I have figured out my GST-9 build problem **watch your torque!!!**

Tesoro

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edit: I spoke to the tech at gst9 shop and cinching down the 2 jig halves firm is what supposed to do. So I believe that all their jigs are not dead nuts. i was told they have 8 machines that make the jig. Maybe there are variances that result in the trigger housing/rear rail pin to be off a slight amount that causes the rear rail to not be parallel with the front.


Project #1 = all good but the rear rails were .02-.03 lower than front. Ie the holes were drilled a tad too low.
project #2 = Blank drilled in leveled quality drill press with the bit square to the floor like in #1. The rear rail holes on this one were .03 on one side and .02 on the other too far to the rear so the rail pin holes did not line up. WTF!!

Both #1 and #2 rails have same measure from pin hole to rail +/- .002.

I had 2 jigs with 2 frames and the 2 block pins were positioned fine on both frames. After lots of measuring and thinking and comparing I came to the conclusion that the rear part of the jig with the trigger pin guide gets slightly warped once the 2 jig sides are bolted together TIGHT. This makes the rear parts of the jig bend slightly together creating an angle to the guide hole that misses target.

By over tightening down the bolts I bent the jig! Of course after figuring out the above I read through the instructions to find their emission error but they clearly say DO NOT OVER TIGHTEN!!

So there ya go! Attached is a pic of the jig and you can see that the center portion mates up but there is a gap on the outsides. The front dosent matter but the rear does. I had assumed that the jig was flush so never looked when it did it..twice in a row.

I made a post somewhere bitching about polymer80 and their rear rails so I take it back! be calling them tomorrow. Hope this helps others who know it all and dont read instructions fully. But in my defense the jig should be flush! it might be better to just tape this one like you do with P80 jig.

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I actually like the gst9 better than the p80 because I have large hands. Not sure how much my final one is gonna cost me! probably close to a gold cup!
 
I remember reading / learning somewhere (probably on old MGB forum or his videos) that even though the P80 jig has holes that can be used to bolt / screw the jig together, that it's a bad idea because it would be too tight. Just tape it closed.
 
EDIT:! I spoke to the tech and cannot over torque the jig and I was doing it correctly! they just put the do not overtighten bit in instructions to stop people from stripping out bolts! So back to square one in figuring out why I got such variance in the trigger housing pin holes. They will refund me and I am ordering another with the new jig that they say is reusable and is practically impossible to drill crooked. Ie idiot proof. See how this one works!
 
What do other people do? I will be ordering I hope soon.
 
FWIW, I did use the nuts & bolts to join the halves. But I didn't gorilla-tighten the blots, either. lol. Just hand-tightened them enough to snug 'em, and not warp or buckle the jig halves. Then ran a bead of tape around the outside.
 
yeah well i didnt try to break the threads either!..I just tightened them to where the 2 halves were tight against each other. Did you lay a good metal straight edge on your front and rear rails to see if they are even?
 
yeah well i didnt try to break the threads either!..I just tightened them to where the 2 halves were tight against each other. Did you lay a good metal straight edge on your front and rear rails to see if they are even?
Nope. snort. Just set the jig on a nice, perfectly level surface vertically and hand-snugged them. So far, so good, bro!

I will offer that the first two GST9's were my introduction into 80% builds. I made a few small gaffes along the way, but nothing catastrophic. hehe. Then did a number P80's of various flavors. Then did another GST9, right before they released the MOD one. By that time, I'd learned a LOT with the help of MGB's site and these beloved regulars, backbone members here. That and a bit of trial & error and some small innovations.

Be encouraged, Tesoro. You're doing fine. Oh and, don't forget that the P80 jigs snap together, then you tape the seam. I suppose that snap-fit eliminates the risk of stress on the plastic and keeps it uniform. That, and the internal frame support in the jig halves are plenty. In fairness to 80% Arms, I didn't find the jigs lacking in internal frame support, or in how they are joined. But the snap-closed P80 jigs may be more foolproof, if you will. No risk of overtorquing there. And, if it's any encouragement, after quite a few builds now, I'm still learning. So be encouraged!
 
HI I am not discouraged one bit!! havent had any issues other than pst9 rear rails.
 
Is the drill press absolutely necessary.

no.. but you need to have a quality drill that has no play in the head. or a quality one that is not worn out. A smaller sized hand drill would be better and one that you can operate at low rpm. You dont want the bit melting the plastic. I did low speed with some oil on my ones. Oil cant hurt!
 
no.. but you need to have a quality drill that has no play in the head. or a quality one that is not worn out. A smaller sized hand drill would be better and one that you can operate at low rpm. You dont want the bit melting the plastic. I did low speed with some oil on my ones. Oil cant hurt!
I have a Milwaukee 12v that is small so that's what I'll be using.
 
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