Making a Smoke-Free Muzzleloader Ignition Module

Working with anew breakopen-type .45-caliber muzzleloader made by Millennium Designed Muzzleloaders, Ltd. (MDM), I noticed the action getting increasingly more smoked up with each shot. The number 209 shotgun primers would virtually disintegrate, allowing the smoke and primer mixture to blow against the breechface, along the firing pin, and into and around the action. Cleaning the gun under such conditions was most difficult. Making some sort of correction seemed absolutely necessary.

I noticed the 209 shotgun primer was not being held firmly against the breechface, which accounted for part of the problem; however, I abandoned this particular type of ignition as away of correcting the problem. Here’s what I did: Making Things Right As a means of making a perfect gas seal, I modified anew breech plug. In this way, I could save the original Right top: This .45-caliber breakopen muzzleloader was used in the breech-plug conversion.

The conversion enabled the use of a special ignition module to replace the 209 shotgun primer. Right bottom: From the left are two unfired No. 209 shotgun primers with four fired primers. Note that the fired primers vary from totally shattered to excessively flattened. unaltered breech plug should my plan of correction not work to my expectations.

The common thread size used on this type of breech plug is 5/8-18, so I had no problem finding a replacement to work with that fit the threaded hole and formed a gas seal at the inner shoulder. As a suitable substitute, however, I needed a different type of breech plug with a larger diameter at the rear end. From there, I bored out the rear of the larger-diameter breech plug to create an entirely different type of ignition system.

I’ll call this new means of ignition the "ignition module." The principle here involves the use of a shortened section of a small centerfire cartridge case complete with small-rifle primer. Here, I chose to use a 0.770-inch length of a .22 Hornet case head for the ignition module. This is a rimmed case, which provided easy extraction. It’s small in diameter with optimal taper, and provides plenty of primer flash to ignite both

At the left is the original breech plug used in the .45 caliber MDM break-open action for use with 209 shotgun primers. In the center is the type of breech plug used in ignition on the Knight model TK2000 or USAK, and is threaded for a percussion-cap nipple. This type of breech plug is not used in a conversion as it has no coned flash hole. On the right, the breech plug used in the ignition conversion has a mini-chamber cut for an altered .22-Hornet ignition module.

This finished conversion has a coned flash hole for small-rifle primer ignition, and works perfectly for ignition of all types of black powder or substitute preformed pellets. black or Pyrodex-type powders’including the newer preformed pellets’ even under sub-zero temperature conditions. Making the New Breech Plug And Fitting the Ignition Module With the threaded breech plug centered in the lathe, I drilled a 15/64inch starter hole into the breech plug to a depth of 0.560 inch.

This starter hole is approximately 0.060 deeper than the depth of the shortened case, allowing for case-mouth contact against the newly formed shoulder and still enough case rim protruding for easy extraction. Essentially what we are doing is cutting a short cham- The primer is in place ready to be fired here. The primer is blown with burned powder soot forced into the action. ber into the breech plug, and headspacing from the case mouth to the breechface of the gun.

After drilling the starter hole in the breech plug, I used a special carbidetipped boring bar to cut the miniature chamber. The boring bar was set into the lathe’s compound rest at a 1.5degree angle. Then, by advancing the cutting tool with the compound rest preset to exact cutting depth, the existing small-coned flash hole remains in the modified breech-plug body at full depth. The strength of the breech plug is not compromised in any way.

As the newly formed chamber nears completion, the ignition module is checked for fit. As the case approaches proper depth, the case mouth will finally touch the inner chamber shoulder. By applying a small amount of additional taper to the chamber, the case mouth forms a perfect gas seal and is easily removed with the fingers after firing. A few thousandths of clearance taper near the base of the ignition module is helpful here.

At this point it is best to try a few cases for headspace with the breech plug screwed fully into the barrel. Trying a few cases for a slight bump fit works well, as the case mouth is felt against the inner shoulder with the action closed. Actually, it’s best to fit a control case to the chamber and later cut the remaining cases (ignition modules) under carefully controlled conditions to the same length. You may decide to make a dozen or more.

I simply used a cutoff tool to cut 15 cases a few thousandths long and trimmed them to a uniform length

22-Hornet cases to exact length for the chamber bored into the breech-block conversion. 5-degree angle in a compound rest is used to precisely form the ignition module chamber in the substitute screw-in breech block. using an RCBS "Trim-Pro" powered case trimmer. This was a good time to check the ignition modules in the gun for precise headspace before trimming all of them. On firing with normal powder charges, cases are fire-formed to some degree, forming a perfect smoke-free seal in the new chamber.

Case extraction is easy, either using the forked 22- Hornet case being inserted into the chamber bored into the screw-in breech plug. Cases are conveniently inserted and extracted with the fingers, leaving the action totally free of smoke and residue from burned powder. tool that came with the gun or bare fingers to remove shotgun primers. I later discovered a small-rifle magnum primer gave me even better ignition.

Positive powder ignition at minus-10 degrees Fahrenheit showed no ignition lag while using all types of available powder, including Pyrodex preformed pellets. Neither velocity nor bullet impact changes were noticed when firing the gun under such varying conditions, and no smoke leakage was present around the action or alongside the new ignition module. Conclusions The foregoing method of muzzleloader-ignition enhancement accomplishes several positive things.

It alleviates the troublesome smoke leakage after each shot, leaving the action perfectly clean. It is also much easier to install and remove the new ignition module than to work with primers requiring a special tool. And the breech-plug flash hole remains open after succeeding shots, with no debris clogging the flash hole, resulting in more reliable ignition.

If a change in the ignition system on a muzzleloader can accomplish all this, I wouldn’t hesitate to recommend it for any gun on which this modification could be made. I