L9X25

I used SR exclusively for thousands of rounds with NO problems, with no leakage.

You are combining two different issues. Firing pin failure seems to affect most pin types across several brands. The firing pin that came with new Taccom bolts was of a traditional design that had a small round head at the spot where the hammer strikes it and they are prone to failure. Rather than using better materials, or strengthening the failure point, they opted to redesign parts of the pin that were causing the pins to fail. Having to replace a pin because the head peened too far to remain functional is not a widespread problem, as breakage is. The new design features a large head, intended to eliminate the head peening problem, but many hammers strike the large head at the lower edge (well off-center) and cause the pin to "yaw" as it moves forward. The pin is no longer in perfect alignment with the hole in the bolt and loses energy by impacting the sides on the way to the primer. This results is decreased energy to ignite the primer.

Small Rifle and small pistol are the same size and interchangeable. Many of us also load other "Major" pistol calibers like 9x21 or 38 Super and have a healthy supply of small rifle primers in the cabinet. Large pistol and large rifle have different dimensions and are not interchangeable. When you are attempting to make minor power factor with a 14"+ barrel, we barely produce enough pressure to blow your nose. The nose of the firing pin is deformed from not being perfectly aligned with the hole in the bolt and banging on the top on the way out.

Thanks guys. That modification works and you can perform it with a grinder or file, no machine tools are necessary. Since I have a milling machine, I duplicated the Taccom cut on the bottom side make mine lighter yet functionally similar to what they have done.

@alvinsmith75 The only image I can find is of the 2nd generation "big Head" pin, not anything after that. Do you have a link or copy of the pics?

Making them from softer metal can reduce the stress cracking at the expense of deformation, hardening them will help solve the deformation at the expense of cracking. Hardening may reduce the deformation, but that is just a "band-aid" to hide the underlying bad geometry of the design. They are not transmitting all of the energy they receive to the primer, they are wasting some of it bouncing around in the tunnel while trying to get to the primer.

FWIW, I have had 100% function from the LRBHO on the NFA Upper. That is a pretty easy way to get LRBHO if you want it and do not have and you can get side charging thrown in with it.

Not that I can find on my phone.

Just duplicate the cut on the opposite side and you should be good. You can put a slight bevel on the sharp edge, to narrow it slightly more. In the end, you should end up with an impact strip about the same width as the original round pin head.

I machined the bottom to match the top recess, so that the hammer is forced to hit the center of the pin. I have a JP trigger with the Light hammer spring. I have 2 guns with the same trigger/springs and they are both 100% on small rifle primers. When the stock Taccom pin broke, I replaced it with the "improved" model (as shown above) and the misfires started. By hitting the pin significantly off-center, some of the energy is lost inducing the yaw and bouncing the pin around in the tunnel. That loss of energy was causing the misfires. You could examine my pin and see where it was impacting along it's path and it has deformed the tip as shown in the initial picture. Once the pin was modified and polished, the marks did not return and the misfires ended.

Take a close look at the back of the pin and see where the hammer is hitting it. I bet that you will see that the hammer is hitting it at the outer edge of the pin and causing it to "yaw" from the off-center impact. When I installed this pin, I only had about 50% ignition with small rifle primers, while I had 100% ignition with the old pin before it broke. I had to modify the rear of the pin to make the hammer hit centered and then the pin worked 100% again. It also stopped bouncing the pin around in the tunnel too.

My NFA lower has never had a "jam" of any type. It has had a broken firing pin, and an idiot that installs the primers sideways or upside-down, but no jams at all. I have various magazines from 10 rounds through 66 rounds.

It might be that the clearance is not consistent from gun to gun, or they adjusted that dimension, because mine is not that loose. I only have one to check, and that is not any more statistically significant than the one example that Tim shows, but I am curious about what everyone else with an NFA is seeing?

You can't buy the parts to build one for what he is asking...

I have a JP that is great and built another rifle with an NFA lower. I liked the fact that the NFA did not use pins (uses threaded set-screw style pins) and included a upper/lower fit tensioner. The NFA has the correct mag angle and I have not had any problem with Glock or ETS mags, they both fit snug and drop free.

Make sure that the ejector is very tight in the upper/inner corner of the bolt channel. The 9mm case is pretty small in diameter and the ejector only contacts the outer edge. If the ejector is not located properly, it can slip off the edge of a piece of brass with a rounded edge. Making sure it is almost scrubbing against the bolt towards the centerline, and as high as the bolt channel will permit, will make sure it kicks out all the brass.

The proven triggers are Hiperfire and JP, they are both reliable with almost every combination. Anything else is hit or miss, depending on the combination of parts.

I watched a video where Jones Arms explained that they modified the magazine location and angle to improve the feeding of their Glock magazine lowers. I thought that was the greatest idea ever. I pulled my JP GMR out of the safe and checked to see what the magazine angle looked like and it was just as they described theirs to be. With the 115 FMJ bullets that I was shooting at the time, the projectile was pointed directly into the chamber of the barrel and was just barely outside of the chamber. Practically any movement forward and the point of the projectile would be technically in the chamber. That lower has never mis-fed with ramped or unramped barrels. The point of this post is to say that some lowers have proper/improved geometry and some do not. I can say that the JP and NFA both have improved geometry, and I am told that the QC10 also has the improved geometry. Picking any one of these 3 lowers should give you similar feeding characteristics. This is not a "one brand that has it right and everyone else is wrong" type of thing. Lots of people have brand loyalty, but I think that it is just that. I am pretty loyal to JP, but currently shoot an NFA with a JP trigger. YMMV.

But the JP rifle has a match trigger and the SCS buffer already in there. Those two items are the $200 you are saving.

What features do you like and value the most? Can you get those exact features in a "store bought" PCC at a comparable price to building? I purchased a JP and was very happy. Soon after getting exposure to several other guns, I realized that the JP was heavier than what was optimal for me to compete in USPSA. I had the option of changing out parts on my JP or building an upper to replace the heavy parts. Since the JP had always run flawless, without a single jam, I chose to leave it alone and build an alternate upper for my JP lower. That accomplished exactly what I wanted to do. Eventually, I ended up building another lower, so that I could put the JP back together and have a complete spare, and now have two complete guns. Knowing what I know now, I would build exactly what I want from parts. Before I knew exactly what I wanted, a factory built gun was a better choice.

100% agree. The pin is so slender at the tip, it does not take much energy to dimple the primer. The rest of the energy is dissipated when the skinny end of the pin impacts the backside of the breech face. That is a lot of energy being absorbed by a skinny pin.

4.5lb pull?

I can tell you that the hammer face is not perpendicular to the firing pin at the point of impact. At rest against the bolt it may be perpendicular, or very close to it, but it is short of perpendicular at impact. I installed a pin with a broad striking surface and the impact was exclusively at the bottom edge of the impact area and I suffered with a high percentage of light strikes. I also noticed that the firing pin was banging around inside of the tunnel, on it's way to the primer (from the torque induced from the off-center hit) and there were marks on the pin from the impacts. I machined away the head impact area, forcing it to strike much closer to the center, and the light strike problem went away along with the marks along the top of the firing pin.

I have the "standard JP two piece trigger" with the reduced power (yellow) spring and broke a pin in less that 1,000 rds.

The reason that I asked is that uppers are available with features like "side-charging" and LRBHO, for those that want those features and have a lower that does not have LRBHO.