MGC Thompson mis-feeding

Having waited a long time for my steel bolt to arrive, it finally came in the post this morning together with the MG caps I ordered. I followed Cerwyn's loading guide (which was very good) and loaded the 20 rd Auto Ordnance converted stick magazine I purchased from John at PFGCUK with 5 rounds to try out.

When I selected full auto and squeezed the trigger, only two rounds fired consecutively and the rest mis-fed either tumbling as the bolt picked them up from the magazine or not seating home into the detonatingg chamber fully and therefore not striking the firing pin. Any one got any suggestions?

Neil

Hi Neil.
Welcome to the best forum on the internet!

Your MGC Tommy is a great modelgun - truly a favorite of my own and many others here. Now that you have a steel bolt in it too - it is a terrific combo!

I will share my experience in getting mine to fire quite well with a stick mag. I found, despite however seemingly minor, every gun and every mag is just a little different. 99% of the time, you can get everything sorted by adjusting your mag lips.

I would load the cartridges into the chamber slowly by controlling the release of the bolt with your hand and see how it goes. Then you may be able to determine where you need some tweaks. Then when it seems to load smoothly in that fashion, try dry firing it with empty carts. Once you get that sorted, you should be in business!

Mine took a bit of tweaking to get firing smoothly, but it is worth it. I used a set of precision duck-bill type pliers to adjust the mag. They have smooth jaws so as not to mark the magazine with scratches. 15 or20 rounds at a time with no hiccups now. It will bring a smile to your face for certain!

Good luck.

ljerr2 wrote:

Hi Neil.
Welcome to the best forum on the internet!

Your MGC  Tommy is a great modelgun - truly a favorite of my own and many others here.  Now that you have a steel bolt in it too - it is a terrific combo!  

I will share my experience in getting mine to fire quite well with a stick mag.  I found, despite however seemingly minor, every gun and every mag is just a little different.  99% of the time, you can get everything sorted by adjusting your mag lips.

I would load the cartridges into the chamber slowly by controlling the release of the bolt with your hand and see  how it goes.  Then you may be able to determine where you need some tweaks.  Then when it seems to load smoothly in that fashion, try dry firing it with empty carts.  Once you get that sorted, you should be in business!

Mine took a bit of tweaking to get firing smoothly, but it is worth it.  I used a set of precision duck-bill type pliers to adjust the mag.  They have smooth jaws so as not to mark the magazine with scratches.  15 or20 rounds at a time with no hiccups now.  It will bring a smile to your face for certain!

Good luck.

Hi Jerr,

I guessed it was something to do with the magazine regarding the pick up, but why won't the bolt go home fully over the round on some that do pick up correctly?

Neil

Without observing it first hand, I can give you some thoughts.
Of course, I am assuming your MGC is in otherwise good condition - main spring not weak, feed ramp of the model in good shape, chamber, etc.

I've never fitted a real mag to my MGC, but if it came as a modified piece from John you should be good to go.

It may be possible that the bolt is getting slowed when it comes forward as a result of the potential minor misalignment of the feed lips. If slowed sufficiently, it may not have enough force for the extractor spring to be overcome and cause it to seat over the cartridge rim. You may also want to visually inspect the bolt face to make sure the cartridges seat fully and squarely inside. I've actually seen some minor variations in cartridge rim thicknesses if interchanging the Hudson cart with the MGC cart. If that is your case, some minor fitting may be required.

Make sure everything cycles smoothly - that is the key, I think.

Keep working at it! You've got the components for a great firing model. Lots of knowledgeable guys here, too to help you get there.

Keep us posted!

ljerr2 wrote:

Without observing it first hand, I can give you some thoughts.
Of course, I am assuming your MGC is in otherwise good condition - main spring not weak, feed ramp of the model in good shape, chamber, etc.

I've never fitted a real mag to my MGC, but if it came as a modified piece from John you should be good to go.

It may be possible that the bolt is getting slowed when it comes forward as a result of the potential minor misalignment of the feed lips.  If slowed sufficiently, it may not have enough force for the extractor spring to be overcome and cause it to seat over the cartridge rim.  You may also want to visually inspect the bolt face to make sure the cartridges seat fully and squarely inside.  I've actually seen some minor variations in cartridge rim thicknesses if interchanging the Hudson cart with the MGC cart.  If that is your case, some minor fitting may be required.

Make sure everything cycles smoothly - that is the key, I think.

Keep working at it!  You've got the components for a great firing model.  Lots of knowledgeable guys here, too to help you get there.

Keep us posted!

Thanks to your tips regarding the mag lips, I have now as we say on this side of the pond "fettled it" and the rounds pick up smoothly from the mag. The spring is in good nick and I have had to make some adjustments to the extractor claw to facilitated clean extraction so I think I am 90 percent there.

However, when I cycle the bolt slowly manually as you suggested, the bolt seems to pick up somewhere and will not go fully home. If I move the bolt back and forwards about a quarter of an inch, eventually the bolt closes over the round and the extractor locates in the gore in the casing. I have stripped the weapon to see if there is any obvious cause, but I can't find it yet. I will keep trying and then get back to you. Thanks for the help so far.

Neil

P.S. the Tommy is an early one that was made for US export with a non functioning bolt and a vented barrel. When it fires it looks very realistic with the smoke curling out of the muzzle.

Ah yes, the open-barrel version gives a great effect!

Does the bolt cycle smoothly without any carts? If it does, I think you can rule out any interference issues before the chamber area or that don't involve the cartridge.

Also, cycling slowly gives a good baseline. Next I would recommend operating the bolt very quickly. You may not have any issues once you let the bolt work at "normal" speed.

We all would love to see your Tommy in action!

ljerr2 wrote:

Ah yes, the open-barrel version gives a great effect!

Does the bolt cycle smoothly without any carts?  If it does, I think you can rule out any interference issues before the chamber area or that don't involve the cartridge.

Also, cycling slowly gives a good baseline.  Next I would recommend operating the bolt very quickly.  You may not have any issues once you let the bolt work at "normal" speed.

We all would love to see your Tommy in action!  

The bolt cycles smoothly without any cartridges, but with the action stripped, I have now observed that the extractor claw spring is quite strong and that the claw it self does not go smoothly over the groove in the cartridge and pushes the cartridge off centre. I am going to do a little more work on the extractor to smooth this part of the action out. I also note that the cartridge is a loose fit in the detonator chamber and the round can move off centre. Is this normal?

Regards,

Neil

I believe the use of the more modern plug-fire cartridges allows a looser fit or more tolerance in fit between the cartridge and the detonator/chamber. This should be ok. You might keep an eye on the nose of your carts to see if they are getting deformed. If not, you are just fine. Are you using an old cast chamber with a modified pin or the newer stamped chamber/det combo?

The older carts needed a very tight fit between cart and chamber/det to ensure operation as they had no rubber o-ring seal, so the carts had to be dead-on basically.

Models involve a very sometimes delicate balance between spring rates, tolerances, etc.

We'll be waiting for your vid!

ljerr2 wrote:

I believe the use of the more modern plug-fire cartridges allows a looser fit or more tolerance in fit between the cartridge and the detonator/chamber.  This should be ok.  You might keep an eye on the nose of your carts to see if they are getting deformed.  If not, you are just fine.  Are you using an old cast chamber with a modified pin or the newer stamped chamber/det combo?

The older carts needed a very tight fit between cart and chamber/det to ensure operation as they had no rubber o-ring seal, so the carts had to be dead-on basically.

Models involve a very sometimes delicate balance between spring rates, tolerances, etc.

We'll be waiting for your vid!

Hi I have done a little more work on the extractor claw and I am very nearly there with getting a burst of five rounds off. I managed a burst of three before a stoppage occurred and when I had cleared this the last two went through. So a little more work with a couple of warding files and I will have a smooth action.

The detonator/chamber was supplied new by John as well as the bolt. I obviously made the mistake of expecting the replica to be made to the tolerances of the original so a bit of old fashioned gunsmithing is required to get it right.

Enough for today though, my good lady is getting tired of the 'bangs' and smoke I will keep you posted on my progress,

Kind regards,

Neil

Hi Neil
One thing to check:
Strip the gun and turn top reciver upside down with just the bolt in place,
Slide the bolt up and down a check if the extractor catches on the reciver, just before the magwell area.

This can cause problems on the older castings on the open barrelled models, this is discussed somewhere on this forum but cannot find thoses postings right now.
ljerr2 is 100% good in his info
If it does catch at all let us know here and I will pst on how to cure this issue
ATB
John

Hi Guys,

I now have a fully functioning MGC Tommy Thanks for all your helpful tips, I narrowed the problems down to a. Mag lips not aligned correctly. b. Extractor needing a little work with warding files to make it function correctly with the PFC modern rounds. c. Adjustment of the detonator chamber in the breech to ensure that the rounds seated and detonated correctly.

After a lot of dry firming and tweaking, I loaded up ten rounds and let rip Deep joy

Thanks ljerr2 for all your help in sorting out the snags, when I can get my son to film my tommy in action and when I can rig up something to catch the rounds (I have lost one already indoors) cos at £3.50 a pop I don't want to loose any more, I will post a vid on the forum.

I must admit letting fly with the MGC Tommy is almost as good as the real thing

Kind regards,

Neil

Nice job Neil !
With a little effort put in they really are one of the nicer models!
Some times they can frustrate, but with patience and effort the rewards are truly worthwhile.
Looking forward to the video!