I put this up so that others can refer, try or discount. One thing that I am not prepared to do is physically alter any aspect of the rifle as that will void any warranty etc.
My carbine has had feeding problems from the issue converted UZI magazine of which I only have the one. I have now several aftermarket magazines and they are all behaving the same as the issue magazine, although I am told that they should not work at all.
I have now put close to 800 rounds through the gun and have experienced the same problems throughout with varying degrees of consistency.
I can break down the feeding problems into 2 different sections with the later having an (a) and (b).
Firstly the gun was failing to feed a round from the magazine in to the chamber. The round would get stuck at an angel between the bolt face and the upper assembly where it meets the back of the barrel. This could happen at any time and had no regular features, For example it could be any round in the magazine, left or right feed.
After much playing with dummy rounds last night I believe that I have now worked out that this is caused by the ammunition being too short in OAL.
OAL in this case being measured from base to tip.
As I have used a number of different makes of factory ammunition and different weights, this would answer why some makes work better than others. Measuring the factory "Limit" rounds that I have I was surprised to find that they were slightly under SAMMI spec.
I made a number of dummy rounds at 1.200" and cycled them through the gun; at no time did I have a jam as described above. I also made up some dummy rounds at 1.100 and they were jamming as described.
Despite recommendations that you are only supposed to use factory ammunition through this gun, I recommend that should you make home loads, they are as long as your projectiles and magazine will let you. In my case it was 1.180". Should you have a range of factory 9mm to purchase, I suggest that you measure it and buy nothing shorter than the SAMMI spec of 1.169".
A trip to the range this morning has proved this theory correct and no feeding problems as descibed were encountered - and the group size was good to boot!
The second (a) feeding issue that I have had, both with the UZI issue mag and with a couple of my aftermarket mags, is of the last round consistently not feeding - as in almost 100% of the time. The above longer rounds have not stopped this issue.
I had noticed when cleaning the carbon fouling off the gun that the feed ramp in front of the magazine has no marks on it ie it appears not to be doing anything.
This played on my mind and I had a good look at it and how it was fixed in place. Some had mentioned taking a power tool to it to change the angle of the ramp, but I was not prepared to void the warranty and second, it was doing nothing at all so changing the angle was not going to help.
I had a feeling that the whole block could be raised so I set about investigating that possibility.
It is fixed in place by one grub screw (the higher one, the lower is just a hole for some unknown purpose) here:
Being careful to use a tool of the right size it came undone after a squirt of GT85 and being left to sit for 5 mins. Being careful not to damage the ears on the block I started to pull it out then to my horror felt it twist. It was then that I noticed that the head was on a round stem and it came out easily.
On the second picture you can see where the grub screw had been sitting.
After cleaning the ramp up, I put it back slightly higher than before. On closing the bolt this has to be done slowly, as if the ramp was too high, I suspect there is enough mass and energy there to damage the bolt and the ramp if it was so high to get in the way. Once a height that did not obstruct the bolt was found I fixed it in place. As can be seen there is a reasonable amount of difference:
Sadly on returning to the range this morning this has not fixed the last round feeding issue. On returning home I can see a couple of faint scuff marks on the left ear, so it has done something – but not enough.
I cannot help wondering if the ears need to be shorter, so not to interfere with the operation of the bolt and the ramp brought up even higher. Clearly this is not something that I will be doing, hopefully the designer can explore this avenue if need be.
Lastly feeding issue No2 (b) only happens with the UZI mag. On the last round only, the last round will be picked up as the bolt slides rearwards and will end up behind the magazine and the r shaped bit of metal that hangs over the magazine and the bolt slides over. Luckily for me, on these occasions my range drills have been good and a proper check has always found this round. For someone not familiar with this gun or who only checks the chamber for a round I believe there is the possibility for the gun to be passes as clear when it is not.
I have no idea how to solve this issue minus not using that magazine. It must have something to do with the angle of the follower, but put all the magazines side by side and you can see no difference in angle.
One thing that I did notice re my aftermarket magazines is that they all now have a tiny chip out of the rear follower, which in these magazines is plastic, where the bolt has hit them. This resulted in the first time I used them failing to feed the last round but there after they are ok – perhaps the metal follower on the UZI mag is part of the problem.
And that is as far as I feel I can take it, the rifle is going back to see if the designer can work out what is going wrong, I look forward to having it back and in full working order, it is a great gun and I look forward to competing with it,
DM
