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Ljungman adjustable gas system, another option

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KneverKnew
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Ljungman adjustable gas system, another option

#1 Post by KneverKnew » Mon Jul 17, 2017 1:51 pm

Best I can figure, there are only a couple options going around to create an adjustable gas system for the Ljungman. None seem to be conducive to not messing up our original rifle parts. Here's what I've come up with so far.
1. Change out original gas bock and drill and tap for adjustable set screw. I've ordered an extra gas block from Springfield Sporters with the intent of doing just that. But, apparently removing the original block would screw up my barrel since they are tightly pressed onto the barrel. So unless someone has pointers on how to do this without damaging the rifle, it's not an option.
2. Drill and tap the existing gas block to a more common screw size for gas adjustment. This would obviously cause permanent harm to the original gas block, so not an option either.
3. Replace existing clean out screw (4mm x .5) with longer beveled set screw to adjust gas fow. This is most desirable option, but locating correct thread screws seems daunting. Anyone have a source for these, please speak up.

Now, one other option just came to mind.

4. Replacing the gas tube sleeve that protrudes from the receiver face and directs the gas tube into the bolt carrier gas cup, drilling out to larger inside diameter and threading the replacement sleeve for a threaded vented gas plug with a smaller diameter orifice to restrict gas flow. This would be the same idea as the "shooters kit" that was created to solve the same over gassing problems found in the German G43 8mm semi-auto (Hitlers Garand.)
This is what the threaded gas plug looks like in the end of the G43 Gas piston.
Image

This is the gas sleeve that would be replaced and threaded to accept the new gas plug. Different sized orifices could be tried until one is found that cycles the Ljungman gently but reliably with the specific ammo you select. A set of different sized orifices could be kept on hand for use with a variety of ammo.
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Re: Ljungman adjustable gas system, another option

#2 Post by Rapidrob » Mon Jul 17, 2017 7:53 pm

Along with the lost info on SRF, I did an article on how to make an adjustable gas "valve" using a stainless steel set screw.
I'll try to find a copy of the article I did years ago.
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Re: Ljungman adjustable gas system, another option

#3 Post by KneverKnew » Mon Jul 17, 2017 8:08 pm

I appreciate the offer to repost the article. I don't think there's any confusion on how to perform the installation of a set screw in the gas block. What I'm trying to figure out how to do is to end up with a adjustable gas system without modifying any original parts Since removing the gas block and installing a replacement to drill and tap will most likely damaged the barrel and drilling and tapping the original gas block is out of the question I'm trying to locate one of the elusive Swedish threaded set screws that will fit in the original gas block And allow us to adjust the gas system without any further modification

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Re: Ljungman adjustable gas system, another option

#4 Post by Rapidrob » Tue Jul 18, 2017 8:41 am

There was no drilling or tapping. You removed one screw and replaced it with a metric set screw. rifle is not harmed.
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Re: Ljungman adjustable gas system, another option

#5 Post by KneverKnew » Tue Jul 18, 2017 9:42 am

I believe I did read that post. That is exactly what I am trying to accomplish. Finding the correct screw and lock nut is the problem. Mind sharing what screw you used and its total length? Did you use a lock nut?

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Re: Ljungman adjustable gas system, another option

#6 Post by Rapidrob » Tue Jul 18, 2017 11:03 pm

It is a metric screw and there is a lock nut. It's been so many years since I did it I will have to measure the parts and get back to you.
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Re: Ljungman adjustable gas system, another option

#7 Post by KneverKnew » Tue Jul 18, 2017 11:39 pm

Rapidrob wrote:
Tue Jul 18, 2017 11:03 pm
It is a metric screw and there is a lock nut. It's been so many years since I did it I will have to measure the parts and get back to you.
That would be a big help, thanks! I'm getting cross eyed searching the net for those oddball screws. I shot mine today for the first time since I sold it over 25 years ago. I posted pictures in another post here. I was very pleased. Now that I've seen how well it can shoot with the Swedish Surplus stuff, I can only imagine it will do even better with my hand loads, but I really don't want to cause excessive wear to it or the brass. Fine tuning the gas system seems to be the way to go.
Please share your findings as soon as possible. Thanks again.

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Re: Ljungman adjustable gas system, another option

#8 Post by Ernest T » Sat Oct 14, 2017 11:05 pm

I know this is an older post, but I thought I'd post this link for anyone looking for the correct screw to make an adjustable gas system for the Ljungman. The correct screw size is M4x0.5 and you can find them here: http://www.probolt-usa.com/titanium-dom ... 2mm-4.html

You can get this screw in various colors including black to match the rifle. When I bought several of these screws, they came with washers. What I did was cut the screw off at a level that just prevents the bolt from cycling. Then add washers to find the best cycle for your particular ammo. This eliminates the need for the harder to find nut. If you change loads, you can add or subtract washers to find a good cycle for the rifle.

For those of you who would also like the nut, it can be found here, but they only come in packs of 25: https://www.mcmaster.com/#91415a020/=10jadt7

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Re: Ljungman adjustable gas system, another option

#9 Post by KneverKnew » Sat Oct 14, 2017 11:36 pm

I do appreciate you posting where you were able to locate the screws. I did find them myself a couple months back, and my wife, who is an engineer and deals with parts suppliers every day, was able to find me a bag of the nuts as well. I actually got one bag of the titanium screws and one of the black. Both screwed down into the hole just fine, but the issue I came across was that the threads down in the hole only wend down to the top of the gas tube. So even at its deepest position and using lightly loaded Federal 170 grain ammo it was still cycling quite harshly. I was able to "force" the threads down just bit more so the gas tube is obscured by about 1/3 which did help but still not doing the intended job. So I hunted around and found a tap set that will allow me to chase the threads on down and continue cutting until I can completely close off the gas tube. Unfortunately, a couple of hurricanes got in the way of that project, so it is on the back burner while we do some renovations to the house. The good news is, I am completely confident it will work. I will find the proper setting for the Swedish ammo first, and then try and work up a duplicate load that performs just as well, probably better. Thanks again for sharing your findings.

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Re: Ljungman adjustable gas system, another option

#10 Post by Rapidrob » Sun Oct 15, 2017 7:36 pm

OK, you should have been able to almost block off all gas pressure. I would now look at the recoil springs. If weakened ,you will get harsh recoil and 50 foot ejection.
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Re: Ljungman adjustable gas system, another option

#11 Post by KneverKnew » Sun Oct 15, 2017 8:41 pm

I think the gas tube is interfering with the screws ability to go far enough down to close off the gas flow. If I simply cut a few more threads into the opening in the top of the gas tube the screw should be able to continue on down for complete gas cut off.

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