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 MGC .45 Carts... Firing Pin "Swells" after time

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Cerwyn
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PostSubject: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 8:57 am

Post by tiksom

Fine Folks,

I have noticed a problem with all my MGC .45 cartridges.

In this design the detonator pin (in the barrel) hits the firing pin (in the cartridge) to push it into the cap. This is a forceful hit, so the firing pin develops an indentation on the front (up) right where it is struck by the detonator pin. Of course the amount of metal material in the firing pin stays the same, so as it gets beaten the metal expands to the sides and the pin "swells".

It has come to the point when I am no longer able to fit the firing pin inside the cartridge.

I'd guess this is a part of "that's just the way it is!" experience, but would you have any comments if it's possible to restore the pins? All other elements of the cartridge (including o-rings) are in excellent shape.
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Cerwyn
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 8:57 am

Hello Tiksom,

I've noticed that all of my MGC cartridge pistons, be they .45, or 9mm are marked by the gun's detonator pin, almost like a Centre Punch tool has been used.
I've not experienced any swelling, certainly not to the point where the piston won't enter the cartridge yet, but I don't get to fire mine as often as I would like!
My thoughts are that as the cartridges are soft brass, they will get beaten up by the gun and could be regarded as normal wear and tear I guess.

It does surprise me that your pistons are swelling so much they no longer fit inside though. Either you must fire them a LOT, or perhaps there could possibly a problem with your det pin? Is the chamber seated correctly in the gun? Could it be set too close to the round so it hits the piston harder than it should?

Your guns must fire really well if you wear out your rounds so it can't be a big problem with the gun itself!

Luckily Francky sells new pistons in packs of 10 for a nice low price. Might be worth you buying several new ones?

Cerwyn
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 8:58 am

Post by Mark

Hi tiksom,

The detonators are made out of very hard stainless steel so, unless you have a defective detonator, I would look to some other problem like residue build up on the detonator tip. The residue from fired caps builds up fast during firing sessions. If the gun is not cleaned between firings the build up will prevent the cartridges from entering the barrel.

Cerwyn is correct that modelgun cartridges are made out of soft brass (for tooling life etc.) so they tend to become distorted in many areas. Now, if the manufacturers had made the cartridges out of "cartridge"brass, our modelgun cartridges would last far longer. Now, as Cerwyn relates the pistons can and will grow due to the detonators "peening" effect which will displace the pistons brass.
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MGC MP40 Marushin MP40 Nakata MP40 TRC MP40

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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 8:58 am

I seem to remember reading posts awhile back about "How long do Cartridges Last?"
Lifespan of about 500 firings was about the best if I recall?

I guess it depends on the gun too, my Marushin MP40 has a plastic bolt and the steel det pin is held in plastic chamber. That probably cushions the impact to some degree so my rounds still look like new.

My MGC .45's are used in my all metal Thompsons and they show signs of wear on the piston as tiksom relates, but also on the rim where the extractor claw grabs them, and the hole in the bullets' nose caused by having the det pin thrust into it.

My all steel Sten gives the 9mm MGC rounds a real beating, but at least the gun ain't wearing out. Both det pin and bolt aren't even marked.

The Marushin UZI I own stovepipe jams often so rounds get crushed between the open bolt and receiver,

Some rounds like the p220 9mm MGC get deformed by repeated use, the case and bullet' nose are forced together about the threads, you can see them mushrooming out after awhile.

The sooner those disposable rounds appear the better!

Cerwyn
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 8:59 am

Post by erikthecat

this Hudson AK, assuming it worked, would manage to totally demolish the base of a dummy round after about 40 strikes.
i'm sure i have a single round that has been cycled / dry fired more than a few times. if this was reliable it would be an expensive hobby?

i recall that the instructions had a section on how to reshape the bases to that they load and extract.
i'll see if i can find an image and the instruction.

one has to smile?

i'm NOT bitter honest! Smile

regards,

GaRy:)
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:00 am

Post by Mark

Yes Cerwyn,

Certain modelguns do terrible things to their cartridges like the Marushin Uzi for an example. Some do in fact, "baby" their cartridges due to the modelguns construction materials (ABS/HW) and their design.

Some cartridges look great after tons of use other than the ejector marks on their rims etc. while others are battle scared after one shot! My CMC Sten (all steel) is hell on the KSC M93R/MGC Beretta cartridges that I use in it. But they run great so, its worth it! My MGC MP40 uses the Marushin Uzi/MP40 cartridges that are plentiful and inexpensive so if it eats them oh well.
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MGC MP40 Marushin MP40 Nakata MP40 TRC MP40

Modelgun manufacturers, past and present:CMC,CAW,Hudson,HWS,LS,MGC(R.I.P. 1960's~2007) Marushin,Marui,Kokusai,Shoei,Tanaka and Western Arms
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:01 am

Post by rizzo


I've had exactly the same experience with some of my .45 mgc carts. Fixed by lathing out the cartridge a bit. No idea why it happened
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:01 am

Post by Mark

erikthecat,

Unfortunately, the older versions of the Hudson AK does have a non-intelligent firing pin design that mangles the cartridge rim badly. The SE version of the AK doesn't hit just one small section of the cartridge rim it instead hits the entire rim/base of the cartridge. If anyone ever wants to shoot any of the Hudson AK's they need to buy the SE version. The average modelgun will use up a few cartridges by either firing them or just cycling the cartridges through their actions. Of course, the modelgun hobby relies on cartridge availability either from firing or just having them around...
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Wanted to buy: MGC Sten MK3....trades?(still)

MGC MP40 Marushin MP40 Nakata MP40 TRC MP40

Modelgun manufacturers, past and present:CMC,CAW,Hudson,HWS,LS,MGC(R.I.P. 1960's~2007) Marushin,Marui,Kokusai,Shoei,Tanaka and Western Arms
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:02 am

Post by tiksom

cerwyn wrote:

I've noticed that all of my MGC cartridge pistons, be they .45, or 9mm are marked by the gun's detonator pin, almost like a Centre Punch tool has been used.
I've not experienced any swelling, certainly not to the point where the piston won't enter the cartridge yet, but I don't get to fire mine as often as I would like!
I've fired ~400 shots through all the cartridges combined, that would be <50 shots per single one.
The pistons (the firing pins inside cartridge) did expand so much that they don't fit the cartridge over the last few shots. I agree with you that it looks as if the detonator hit them too hard - the "hole" is punched at least a millimeter deep, the rim has now larger diameter than the o-ring. I have inspected the gun's firing pin and the whole chamber assembly, but couldn't find anything that would be visibly wrong. Carts seem to sit at the same depth, parts all cleaned regularly...
Next steps:
- slightly file a piston to make it fit inside cartridge,
- do some testing with modified piston,
- also try firing with a brand new piston,
- get new detonators from Francky and/or investigate the cause for deformation, depending on results.
Thanks to everybody for sharing your experiences!
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:03 am

Post by 8ace

Hi tiksom,

Any chances of taking some pictures of the deformed pistons, the det pin and the brass insert inside the cartridge which the firing pin strikes

I love the MGC cartridge design which seems to give less problems than the Marushin and Hudson designs (Haven't got around to putting 50 shots each with them though)
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:05 am

Post by tiksom

8ace wrote:

Any chances of taking some pictures of the deformed pistons, the det pin and the brass insert inside the cartridge which the firing pin strikes
Here's three photos showing how the cartridge firing pin (naming as in http://www.modelguns.co.uk/images/pcart1.jpg)
View showing the indentation in the middle. Some of the marks are off-center, as once the detonator (in the barrel) has shifted slightly and I fired a few shots before noticing. Currently it hits the middle and didn't seem to obstruct the cartridge when moving in/out (but read later).

Side shot shows the problem - the top of the firing pin (here at the bottom) is much wider than the oring (in the middle).

Filing one of those firing pins to a smaller diameter hasn't really helped, it has expanded again after three-four shots with such a modification. Also there were problems with ejecting shells - they either get stuck in the chamber, caught mid-way by returning slide or just barely fall off the side.
This is definitely different now from the original behaviour, when spent cartridges were flying all over the room :-/
I'd say it could be detonator problem (sticking too far into the cartridge, thus deforming firing pin and preventing proper ejection) but there doesn't seem to be enough evidence for that.
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:06 am

Post by MT01

Wow thats some wear you have there.
However. its quite a strange wear pattern on your piston. It looks way to wide?

The MGC .45 chamber detonator shape comes more to a point at the end (you can see the shape on Francky's site under accessories-parts), and should produce a fairly small diameter wear pattern?

I would check the detonator pin is definitely seated correctly and then invest in some new pistons. Relatively cheap as Cerwyn has pointed out.
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PostSubject: Re: MGC .45 Carts... Firing Pin "Swells" after time   Sun Aug 17, 2008 9:06 am

Post by Mark

Tiksom,

I would say that your barrel is the problem as the detonator is held in place mostly by plastic. If the plastic deforms for whatever reason then the detonator can shift it's location in the barrel. If the detonator shifts the cartridge nose will be hit by the detonator and if the detonator doesn't hit the nose of the cartridge it will hit the piston off center and cause problems. The piston has to move without any friction and, it has to move in a nice straight linear fashion. If the detonator is contacting the piston off center then the piston tries to move sideways in the bore of the cartridge.
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MGC MP40 Marushin MP40 Nakata MP40 TRC MP40

Modelgun manufacturers, past and present:CMC,CAW,Hudson,HWS,LS,MGC(R.I.P. 1960's~2007) Marushin,Marui,Kokusai,Shoei,Tanaka and Western Arms
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