Rossi Overland lock

**4V50 Gary** · May 6, 2016, 07:14 AM

It's a lock from h*ll. Instead of V springs like the original back action lock, it uses coil springs. It also uses polymer shims between the hammer and the lockplate.

My new issue is pressing the hammer onto the tumbler. I've placed them in copper lined jaws of a vise and squeezed them hard, but there's still play. The trouble with the play is that if the tumbler cants to the side because of pressure on the hammer, there's enough disengagement for the sear to slip. So now I'm thinking of using an arbor press to press (with a block beneath the bridle to support the lock and prevent it from being crushed) to push the hammer onto the tumbler.

My question is how did they assemble them at the factory?

James K · May 6, 2016, 03:04 PM

My guess would be that they made both the hole in the hammer and the tumbler a bit over/under size, and the fitter had a square file and a big lead hammer.

Jim

Dixie Gunsmithing · May 6, 2016, 05:31 PM

This is right about the same problem as the guy had the other day, with his Springfield P9, where the sear would cant in the ejector housing.

Gary, can you snap a photo of what you have? I'm like Jim, in that the sear should not be able to move, only rotate about the pin/shoulder screw. If the screw can move or wobble (be canted) between the bridle (holding plate in Rossi lingo) and the lock plate, then the gun has some issues. If the sear wobbles or is canted on the shoulder screw, then either the screw or sear is badly machined. That sear looks to be a casting too, by looking at Numrich, and I wonder if it was hand drilled, etc?

It looks like the bridle could have a better fit also. The working surface of the bridle shoulder screws look terrible, rough as a gnawed on corn cob. It looks like they've bumped the hammer's pivot hole in the bridle, over things being over sized. You may have to make some new bridle screws, or try your luck with the ones from Rossi.

Copyright (C) Numrich

I sure don't like the idea of plastic shims. They're trying cheapen things more, each year. However, I don't see any shims at Numrich.

Edit: I noticed that they had what was called a sear busing. However, as large as it is, it looks to be a spacer, as the OD is 0.218". The diagram seems to allude to a small busing or something for the sear, but they give no part number on the drawing for them. I couldn't tell for sure what they have over that. If the screws shoulders are as rough as that one photo, I could see them wearing down quick, allowing the sear to be too loose on the screw. The tumbler and sear should have no play in them at all, and only revolve about the lock screws. They should have reamed holes in them, if made correctly.

Coil hammer springs are a better idea than V springs, as they wont break near as easy. It looks like the hammer strut goes through a boss that has either been riveted or welded to the lock plate, at the rear. That might break one day, as it looks to be a piece of stamped metal, that was split on the outside.

**4V50 Gary** · May 7, 2016, 06:26 AM

I made the bushing replacement out of 0.020" brass (the polymer original mic at that dimension).

Will see if I got those spacers right (any misalignment will result in a gap). I suspect now they've a gorilla with a huge mallet to whack in the hammer.

gyvel · May 7, 2016, 12:57 PM

Far fetched, maybe, but it could be that they use the freeze/heat method, i.e. freeze one part and heat the other. That's one method we used to assemble close tolerance bearings on turbine shafts.

Dixie Gunsmithing · May 7, 2016, 01:20 PM

gyvel, I've done the same, using either CO2 from a bottle; applying the gas to the part from a hose hooked to the regulator, or pack with dry ice, and heat from a rosebud torch on the opposing part. We used to seat large diameter Timken races in bores, and the bearings on shafts, that way. I've performed the same on gun parts, to open a hole in a part so I could slide in a close fitting pin, and after it shrinks, it doesn't come out, unless you pound it out. It's a good trick for installing press-fit brass/bronze bushings too.

Dixie Gunsmithing · May 7, 2016, 01:44 PM

Gary, if you're fabricating bushings, and need two the same length, before you part or face the first one off, put a piece of round rod in the tail stock's drill chuck, and lock it down for a length stop, by butting the rod against the part. Part or face the first one off, then slide the brass tubing or bushing against the stop, to get a matching length, tighten the lathe chuck, then part or face that, leaving the tool post and carriage set in the same place between the two. You can grind or mill off one side of the rod, to a little past the center, so it is similar to a dead center, where the stop will allow the tool to cut to the center. That is similar to how a turret lathe is ran.

That, or use a good dial indicator on the lathe bed, with the probe against the carriage, but you can get a small error that way, say 0.0005" or so, when you reset the carriage, providing the indicator doesn't move any.

For future reference, you can buy indexed turret tail stocks for some brands of lathes, even the smaller 36" beds, with about 5 to 6 stations, and they do come in handy if you're going to run many of the same parts. Some school shops will have a small turret lathe in them, with a 5C collet, for running parts. I used to run a big 10' bed, Gisholt turret lathe making pump parts, years ago. Once you get it set up, you can fly with it.

**4V50 Gary** · May 8, 2016, 05:09 AM

Dixie - I made the flat brass bushing replacement that fits on the tumbler and is between the hammer and the lockplate and not the two round bushings that served as a spacer between the bridle and the lockplate. Still, even the flat bushing is not reponsible for the hammer/lockplate gap.

Dixie Gunsmithing · May 9, 2016, 10:11 PM

Ah, so the hammer is fitting too tight when pressing onto the tumbler's stud? By looking at the part, it looks like they turned a round large diameter boss on it, then cut flats onto the boss, to accept the square hole in the hammer. The other side just looks to be a round boss/stud, that goes into the bridle. You had me thrown by mentioning those shims, which I thought were those spacers.

The hammer doesn't need to be a press fit. You can relieve those flats a little with a file, so the hammer will pretty much slip on, or at least press on easier. Their parts drawing doesn't show those shims, if they have some between the hammer and lockplate.

The main thing is for the inside lock to work correctly (sear and tumbler). The hammers fit (clearance) between it and the lockplate isn't that critical, as long as it clears the lockplate, and doesn't rub it, since its hitting firing pins, and not caps.

If it were me, I'd file those flats to give the hammer a good slip-on fit, with no play, and be done with it. Also, if the tumbler is canting, from applying pressure to the hammer, say as to cock it, the bosses diameter on the tumbler is probably worn down, or the lockplate's hole is wallowed out. You may have to do something to tighten the fit of the hole or boss up. You might be able to stake the hole, and ream it. You may have to stake the hole in the bridle too. Worst comes to worse, you may have to buy a lockplate and bridle, to get rid of the slop causing it to cant.

Dixie Gunsmithing · May 9, 2016, 10:52 PM

Gary, let me add to my last post. The tumbler has two bearing surfaces, the two studs. One stud goes through the lockplates hole, and revolves in it. That fit should be a tight but slip fit, so it will only rotate, but should have no slop. The stud on the bridle side is the same, as is the hole it rides in. If either are worn, and both generally will be worn the same, then when you try to cock the hammer, the spring tension, will allow the tumbler to cant over the wear, due to the leverage of cocking the hammer.

I've seen this happen in worn out locks, and there isn't much you can do, but to tighten the fit of the two bearing surfaces, generally the holes. When that tumbler rotates, it should have no noticeable play to it, with or without the spring acting on it, nor should it be able to cant in any direction. It should only rotate freely, but not move in any other direction. Those fits on either side determine that. Ideally, one would install the bridle to the lockplate, and line bore or ream those two holes together, but that is about impossible on this.

**4V50 Gary** · May 11, 2016, 06:50 AM

My biggest problem with this lock was not being able to press the hammer far down enough on the tumbler. This allowed for some side to side play and if the hammer was pressed to the side, it would swing the tumbler out of engagement with the sear, allowing the hammer to drop.

The following corrective measures were taken:

1) Tumbler notch for sear deepened.
2) Top of sear filed lightly to allow the sear to ride higher into the tumbler's notch (more engagement).
3) Shim for hammer/sear opened so as to allow the hammer to sit closer to the lockplate (this was the main culprit).

With these modifications, the hammer was pressed onto the tumbler in a copper jaw lined vise. It pressed down the furthest it has even been done by my hands. In fact, I slipped on the vise and was hanging on the handle to keep from landing on the floor.

ETA: as to how the factory assembled them, who knows? However, a polymer shim is more forgiving (flexes) than the brass replacement. When the brass shim's hole was opened for the tumbler, everything really went in easy this time. There is a tight fit between the hammer, shim tumbler and lockplate.

May 6, 2016, 07:14 AM	#1
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 21,833	Rossi Overland lock It's a lock from hll. Instead of V springs like the original back action lock, it uses coil springs. It also uses polymer shims between the hammer and the lockplate. My new issue is pressing the hammer onto the tumbler. I've placed them in copper lined jaws of a vise and squeezed them hard, but there's still play. The trouble with the play is that if the tumbler cants to the side because of pressure on the hammer, there's enough disengagement for the sear to slip. So now I'm thinking of using an arbor press to press (with a block beneath the bridle to support the lock and prevent it from being crushed) to push the hammer onto the tumbler. My question is how did they assemble them at the factory? __________________ Vigilantibus et non dormientibus jura subveniunt.* *Molon Labe!*

May 7, 2016, 06:26 AM	#4
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 21,833	I made the bushing replacement out of 0.020" brass (the polymer original mic at that dimension). Will see if I got those spacers right (any misalignment will result in a gap). I suspect now they've a gorilla with a huge mallet to whack in the hammer. __________________ Vigilantibus et non dormientibus jura subveniunt. *Molon Labe!*

May 7, 2016, 12:57 PM	#5
gyvel Senior Member Join Date: August 30, 2009 Location: Northern AZ Posts: 7,172	Far fetched, maybe, but it could be that they use the freeze/heat method, i.e. freeze one part and heat the other. That's one method we used to assemble close tolerance bearings on turbine shafts. __________________ As always, YMMV. __________________________________________ MIIAA SIFE

May 8, 2016, 05:09 AM	#8
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 21,833	Dixie - I made the flat brass bushing replacement that fits on the tumbler and is between the hammer and the lockplate and not the two round bushings that served as a spacer between the bridle and the lockplate. Still, even the flat bushing is not reponsible for the hammer/lockplate gap. __________________ Vigilantibus et non dormientibus jura subveniunt. *Molon Labe!*

May 11, 2016, 06:50 AM	#11
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 21,833	My biggest problem with this lock was not being able to press the hammer far down enough on the tumbler. This allowed for some side to side play and if the hammer was pressed to the side, it would swing the tumbler out of engagement with the sear, allowing the hammer to drop. The following corrective measures were taken: 1) Tumbler notch for sear deepened. 2) Top of sear filed lightly to allow the sear to ride higher into the tumbler's notch (more engagement). 3) Shim for hammer/sear opened so as to allow the hammer to sit closer to the lockplate (this was the main culprit). With these modifications, the hammer was pressed onto the tumbler in a copper jaw lined vise. It pressed down the furthest it has even been done by my hands. In fact, I slipped on the vise and was hanging on the handle to keep from landing on the floor. ETA: as to how the factory assembled them, who knows? However, a polymer shim is more forgiving (flexes) than the brass replacement. When the brass shim's hole was opened for the tumbler, everything really went in easy this time. There is a tight fit between the hammer, shim tumbler and lockplate. __________________ Vigilantibus et non dormientibus jura subveniunt. *Molon Labe!*

May 6, 2016, 03:04 PM	#2
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	My guess would be that they made both the hole in the hammer and the tumbler a bit over/under size, and the fitter had a square file and a big lead hammer. Jim

May 6, 2016, 05:31 PM	#3
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	This is right about the same problem as the guy had the other day, with his Springfield P9, where the sear would cant in the ejector housing. Gary, can you snap a photo of what you have? I'm like Jim, in that the sear should not be able to move, only rotate about the pin/shoulder screw. If the screw can move or wobble (be canted) between the bridle (holding plate in Rossi lingo) and the lock plate, then the gun has some issues. If the sear wobbles or is canted on the shoulder screw, then either the screw or sear is badly machined. That sear looks to be a casting too, by looking at Numrich, and I wonder if it was hand drilled, etc? It looks like the bridle could have a better fit also. The working surface of the bridle shoulder screws look terrible, rough as a gnawed on corn cob. It looks like they've bumped the hammer's pivot hole in the bridle, over things being over sized. You may have to make some new bridle screws, or try your luck with the ones from Rossi. Copyright (C) Numrich I sure don't like the idea of plastic shims. They're trying cheapen things more, each year. However, I don't see any shims at Numrich. Edit: I noticed that they had what was called a sear busing. However, as large as it is, it looks to be a spacer, as the OD is 0.218". The diagram seems to allude to a small busing or something for the sear, but they give no part number on the drawing for them. I couldn't tell for sure what they have over that. If the screws shoulders are as rough as that one photo, I could see them wearing down quick, allowing the sear to be too loose on the screw. The tumbler and sear should have no play in them at all, and only revolve about the lock screws. They should have reamed holes in them, if made correctly. Coil hammer springs are a better idea than V springs, as they wont break near as easy. It looks like the hammer strut goes through a boss that has either been riveted or welded to the lock plate, at the rear. That might break one day, as it looks to be a piece of stamped metal, that was split on the outside.

May 7, 2016, 01:20 PM	#6
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	gyvel, I've done the same, using either CO2 from a bottle; applying the gas to the part from a hose hooked to the regulator, or pack with dry ice, and heat from a rosebud torch on the opposing part. We used to seat large diameter Timken races in bores, and the bearings on shafts, that way. I've performed the same on gun parts, to open a hole in a part so I could slide in a close fitting pin, and after it shrinks, it doesn't come out, unless you pound it out. It's a good trick for installing press-fit brass/bronze bushings too.

May 7, 2016, 01:44 PM	#7
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	Gary, if you're fabricating bushings, and need two the same length, before you part or face the first one off, put a piece of round rod in the tail stock's drill chuck, and lock it down for a length stop, by butting the rod against the part. Part or face the first one off, then slide the brass tubing or bushing against the stop, to get a matching length, tighten the lathe chuck, then part or face that, leaving the tool post and carriage set in the same place between the two. You can grind or mill off one side of the rod, to a little past the center, so it is similar to a dead center, where the stop will allow the tool to cut to the center. That is similar to how a turret lathe is ran. That, or use a good dial indicator on the lathe bed, with the probe against the carriage, but you can get a small error that way, say 0.0005" or so, when you reset the carriage, providing the indicator doesn't move any. For future reference, you can buy indexed turret tail stocks for some brands of lathes, even the smaller 36" beds, with about 5 to 6 stations, and they do come in handy if you're going to run many of the same parts. Some school shops will have a small turret lathe in them, with a 5C collet, for running parts. I used to run a big 10' bed, Gisholt turret lathe making pump parts, years ago. Once you get it set up, you can fly with it.

May 9, 2016, 10:11 PM	#9
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	Ah, so the hammer is fitting too tight when pressing onto the tumbler's stud? By looking at the part, it looks like they turned a round large diameter boss on it, then cut flats onto the boss, to accept the square hole in the hammer. The other side just looks to be a round boss/stud, that goes into the bridle. You had me thrown by mentioning those shims, which I thought were those spacers. The hammer doesn't need to be a press fit. You can relieve those flats a little with a file, so the hammer will pretty much slip on, or at least press on easier. Their parts drawing doesn't show those shims, if they have some between the hammer and lockplate. The main thing is for the inside lock to work correctly (sear and tumbler). The hammers fit (clearance) between it and the lockplate isn't that critical, as long as it clears the lockplate, and doesn't rub it, since its hitting firing pins, and not caps. If it were me, I'd file those flats to give the hammer a good slip-on fit, with no play, and be done with it. Also, if the tumbler is canting, from applying pressure to the hammer, say as to cock it, the bosses diameter on the tumbler is probably worn down, or the lockplate's hole is wallowed out. You may have to do something to tighten the fit of the hole or boss up. You might be able to stake the hole, and ream it. You may have to stake the hole in the bridle too. Worst comes to worse, you may have to buy a lockplate and bridle, to get rid of the slop causing it to cant.

May 9, 2016, 10:52 PM	#10
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	Gary, let me add to my last post. The tumbler has two bearing surfaces, the two studs. One stud goes through the lockplates hole, and revolves in it. That fit should be a tight but slip fit, so it will only rotate, but should have no slop. The stud on the bridle side is the same, as is the hole it rides in. If either are worn, and both generally will be worn the same, then when you try to cock the hammer, the spring tension, will allow the tumbler to cant over the wear, due to the leverage of cocking the hammer. I've seen this happen in worn out locks, and there isn't much you can do, but to tighten the fit of the two bearing surfaces, generally the holes. When that tumbler rotates, it should have no noticeable play to it, with or without the spring acting on it, nor should it be able to cant in any direction. It should only rotate freely, but not move in any other direction. Those fits on either side determine that. Ideally, one would install the bridle to the lockplate, and line bore or ream those two holes together, but that is about impossible on this.