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Dies Irae
Picture of Opus Dei
posted
Is it strictly necessary to use a dedicated PCC stripped upper, or can an ordinary AR upper work? Dedicated stripped uppers seem pretty costly, but maybe the ejection port size keeps brass cleanly ejected? Thanks in advance.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
Prepared for the Worst, Providing the Best
Picture of 92fstech
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A normal upper will work. CMMG actually recommended an oversized ejection port for their 9mm system, so I went with an Aero XL upper...I've had zero problems with it.
 
Posts: 8684 | Location: In the Cornfields | Registered: May 25, 2006Reply With QuoteReport This Post
Dies Irae
Picture of Opus Dei
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Thank you; that will make it a lot less costly.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
Green grass and
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Picture of old rugged cross
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I do not understand. You need a barrel, bcg and other items. How much are you saving?



"Practice like you want to play in the game"
 
Posts: 19257 | Registered: September 21, 2005Reply With QuoteReport This Post
Dies Irae
Picture of Opus Dei
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quote:
Originally posted by old rugged cross:
I do not understand. You need a barrel, bcg and other items. How much are you saving?
This isn't about an overall build price point, but a single component cost. This has nothing to do with pinching pennies. It's a matter of do I need to spend more for no reason; $35 regular or $70 PCC is roughly the current spread on commodity-grade stripped uppers. Now, if I had been advised that Yes, a smaller or more precisely-placed ejection port is necessary for clean ejection, the price would've been worth the premium.

From what I've seen, once you got to boutique milled stuff or big name brands, the price is pretty much a wash.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
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I have no idea from personal experience. I'm sure there is enough web info to get some advise. But I started my 9mm carbine 'adventure' many many years ago with a colt. And colt changed the ejection port. Now if it didn't matter then why would they. Maybe it only matters in a subgun. I have no idea. But I have duplicated the colt 9mm upper in every gun I have built.
But in this case you are risking almost nothing to try a std. upper. Worse case you have an extra upper...


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 11021 | Registered: October 14, 2004Reply With QuoteReport This Post
Dies Irae
Picture of Opus Dei
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quote:
Originally posted by hrcjon:
I have no idea from personal experience. I'm sure there is enough web info to get some advise. But I started my 9mm carbine 'adventure' many many years ago with a colt. And colt changed the ejection port. Now if it didn't matter then why would they. Maybe it only matters in a subgun. I have no idea. But I have duplicated the colt 9mm upper in every gun I have built.
But in this case you are risking almost nothing to try a std. upper. Worse case you have an extra upper...
Fair take, and Thanks. I haven't bought one, yet. Stern bolt and Matador magwell are here, and barrel is incoming.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
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Picture of Rustpot
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Colt's 9mm conversion adds a 9mm shell deflector which shortens the ejection port opening, using a standard port cover that's cut down to accommodate. The 9mm bolt doesn't need to travel as far rearward as it extracts in a shorter distance.

With a standard M4 upper the shell deflector is useless, the ejection port is longer than necessary, the gas tube hole is not needed, the feedramps are not used, and the forward assist probably won't work as 9mm bolts aren't normally cut with the forward assist notches. Most 9mm uppers omit or change these aspects as part of their design.

You can use most any "standard" AR upper to build a 9mm.
 
Posts: 6033 | Location: Romeo, MI | Registered: January 03, 2009Reply With QuoteReport This Post
Green grass and
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Thanks hrc and rust, pretty much confirms my thinking. I see no benefit and several potential issues that may or may not arise. I just do not see the value in it.



"Practice like you want to play in the game"
 
Posts: 19257 | Registered: September 21, 2005Reply With QuoteReport This Post
Dies Irae
Picture of Opus Dei
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quote:
Originally posted by old rugged cross:
Thanks hrc and rust, pretty much confirms my thinking. I see no benefit and several potential issues that may or may not arise. I just do not see the value in it.
Alright, what several potential problems are your perceiving that "may or may not" manifest? I already addressed ejection concerns in the opening post. I asked for advice if it'd work, so if you have practical experience, I'm all ears.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
Green grass and
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Not really, just as I said. Seems like a solution in search of a problem.

Curious how expensive a dedicated upper is in comparison?



"Practice like you want to play in the game"
 
Posts: 19257 | Registered: September 21, 2005Reply With QuoteReport This Post
Dies Irae
Picture of Opus Dei
posted Hide Post
quote:
Originally posted by old rugged cross:
Not really, just as I said. Seems like a solution in search of a problem.

Curious how expensive a dedicated upper is in comparison?


No, you said several potential problems you could see. You get confirmation bias from a couple of posts and ignore one that says a regular receiver is fine. All I wanted to know was if there would be ejection issues.

The internet is full of pre-built uppers for you to price. But I'm wanting to build one, and there's things about it that dictate some specific components and some (like receiver type) that may not matter.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
Green grass and
high tides
Picture of old rugged cross
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So doing some surfing as 92 say's and many other sources say, yes. Use all you want. Not seeing a lot of ejection issues. A few.
Doing it that way would not be my choice. Ymmv

Maybe ask the manufacturer of the upper you plan to use.



"Practice like you want to play in the game"
 
Posts: 19257 | Registered: September 21, 2005Reply With QuoteReport This Post
Certified All Positions
Picture of arcwelder
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A normal upper will be fine.

The doodle on the side of the Colt is for gas blowback, not a shell deflector. It's designed as a submachinegun. (semiauto) 9mm uppers without it don't suffer issues. You adjust ejection with spring and buffer weight.

There are common issues people suffer with 9mm guns, but many boil down to the ammo. It can't be weak. If all you shoot is WWB, then you're going to have problems with a spring and buffer meant for defensive ammo, and vice-versa. One won't cycle, the other will beat the hell out of the gun.

Make sure you ramp the carrier, so you can use any trigger group. Without the ramp, rearward velocity will punish the trigger group and if you really pay no attention, elongate the holes in the lower (the differences in "stock" colt 9mms are all about the beating full auto dishes out. Without the ramped carrier, you need to pay attention to the design of the hammer itself.


Arc.
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Posts: 27027 | Location: On fire, off the shoulder of Orion | Registered: June 09, 2004Reply With QuoteReport This Post
Dies Irae
Picture of Opus Dei
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quote:
Originally posted by arcwelder:
A normal upper will be fine.

The doodle on the side of the Colt is for gas blowback, not a shell deflector. It's designed as a submachinegun. (semiauto) 9mm uppers without it don't suffer issues. You adjust ejection with spring and buffer weight.

There are common issues people suffer with 9mm guns, but many boil down to the ammo. It can't be weak. If all you shoot is WWB, then you're going to have problems with a spring and buffer meant for defensive ammo, and vice-versa. One won't cycle, the other will beat the hell out of the gun.

Make sure you ramp the carrier, so you can use any trigger group. Without the ramp, rearward velocity will punish the trigger group and if you really pay no attention, elongate the holes in the lower (the differences in "stock" colt 9mms are all about the beating full auto dishes out. Without the ramped carrier, you need to pay attention to the design of the hammer itself.
Thank you for the advice. I've got a lot to sort one everything's here, it seems. I've also been watching Blowback 9's YT channel for tips. I did find a 9 upper for a reasonable price, so it's on the way.

Thanks again, all. And ORC, thank you. You kinda missed my intent, but I know you had your head in the right place of optimization concerns.
 
Posts: 5766 | Location: Fort Heathen, Texas | Registered: February 25, 2008Reply With QuoteReport This Post
Firearms Enthusiast
Picture of Mustang-PaPa
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Will the dedicated upper have or change the travel length the bolt has or is that controlled by the buffer and or buffer tube length?

Reason I ask is when I built my 9mm ar i had trouble with it breaking bolt catches. Its travel length was longer for the .223 length bullet so it was building up to much speed and momentum on the forward stroke and when the mag was empty the catch would pop up and get broken every time.

I finally found the cure after much reading which was a spacer made to shorten the travel or to stack quarters 10–14 in the bottom of the buffer tube to shorten the travel but to allow the shorter 9mm bullet to be picked up from the mag.

At the time the spacer was out of stock and on back order so I did the quarters until the spacer was available.

When I bought my spring and buffer it was for 9mm setup but the buffer didn't address the shorter 9mm bullet length. As I recall now a 9mm buffer was available but the spacer/quarters were cheaper.

Have had no more issues with my 9mm ar since the correction was made. It is fun shooting the 9mm ar.
 
Posts: 18050 | Location: South West of Fort Worth, Tx. | Registered: December 26, 2008Reply With QuoteReport This Post
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