September 23, 2010
A lot of guns come into a gunsmith shop for one reason or another.
Alignment and slave pins (right) can prevent a lot of fumbling with numerous small parts and springs during reassembly.
A lot of guns come into a gunsmith shop for one reason or another. Some are easier to work on than others. Some you look forward to workin' on, while others you hate to see come through the door.
My all-time least favorite gun was not a particular brand or model. In fact, it wasn't a specific caliber or gauge, or even firearm type. The gun that caused me to cringe whenever I walked up to the counter to meet the customer was the "bag gun." If you've not worked in a gunshop, you've probably never even heard of a bag gun.
Bag gun is the term gunsmiths have given to any firearm brought into the shop in a bag or box. Normally, the owner had disassembled the gun for cleaning or other work, and the poor soul then discovered that he couldn't figure out how in the heck to get the darn gun back together.
Often, this would be a source of embarrassment for the owner. Frequently, he would sit on his collection of parts for years before working up the courage to bring the gun into the shop. I've also had more than one person with a bag gun go to great lengths to make sure I understood that it was not he who had taken the gun apart. It was always "the kid" or his "idiot brother-in-law."
I remember one fellow who went on at length about how his son-in-law disassembled his favorite Browning A-5 shotgun and then couldn't get it back together. Of course, he could do it, but he just didn't have time right then to take care of it, so he dropped it by the shop.
After he left, my partner looked over at me with a grin on his face and told me he knew the fellow's family. He had two daughters, neither of whom was married. In reality, there was no son-in-law.
There are a number of ways to avoid a bag gun. The first is to make sure you have a good instructional guide or manual if you're not completely sure of how the gun goes together. There are a number of good assembly/disassembly guides available. Two of the best are the two-volume set published by the National Rifle Association--one volume on pistols and revolvers and the other on rifles and shotguns--and the beautifully done guide dealing exclusively with military arms by Stuart Mowbray and Joe Puleo entitled A Collector's Guide to Military Rifle Disassembly and Reassembly. Both are excellent and provide step-by-step instructions that even an idiot brother-in-law could understand. Both are available just about anywhere firearms books are sold.
A lot of problems in reassembly can be avoided simply by carefully studying the relationship of the parts as you disassemble the gun. Spend the time to look closely at the parts and their relationship before you take them out of the gun. If something looks strange, weird, or confusing, make a simple drawing. Better yet, take a digital photograph of that portion of the gun. A drawing or photograph can often provide just the clues you need later to get the gun back together quickly and easily.
Reassembly is also made easier with the use of a couple of simple tools. I have to admit that it took me years to finally realize just how handy and helpful these tools are. However, once you use them, you'll never want to be without them.
Note the difference between the rounded tips and tapered shafts of the alignment pins on the left and the flat tips and straight shafts of the standard punches on the right.
Alignment Pin Basics
The first of these tools is an alignment pin. Alignment pins look a lot like standard steel punches, and many folks make the mistake of using them as a punch. An alignment pin differs from a regular pin punch in that the shaft is tapered, while a standard pin punch shaft is of a uniform diameter. A typical alignment pin will taper from a diameter of 0.070 inch on the small end to about 0.150 inch on the big end. Of course, they can be considerably larger, but the 0.070-to- 0.150-inch pin is the size I've found to be most useful at my bench. The business end of the pin may be flat, but I've seen some that were slightly rounded. You'll find them offered by tool supply houses either as individual items or in sets. Of course, you can even make your own.
Where the regular punch is designed and used to drive out a pin, the alignment pin is only meant to be used to help move or position parts within a gun. Once those parts are properly positioned or aligned, a pin or screw can be used to secure the parts. Have you ever tried to put a pin or screw through a part you had to have perfectly positioned in a place where you couldn't necessarily see the pin or screw hole very well? That can be a real problem.
I often find guns where there's damage around the edge of the hole in a part that's a result of a pin that was improperly aligned when the owner tried to drive it in. This damage in the form of dings or nicks can range from relatively minor to actually ruining the part as well as the pin or screw that holds it in place.
When using an alignment pin, you generally want to use one with a shaft that matches the diameter of the pin or screw. Since alignment pins are tapered, you want the diameter to match far enough up on the shaft to allow all the necessary parts to be correctly positioned. The small end of the alignment pin is handy, as you won't necessarily have to have the hole in the part perfectly aligned initially. Once you get the alignment pin started and push it into place, when it reaches the point on the shaft that's the same diameter as the pin or screw, everything will be properly aligned. Now you just withdraw the alignment pin and insert the pin or screw that secures the part. It's usually just that easy.
But wait. What if the part is under spring pressure or just won't stay in place when you remove the alignment pin? That can be the case especially with compressed springs or spring-loaded hammers in some box-lock shotguns. Another problem area is where you have parts that continually slip out of position due to no internal support. What can you do then?
Reassembly of the Winchester Model 67 bolt is very difficult unless a slave pin is used.
This crossbolt pin fits between the rebound spring and the striker-spring plunger. A slave pin will ensure that it is properly positioned. Note the slave pin positioned between the rebound spring and the striker-spring plunger.The crossbolt pin has been driven in about halfway, and the tip of the slave pin is just beginning to move out of the bolt.
A Slave Pin To The Rescue
Well, my friends, that's when you use a slave pin. A slave pin is typically nothing more than a short pin intended to hold one or more parts in position during assembly. When the primary pin is then pushed into place, the tip of the primary pin moves the slave pin out of the way without disturbing the position of the parts. Slave pins are often just a bit smaller in diameter than the primary pin so they can move very easily. The ends of the slave pin are also generally slightly beveled or tapered to allow the pin to move between parts easily.
While most of the slave pins I've used were constructed of steel, slave pins can also be brass, aluminum, nylon, plastic, or even wood. Any material that works is just fine; more than one toothpick has been used as a slave pin. Remember, this is just an assembly tool. A slave pin seldom has to actually function under a load or pressure.
I don't know of any commercial source for slave pins, so I've always made my own as needed. Not too long ago, I was spending a lot of time working with the old Winchester Model 67 and 67A .22 rimfire single-shot rifles. These are nice, rugged, old bolt-actions. The only problem with them is reassembly of the bolt. The striker spring, striker-spring plunger, and the rebound spring bear against a crossbolt pin. It's virtually impossible to properly reassemble the bolt without using a slave pin to separate the striker-spring plunger and rebound spring on either side of the crossbolt pin.
In this case, the Model 67 slave pin must be of a diameter of about 0.114 inch with a length of just about 0.331 inch. The slave pin can't be longer, as the striker assembly with the slave pin in place must be inserted inside the bolt body. Once it's in place, you use the crossbolt pin to drive out the slave pin. The crossbolt pin is now properly positioned between the ends of the striker-spring plunger and rebound spring. Without the slave pin, you stand a very real chance of damaging the plunger or rebound spring when reassembling the bolt.
Since I was working on a lot of these old Winchesters at the time, I made up several slave pins and kept them in a properly labeled zip-lock bag. Having them on hand saved me a lot of time and frustration and made reassembly so much easier.
Alignment and slave pins will not solve every reassembly problem, but they will help. Who knows, they might just help you to avoid ever having to visit the local gunsmith with a bag gun of your own.
Until next time, good luck and good gunsmithing!