CMC trigger & HP anti-walk pins are a NO GO.

[Nathan_Mack]

So I've got my SPR 90% done and I began barrel break in over the last couple of days. I was initially grouping about 1.5" at 25 yards and then about 4" at 100 yards. I was experiencing inconsistent trigger pulls with the CMC flat shoe 3.5 lb trigger and it felt to be fluctuating in the 7 to 10 pounds range. NOT good.

So I swapped lowers for one with a standard (but polished) mil-spec trigger group in it with about 2000 rounds under its belt. There was a night and day difference. Although a standard 6 pounds, it's smooth and consistent with no jerky sear disengagement. I made .75" at 100 yards and 1.6" at 200 yards with Hornady Steel Match ammo (75gr BTHP).

I am going to measure the JP pin diameters compared to the I.D. of the CMC trigger holes. I am suspecting they will likely mic-out to be .154" on the nose or a couple thousandths of interference fit between them. Either way it is causing binding and jerky trigger movement. More to come.

Nathan

[Ride4frnt]

I has similar problems with my spikes battle trigger and kns pins. For the life of me I couldn't figure out why the gun would fire the first round, chamber the second but not fire it. Upon further inspection I found the firing pin was even following the second round back into the chamber (bad news on some light primers)

Finally found out that the nib coating on the disconnector must be a bit thick, and the disconnector wasn't rocking like it should. When the bolt came back after the first round it wasn't locking the hammer back, this the hammer was riding the carrier back into the second round.

Swapped for milspec pins and viola, problem fixed.

Sorry to hear about your experience, and I hope it's rectified.

[Nathan_Mack]

well, I made the measurements and the holes are .157" and the pins are .1555". this makes my issue a little more disheartening as I fear it might be a misalignment in the lower reciever trigger pin holes. this does beg the question, does Rainier Arms drill the holes in their lower receivers in one step, or not? The lower receiver holes measure .155". that means that the pins are interferenced with the receiver holes by only a quarter of a thousand all the way around.

I may have to just try and drill out the receiver holes a little bit more. I can't remember the drill bit size off the top of my head.

[UWone77]

well, I made the measurements and the holes are .157" and the pins are .1555". this makes my issue a little more disheartening as I fear it might be a misalignment in the lower reciever trigger pin holes. this does beg the question, does Rainier Arms drill the holes in their lower receivers in one step, or not? The lower receiver holes measure .155". that means that the pins are interferenced with the receiver holes by only a quarter of a thousand all the way around.

I may have to just try and drill out the receiver holes a little bit more. I can't remember the drill bit size off the top of my head.

Rainier Forged Receivers are made by Mega and Billet are CMT. They don't drill their own anything.

Rather than take a drill yourself, I'd see which part was out of spec and start there.

[Nathan_Mack]

Rainier Forged Receivers are made by Mega and Billet are CMT. They don't drill their own anything.

Rather than take a drill yourself, I'd see which part was out of spec and start there.

Well, so far I don't see any tolerance issues with the pins or the CMC trigger through-holes. Removed from the lower, the pins have a great fit in the trigger group itself with no binding and no wobble.

I got side tracked in other errands and such so I'll revisit this tomorrow evening and measure everything again 3 times and post up the results for more opinions.

[SINNER]

It's the pins. They pinch the lower and bind with the internal CMC trigger pins. Loosen the screws on the pins and I bet it functions as it should. Use KNS pins or the ones CMC supplies with the C clips. Applying too thick of a coating caused the HP pins to bind up a Timney on me one time. Frustrating to figure that one out.

[Nathan_Mack]

It's the pins. They pinch the lower and bind with the internal CMC trigger pins. Loosen the screws on the pins and I bet it functions as it should. Use KNS pins or the ones CMC supplies with the C clips. Applying too thick of a coating caused the HP pins to bind up a Timney on me one time. Frustrating to figure that one out.

Thank for the information. I will troubleshoot the issue with this new point of view. Thanks!