Making my own CVA Blackhorn breech plug

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snapbang

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Mar 9, 2019
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208
I bought a CVA Wolf about a year and a half ago. It came with a breech plug for pellets. I want to shoot loose powder to have more flexibility and hopefully more accuracy with my rifle. Ive been reloading rifle cartridges for 30+ years so I'm familiar with loose powder. I used the original plug and had no misfires or even a hang fire with the loose powder. It shot very well.

Not being able to leave well enough alone I decided to drill out the breech plug. Im within the influence of the auto makers of Detroit and we are familiar with steel. I simply set it on the bench and selected a 5/16 bill and with a handheld drill (not even a drill press) I slowly began to drill it out. I only did a little at a time and dipped it in oil often. Both to clean the shavings and keep the metal cool.

As I drilled it I see the flame channel open up. (get larger) At this point I'm committed so I keep drilling. Didn't measure how deep but about 3/4 inches. (just so you know I had a real plug already on order in case this went south on me)

So I go to my property and know there is going to be more back pressure because of the larger flame channel. I have used metal washers to get a crush on the primers so the only question is will the primer seal the chamber. I fired a primer through it to clear any oils and such. I could tell by the noise the flame channel was different. I put 70 grains of 777 and a 255 grain saboted bullet in the barrel, place the primer, close the gun and from the hip aim it at a tree. All went well. I opened the gun and no blow back from the shot. So I upped it to 100 grains and had the same result. Then repeated with a 305 grain saboted bullet. All went well.

After that I must have shot about 15 shots with no problem. Im thinking this will be an excellent plug for cold or wet weather.

I would post a picture but it looks the same as the one I bought for $29.00.

Frankly the gun shoots just the same. I didn't run it over a chrony but I still have the wonderful accuracy I did before I drilled it out.

I dont recommend this procedure to anyone. Just sharing my experience. This is a great forum to learn from. Hope I can add a little information.
 

ronlaughlin

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Dec 29, 2007
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3,867
Did you know you can heal the plug, by tapping the flame channel for a vent liner, which is a 10-32 screw with a 0.031" hole drilled through it? Ends up looking like................



 

snapbang

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Mar 9, 2019
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208
Outstanding. Im going to research it. Thank you very much. Is it posted on this forum somewhere??
How deep and what bit size bit did you use to drill your initial cavity.
 

ronlaughlin

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Dec 29, 2007
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Usually i enlarge the 3mm hole all the way through by using a 5/32" drill. Then make a cavity 3/8" deep on the powder end using a 25/64" drill. Then use a 3/8" 82°countersink so the vent liners seat in the hole. Last step is making about 8 or 9 threads with a 10-32 tap.

A 5/16" hole like you made is plenty good, and works fine. However the head of vent liners is 3/8" diameter. The vent liner will need turned down to 5/16" minus, which i have done.
 

snapbang

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Joined
Mar 9, 2019
Messages
208
Thanks Ron. I think I'll shoot it as is for a while. I do have a backup coming just in case the whole business goes south on me somehow. When I shot it the other day there were very little blow-back. I was actually surprised. I figured it was going to get ugly. Without the primer crush I believe it would but with the crush all is well. Thanks again for your expertise. Im going to keep the info just in case I decide to follow your lead.
 

ShawnT

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Oct 4, 2005
Messages
4,645
Are you saying you drilled out the Flash Channel and the Flash hole to 5/16", so that you now have a 5/16" hole all the way though the plug OR just opened the Flash channel to 5/16 and left the Flash hole in the plug?o_O
 

ronlaughlin

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Dec 29, 2007
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What i believe he wrote is he drilled a 5/16" hole in the powder end of his breech plug about 3/4" deep. This would destroy the flash hole. What is left is the flash channel of 3mm diameter. This would allow the powder to flow right up tight to the primer. This is a technique used by smokeless shooters called 'direct ignition'. Pressure is larger than it is when one has a flash hole. MV is also increased, and obviously pressure on the primer is increased. He wrote he sees nothing untoward.
 

ShawnT

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Oct 4, 2005
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4,645
That is what I thought he was saying, and Direct ignition was what came to mind. Just wanted to confirm it. I personally don't like the idea myself.
 

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