FX9 Questions

[Sniffer]

Thanks for this. I have been putting off trying to play with the buffer until now. Put in $1.50 in quarters with the stock spring and buffer and shall see how it runs on the weekend. If there is no change, I can always take out the $1.50 and make a Timmy's run for coffee (does $1.50 even buy you a medium coffee anymore??)

I saw the Blitzkrieg one video comparison and it seemed like for the guy it was a more noticeable difference in the recoil effect...but if it helps keep the red dot on target, that will be a compelling reason.

I always have put off the quarters thing due to not seeing any wear on the bolt catch - but then I haven't checked the travel distance of the bolt when fully retracted back.

The logic of how the Blitzkrieg works is interesting to me. A hydraulic buffer makes a lot of sense and in theory should soften things up.

I have other heavy buffers that are sitting idle these days thanks to King Turdhole so I can try them first and go from there.

Planning to upgrade some stuff on this (tinkering is half the attraction for me) to make it more Race Gun-ish and with Black Friday around the corner I see some shopping on the horizon.

 

[thegazelle]

The logic of how the Blitzkrieg works is interesting to me. A hydraulic buffer makes a lot of sense and in theory should soften things up.

I have other heavy buffers that are sitting idle these days thanks to King Turdhole so I can try them first and go from there.

Planning to upgrade some stuff on this (tinkering is half the attraction for me) to make it more Race Gun-ish and with Black Friday around the corner I see some shopping on the horizon.

Aside from the cost, my hesitancy on the Blitzkrieg is that it looks like it is optimized for short barreled PCCs, though it says it will work with all PCCs. I just don't know whether it will give me the $220+ tax value in performance. I am assuming I use the stock FX9 spring and just replace the buffer.

 

[Sniffer]

Aside from the cost, my hesitancy on the Blitzkrieg is that it looks like it is optimized for short barreled PCCs, though it says it will work with all PCCs. I just don't know whether it will give me the $220+ tax value in performance. I am assuming I use the stock FX9 spring and just replace the buffer.

Word is for optimum performance you should run a heavier AR10 style spring.

Looks like for the FX9 the heavier version is the better fit which makes sense to me (longer barrel needs more dampening)

 

[thegazelle]

Word is for optimum performance you should run a heavier AR10 style spring.

Looks like for the FX9 the heavier version is the better fit which makes sense to me (longer barrel needs more dampening)

So something like the Flatwire AR 308 spring? Assume with that heavier spring and a hydraulic buffer, those quarters will be rendered moot?

I thought I read in an earlier post someone saying that the 308 spring was too strong and they encountered feeding problems as a result.

The FX9 is, for all intents and purposes my most used gun. I have no desire to run it for competition, but tuning it for reliability for various applications is a compelling goal. I just don't want to put add-ons and the performance is worse than stock.

 

[Sniffer]

So something like the Flatwire AR 308 spring? Assume with that heavier spring and a hydraulic buffer, those quarters will be rendered moot?

I thought I read in an earlier post someone saying that the 308 spring was too strong and they encountered feeding problems as a result.

The FX9 is, for all intents and purposes my most used gun. I have no desire to run it for competition, but tuning it for reliability for various applications is a compelling goal. I just don't want to put add-ons and the performance is worse than stock.

I think the issue they encountered with the AR10 spring was that the bolt didnt always lock open on the last round (which is a feature I like).

I'm sure with some playing around it can be made to work.

This is what I imagine:

It sounds like the AR10 spring isn't letting the bolt go back far enough to lock on the last round, which probably also means it shoots very soft as the bolt isn't slamming back against the end of the buffer tube.

Using a lower strength spring (regular AR15 spring) would probably mean the bolt would be slamming back against the end of the buffer tube some more but it should lock open. With the hydraulic action on the Blitzkrieg buffer it should still shoot soft.

 

[Unholysavage]

Gazelle- they make a HD version of that Blitzkrieg buffer for longer barreled PCCs. Supposedly stiffer from what I remember reading.
Every rifle is different. Some can tolerate AR10 springs, others can't. My FX9 worked really well with the 5.8oz Odin buffer and an AR10 spring. Some had better reliability with lighter H2 buffers and the stock spring (with or without quarters in the buffer tube), a couple here bought Odin adjustable PCC buffers that were over 7oz and had excellent reliability. Best advice is to work your way up.
Those Blitzkrieg buffers are intriguing, wonder how durable they are?

 

[thegazelle]

I think the issue they encountered with the AR10 spring was that the bolt didnt always lock open on the last round (which is a feature I like).

I'm sure with some playing around it can be made to work.

This is what I imagine:

It sounds like the AR10 spring isn't letting the bolt go back far enough to lock on the last round, which probably also means it shoots very soft as the bolt isn't slamming back against the end of the buffer tube.

Using a lower strength spring (regular AR15 spring) would probably mean the bolt would be slamming back against the end of the buffer tube some more but it should lock open. With the hydraulic action on the Blitzkrieg buffer it should still shoot soft.

Thanks for the the feedback. As for me, the last round bolt hold open is something I do very like but with the FX9 it has been a constant source of consternation as it has never been consistent with Glock 17 G5 OEM native 10 round mags.

What are your before and after impressions after your upgrade? What wasn't working well before or a better way to ask, what advantages did you discover after the tune? (maybe both expected and unexpected)

Gazelle- they make a HD version of that Blitzkrieg buffer for longer barreled PCCs. Supposedly stiffer from what I remember reading.
Every rifle is different. Some can tolerate AR10 springs, others can't. My FX9 worked really well with the 5.8oz Odin buffer and an AR10 spring. Some had better reliability with lighter H2 buffers and the stock spring (with or without quarters in the buffer tube), a couple here bought Odin adjustable PCC buffers that were over 7oz and had excellent reliability. Best advice is to work your way up.
Those Blitzkrieg buffers are intriguing, wonder how durable they are?

Thanks for the input...so I guess with a different spring, the need for quarters is rendered moot? I'm just trying to figure out an order that won't tax my wallet too much...so with a graduated approach would you suggest:

1. Change buffer first with stock spring with quarters?
2. Change buffer first with AR10 spring and no quarters?
3. Keep stock buffer, change spring to AR10 (with or without quarters?)
4. Something else?

Also if you can also share your observations as to the before and after experience...what were you expecting to happen when you changed the parts and was it to your expectations? Was there any byproducts/effects of the change that came as a surprise? For you, what were some of the the improvements you saw? Thanks for the feedback. I am typically not one to change parts out (I keep pretty much everything stock) but for this gun, I am definitely interested in improving the experience and mitigating some of the quirks of the platform, so to speak.

 

[Sniffer]

Gazelle- they make a HD version of that Blitzkrieg buffer for longer barreled PCCs. Supposedly stiffer from what I remember reading.
Every rifle is different. Some can tolerate AR10 springs, others can't. My FX9 worked really well with the 5.8oz Odin buffer and an AR10 spring. Some had better reliability with lighter H2 buffers and the stock spring (with or without quarters in the buffer tube), a couple here bought Odin adjustable PCC buffers that were over 7oz and had excellent reliability. Best advice is to work your way up.
Those Blitzkrieg buffers are intriguing, wonder how durable they are?

From memory Blitzkrieg quote a "Million round guarantee"

 

[Sniffer]

I know FX9s take Glock mags - but which Glock mags (it feels like there are a million different flavours)?

And are any for better for last round bolt lock back?

 

[Odd Shot]

Out of curiosity, where are different uppers available from? Who carries them?

 

[Neutrino]

Thanks for this. I have been putting off trying to play with the buffer until now. Put in $1.50 in quarters with the stock spring and buffer and shall see how it runs on the weekend. If there is no change, I can always take out the $1.50 and make a Timmy's run for coffee (does $1.50 even buy you a medium coffee anymore??)

I saw the Blitzkrieg one video comparison and it seemed like for the guy it was a more noticeable difference in the recoil effect...but if it helps keep the red dot on target, that will be a compelling reason.

I always have put off the quarters thing due to not seeing any wear on the bolt catch - but then I haven't checked the travel distance of the bolt when fully retracted back.

You're welcome! And no, I believe a medium coffee is a buck seventy-nine at Tim Horton's nowadays.

I had to play around a lot with buffer/buffer spring/coin combos to settle on the closest intersection between what I liked and what worked. Like other's have mentioned, I think mileage may vary on a per-gun basis. I might even cycle back through some of my earlier experimental combos to see if time has softened the springs that were too heavy, and to double-check that I truly am where I want to be with the whole system. I've also never had a casing bounce down into the trigger group area (one of the problems the quarters are supposed to help prevent) as I changed the trigger out immediately for a cartridge style trigger group (Triggertech PCC) so I think may have prevented that. Seems to compress the spring enough for more hearty and reliable chambering on the first round of a new magazine quite nicely though.

 

[thegazelle]

I know FX9s take Glock mags - but which Glock mags (it feels like there are a million different flavours)?

And are any for better for last round bolt lock back?

Based on my experience I can say that the ones that are NOT conducive to LRBHO function are the Glock 17 OEM G5 native 10 rounders. Those consistently DO NOT lock back the bolt when empty. At least in my FX9 and using predominantly 147gr and 124gr rounds (though the same behaviour is seem with the 115gr - not sure the ammo choice is a factor...

The PMAGS GL9 or whatever they are fare slightly better. I have a PMAG that is a 17 pinned to 10 that works maybe 40% of the time, which is better than 0% of the time for the OEM Glocks. The ProMags work about 50% of the time.

I have also tried the Glock OEM 33 rounders pinned to 10 and they work about 40-50% of the time.

 

[Sniffer]

Based on my experience I can say that the ones that are NOT conducive to LRBHO function are the Glock 17 OEM G5 native 10 rounders. Those consistently DO NOT lock back the bolt when empty. At least in my FX9 and using predominantly 147gr and 124gr rounds (though the same behaviour is seem with the 115gr - not sure the ammo choice is a factor...

The PMAGS GL9 or whatever they are fare slightly better. I have a PMAG that is a 17 pinned to 10 that works maybe 40% of the time, which is better than 0% of the time for the OEM Glocks. The ProMags work about 50% of the time.

I have also tried the Glock OEM 33 rounders pinned to 10 and they work about 40-50% of the time.

Interesting.

I have some genuine Glock mags from my Kriss Vector days (I knew there would be a day when I would have something else that ran Glock mags so I kept some) so I will try them (I have no idea what vintage / model they are).

I think I have found some 10/27 Glock PMAGs which I think I am going to pick up. Sounds like the PMAGs are a decent bet.

I did some more reading on the last round bolt hold open but there is no solid answer it seems and it may be a case of compromising.

One article I read states (this makes sense to me):

I had several springs available, but the best match across all the guns was the Sprinco ORANGE .308 Carbine spring. A simple test is to load a magazine with one round, load the SMG, and fire. If the bolt locks back, your bolt is going all the way back. If it fails to lock, your buffer and spring are probably too heavy.

I also looked at the Blitzkrieg "PCC Hydraulic Buffer Competition Package" which includes a spring and weight. The literature suggests this combo is the softest shooting available but when I read further it states:

If you want the absolute best set up for the smoothest running and softest recoiling PCC possible, this is it. In addition to the RB5015HD High Damped buffer and the .308 Carbine Spring, we've added our PCC Buffer Weight/Spacer. The PCC Buffer Weight fits into the buffer tube on top of the buffer, placing it right behind the bolt. It adds 2.5 oz of weight and 3/4" of length to the buffer system. The PCC Buffer Weight keeps the buffer in alignment and ensures a consistent, straight impact from the bolt. The additional weight further delays initial bolt movement. If this package is used in a standard AR15 carbine buffer tube, it creates a short-stroke system with 3/4" shorter bolt stroke. If used in an AR10/A5 carbine buffer tube, it keeps it as a full stroke system and the bolt catch can still be used, while adding the benefits of the PCC Buffer Weight.

So my understanding is adding the weight slows the system down and makes it shoot softer but the physical space the weight takes up makes the system short stroke and as such the bolt cannot travel back far enough to lock the bolt back.

Best option would be to switch to an AR10 carbine buffer tube and so the weight can be used and the bolt can still travel back far enough to lock.

Quite the rabbit hole.

 

[Sniffer]

Based on my experience I can say that the ones that are NOT conducive to LRBHO function are the Glock 17 OEM G5 native 10 rounders. Those consistently DO NOT lock back the bolt when empty. At least in my FX9 and using predominantly 147gr and 124gr rounds (though the same behaviour is seem with the 115gr - not sure the ammo choice is a factor...

The PMAGS GL9 or whatever they are fare slightly better. I have a PMAG that is a 17 pinned to 10 that works maybe 40% of the time, which is better than 0% of the time for the OEM Glocks. The ProMags work about 50% of the time.

I have also tried the Glock OEM 33 rounders pinned to 10 and they work about 40-50% of the time.

Actually now I think about it some more the quarters you added would be "shortening" the system kinda like the weight I mentioned in my previous post which could be the reason or part of the reason why you are not getting the bolt to reliably lock back.

Might be worth trying it without the quarters to see if that helps the last round bolt lock back.

 

[Sniffer]

What are folks using for an optic on these? Please note I will probably compete with this and as such it will be more of a "spray & pray" type deal than high precision.

With this in mind I am thinking something really open like a reflex sight with a large dot (6 MOA ish). I have an itch for a SIG Romeo XL which has a huge window and comes in a 6 MOA version. It may be too low though so a riser of some kind would be required (like the Scalarworks version but I think it is only offered with Trijicon footprints)?

If not that maybe a regular type optic like a Trijicon MRO. From the little bit of poking around I have done these seem to only be offered with smaller dots (2 MOA or 3 MOA) This is more rugged and may already be high enough but I do wonder if the additional chunkiness would make it slower to pick up for competition use.

I dont know a ton about these styles of optic as I have always been more of a LPVO guy which is kinda overkill on a 9mm PCC.

 

[thegazelle]

Actually now I think about it some more the quarters you added would be "shortening" the system kinda like the weight I mentioned in my previous post which could be the reason or part of the reason why you are not getting the bolt to reliably lock back.

Might be worth trying it without the quarters to see if that helps the last round bolt lock back.

Mine never locked back even before I put the quarters in which was only a couple of days ago, I think...I haven't shot it with the quarters in the buffer tube yet (plan to go tomorrow to try it out)

 

[Unholysavage]

Glock mags need the stronger Wolff springs installed to reliably lock back. Mine locked back 95% of the time with PMAGs, but the cheap Korean KCI mags were the most reliable.

As for optics, mine had a Vortex Razor UH-1. Superb optic for a PCC IMO. Has a fine center dot for precision/hunting, big circle for close quarters, large FOV, super bright if needed. Eotech and Holosun have very similar reticles, with the Holosuns giving you the option of turning off the fine dot or outer circle if you want.

 

[Sniffer]

Glock mags need the stronger Wolff springs installed to reliably lock back. Mine locked back 95% of the time with PMAGs, but the cheap Korean KCI mags were the most reliable.

As for optics, mine had a Vortex Razor UH-1. Superb optic for a PCC IMO. Has a fine center dot for precision/hunting, big circle for close quarters, large FOV, super bright if needed. Eotech and Holosun have very similar reticles, with the Holosuns giving you the option of turning off the fine dot or outer circle if you want.

Thats great info - many thanks.

Just to be clear - Wolff springs are required to make the FX9 lock back?

I know exactly what you mean about the Holosun, I have a 508 with the reticle style / options you mention but it lives on my shotgun these days, I could try it on the FX9 and see how it feels but I imagine it to be too small boxy for what I want on it.

 

[RyoTHC]

If anyone is looking for a never fired 4” upper for the FX9, I may have my FX9 and kit sold, so no point keeping the additional uppers I have.

Won’t have a gun range anywhere near me anymore.

I have 1 4” and 1 8” (spf)

 

[Unholysavage]

Thats great info - many thanks.

Just to be clear - Wolff springs are required to make the FX9 lock back?

I know exactly what you mean about the Holosun, I have a 508 with the reticle style / options you mention but it lives on my shotgun these days, I could try it on the FX9 and see how it feels but I imagine it to be too small boxy for what I want on it.

With genuine Glock mags I'd say yes. I never used them, but a buddy did in his FX9 and his Glock mags locked back 100% of the time after that. Some guys have tried stretching their Glock springs, not sure if that helped or hurt. I used PMAGs and KCI mags most of the time in mine, mostly because they were longer and easier to grab than my 10rd Glock mags.