Trapdoor Strength

[StrawHat]

I have an H &R Officer's trapdoor. Lately, the breech has been popping open on ignition. I've loaded my rounds to strictly "trapdoor acceptable" levels. Having it open is pretty disconcerting. I'd welcome any insights as to whether it is dangerous, can be fixed, or ignored.

The H&R did not follow the design of the Springfield 100%. The cam that holds the action shut was mounted on a round shaft rather than a square one. I believe parts from the Italian imports will interchange. You could also pin the cam to the shaft with a setscrew or just a roll pin. If I can find the article or link, I will post it.

[Larry Gibson]

IlWil

This sounds harder to do than it really is.

The cam must be positioned back to the right location on the shaft. A screwdriver was placed in the opening at the top of the cam to lock it in place while turning the thumb latch. I adjusted mine so when the top of the thumb latch is pushed forward as far as it will go (as in opening the action) the cam is rotated enough so its bottom will just clear the rear of the receiver and open. I then removed the breach block from the action and secured it in a padded vise with the left side up. Be careful not to move the cam on the shaft. If you do re-install the breach block in the action and re-adjust.

I removed the set screw and then inserted a drill bit. #43, that was a tight slip fit into the hole. This gave me a guide to line up a straight edge across the end of the shaft centering down the length of the drill bit. A line was scribed across the end of the shaft to use for reference, an idiot mark if you will.

A punch is then used to drive the shaft out of the cam and breach block. Out of the breach block the cam is then put back onto the shaft, the #43 drill bit put into the screw hole and the idiot mark lined back up. The original thread size on both of my H&Rs was 4x40, which is pretty small. I chose to go one size larger, which cleaned up some buggered threads and added some strength (maybe). I used a 5x40 tap and a #38 to drill the hole. Also I was able to find longer screws in 5x40 that would fill the entire hole in the shaft and the cam. The cam was secured in a machine vise on the milling table of my drill press. The job could be done on a mill also. The #38 was run down in front of the cam and shaft lining it up with the idiot mark and the #43 drill bit in the hole. Once lined up the #43 drill bit was removed from the hole and the mill table adjusted to drill the hole. A liberal amount of cutting oil was used, as there was some hardening to the parts. The hole was drilled completely through the shaft and out through the backside of the cam.

I then tapped the hole. Be very careful as it is easy to break a tap that small!!! Once again do not spare the cutting oil.

The new 5x40 screw is screwed in until the end just almost comes out the backside. Measure the excess screw length and remove the screw.

The cam and shaft are separated and re-installed in the breach block. Don’t forget to put the spring in. I initially eyeballed the alignment using the idiot mark and now the #38 drill bit through the enlarged hole. When it is lined up run the tap back into the hole to clean up any burrs created by the removal and re-installation of the cam on the shaft. When everything is lined up degrease the hole and blow it out with compressed air. The little cans sold for blowing off computers, etc. work fine. Put a little dab of lock-tite in the hole and then screw the 5x40 screw in until the measured excess amount that is protruding. Let the lock-tite dry and then cut off the screw and polish it smooth with the surface of the cam. Re-install breach block back in the rifle.

This modification worked for a while. As I was most often shooting sevice 1873 level BP loads it eventually failed and the BB began popping open again. Next post explans the ultimate solution.

Larry Gibson

[Larry Gibson]

My H&R LBH Carbine was the primary TD I 1st replaced the BB with using an original BB. It is not that hard to do if you have any ability while hand tools like a file. I was so satisfied with the BB replacement that when my Officer's Model popped open once i replaced the BB instead of messing with it. I have shot thousands of full level M1873 BP and smokeless loads through both since replacing the BBs without a single problem.

Fitting the original breech-block to the H&R Carbine. First thing was the hinge was a little larger in diameter than the H&Rs so the hinge-pin would not quite line up. I mixed some 220 grit lapping compound with cutting oil to thin it out. A small amount was put into the hinge recess in the receiver. Then with my left hand I put a punch through the left hinge-pin hole and exerted pressure pushing the hinge into its recess. At the same time with my right hand I moved the breech-block up and down lapping the hinge into place. Periodically I cleaned the hinge and checked the hinge-pin to see if it would go into place. It took three or four applications of lapping compound and about an hour to complete this. I did most of the lapping while watching TV. This went a lot easier on the next two breech blocks I fitted to other rifles. They line up a lot closer and took less lapping. On the third breech block fitted I used a small file and very carefully did the initial fit using it. Be very careful and go slow checking the fit frequently as you can't replace the metal you file off.

I then put a piece of flat stock steel across the flats at the rear of the receiver and measured the distance from the underside of the flat stock to the bottom of the receiver. I then ground the bottom of the breech block fore and aft of the arch that distance minus about .01as measured from the flange of the breech block to the bottom. I was careful to maintain the curvature of the bottom of the breech block.

With the breech block cap, thumb latch and cam-lock assembly removed I slightly ground of the hardened surface off the back of the breech-block where it fits into the receiver. A new 1” wide mill bastard file was used to file the back of the breech block down until it was a very close fit. I don’t know exactly how much I filed off but it wasn’t that much. I was careful to maintain the correct angle and used a “file a little – test fit – see where to file a little more, etc.” so the back of the breech-block fits the rear face of the receiver quite well. I stopped filing as soon as the flanges of the breech block rested on the flats at the rear of the receiver. On one of the H&Rs the recess for the ejector did not quite line up. the ejector was a little too far forward. Careful use of a Dremel tool with a small grinder in the forward edge of the breech block recess elongated the hole. One again it didn't take much for a perfect fit.

The breech block cap, thumb-latch and cam-latch assembly was re-installed on the breech-block. A scribe mark was made on the breech-block cap marking how much had to be removed from the end. The assembly was removed and that amount was ground and filed away. The breech-block was assembled and installed in the receiver. The cam-latch fit into the receiver recess perfectly but required a small amount to be ground (to hard to file) off with a large grinding wheel in the Dremel. Once again go slow here taking off only a little at a time untile the breech block closes and opens easily.

As there wasn’t any finish on the breech-block (on the first one I tried, other two had original finish and look pretty good) to begin with, cold blue was used all over giving it a “used” look. I then test fired the rifle with 50 carbine service loads of a 405 gr bullet over 25 gr XMP5744. The rifle has been fired hundreds of times since with no problems. I had some concern as to whether I should have the bolt re-hardened since I had ground and filed away some of the hardened surface. To date there has been no sign of wear on those surfaces. Total time for installation was 4-5 hours.
As the original H&R bolt was so poorly fitted and finished, which I believe is why nothing would keep the action from popping open upon firing, the replacement with an original Springfield breech-block was worth while. It made a dangerous rifle entirely safe, sound and serviceable.

Larry Gibson

[KCSO]

The latch is made different than the REAL trapdoor and you need a spring replaced if I remember right.

IF you mean unlatching, but POPPING open? Where's the hammer when all this is going on.

[StrawHat]

...My H&R LBH Carbine was the primary TD I 1st replaced the BB with using an original BB. It is not that hard to do if you have any ability while hand tools like a file... Larry Gibson

Larry, originally, the breech blocks were fit with some lateral play. Were you able to duplicate that?

[Larry Gibson]

Larry, originally, the breech blocks were fit with some lateral play. Were you able to duplicate that?

Yes, but I did not do it to the extent as many originals. I used and original cadet in very, very good condition (unfortuneately not mine) as an example of how much tight fitting should be done. Again I have fired thousands of rounds through both my H&Rs subsequent to this conversion without a single problem.

Larry Gibson

[trap4570]

The set screw has become loose. Tighten the allen head screw back in then screw another one in behind it. I've repaired a few H&R's with this problem. I also use a locking liquid to hold everything in place. If the set screw backs out far enough the latch will just swing then you have a stuck cartridge and it will require dental picks to release the cam. A very frustrating situation.

[Hang Fire]

HangFireW8
Start with the middle set of loads and work your way up. You may found what many Handi-Rifle owners have found, at a certain amount of recoil (not pressure per se) the rifle will become a self-ejector.

That is, it will spring open immediately after firing. Not unsafe, but very disconcerting. Or, it may not! The difference seems to be some receivers are springier, or stretchier, than others.

Back in 1982 I had a TC Contender in .223 that blew opened on first firing and ejected the case. I didn't try for a second go, but had the dealer I bought the gun and factory ammo from send it and case to TC. Couple weeks later I got a new Contender and barrel back but no explanation.

[44-40]

I was suprised at the load of Bullseye it took to destroy the trapdoor. I can't imagine what the recoil would have been!

I grew up hearing about how weak the Trapdoors were and believed them with out ever knowing what the test were that determined weakness. Then I read Waters article on the 45-70 in Rifle and Handloader magazines and he had four (4) load levels for the 45-70 with the trapdoor in the lowest tier. Several others also did loading guides and the Trapdoor was always in the bottom tier. Too weak, etc. I wonder what the basis for the determination was as reading these pages it seems to indicate the Trapdoor is a bit stronger, and safer, than was previously thought.

I guess my ideas of rebarreling a Trapdoor will get a fresh turn.

Hello StrawHat, I imagine you could blowup just about any modern gun with the amount of bullseye that will fill it's case. How much did it take to destroy the Trapdoor? I have two Lyman reloading manuals, 45th edition (c.1970) which was my first manual and the Lyman 47th edition (c.1992). Both list Unique 11gr. start and and 15gr. MAX for the 405 Jacketed bullet. The 47th edition gives 13.7 gr. Unique starting and 16.5 MAX for a #2 alloy 400 grain cast bullet. I have no idea what #2 alloy is! I load my 45-70's with 11 gr. Unique and 55 gr. Goex 2 FFG. That is about all the 2 FFG I can put in the case and compress it when seating the bullet with my press. I have not tried using an arbor press to get more powder into a case because I think the recoil is as much as I care to stand with 55 grains. I prefer shooting the 11 gr, Unique loads and they are accurate to my tested 100 yards. I would not be afraid of using commercial ammuniton but it will not be as accurate and I don't want the recoil.

[StrawHat]

44-40,

The article states the amount. Let's just say it was a lot. The whole gist of the reports was the Trapdoor is not nearly as weak as it is normally thought to be.

I believe the weak action rumors started with the 1866, which used old barrels and machined them to accept the action and new liners. By 1870, the action was newly made and for the 1873, all the parts were newly made. But the older actions were still available (I still use an 1866) and the rumor started/persisted.

[40-82 hiker]

I've had my 1884 TD since the late 60s. I've shot BP, Pyrodex CTG decades ago, but nothing has given me the accuracy that AA5744 does now. I resurrected the TD a couple of years ago as a project to help me with my disabilities, and I have been shooting the heck out of it since, er, at least when I can.

I don't worry about the strength of the action, as I have always shot the mildest loads I can to achieve the best accuracy. Also, I am very leery of the Hodgon tables, as I think they are a little overly heavy for the TD action. JMHO.

I would also recommend this load for any Handi Rifle, or other light 45-70 where the weight (or lack thereof) is an issue.

Lyman 405gr. boolit (1:20)
24.0 (or 24.2) grs. AA5744 (no filler per Johan Laubser - ballistician for Western Powder - not with them now)
Any good LRP (I use Winchester)
Lyman Moly Lube
My boolit sized to 0.459

I used to use the 500 gr. boolit, but recoil was getting to me due to my back problems. This load is nice to shoot in my Trapdoor, and very accurate. Certainly there are no pressure issues. My bore is good and shiny, but certainly not pristine.

I made a new front site for it out of German silver, but any steel will do. I regulated the front sight on with 6 o'clock hold at 100 yards, with the Buffington sight set in the down position.

As others have stated, it is not the looseness of the breech block that is a problem. They have to be loose. The pressure on the breech block face when firing has to be transmitted to the rear of the breech, and that takes the looseness of the hinge assembly to allow this to happen.

I have the one TD, and a RB in 40-65. I seem to enjoy shooting the TD better than the RB for some reason, though even with the Buffington sight the RB is easier to shoot with my 61 YO eyes. The TD is just a fun gun to shoot. Again, MHO.

My final thought on the TD is this: it is too fun to shoot to worry about the last couple of hundred feet per second you can get out of it. A guy at the range let me shoot my load through his Chrony, and the 405 gr. boolit was going 1420 fps. This surprised me a little, as I did not think it would be quite that fast. However, it is enough recoil for me to deal with, and I don't see any need to get it going any faster. I have to wonder if I have shot my weight in boolits through that gun in my lifetime , and the action is as good as when my Dad bought if for me around '67. I just never took it to task. It may be a strong action, but over time I think it is prone to wearing out if using loads outside of its design strength.

As far as accuracy, I will put the TD up to just about any modern made .45-70. Period. However, even with the Buffington rear sight, it is not an easy gun to shoot. i find the rear sight is just not that easy to use with older eyes (again, MHO). While the sights may have been a marvel in their day, the Buffington rear sights do not match up to what we can put on RBs, Sharps, etc. Can't come close. JMHO again.

[RobsTV]

Started shooting an original Springfield 1884 TD before I had real black powder. Used 777 and 405gr lead. Always horrible accuracy. Then switched to full case of slightly compressed Goex FF and instant accuracy. Chrono'd these new black powder loads at around 1400fps, then chrono'd one of the 777 normal loads I was using, and these ran faster than 1800fps! I pulled all remaining and tossed out the 777. But, the original Springfield seemed no worse for wear after couple hundred of those hot 777 loads.