barrel install problem!!! (tight threads)

[oksooner]

OK.

I have my Imbel gl receiver and I have my Imbel barrel. My barrel will not hand tighten to the 11 o'clock position. In fact, it won't hand tighten at all. By hand I get about 2/3 of it to go and then it gets tough. I have tried on another receiver and it is about the same. I have another barrel that goes on my Imbel gl receiver just fine. This Imbel barrel won't fit any receiver that I have tried.

It seems that I have a barrel problem. It was a real bastard to get out of the receiver stub as well. As a matter of fact it goes back into the stub the same as my receiver!!!

I tried to muscle it on but when the gap between the barrel and receiver is about 3/16" I am afraid that I might start hurting something due to excessive force.

ANY IDEAS??????????

Thanks

[gunsmith_tony]

Threads on barrel could be damaged in some not-so obvious way.
Do you have a 1-16 die?

[Plumbob]

I had the same problem, I took a small knife edge file and recut the threads. I had a lot of little problems like that with my Imbel.

[Bzrkr]

Compare the threads on the other barrel that works to the one that does not especally in the area where it seems to get tight. The threads should have sharp crowns on the tops of them. If the barrel is droped or some thing gets in the threads when the barrel was installed it will deform them enough to not work. There are 3 ways to fix it. 1 Use a 1"-16 threading die to clean up the threads. 2. You can use a 60 degree file (3 sided- triangle shaped) or a 16 pitch thread file 3. You can try a wire brush in case its just grit or very small burrs binding up the threads.

[W.E.G.]

I hesitate to say "just force it" without seeing it.

But, I have seen a couple jobs where the barrel did not want to hand tighten to anywhere near full "hand-tight" contact. We forced those. They gave about 40# resistence during the forcing process until they bottomed out. They are shooting now.

If the thread pitch is correct, and there is no obvious defect in the threads, the "force it" method is probably OK. Be sure to put a film of good-quality grease on the threads if you do this.

[MM in NM]

I use "Clover" lapping compound but I'd bet any other common abrasive or valve lapping compound would work. Maybe something like kitchen scouring compound, Brasso or maybe even toothpaste. Use common sense, screw it in until it gets tight then screw it out and screw it in, repeat as necessary.

[Radio]

If there's a defect in the threads, the use of lapping compound will transfer that defect to the part that's normal. Now both of your parts (barrel, receiver) will have a part of that defect. Neither will ever want to fit anything else, but each other, again.

Some builders have used the lapping compound method to install an Izzy barrel into a standard (non-Izzy) receiver. Now their threads aren't Izzy and they aren't Metric/Inch. They will go through hell when it comes time to rebarrel.

I'd seriously try all the other fixes first. My opinion.

--Radio

[PCSinc]

Some good advice above. Get a 1" x 16 tpi die and chase the threads or send it out to have done.

[MM in NM]

Originally posted by Radio
If there's a defect in the threads, the use of lapping compound will transfer that defect to the part that's normal. Now both of your parts (barrel, receiver) will have a part of that defect. Neither will ever want to fit anything else, but each other, again.

Some builders have used the lapping compound method to install an Izzy barrel into a standard (non-Izzy) receiver. Now their threads aren't Izzy and they aren't Metric/Inch. They will go through hell when it comes time to rebarrel.

I'd seriously try all the other fixes first. My opinion.

--Radio

I respectfully dissagree and think the above is alarmist. There should be no doubt that using a tap it chase the threads will remove more metal by cutting than lapping the two parts together. Perhaps the problem is that the threads on the barrel were mishapen from overtorquing when the barrel was first installed at the factory but it could also be the new threads in the receiver weren't either cut right to begin with (dull tap) or there's some blast crud left in there from finishing. The fact is that by using lapping compound you would be removing very, VERY little (if any) metal, probably only some park or contaminating crud, i.e. polishing the threads and really only mating one surface to the other.
If you're worried at all you could just oil the threads and repeatedly screw them together and apart and they would eventually mate themselves. If it's crud that's causing the problem that should eventually clean it out. My first couple of builds I did just that but found just a small dab of lapping compound speeds things up considerably.
All that is said without looking to see if there were some other problems like a dent in the threads, perhaps like if you dropped the barrel, that could more easily be cleaned up with a needle file.
Another problem could be that the ledge at the rear face of the barrel could be interfering with the corresponding ledge inside the receiver. I routingly clean that face and outer edge with a file and then blacken them with a black marker to see if they're rubbing anywhere when timing the barrel. There should be no interference there as the barrel shoulder should torque against the front of the receiver face and have no contact inside the receiver.

The fact is that Izzy barrels were originally manufactured with a slightly different thread so cutting/chasing a new thread to them is an entirely different matter than fitting an Imbel to an Imbel. Still,, IF there was ever a need to rebarrel. you would just go through the same lapping or cutting/chasing a new thread rather than "go through hell" again.

The basic concept is that threads are nothing more than an inclined plane, discovered thousands of years ago. Their purpose is that to "wedge/torque" the locking shoulder to the front of the receiver so as long as the male and female threads fit together
reasonably tight to transfer the torque without binding in themselves it shouldn't make any difference, certainly not if they were lapped together.
Whenever any of us build these things we are not a factory with bins of brand new interchangable parts. For the most part we're "fitting" used parts to other parts that may or may not be made to exact spec and certainly not by the same factory at the same time to make a serviceable safe shootin iron. To me fitting by lapping, or any other means (some guys get out a Dremel!), is the name of the game as long as it's done with some common sense without an alarmist "the sky is falling" devil may care attitude you should be OK.
We each have to make individual decisions, so to the original poster, you can feel free to check for other interference and try lapping, buy a tap for maybe a one time use or hire someone to chase the barrel and/or receiver threads (they'll probably just lap them together). It's up to you.

[billiboy]

see my post on msc die, good buy and the way to get the threads back to factory spec, overtightening at factory deforms threads, growing diameter, tapping will clean to correct size.

I would have concerns about lapping, which mates parts rather than fits them, i.e. valve seats, both parts that are being lapped will become unique to each other since both are of equal hardness, and will wear (lapping) to fit each other.

SCREWING UP A BARREL THREAD IS BAD ENOUGH, DO YOU REALLY WANT TO WEAR DONE THE THREADS IN THE RECEIVER ???

[Radio]

Use lapping compound as a LAST RESORT! Otherwise you will DESTROY YOUR BARREL AND RECEIVER! Use of lapping compound is HORRIBLE and will cause your rifle to EXPLODE!!

Now THAT's alarmist...

I guess this is going to sound patronizing, MM in NM, sorry about that in advance, but have you ever tried to screw in an Izzy barrel? Probably you have, but for you new kids out there, those threads are only slightly different in pitch from the "standard" Metric/Inch pitch, yet they're sure one tough hombre to try to screw in. More muscle power needed than I've got. The MSC die I bought for my Izzy projects is (unfortunately) tapered on both ends, so only the last few threads weren't "corrected" to "standard" pitch; yet those Izzy barrels were still a tough hombre to install... with only a couple aberrant threads involved.

Getting stuck with unique thread pitch in both Izzy barrel and Metric/Inch receiver from lapping the two together, THEN having to "repeat the mistake" as the only method subsequently available to re-barrel... yup, my friend, that's what I call "going through hell."

The use of lapping compound most certainly results in "mating one surface to the other." Using a tap/die, on the other hand, will only remove metal that is OUT OF SPECIFICATION to the "correct" thread pitch. This is called FIXING THE ORIGINAL PROBLEM. Otherwise it does a dandy job of cleaning out crap. "Chasing the threads" with a tap/die is a standard procedure in rebuilding engines, very expensive racing engines at that. If you're that timid about their use, for pete's sake put a sharp dental pick to good use or grab some brass brushes and elbow grease.

MM in NM's comments about the breech face contacting the inside of the receiver are entirely correct. Make sure this is not happening.

"Their [threads] purpose is that to 'wedge/torque' the locking shoulder to the front of the receiver..." I think he meant the barrel, not the locking shoulder.

Now that I've pontificated from my soapbox, lapping compound does have many handy uses. Fine-tuning the bolt carrier into the receiver rails after both have been freshly parked, for example, or polishing the inside of the recoil spring tube. In my view, however, correcting warped or damaged threads is NOT one of them.

I am an experienced builder. These are my opinions. Others may have a different viewpoint... and they're experienced builders, too. Lots of room in here for that. "We each have to make individual decisions." Absolutely true.

--Radio

[ratas calientes]

At one point I had two IMBEL kits, two IMBEL receivers and one Entreprise "file to fit" receiver. Neither barrel would "hand tighten" onto either IMBEL receiver, but both barrels would hand tighten onto the Entreprise. (It actually felt a little loose!) And I removed both receiver stubs from the IMBEL kits without using the Dremel - so there was no cutting into the threads.

I built one kit onto the Entreprise. When I eventually do the IMBEL to IMBEL, I will get the die and clean up the threads on the barrel. I also recommend an adjustable split die, so that the amount of cutting/cleaning of the threads can be varied.

Ratas

[oksooner]

Thanks for the help. A die is about the same price as a whole new barrel and for a one time use I really don't want to spend the money. Lapping as a last rtesort sounds like something I want to avoid. So I called Dan's and told him my problem. He said send it back and he would take care of me.

So for about 6 bucks shipping I should be fixed up.

Thanks for the replies.

[Radio]

Actually, as memory serves my 1-16" die from MSC ran somewhere in the upper $20s...??? Hardly the cost of a new barrel, unless you know of sources I don't...

But I certainly see your point when you're only dealing with a single barrel. Consider yourself lucky... the FAL addiction hasn't affected you that strongly...YET!!

--Radio

[omar]

Examine the beginning of the thread for cross-threading. 3/16 is a lot of space. My first build wouldn't hand tighten on a CAI receiver, so I cleaned the threads with a wire brush and a rough dish towel, continued to SLOWLY AND CAREFULLY tighten it in a barrel vise while using the receiver wrench. I screwed it on and off until it did tighten by hand, although I did not ever force it. Sometimes the threads are just.....a little rough. Didn't have the same problem with the FAC though. It went together bootyful.

[Falfegnügen]

Get the Die AND Handle from MSC. It's definately the way to go. Simple, effective, and you know it's right.

You'll be needing that die agian anyway when you biuld your other FALs.

[gunsmith_tony]

Originally posted by Falophile
Get the Die AND Handle from MSC. It's definately the way to go. Simple, effective, and you know it's right.

You'll be needing that die agian anyway when you biuld your other FALs.

Yeah...what he said.

[W.E.G.]

I'll dredge up an old thread here to share my most recent experience on this.

IMBEL barrel
IMBEL 2002 receiver

I wish I had bought the die. This pair was tighter than any I have encountered. It wouldn't go more than about two turns before it got so tight that I had to put a wrench on it. By the time I got the barrel halfway into the receiver, I was looking for my cheater bar. I wrenched it off and on a couple times by brute, vein-bulging-on-the-forehead force.

I put JB bore paste on the threads and wrenched it back and forth in and out for 30 minutes. I shoulda been a porn star! By then I was pumped. But that pair is still tight as... (somebody said something yesterday about being "hard as a whore's heart")... well this pair was still tight as (uh...ummm...ah...maybe I better not go there ).

I wish I had bought the die.

Gonna try to slick it up some more tomorrow after my lapping muscles are uncramped.

[Court in Fl]

I have cleaned up barrel threads with a small triangular file.
It takes a little time but always works.

Court in Fl.

[shootist87122]

Originally posted by ratas calientes
I built one kit onto the Entreprise. When I eventually do the IMBEL to IMBEL, I will get the die and clean up the threads on the barrel. I also recommend an adjustable split die, so that the amount of cutting/cleaning of the threads can be varied.

Ratas

Ratas,

Let me know when you get that die, I have a something we can, uh...use for beta testing.

[W.E.G.]

I removed the first accumulation of JB, and replaced it with a fresh coat. Another 10 minutes of wrenching and all was shmoooothe.

[Temp]

I've noticed that a lot of the Imbel barrels have the threads pulled a bit. They must have Popeye the Sailor Man working in the barreling pit down there. Those things are screwed on *TIGHT!*.

I bought a new, premium quality 1-16 die. It's nice and sharp. I run it over the threads just by holding it in my hand and screwing it on like a nut. It'll cut a thin string of steel off of the pulled threads and makes the barrel shank look brand new.