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Lewis Gun Problems


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I have a 303 Lewis Gun that is just driving me crazy. Got it back in October and attempted to shoot it. Set the spring weight from 8-15LB using a scale and it made no changes. Gun would fire 1-2 rounds and short stroke, on high speed footage the pan doesn't spin clockwise all the way so then it backfeeds and leaves a round partially out of the pan. Total pain in the ass to get unstuck. So I put the gun up for awhile while I inspected parts and got different ammo. In the meantime I noticed the gun was on the smaller gas setting and figured this was the problem.

Today I went to the range with it on the large gas setting, set the main spring to 14LB and progressively worked my way down to about 9LB. High speed camera again the carrier reciprocates back within about 1/2" of making a full stroke then the carrier goes forward where it gets stuck about 2" before going to battery on an empty.

Even putting 1 round in the feed tray and pulling the trigger rapidly yields the same results

Things I have tried

*Different gas settings
*Different ammo
*Checked the feed mech it all appears in order the drum feeds at it should and the pawls are grabbing correctly
*Took the gun apart and the radiator out, the gas block is on the barrel very tight so I do not feel there is any leakage there.
*Action is smooth as can be, do not observe any dragging or anything parasitic that could cause an energy loss

Things I have not tried
*Different pan
*Different carrier/OP rod

I have noticed the *Nozzle or Gas Chamber Gland* that screws on the end of the barrel its threaded almost like there is supposed to be a booster on it for more backpressure? Am I missing something here, because at this point either I am or there is some magic rain dance I am not doing right to get this thing working lol.

I have video of it shooting if it will help anyone help me out with this bastard child.

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Lewis guns require a reliable balance between the recoil spring strength and the gas available to cycle the action. Once the gas system is compromised it is not possible to set the spring rate high enough to reliably cycle the action and that balance is lost. A common problem with well used Lewis guns and parts is worn joints in the gas system including the gas tube to gas block joint as well as worn fit of piston in gas tube which can significantly reduce gas to the piston and create short stroking. The small threads on the gas block that screw into the barrel port are almost always overtightened or compromised with leakage resulting. The gas seal at this joint must be tight. The joint of the gas tube and the gasblock must be tight and are almost always compromised from over tightening. The two position gasplug must also be tight or it becomes another leak.

These are not easy joints to repair. I've seen a number of Lewis gas systems that were soldered or braed together to seal the joints.

The fact that the gas block position is "timed" so the gastube port faces back along the axis of the barrel and the gas tube must be timed so the rear raised boss fits properly into the recess means that looseness in these joint can't be eliminated easily.

Thin copper washers that can crush between the bottom of the barrel gas port ant the lip of the threaded shank of the gas block can be made and used to seal that joint. This takes careful fitting so that the threads of the port and the block are not stressed.

A shim steel or brass washer can be made to fit the gas tube to gas block joint to reduce leakage there. Making it sufficiently thick to fit and seal takes considerable care but will help in reducing gas loss. It is possible to reduce the length of the threaded portion of the tube that has been over tightened so that the joint closes and seals just as it tightens up at its 'timed' position but the length must not be reduced to where the tube no longer reaches its rear alignment position. There is not a lot of spare length.

The fit of the regulator plug can also be adjust with fitting a thing washer mae form shim material, either brass or steel. Again, getting the fit right is important.

The piston head and the gas tube also can wear sufficiently to allow leakage of gas past the piston further reducing the gas supply. Years ago, there were new made pistons that were oversized on the OD so that they could be turned and fitted to a specific tube. Also, there was a single piston ring system made by another fellow that could be fitted to a standard Lewis piston. None of thee parts are available any more to repair the fit of the piston in the tube but they can be reproduced if needed.

Well worn bore and chamber can reduce available gas as well so use a good barrel.

I am assuming that the bolt carrier and the bolt move freely in the receiver and the bolt functions properly without obstruction, etc.

Also, that the actuating arm and indexing of the pan are functioning properly.

If you have a small quantity of dummy .303 cartridges, cycle them through the pan to insure that feed is OK. You can remove the firing pin from the oprod and cycle live cartridges as well. I assume you have tested the feed cycle.

Hope this helps.


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Great info above!

 

First off my experience is only in the American Savage 1918 "Aircraft" 30.06 Lewis

 

Is the cartridge feed spring putting enough pressure on the rear of the cartridge?

It is a delicate balance to hold it at the right angle as the bolt comes forward to push it into battery.

Ejector toggles freely.

I have seen 2 types of blank fire adapters, brush style which can have the "recoil check assembly" threaded back onto it, the second is just threaded on and gives the right amount of back pressure to fire blanks. Handy if the load of the blank matches what you are firing.

 

Using good ammo is a cure to alot of issues, .303 being harder than 30.06 to fine. Unless being a reloader of course.

 

I understand yours seems to be possible pressure issue, (American 30.06 has four ports) But I chased a main spring/pressure for awhile and found a feed spring issue.

 

There is a answer somewhere. Good Luck

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I have a US .30 Lewis M1917 ground gun. I have one pan that does not spin very smoothly. It caused exactly the problem described above.

With the pan mounted on a loading handle, does the pan spin smoothly all the way around as you move it? Or does it stick in spots?

Another possible pan issue is mis-alignment. If the pan has some spots where the outside edge is slightly bent, it can cause sticking during firing. This can be hard to detect visually. I made a gauge from coat-hanger wire that fits on my loading handle that allows me to detect if a pan edge has gotten bent.

 

Dummy cartridges are extremely useful in checking for feeding and magazine issues. I highly recommend that you make or find a dozen or so.

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