Unusual RT Pro Issue. . .Now confirmed as micromag 2k9 problem!

[sniper42]

So it seems my feed hole is indeed too far forward. It is about 3.65" from the back of the feedhole to the field strip screw. That most likely is what is causing the blowback up the feedstack and the low velocity.

[nak81783]

I'm trying to put a quick sketch together using AGD CAD dimensions, OPBN's dimensions, and sniper42's dimensions. I think there's enough here to show different degrees of feed tube blow out. If you recall from one of my previous posts, I can stack two balls on top of a chambered ball, and the top ball barely jostles in both my ULE body and X-Mag.

Spoke too soon. I still need the dimensions from working and non-working bodies that I posted in the other thread. http://www.automags.org/forums/showt...-2k9-mag/page2

Edit: And sniper42 posted while I was typing this, and, I believe, just solved the mystery.

[sniper42]

And I have my buddy's 2k9 that has the same issue. Same velocity problems and feed hole is the same measurement as mine.

[nak81783]

So here's the summary I have from the two threads. The distance is from CENTER (NOT edge) of rear field strip screw hole to aft edge of feed tube (NOT removable breech piece).

Henchman TAC1: Please report
Henchman MM2K9: Please report
OPBN TAC1: 3.375" - Properly functions. No feed tube blowout.
OPBN MM2K9: 3.5" - Proper velocity, but ball on top of chambered ball shoots up when fired. Please quantify compared to sniper42's.
sniper42 MM2k9: 3.65" - Low velocity. Ball on top of chambered ball shoots up when fired. Quantified as "shoots up a few feet".
sniper42 friend's MM2k9: 3.65" - Low velocity. Ball on top of chambered ball shoots up when fired. Please quantify compared to sniper42's.
Dukie Classic PF: 3.5" - Proper velocity. No feed tube blowout.
Dukie Minimag: 3.5" - Proper velocity. No feed tube blowout.
Dukie ULE: 3.5" - Proper velocity. No feed tube blowout.
nak81783 X-Mag: 3.5"- Proper velocity. No feed tube blowout.
nak81783 ULE: 3.5" - Proper velocity. No feed tube blowout.

So we need to:
1. Confirm Henchman's measurements. The ones he posted in the other thread were to the bolt spring seat, not the feed tube edge.
2. Confirm OPBN's measurements. The AGD body is different from all the other AGD bodies. The MM2K9 appears the same as most stock AGD bodies, but if there is some other design difference, it could accout for the blowout...or the measurement needs to be verified...lol
3. Confirm sniper42 friend's body has the same ball blowout issue from the feed tube.
4. Confirm Dukie's bodies have no ball blowout from feed tube.
5. See if increasing deviations from AGD stock bodies cause increasing amounts of feed tube blowout. Does the ball fly up further as the 3.5" dimension increases?

[OPBN]

So it seems my feed hole is indeed too far forward. It is about 3.65" from the back of the feedhole to the field strip screw. That most likely is what is causing the blowback up the feedstack and the low velocity.

[nak81783]

That's one of the hardest measurements to take in my opinion. There's probably some error there. Plus, how far in the detent sits can throw that dimension off from marker to marker.

[Dukie]

I have no blowback issues on any of mine. i can fire 2 balls in the feed port without launching #2 out the top. mind toy the classic is a pf, and the minimag is a vert conversion.

It might be a good idea to also get a measurement of center of field strip to rear of feed block. that should confirm weather the feedblock is the issue or the bottom drilling / milling.

I am betting on the feedblock being machined backwards. that at least should be a relatively easy fix. just get a good one.

However..... the bottom frame screw and sear milling beeing out of position would also explain the extra .150 od depth in the bore. that would suck. i still dont buy it though. why do two complete setups for holes on the same face? thats silly. if it is that it could be fixed with a custom breech.

[Dukie]

The scenario i can see- material roughed and feed port machined. part loaded backwards and the front-or- rear features were milled. opposite end milled. the part is now correct except for the feedport being on the wrong side of center. part loaded correctly since it is now obvious, (and the keying feature on the front was probably used,) detent holes machined. that would put the detent holes in the correct location in regards to bolt face, leaving the feedport incorrect.

All of that is provided they didnt use a fourth or fifth axis. i remember the delays due to some big orders that came in. these may have been pushed on to a 3 axis machine which would mean many more operations and chances for mistakes.

[nak81783]

I'm glad you've joined the discussion. These are all things I've touched on and/or asked about. It's nice to have a consenting opinion.

[OPBN]

Alright, I pulled my feedneck off and did some further gleening. On my MM2K9, the feed neck hole/port is not centered from front to back. It sits farther to the back of the breach than the front. Sniper or whomever else, where does yours sit? I am trying to measure it, but its a bit difficult because the edge of the hole is beveled inward.

Micro 001.jpg

The top of the pic is the direction towards the back of the marker.

[nak81783]

While the feed tube is out, shoot some balls with and without covering the feed hole to see if your velocity goes up as athomas suggested.

[OPBN]

While the feed tube is out, shoot some balls with and without covering the feed hole to see if your velocity goes up as athomas suggested.

Sure. Have to go play lumberjack today and cut up some wood, but I'll sneak in some play time in between.

[sniper42]

The feed hole in mine also sits farther to the back. It looks to be about 0.175" from the back edge. In this picture the bottom of the picture is the back edge.

i-R6zKndJ-L.jpg

[nak81783]

Now we still need from center of rear field strip screw hole to start of breech slot on the main body piece for both markers, please. That should complete the puzzle.

[OPBN]

Now we still need from center of rear field strip screw hole to start of breech slot on the main body piece for both markers, please. That should complete the puzzle.

From the center of the FS screw to meeting of the back of the breach block is 3.39" according to my calipers.