March 9, 2011

Repairing The Trapdoor Springfield Carbine

Getting parts for the Trapdoor Springfield Carbine is easy, but give a quick course in reloading cartridges for the gun—modern loads are dangerous and shouldn’t be used. From American Gunsmith’s Book of the Rifle.

certainly as the percussion cap superseded flint and steel, the breech-loading gun will replace those that load from the muzzle.” So predicted Secretary of War John Holt in 1860. The Civil War proved he was right. Before it ended, Sharps, Spencers and other breech-loaders prevailed with cavalry troops. The infantry, on the other hand and with few exceptions, employed muzzleloaders. Right or wrong, they had their reasons.

The Sharps was expensive and frequently leaked gas at the breech. It also required a special cartridge, which wasn’t waterproof or self-primed. The Spencer and the Henry were considered underpowered by comparison with the foot soldier’s standard-issue .58-caliber musket. As a result, in January 1865, the Ordnance Department had more than a million totally obsolete big-bore muskets in its inventory.

Accordingly, Erskine Allin, the master armorer at Springfield Armory, was directed to work out a way to convert all those muskets into breech-loaders accepting a metallic cartridge. Allin wasted no time. On September 19, 1865, and unbeknownst to the Chief of Ordnance, he was granted a U.S. Patent for his breech-loading system.

Allin’s conversion required milling out the top portion of the barrel to accept a breech block, then attaching the hinged portion of the block to the barrel with one screw and some soft solder. The block tipped upward and forward to open the breech for loading, was held in its closed position by a thumb latch at its rear, and housed the firing pin. The original cartridge was a copper-cased rimfire holding a 480-grain lead bullet and 60 grains of blackpowder.

By 1866, extraction and ammunition problems that showed up during troop trials had been corrected, and the trapdoor became a .50-caliber rifle. The first experimental cavalry carbine versions were produced in limited numbers in 1868. The Model 1873 rifle and carbine came into existence after a long series of experiments convinced the War Department that the proper caliber for small arms was .45.

Briefly, that’s the story of the .45-70 Trapdoor Springfield. In the hands of the U.S. Cavalry, it speeded up the opening of the West. In the hands of American Indians who didn’t want their West opened, it slowed it down. After a number of design and production changes, it went out of production in 1893 when Springfield Armory started tooling up to manufacture the Model 1892 Krag-Jorgensen.

American Gunsmith Book of the Rifle, Chapter 33

Courtesy, American Gunsmith Book of the Rifle

The stock of the Trapdoor was nearly split in two at the comb. Though worth a quick fix to serve as a pattern, it wasn’t original Springfield wood and had been painted with enamel.

As a collectible, a trapdoor can command considerable value, so if one finds it way into your shop, don’t be too quick to turn down the opportunity of fixing what’s wrong with it. I recently repaired a Model 1873 carbine with good results, as I relate below:


The Model 1873 carbine shown here was definitely salvageable and more than worth its owner’s investment in replacement parts, plus my time and labor. As you can see, its stock was a wreck. It wasn’t an original either, having been replaced with one of birch and crudely finished off in brown enamel at some point in its past. Still, doing a quick fix on it would serve a couple of useful purposes.

First, the old stock was clamped to close up the awful split and a #14 screw inserted aft of the receiver’s tang to hold it closed. Other gaps on the lockwork side were filled and roughly sanded. The old stock thus made a good pattern for a replacement and was shipped out to Wenig Custom Gunstocks in Lincoln, Missouri. In other words, they know their wood and how to work it. What they sent back was a really nice piece of American walnut that was 90 percent machine inletted to match the inletting of the old stock.

With the old stock as a guide, I set about inletting the action, lockwork, butt plate, and trigger guard assembly the remaining ten percent. This was entirely accomplished with hand tools. Barrel channel scrapers, small chisels, assorted files, rasps and astute applications of a Dremel or Foredom tool turning at low revs were employed in various orders to remove small bits of material at a time. Each and every time material was removed, the piece being fitted was rubbed over with a red wax pencil and tapped lightly down into the stock. When lifted free, the red marks left behind showed where there was still interference and a little bit more needed to be scraped, filed, chiseled or rasped away. There was also surgery to be performed internally.

This involved deepening the trigger slot in the stock enough to allow the trigger to contact the sear, trip it and release the hammer. It was accomplished by drilling a series of 1/16-inch holes as close together as possible in the slot and clearing them out with a flat needle file. The end result after a few hours of scraping, chiseling, filing and rasping was a snug, finger pressure fit between barreled action, lockworks and trigger assembly with all mechanical functions in smooth working order. The receiver tang, lockworks, butt plate tang and trigger guard were seated 1/32 of an inch deeper than an ideal interface with the wood to allow for final sanding and finishing.

American Gunsmith Book of the Rifle, Chapter 33

Courtesy, American Gunsmith Book of the Rifle

This is the inletted barrel assembly for the Springfield Trapdoor Carbine restoration project. Note the extra depth to which the tang has been seated to allow for final sanding and finishing. All the inletting tools are sold by Brownells.


While waiting for the gun’s new stock to arrive, I set about repairing the mechanics of the Springfield. Fortunately, they weren’t in bad shape at all.

The firing pin was broken. The firing pin screw, cam latch spring, ejector spring and front sight were missing. I had turned replacement firing pins and manufactured screws to get other trapdoors back into shooting shape before this, but I knew the hours would be piling up because of my own fussiness during the inletting process, and I didn’t want to sour a good customer on my services by handing him a bill that would choke a horse. It was time to turn to Dixie Gun Works, which doesn’t manufacture anything but has a thick catalog that includes antique gun parts. Even more helpful was that when the parts arrived, they needed no fitting whatsoever. I merely had to drop them in, solder on the front sight and assemble the gun for a final function check before turning it back to its owner.

I function fired it with him the next day, being careful to warn him about not using modern factory ammo in his now almost-restored prize. When he asked why, I told him things happen to gun metal that’s 100 years old. It can develop microscopic cracks, become weakened and literally blow up in his face. I also reminded him that his Trapdoor Springfield started life as a blackpowder gun and it would be dangerous to ask it to tolerate the pressures generated with modern, smokeless powder loads. If he must fire it, I said, he should use reduced black or smokeless powder reloads. If his choice was blackpowder, I advised him to keep in mind that the 1873 carbine never carried as much propellant as its larger kin, the rifle, which held 70 grains. For safety’s sake, he should figure on using 50 to 55 grains of blackpowder behind a 405-grain lead bullet. If he opted for smokeless powder, 25 to 28 grains of Hodgdon H1198 would suffice for the same bullet. In both cases, I urged him to stay on the low side with his propellant charges.