Difficult breech plug removal

[vaguru]

FYI, after considerable thought, I decided to reseat my original Knight Magnum Sure Fire breech plug. After thorough cleaning, I peened the brass sealing end to gain some "size" to the diameter and peened the edges to eliminate the pitted spots. After reseating the plug and torqueing it a good bit I noticed a complete seal ring in the brass at removal. I also checked the seating on the original breech plug and got a good seal ring on that as well. I did then use Teflon tape on the plug, greased it up with Knight BP grease and reinstalled the original just to see what if any improvement all that made.

If it does not work to my satisfaction, I will get out the valve grinding compound and have at it.

I do believe that the Magnum plug eliminated the seizing as it completely sealed the barrel to the nipple. I may just go back to my "repaired" magnum plug.

I do believe Sideshow has the method to cure the issue. Stop the blow back and the threads can't seize. I will have to get some of that Permatex he mentions.

Thanks to all that replied.

 

[flounder]

I have one of those plugs that came in a .54 back country carbine mk 85. I haven't shot it with that plug. It seems there is something I didn't like about it, might be the nipple you use with it, I'll have to look.

 

[ShawnT]

This is a good, Cheap Little tool for working on MK-s at the range. It does require removing the barreled action from the stock. I made and been using this one since about 1997. Made of Oak.

 

[flounder]

I mentioned that I had one of those Knight Magnum Sure-Fire Breech Plugs that I had gotten with a lightly used 54 caliber Back Country Carbine MK 85. This is what it looks like

I like the idea of the brass end to mate with an individual barrel. I don't like the nipple with the hole in it or the fact that the nipple has a .60" flash hole and the flashhole in the brass is also quite large at .38". The nipple is a larger thread than the 1/4 " in my other Knight breech plugs. I guess that's why I haven't used this plug yet.
For those interested, Here is the literature on this type of breech plug:

 

[vaguru]

I mentioned that I had one of those Knight Magnum Sure-Fire Breech Plugs that I had gotten with a lightly used 54 caliber Back Country Carbine MK 85. This is what it looks like

I like the idea of the brass end to mate with an individual barrel. I don't like the nipple with the hole in it or the fact that the nipple has a .60" flash hole and the flashhole in the brass is also quite large at .38". The nipple is a larger thread than the 1/4 " in my other Knight breech plugs. I guess that's why I haven't used this plug yet.
For those interested, Here is the literature on this type of breech plug:

Yes the Magnum plug uses a different nipple. The standard nipples are 1/4-28 TPI and the Magnum nipple is 5/16-24 TPI. The objective of the Magnum plug is to seal the breech plug to the barrel and the nipple to the breech plug. The brass on the forward end of the BP seals against the barrel and the nipple seals against the brass insert that screws into the SS breech plug. I wish they still offered this BP as I have never had a seized BP using it and it gives about 200 fps more than a standard plug. Win win in my book.

 

[flounder]

I think the idea has merit. However I have issues with a flash hole that large, that is where the majority of the blowback will occur, not through the threads of the breech plug and nipple. You stated that it gives 200 fps more velocity than a standard plug, Have you done side by side experiments with a chronograph to document this? Frankly, I find it hard to believe.

 

[vaguru]

I think the idea has merit. However I have issues with a flash hole that large, that is where the majority of the blowback will occur, not through the threads of the breech plug and nipple. You stated that it gives 200 fps more velocity than a standard plug, Have you done side by side experiments with a chronograph to document this? Frankly, I find it hard to believe.

Yes, chronographed results with GOEX FFg and Pyrodex RS back when I first started with MK-85 Knights back in '91.

From my log book dated 10-5-92: Temp 33*F, calm morning, 10' from muzzle

Hornady XTP 240gr, std sabot, CCI # 11 caps

Magnum breech plug: all powder charges by volume
100gr GOEX FFg - 1654 av, ES 10
100gr Pyrodex RS - 1912 av, ES 7
110gr GOEX FFg - 1807 av, ES 27
110gr Pyrodex RS - 1963 av, ES 23

From my log book dated 10-6-92: Temp 32*F, calm morning, 10' from muzzle

Standard breech plug: all powder charges by volume
100gr GOEX FFg - 1646 av, ES 12
100gr Pyrodex RS - 1722 av, ES 6
110gr GOEX FFg - 1719 av, ES 27
110gr Pyrodex RS - 1772 av, ES 53

This was when I was shooting my 2 MK-85's (a blued laminate from '91 and then a SS laminate in '92) a lot and discussing results on the phone personally with Tony Knight. I ended up using Knight HP sabots with 110gr Pyrodex loads as the standard sabots would occasionally blow out. I finally settled on 100gr of Pyrodex RS for hunting use as it was a tad more accurate.

Believe it or not, these were the results. Tony Knight preferred a 250gr bullet and was getting 1911 fps with magnum plug and 110gr Pyrodex RS.

 

[Idaholewis]

I mentioned that I had one of those Knight Magnum Sure-Fire Breech Plugs that I had gotten with a lightly used 54 caliber Back Country Carbine MK 85. This is what it looks like

I like the idea of the brass end to mate with an individual barrel. I don't like the nipple with the hole in it or the fact that the nipple has a .60" flash hole and the flashhole in the brass is also quite large at .38". The nipple is a larger thread than the 1/4 " in my other Knight breech plugs. I guess that's why I haven't used this plug yet.
For those interested, Here is the literature on this type of breech plug:

That is interesting Art, i am almost Positive the Original Plug in my Old MK-85 .54 Cal was Identical to this one, it sure looked like this anyway. I ended up Switching over to the Hex Head Plug, The .54 MKs were another Challenge there, Some of them had 11/16 Plugs, and others were 5/8”, Mine was the 11/16, I had to use a .52 Cal Bighorn Plug I believe?

 

[Sideshow]

I mentioned that I had one of those Knight Magnum Sure-Fire Breech Plugs that I had gotten with a lightly used 54 caliber Back Country Carbine MK 85. This is what it looks like

I like the idea of the brass end to mate with an individual barrel. I don't like the nipple with the hole in it or the fact that the nipple has a .60" flash hole and the flashhole in the brass is also quite large at .38". The nipple is a larger thread than the 1/4 " in my other Knight breech plugs. I guess that's why I haven't used this plug yet.
For those interested, Here is the literature on this type of breech plug:

That is interesting Art, i am almost Positive the Original Plug in my Old MK-85 .54 Cal was Identical to this one, it sure looked like this anyway. I ended up Switching over to the Hex Head Plug, The .54 MKs were another Challenge there, Some of them had 11/16 Plugs, and others were 5/8”, Mine was the 11/16, I had to use a .52 Cal Bighorn Plug I believe?

Yea , Tony Knight knew the score .

That brass was the only way to get a good seal in a production product . This plug and his power stem plug for T7 were the 2 most innovative designs i think . Folks just didnt "get it" i believe . Mr Knight was no dummy !!! Ive tried a brass and a copper washer both . No class . I think lapping in the plug is a better cure in the long run . The washers get ringed and also are able to move around . Because of that your fix becomes a problem too .

Lapping is definately the most durable , permanant fix .

The powerstem added velocity too with T7 . Made it nearly Blackhorns equal that way by just a FEW fps. Do you know WHY ??? It too is no longer available !!! Another good example was the powerdome . US MILITARY CANNONS use that design !!! Its claim to fame is sound waves !!!
The 5/32 channel for 209's today , all that is a storage tank like a compressor has lengthening duration . Blackhorn MUST burn from the rear .

Theres ALOT MORE to be had than just lighting the fire !!!!

Problem is if it defies logic to THEM (folks) its not recieved . Hows that for tunnel vision.....

 

[50calsabot]

Thank you for sharing this topic. It seems that this is a good idea and would benefit knight owners and others.

 

[flounder]

Thanks for providing the data vaguru! Seems like the difference while using real black powder is not nearly as great as it is with pyrodex.

 

[vaguru]

Thanks for providing the data vaguru! Seems like the difference while using real black powder is not nearly as great as it is with pyrodex.

Yup, Tony Knight told me that the Magnum Plug was developed specifically for Pyrodex. Intended to give more consistant ignition and cleaner complete burn in order to make full use of the powders energy.

I just re installed my refitted Magnum Sure Fire plug and will get it out to shoot as soon as the wind stops, 15 mph currently. It will be interesting to see just what it does with the T7 3f accuracy wise. The standard plug was difficult to remove with T7 as mentioned in the original post. This MK-85 may just be a Pyrodex gun and set back in the safe for backup. If time permits I will set up the chrono as well.

I wish my Optima V2 would hurry up and get here. We are already in our late MZ season, though I have to wait for antlerless days as I am tagged out for bucks.

 

[Sideshow]

Yes, chronographed results with GOEX FFg and Pyrodex RS back when I first started with MK-85 Knights back in '91.

From my log book dated 10-5-92: Temp 33*F, calm morning, 10' from muzzle

Hornady XTP 240gr, std sabot, CCI # 11 caps

Magnum breech plug: all powder charges by volume
100gr GOEX FFg - 1654 av, ES 10
100gr Pyrodex RS - 1912 av, ES 7
110gr GOEX FFg - 1807 av, ES 27
110gr Pyrodex RS - 1963 av, ES 23

From my log book dated 10-6-92: Temp 32*F, calm morning, 10' from muzzle

Standard breech plug: all powder charges by volume
100gr GOEX FFg - 1646 av, ES 12
100gr Pyrodex RS - 1722 av, ES 6
110gr GOEX FFg - 1719 av, ES 27
110gr Pyrodex RS - 1772 av, ES 53

This was when I was shooting my 2 MK-85's (a blued laminate from '91 and then a SS laminate in '92) a lot and discussing results on the phone personally with Tony Knight. I ended up using Knight HP sabots with 110gr Pyrodex loads as the standard sabots would occasionally blow out. I finally settled on 100gr of Pyrodex RS for hunting use as it was a tad more accurate.

Believe it or not, these were the results. Tony Knight preferred a 250gr bullet and was getting 1911 fps with magnum plug and 110gr Pyrodex RS.

Your results should be magnified even more with the higher energy T7 3f powder . As a result you MAY run into sabot instability containing the power . IF you do i suggest harvester crushribs black or smokeless rated red for 45 bullets . MMP sabots also has high preformance sabots on their website . I think this is where the ES number increases are coming from in your previous tests at higher charges .i know it was in mine . T7 tendancy is for even better accuracy with increased velocity---as long as tbe sabot seal remains stable . That is the key . Its also possible that the answer to that lies in the bottom of the grove . Food for thought.......

 

[vaguru]

Your results should be magnified even more with the higher energy T7 3f powder . As a result you MAY run into sabot instability containing the power . IF you do i suggest harvester crushribs black or smokeless rated red for 45 bullets . MMP sabots also has high preformance sabots on their website . I think this is where the ES number increases are coming from in your previous tests at higher charges .i know it was in mine . T7 tendancy is for even better accuracy with increased velocity---as long as tbe sabot seal remains stable . That is the key . Its also possible that the answer to that lies in the bottom of the grove . Food for thought.......

I examined the sabots after shooting and noticed no "blown" sabots during these tests. I did go further with more powder later on and started "blowing" sabots at about 120gr of Pyrodex. That is when I switched over to the Knight High Pressure sabots, no problem using them. I also shot both with a felt wad under the sabot and that also stopped "blown" sabots. Due to the lighter powder charges giving better accuracy I didn't experiment further with the heavier charges.

Some of the ES could have been me not holding the rifle exactly the same with the heavier charges as there definitely was more recoil.