Making a QRBP from a 5/8" x 15 x 2" bolt

Discussion in 'Inline Muzzleloading' started by Danny Ross, Jul 17, 2019.

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  1. Jul 17, 2019 #1

    Danny Ross

    Danny Ross

    Danny Ross

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    Most CVA and Rossi muzzleloader rifles take breech plugs that are 5/8" x 15 threads per inch. The easiest way to make a breech plug to fit these rifles is to start with a Grade 8 bolt that can be purchased for a couple of dollars online. I have found them on Ebay and at Home Depot. If you are a competent machinist, a neater job can be done starting with 1" stock and cutting your own threads.

    upload_2019-7-16_18-12-36.jpeg

    I start my project by running my bolt through a 5/8 x 15 die. I've found by trial and error that bolts generally are a couple of thousandths oversized and they turn into the threads of my rifle more easily if I do this. These dies can be purchased on Ebay.
     
  2. Jul 17, 2019 #2

    Danny Ross

    Danny Ross

    Danny Ross

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    The next step is to cut the bolt to length. I have a Grizzly metal cutting bandsaw, but a hand hacksaw or an angle grinder with a cut off wheel will do the job.

    upload_2019-7-16_18-32-9.jpeg
     
  3. Jul 17, 2019 #3

    Danny Ross

    Danny Ross

    Danny Ross

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    Next step is to round the edges of the bolt head so the bolt head will be clear to turn into the barrel. For the CVA for which this QRBP is being made, this is a few thousandths smaller than 1". I start using my grinding wheel, then finish off on my lathe. By rounding first on the grinding wheel, a lot of time and wear-and-tear on the lathe is saved.

    upload_2019-7-16_18-39-21.jpeg

    The rounding can be seen in this picture.

    upload_2019-7-16_18-40-18.jpeg

    This picture shows finishing the turning in the lathe.
     
  4. Jul 17, 2019 #4

    Danny Ross

    Danny Ross

    Danny Ross

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    Next step is drilling out the center of the breech plug for the cartridge, since I will be using 32 H&R Magnum primed cartridges. Almost any sort of primer can be used, from .25 ACP, through 209 shotgun primers, to .45 Colt. I have tried them all.

    In this case I start with a center drill, then use a 3/16" twist drill, then a 5/16" twist drill, and then finish with a .346" reamer. I then smooth the inside of the chamber with a piece of 220 grit emery cloth on a piece of 1/4" round stock. A 32 H&R Magnum cartridge will slide in and out from just its weight.
     
  5. Jul 17, 2019 #5

    Danny Ross

    Danny Ross

    Danny Ross

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    Hmmmmm. My pictures disappeared in that last post.

    upload_2019-7-16_19-2-35.jpeg

    upload_2019-7-16_19-3-24.jpeg

    upload_2019-7-16_19-4-13.jpeg
     
  6. Jul 17, 2019 #6

    Danny Ross

    Danny Ross

    Danny Ross

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    Next step is to open up the mouth of the breech plug. I use a 1/2" ball reamer, but other tools work. The trick is to allow the powder to enter the breech plug and get to the primer.

    upload_2019-7-16_19-7-52.jpeg
     
  7. Jul 17, 2019 #7

    Danny Ross

    Danny Ross

    Danny Ross

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    The penultimate step is to shave off the bolt head until the rifle breech just closes and the hammer will cock. I do this with a lathe, but it can be done with a grinder or files.

    upload_2019-7-16_19-12-38.jpeg
     
  8. Jul 17, 2019 #8

    Danny Ross

    Danny Ross

    Danny Ross

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    Last step is to cut out a place for the rim so the cartridge will be enclosed when the breech is closed. The rim of this cartridge is about .050" thick, so I indented the breech plug about .054"

    upload_2019-7-16_19-16-0.jpeg

    I hope this thread will inspire others on this forum to innovate with their weapons. Just because something is usually done one way does not mean there are no other ways of doing it.
     
    michiganmuzzy likes this.
  9. Jul 17, 2019 #9

    jerseyjimk

    jerseyjimk

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    5/8-15 or 5/8-18 thread
     
    Last edited: Jul 17, 2019
  10. Jul 17, 2019 #10

    Danny Ross

    Danny Ross

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    Thanks for catching that. 5/8" x 18 threads per inch.
     
  11. Jul 17, 2019 #11

    Danny Ross

    Danny Ross

    Danny Ross

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