always trying something to get a little more. Any help ?
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Re: Barrel twists

Postby GMB54-120 » June 12th, 2013, 10:28 pm

You didnt mention what caliber you have.

VERY old Mks might have a slower twist which works better for round balls. Not many of them are still around. All the later 50 and 54cals had the common 1-28. At least some of the MK 45cals had a 1-24 twist. All 50cal DISCs have a 1-28 also except some prototypes. DISCs in 45cal were 1-20 and 1-30. Any twist 1-30 or faster will shoot modern projectiles just fine. You could probably even go a little slower depending on the bullet weight.

Ditch the APP powder, its a very poor performer. Try some 777 2FG or 3FG loose instead and forget about pellets too, especially square ones. :lol: Loose is more affordable and easier to fine tune your load.
Green Mountain 54-120 Brush Gun
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LRH 52cal
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Re: Barrel twists

Postby marshninja » June 13th, 2013, 11:21 am

The MK85 is a 54 cal......The DISC is a 50 cal.........Are you able to shoot the 150 grain or equivalent ? I was reading about the APP or Jim Shockeys' super stick 100 and 150 grainers. No good ?
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Re: Barrel twists

Postby GMB54-120 » June 13th, 2013, 1:37 pm

marshninja wrote:The MK85 is a 54 cal......The DISC is a 50 cal.........Are you able to shoot the 150 grain or equivalent ? I was reading about the APP or Jim Shockeys' super stick 100 and 150 grainers. No good ?


Yes i can in my 50cals but why do you need 150gr? The MK 54cal was rated at 120gr max IIRC. A 150gr pellet load seldom shoots well and a square peg in a round hole is not a good idea. APP/Shockleys powder are VERY poor performers. Their square stick powders are even worse. I use Blackhorn209 in my DISCs with a bare primer breach plug conversion. Triple7 works very well with the same conversion also and in the MKs with cap or FPJ 209 ignition. FPJs are the "jackets" for 209 primers.

Pellets IMO are a total waste of time and money. A few people have ok results with Pyrodex two pellet loads in the MK85 54cals but that is considered a max load. There is no other 54cal pellet option besides 1 or 2 pellets at 60gr equivalent each. How can you tune your load with only two powder weight options? The short answer is you can not.

If you want performance from your MK85 54, try 90-110gr of loose Triple7 2FG or even 3FG with MMP 54x50cal sabots and the Speer 50-325gr JHP. That is the bullet and sabot knight used to supply with new MK 54cals. A soft lead conical works pretty good too but i would start with a bit less powder and work up.

50cal DISCs shoot well with a wide variety of loads but usually 90-120gr of Blackhorn209 or Triple7 will be the sweet spot with sabot loads. New DISCs are rated upto 150gr of loose but very few people get acceptable accuracy with loads over 130gr by volume.
Green Mountain 54-120 Brush Gun
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Original DISC 45 SS
LRH 52cal
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Re: Barrel twists

Postby marshninja » June 13th, 2013, 10:22 pm

Thanks for the information. I have had good groups with the APP granular. It still fouls the barrell but in a different way. It almost slicks the barrell. I use a real tight fitting bullet / sabot combo with it. The loads that work good with pyrodex pellets are a little loose fitting loads. The difference is made up by the fouling. These same combos do not work well with APP. None of them work well with the big charges. I had that blackhorn in my hand the other day looking at it but put it back down. I have been seeing some positive remarks on it lately. I also had some real good groups with the 54 cal using the thicker sabots and the .451 ballistic tips 100 gr APP loose. I was concerned about only getting 1385 fps on average out of these loads. I was hoping for a little more.
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Re: Barrel twists

Postby crockett » June 13th, 2013, 11:20 pm

My MK 85'S in .54cal. both perform excellent with speer .50 cal deep curls/mmp sabots and 90gr's 777 fff.
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Re: Barrel twists

Postby GMB54-120 » June 14th, 2013, 12:10 pm

MidwayUSA sells a nice cheap 50cal 335grJHP made by Rainier. Its plated like the Speers but half the cost. They have them in both 300gr and 335gr. I like the 300gr Speer better than the Rainier 300gr. The 335gr though is tougher than the Speer 325gr and cost under $30/100.

http://www.midwayusa.com/product/105014 ... llow-point

Another good bullet for lower velocity 54s is the Barnes 50-275gr XPB or a very similar bullet from C.O.P. (Copper Only Projectiles) The COP bullet is also about half the cost of the Barnes if you can ever find them in stock. I used to shoot the 275gr Barnes exclusively in my older 54cals. It flies like a brick but hits like a wrecking ball on deer sized game.
Green Mountain 54-120 Brush Gun
Elite 45 blued
Original DISC 45 SS
LRH 52cal
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Re: Barrel twists

Postby marshninja » June 18th, 2013, 10:24 am

GM854-120.......I have converted my Mk85 from cap to 209 FPJ.......Can I also convert that breech plug to a Bare primer breech plug ? On knights web site they say I can convert a DISC Extreme to a Bare breech plug. Is the conversion kit to 209 FPJ considered a true DISC Exreme? Their DISC Extreme Rifle photos on their website have bolts like my DISC rifle. I would only need the new breech plug as i have already paid for the 209 conversion. To convert my DISC it is fairly expensive if you look at the prices on Knights web sites. I would need to convert to the Extreme DISC from a regular DISC plus buying the Bare breech plug. I might as well leave that one alone as i am fairly satisfied. Might as well use the $190 needed for converting towards buying a new Encore........I have tried to get ahold of Knight but they are on off season hours and have not yet returned my call. Have had good service out of Knight in the past.
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Re: Barrel twists

Postby GMB54-120 » June 18th, 2013, 3:19 pm

I don't believe you can convert a MK85 to bare primer, at least not by using any current conversion. I think at one time there was a plug but it had some problems. Cap ignition actually works just fine for Triple7 and the crud ring is usually much better. I would NOT use the FPJ conversion to shoot BH209 in the MK85.

The bare primer plug Knight sells is for the DISC Extreme, Elite and Long Hunter. That one will fit a DISC Original also IF you converted the DISC to use the red jackets.
Green Mountain 54-120 Brush Gun
Elite 45 blued
Original DISC 45 SS
LRH 52cal
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Re: Barrel twists

Postby marshninja » June 18th, 2013, 8:10 pm

I talked to Sam from Knight today. Can't convert a Mk85 to a bare primer breech plug. Can't convert a DISC original either unless I also convert it to a DISC Extreme which is kinda pricey for both.. I have heard the most good reports about Tripple Seven than any other product so far that I can use. I have learned much. I have owned the Knights for some time but have never shot them much do to running out of deer tags by the time muzzleloading season opens in Michigan. Last year I got pneumonia right before regular firearm deer gun season. Had to break out the DISC Rifle during muzzleloading season to fill the freezer. I laid one out real nice from about 75 yards. I was really impressed with it. Now I think I might use it over my shotgun for firearm deer season. That is why I wanted to learn everything I could and get the most out of it. I am almost back to where I started. I was using two 50 grain 777 pellets with a 250 grain Barnes ballistic tip round out of my 50 cal DISC. Now I will probably switch to 777 granular but shoot about the same load. I will see how it shoots higher and lower and settle in on a good combo. Anyway.....thanks for the suggestions.......Rick
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