Chambering Problem (Long)

[BigBoy1]

I’m having a chambering problem and would like to get ideas/thoughts from the experts. What I have is a sub-caliber conversion kit for the FAL rifle. It is a military training kit where .22LR is used in place of 7.62x51mm ammo. The .22 barrel is inserted into the 7.62mm barrel and the large caliber bolt is replaced with the .22LR bolt. The full caliber size magazines have an insert magazine for the .22LR rounds.

I have a functioning sub-caliber conversion kit and I is was sent a non-functioning kit to me to see if I could get it to work. It’s problems were failure to feed and failure to fire. Using my functioning sub-caliber conversion kit, I tried the magazines from the non-function kit (NFK). After adjusting the lips on the magazines from the NFK, I was able to make both of the magazines from the NFK feed correctly by using my barrel and bolt. When the magazines were tried with the barrel and bolt from the NFK, the feed problem was fixed but the failure to fire problem still existed.

By swapping different components between mine and the NFK, I was able to determine that the barrel from the NFK was the problem. From what I can observe, someone opened up the face of the chamber and removed the sharp edge around the chamber to solve the feeding problem instead of adjusting the lips of the magazines. This can be seen in the picture below. (My unaltered barrel in on the left and the barrel from the NFK is on the right.)

http://i163.photobucket.com/albums/t308/i422twains/PICT0228.jpg


The problem with the failure to fire is the removal of the sharp edge of the chamber. When the firing pin strikes the rim of the case, there is no sharp edge of the chamber behind it to cause the crushing action on the case rim and the firing pin pushes the case into the chamber. These are causing the failure to fire. This can be seen below. (As before, my unaltered barrel in on the left and the barrel from the NFK is on the right.)

http://i163.photobucket.com/albums/t308/i422twains/PICT0232.jpg

As to solutions, I proposing to cut away the bevel portion of the chamber and make a small insert, like a very thick washer, to re-establish the sharp edge of the chamber. I’m thinking the insert should be just deep enough to remove the bevel put on the chamber edge.

Now my questions:

- Is this a reasonable approach/method the fix the problem?
- Any suggestion or modifications to this idea?
- What should be my concerns about re-chambering after I’m done?
- Are .22LR chambering reamers available?
- How would I secure the “washer” in place?
-Would silver solder/brazing remove the heat treatment from the barrel and chamber area?
- Any other factors/concerns that I should be aware of?

Appreciate any help or assistance. Thanks.

[RetiredFAE]

Your approach should work, but it's not one I've tried with this conversion kit.

The silver solder adhesion method should not change the heat treat of the barrel, brazing might get it hot enough to be a problem. Depends on the conversion kits steel and heat treatment.
One I worked on was aluminum with a steel liner, that one would have been a problem to braze or solder. I epoxied the liner segment into that one.

If the barrel insert is thick enough for its entire length, you can drill it out and fit in a piece of a .22LR Barrel Liner (Available from Redman, or Brownells or MidwayUSA) and silver solder or epoxy it back in.

If not the full length liner fix, then a piece of the liner an inch or so long and drill the insert for a portion of the length of the 7.62x51 cartridge case would probably be easier than a thin washer. But it could be fun getting the end of the hole you drill flat so that the squared off end of the piece of liner will fit tightly up against it.
You can both buy and rent .22LR chamber reamers, Google it to find the rentals,
Brownells and Midway both carry them.

If you are really good with a Tig, it might be possible to build up the end of the chamber where it has been ground, and then re-cut it with the reamer.

[Bguns]

Reamers available from Brownells.com not cheapest, but great service...

Make the washer/insert a tight press fit. If it works loose (doubt it, locktight it)
Make ID of washer slightly under chamber diameter so reamer cleans it up to match chamber.

If all else fails, it can be relined with a rifled liner and new chamber cut.
Brownells sell the equip and liners for that too...


This is not a target grade adapter, so above repair will work fine...

At rimfire pressures, insert will work fine...

Most .22 barrels are very soft, and heattreat is not an issue.... a Medium temp solder should work as well...

Edit: faster fingers above... :)

[JCHannum]

While the washer might work OK, another approach is to sleeve the chamber with a short length of tubing and rechambering it. The sleeve need not be as long as a cartridge casing so the rifling is not affected. A close fitting sleeve can be Loc-Tited or JB Welded in place.

[38_Cal]

If you sleeve the chamber, make sure that it is shorter than the .22 long rifle cartridge case. You want to keep the expanding gas in front of the joint, otherwise it can eventually erode the joint and cause the chamber sleeve to act as a piston against the bolt. Not good for the rifle or your customer's faith in your abilities! I would use a silver-tin solder, with both parts well tinned before joining. Rather than drill out the chamber, I would set it up in the lathe and use a boring bar, then make a matching insert out of a piece of .22 rifle barrel. You've got a much better chance of getting both the original bore and the liner concentric that way. Cut the chamber and match the contours to your existing conversion kit. A chamber reamer from Brownells will run you about $40 plus shipping, about the same from Midway.

Keep us in the loop on this one!

David

[Bguns]

A good Tig Welder might be able to run a bead around chamber edge with a mild steel rod, and it would just need a chamber reamer cleanup..

Firing pin area needs most build up...

Not many people reloading slightly bulged .22 rimfires ...

Just another idea...

[BigBoy1]

The TIG idea sounds like a good, easy fix. However, my welding skills are ZIP! Is there anyone of you out there that would consider attempting to do this? If anyone would like to do this, please send me a PM and we can talk off-line.

Thanks.

[motorcyclemac]

Make a sleeve to go in the chamber that is 2/3 the length of the 22 case. I would make it from 4140. I might look at putting a shoulder on the sleeve to allow some bearing strength from firing pin strike. The shoulder would also permit you to replace the face where they got frisky with the dremel tool. Gosh that is a helluva chamfer!!

Solder the sleeve in place with Hi Force 44 or Eutectic 157 solder. Flux it good with the proper flux recommended by the solder maker and have at it. By the way...don't forget to put some patch material in the bore just at the lead of the rifling to prevent soldering flux and solder from running down the bore.

Clean up your sleeve with a chamber reamer and don't forget to recut the extractor groove

Double check your firing pin protrusion and make sure it is no more than .040. You wouldn't want to go to all the effort to fix it and have the pin wreck your work if dry fired.

[argon99]

This is my first post here an it's probably to late to help bigboy1 but the picture doesn't look right to me. In the one that does not fire the round is sitting proud of the chamber. It looks to me like it is not chambering all the way. I would suggest just running a chamber reamer in it first before doing any work to try and correct the dremel wizards work.

If that is not the problem I would just braze the side of the chamber where it has been dremeled away. After the metal has been replaced you just decide if you need a chamber reamer or just a drill bit to open the chamber. Remember the chamber only had a little bit of metal removed from the breach. The whole chamber wasn't ground away. So a little braze should replace what was removed. But I would want to know why the round is sitting proud. That's the problem that needs to be fixed first.

Dremels are the best thing that ever happened to gunsmiths.

[BigBoy1]

This is my first post here an it's probably to late to help bigboy1 but the picture doesn't look right to me. In the one that does not fire the round is sitting proud of the chamber. It looks to me like it is not chambering all the way. I would suggest just running a chamber reamer in it first before doing any work to try and correct the dremel wizards work.

If that is not the problem I would just braze the side of the chamber where it has been dremeled away. After the metal has been replaced you just decide if you need a chamber reamer or just a drill bit to open the chamber. Remember the chamber only had a little bit of metal removed from the breach. The whole chamber wasn't ground away. So a little braze should replace what was removed. But I would want to know why the round is sitting proud. That's the problem that needs to be fixed first.

Dremels are the best thing that ever happened to gunsmiths.

Argon,

Since my welding skills are non-existant, I has sent the barrel to gunsmith friend who is an excellent TIG welder. He is going to replace the metal that was removed and I will do the machining to true up the chamber and lip. As a fall back position, if the TIG welding doesn't work, I will then make a sleeve for the chamber to regain the sharp lip.

To change your statement: Dremels are the WORST thing that ever happened to AMATUER gunsmiths.

[argon99]

Argon,

Since my welding skills are non-existant, I has sent the barrel to gunsmith friend who is an excellent TIG welder. He is going to replace the metal that was removed and I will do the machining to true up the chamber and lip. As a fall back position, if the TIG welding doesn't work, I will then make a sleeve for the chamber to regain the sharp lip.

To change your statement: Dremels are the WORST thing that ever happened to AMATUER gunsmiths.

Did you find out why the round was sitting proud? You already sent the piece to a welder but you might have not needed to.

And you should consider getting an oxy-act torch setup. They are cheap. Then learn to braze. It's different then welding. With welding you melt the parent metal and add filler rod. With brazing you get the work piece up to temp and just melt on the braze. It's actually very strong. I used braze to fix an op rod on a garand. The part that fits in the receiver was damaged ( god only knows how. It was like that when I bought the rifle). I brazed it up and then used a dremel to reshape the braze to get the proper shape back. It's been working for years now. And it was a lot cheaper then a new op rod.