Friday, July 28, 2017

Tips & Tools with Fred Stutzenberger – Part 18

Tips & Tools #18 Triggers

If you page through the premier books describing the American Longrifle (such as Kindig’sThoughts on the Kentucky Rifle in its Golden Age, Johnston’s Kentucky Rifles and Pistols 1750-1850 or Shumway’s Rifles of Colonial America), you’ll certainly notice that most of them have simple single triggers. Of the old original Jägerrifles featured in Shumway’s series Our Germanic Rifle Heritage in Muzzle Blasts 1991-93, about 40% had single triggers. Yet it seems that a much higher percentage of the longrifles made today are equipped with double blade double set triggers that can be tripped. Why is that when the simple trigger, if properly designed and constructed, meets most requirements other than long-range bench competition and the stylistic requirements of a particular historic rifle? I believe, with no statistics to back up my perspective on this matter other than logic, that it was expensive to hand-make set triggers in the old days compared to today when set triggers are so widely available to any builder no matter what the skill level. The variety of set triggers commercially available is amazing (Fig. 1). If availability rather than necessity is the answer, then it begs the question why have anything other than a well designed and properly constructed single trigger.Therefore the short space I have available to discuss triggers will be largely devoted to the simple single trigger.

fig 1

Fig 1
Set trigger assemblies are commercially available in many conformations: single blade/single set, compound single set, double blade single set and double blade double set.

Before I inlet the trigger(s), I like to shape the lock panel a bit to orient myself to the proper shape of the wrist into which the trigger plate will be inlet. At this point in the shaping of the lock area, there are oodles of wood to be removed. The final panel shape will be just a thin rim of wood around the lock, but for right now, I leave the panel oversize with special attention being paid to keeping plenty of wood at the nose of the panel to extend it to prevent a case of the “stubbies” (Fig. A). After rough shaping the lock panel, put a piece of paper over it and do a pencil rubbing like you would a tombstone (Fig. B). Then poke through the bolt holes to mark their location and transfer the template to the offside with the bolts holding it in a matching position (Fig. C). People might say: “Hey, why bother with that? You can’t see both sides at once.” Agreed, but if you look down on the rifle as you hold it at the ready, you can tell if the panels are asymmetric. That’s poor architecture.

Fig.A

Fig.A

Fig.B

Fig.B

Fig.C

Fig.C

Back to the trigger.The simple trigger has many merits. It is relatively simple to make.It requires neither heat-treating nor spring tempering.  I have been making trigger/plate assemblies for years using materials you can find in the dumpster behind any tech school machine shop building. A few lengths of 3/8 x 1/8” mild steel plate, some scraps of 1/16” cold rolled sheet metal and a length of 1/2 x1/2 by 1/8” angle iron can fabricated and forged into some very pretty, even fanciful triggers (Fig. 2). I usually make a few assemblies ahead of time, sometimes forging the triggers to final form, sometimes using commercial trigger blades (see suppliers) and sometimes just pinning in the trigger blank with 1/16” diameter drill rod (Fig. 3) to keep them for future installation.

Fig 2.

Fig 2.
I hand-forged this trigger and made it as fancy as I had room. The plate has a clearance adjustment screw for wear and is recessed to fit closely with the guard. I also installed an adjustment screw in the plate. Note where the tang bolt comes through in front of the trigger.

Fig 3.

Fig 3.
Here are some of my single blade/plate assemblies that I have cobbled together over the years from scrap metal. I slotted these plates and trigger supports with a slitting saw on a milling machine and then soldered them together. The old timers heated the plates, folded them over, sawed through the double thickness and then straightened the plate back out. Those old fellows were pretty ingenious in ways to compensate for lack of equipment.

 

I like to make my single trigger plates, whether I use a commercial blade or not. A long single trigger plate allows me to attach the trigger plate to the guard. If I am using a set trigger assembly, I usually have to solder on an extension to the rear of the plate (Fig. 4) to create a much stronger unit than the conventional separate trigger and guard. Indents are milled into the forward and rear guard returns (Fig. 5) where the ends of the trigger plate are attached with 4-40 screws threaded in from the inside to the guard. The indents allow the guard to be inlet flush with the trigger plate.

Fig 4.

Fig 4.
The plate of this trigger assembly has been extended to provide attachment to the rear guard return.

Fig 5.

Fig 5.
The guard’s front return is recessed to receive the trigger plate. Guards are difficult to hold for milling, so I designed a special fixture with hold-downs that clamp on the returns.

 

The twin spans of this rigid unit acts like a buttress to reinforce the wrist of the rifle (the weakest point most susceptible to breakage). Besides that advantage, the guard now acts as a “handle” by which the trigger/guard assembly can easily be removed from the stock for inspection or adjustment. Of course, if you buy a trigger and plate assembly, you can gain the same advantages by soldering extensions on to both ends and attach them to the guard via screws threaded into the guard returns. I once spent an hour with a riflemaker friend who was fretting over trying to get the proper clearance between trigger and sear using a traditional trigger pinned through the lock mortise. Of course, that was the way triggers were done in those days with no direct mechanical attachment to the plate (Fig.6). I would rather have the assembly all together as a unit strong and easily removed for adjustment.

There are those who will wring their hands at the thought of removing tiny snippets of wood on each side of the trigger to provide room for a steel support firmly attached to the plate. “Weaken the stock!” they say. Never mind that in their traditional trigger pinning method, the pin goes all the way through the stock at its weakest point and conflicts with the sideplate as well. Ron Dillon showed me the integrated all-in-one trigger assembly on an English Gibbs-Metford “thousand yard rifle”. The trigger was hinged high on a sturdy support post cast integral with the plate. There was a hefty boss into which the tang screw was threaded and there was a fine wire return spring secured at the back of the plate. This was good enough for one of the most sophisticated rifles at the peak of refinement toward the very end of the muzzleloading era. I guess it’s good enough for me too.

No matter what sort of trigger/plate combination you choose, remember that you want a dependable trigger pull, both for performance and safety. That means getting the most leverage by pinning the trigger pivot point high up in the stock. While the traditional method of pinning through the lock mortise does that, one end of the pivot pin is supported by a very thin web of wood between the lock mortise and the trigger mortise. On the early rifles with heavily swamped barrels, there was enough wood left in the lock mortise to support the right side of the pivot pin. However, as rifles got skinnier, the residual wood between the lock innards and the trigger got thin to the point of being fragile. Eventually tugging on the trigger thousands of times wears that little hole bigger and the trigger becomes less dependable. Better that the trigger is pinned in steel attached to the plate. I fear the traditionalists are rending their garments and tearing their hair at this heretical statement….

The foot of the trigger brackets on my simple trigger plates are silver soldered onto the plates using Hi-Force 44TM low temp silver solder (see suppliers). That provides a double thickness of material to be threaded for the tang screw and provides mutual support for the bracket, the plate and the thread engagement of the tang screw. What’s not to like there?

“Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.”(Archimedes 287-212 BC). The muzzleloadingrifle trigger doesn’t need that much leverage, just enough to easily and reliably move the sear to disengage itself from the tumbler. Just how much is easily…2 pounds, 4 pounds, 8pounds? Some of the factory-made modern rifles have trigger pulls so hard that they could double as an exercise machine at the local gym for strengthening handshakes. Our Clemson University air rifle coach, John Cummings, looks at 3-5 pounds as a safe and sensible pull weight for a field gun. He adjusted his team’s trigger pulls to the range of 400-500 grams (there are 454 grams in a pound), way too light for a field gun but just fine for competition—he should know—he coached his teams to two national championships.

The thing about levers is that the shorter the lever is on the other side of the fulcrum compared to your side, the easier it is to lift a load but the further you have to move your end to get the job done on the other end. Works with triggers just the same. Look back at the crude mock-up in Fig. 6. If I moved the trigger way forward so the blade contacted the sear arm1/2” from the trigger pivot point rather than the indicated 5/16”, you would shorten trigger travel but add poundage to the trigger pull. Ah, compromises, compromises…

Fig 6.

Fig 6.
This crude mock-up illustrates the relationship between the sear and the blade of the traditional trigger that pivoted on a pin through the lock mortise.

Whatever trigger assembly you use, simple or double set, you are going to have to inlet it so that it mates well spatially with the lock for dependable action.  That is where most of the work is involved. Before you start the inletting process, be sure that your lock works freely within its mortise. Once you get the trigger inlet and find a problem you have to determine whether it is lock or trigger related. Best to eliminate half of that question. Mark the position of the sear arm with a long line across the plate and panel. After locating the position of your trigger plate, drill a hole up through the mid-line to the sear arm hole so that you can insert a pushrod. I use a nail (Fig. 7) that is just a slight resistance fit in the hole. The nail takes the place of the trigger in tripping the lock. If it does so with ease, and if the lock comes to half and full cock with nice crisp action and reassuring clicks, and if there are no black rub marks on the mortise, you can assume that any problems associated with triggering the lock are in the trigger mechanism, not in the lock.

Fig 7.

Fig 7.
You can check the action of the lock sans trigger by pushing a nail up against the sear arm.

Now that I am well into my 70s, I take the easy way out and cut the mortises on my drill press (Fig. 8). I used a swinging support (I called it the trapeze) hung from the center joist of my basement shop to support the muzzle end of the rifle while the mortise was being cut for the trigger assembly. Then lay your trigger assembly along side the stock under the lock mortise and work the trigger to see how it will come up through the sear arm hole. Use your dial caliper to measure the working dimensions of your assembly to determine how deep you need the mortise for the trigger blade to come up into the bottom of the hole. Take off wood underneath the stock if necessary…no need to inlet through more wood than you have to.

T&T#18-Fig.8

Fig 8.
The arrow points to a free-swinging support for the barrel during the cutting of the trigger mortise on my drill press. Note inset, it shows the muzzle end of the rifle resting on a transverse dowel inserted in the proper hole of the support.

You can mill the trigger mortise or go at it with chisel and mallet after drilling a series of holes to the required depths. Be sure to draw dark, easy-to-see guidelines to mark off the different depth requirements of your trigger assembly in the mortise. Don’t just hog out a long trench to the depth of the most prominent part of the trigger assembly. A disadvantage of my system is that it generates a mass of chips (Fig. 9) that obscure your reference lines. If you are milling, mill a little bit, vacuum out all the chips and lay the assembly alongside the mortise to make sure you get a clean job (Fig. 10). Carefully cut the mortise for the “action area” first, not taking out more wood than necessary at each depth and width (measure with your dial caliper), then cut the plate mortise last. That way, if you need a little “adjustment”, it will be covered by the plate.

Fig 9.

Fig 9.
The major difficulty in my trigger mortise milling is the profusion of chips that obscure my guidelines. Lately I have been hooking up a shop vacuum suction pipe at the drill press.

 

Fig 10.

Fig 10.
This is a nice clean trigger mortise that removes no more wood than necessary and fits tightly. Just because the trigger is under the rifle and out of sight under the guard is no reason to be careless with the inletting.

Traditionally, the trigger plate was held in its mortise on the forward end by the tang bolt and is driven into the undercut wood of the mortise on the rear. You can understand why the old gunsmiths did that, because making screws was a chore and every one omitted was work time saved. Nowadays, unless you are a diehard traditionalist, secure that plate in its mortise at both ends so there is no room for movement of the plate;it must not move either horizontally or vertically. Either way will alter trigger/sear interactive geometry and potentially create an unsafe or unreliable situation. Remember that when you pull the trigger, it presses upward  on the sear; the sear’s resistance creates a downward force that could force the plate back out of its mortise.

Getting the tang to go through the tang at the right angle, down through the wrist and exactly into the hole in the trigger plate can be an adventure (aka a bad trip) if you don’t use the right strategy. You can use the index point strategy to line up the two holes on the drill press as you did with the sideplate/lock combination. An easier strategy is to use the drill guide (Fig.10a)that I described five years ago1. It’s not as hard to make as it is to remedy a misguided hole through the wrist of the rifle. I felt so proud of myself, using just a scrap piece of steel plate and a piece of all-thread rod to make a fool-proof jig for aligning a bit to come out exactly where I wanted it. Then within a year, I got a package from Scott Coy up in Minnesota. He came up with a jig like mine only much more sophisticated and more easily adjustable (Fig.10b). I admire his mechanical skill. I hope that he can sell his idea and make some money off of it. If you get a chance to buy one of Scott’s drill guides, do it because it will save you a lot of frustration in your rifle building, particularly if you plan more than one rifle.Every one of those needs a hole drilled precisely through the tang, the wrist and the trigger plate. Don’t just run a wood screw down through the tang; you want to lock the tang and the trigger plate together with a sturdy bolt (either 8-32 or 10-32).

Fig. 10a.

Fig. 10a.
To use this drill guide, put the end with the bit into the countersunk hole in the tang. Put the pointed end in the hole in the trigger plate and tighten up the jig so that the two arms are firmly pressed into their respective holes. Drill down 90% of the way through the wrist. Take off the guide. The drill will track the rest of the way dead on into the hole in the trigger plate.

 Fig. 10b.

Fig. 10b
Scott Coy’s version of the drill guide is more sophisticated; it has a reversible point and guides for 8-32 and 10-32 bolt size bits. However, it is not as versatile as my homemade version because because it can’t double as a patchbox pushrod hole guide as well as a tang bolt/trigger plate alignment tool.

One of the most annoying conditions one can encounter in simple triggers (other than misguided holes) is a case of the “rattles”, also known as “trigger slop”. The condition is actually not the fault of the trigger design or manufacture—it is the fault of the lock not having a one-position sear. In a well-designed lock, the sear arm comes to the same position at rest, at half cock and at full cock. That enables it to keep in light contact with the trigger blade so that it does not flop loosely or rattle up and down. Many locks have tumblers that put their sears at different elevations at the three positions. While the sear may be in contact with the trigger blade at one position, it may be left on its own to rattle at the other two. I have changed the conformation of the belly of the tumbler to remedy this condition by grinding a bit of a notch for the nose of the sear to rest in. The notch is ground precisely by mounting the tumbler on a plate and securing it with its screw (Fig. 11).  Another cure for trigger rattle is a light anti-rattle spring on the tail of the trigger blade (Fig. 12). It doesn’t add much to the trigger pull, but it does cure the rattles.

Fig 11.

Fig. 11
Here a little notch is being ground in the belly of the tumbler to let the sear down on the trigger blade when the lock is at rest. The conformation of the rest of the tumbler is unchanged. The fixture plate has a variety of holes to accommodate tumblers from several types of lock.Be sure to use a precision grinding point rated for high RPM.

Fig. 12. This anti-rattle spring bears very lightly on the heel of the trigger blade. It takes up the slack formed by the differences in sear arm position from full cock to half cock to rest.

Fig. 12
This anti-rattle spring bears very lightly on the heel of the trigger blade. It takes up the slack formed by the differences in sear arm position from full cock to half cock to rest.

 

Remember that the trigger is the mechanism that sets the rest of the rifle into motion. An unreliable trigger, a trigger set too light, a trigger that does not allow the sear to fully engage the tumbler notches, a trigger that hangs on the wood of its mortise, all of these conditions can potentially be malfunctions or accidents waiting to happen. Don’t let either happen to you. Play it safe.

            Speaking about setting triggers too light,I had gotten so used to light trigger pulls on double set trigger rifles that I didn’t realize that I was operating in a very dangerous range with my back action .40 caliber halfstockcaplock. I had never gauged its trigger pull, supposing that it was in the range of a pound or two. After I got my Lyman Electronic Digital Trigger Pull Gauge (suppliers list), I was in for a surprise (Fig. 13). One hundred and fifty-two grams…that’s just a third of a pound! Way too light for shooting of any kind. After backing it off to about 500 grams (a little over a pound), I started gauging some of my other guns with set triggers. Most were set less than a pound and all were under two. As a comparison, I gauged the pull of my discount store Mossberg Model 500 pump shotgun. It averaged out at 6 pounds, 8 ounces. Today, in the context of modern over-the-counter firearms, that would probably be considered light. Before I went in and slicked it up a bit, it was terrible.I concentrated more on the trigger than tracking the target. Trigger pulls can range between too light to be safe and too heavy to be practical. A reliable trigger pull gauge will tell you which.

Fig. 13.

Fig. 13
A trigger pull gauge is an easy way to tell if you are getting into dangerous territory by adjusting triggers to release under the lightest touch.

These chapters are getting longer as I remember more of what I forgot to mention earlier. We’ll be working on the buttstock next.

References

Stutzenberger, Fred. Patchbox Push Rod Drill Guide, Muzzleloader, Nov./Dec., 2009, p. 65

Suppliers

Brownell’s Inc., brownells.com, 800-741-0015 for low temp silver solder, Lyman trigger pull gauges and a wide range of gunsmithing materials and tools

L&R Lock Company, for single and double set trigger assemblies

Track of the Wolf for a wide range of single simple and double set triggers

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