"Overgassing" question. AR pistol build coming. Newbie.

[Tallbald]

I've been a shooter for 50 years. Daddy, my mentor and long departed best friend had no love for the AR platform (Korean era Air Police, and a lover of the M14). SO we never had one and I only recently decided I do want one. So I'm assembling one of my own---a pistol. Inexpensive to build these days I look forward to the process.Using a PSA 10.5 inch nitrided barrel set, fully assembled upper, I'm starting simply.
OK.One reason I've never taken the plunge with an AR platform anything is that they always seemed ( I read it on the internet so it must be true wink wink) to require a very delicate balancing act be performed to make one's gun run well. Finicky? Don't get upset with me friends. Teach me.
I've ordered my PSA pistol kit but it hasn't arrived. Folks here have answered many questions about the platform for me and I appreciate it. As I've studied more the last several days, more questions have popped up for me.
" Overgassing" in a pistol. I understand the concept and the physics involved. Many of the instructional videos and articles I've studied on pistol builds with overgassing issues use as an example a 7 or 7 1/2 inch barreled pistol. I understand in theory about pigtail gas tubes, adjustable gas blocks and heavier buffers and buffer springs to correct overgassing. But, the kit I chose for my first build is the PSA 10.5 inch nitrided barrel model. Carbine length gas tube. On this 3 inch longer barrel, is the gas port farther from the chamber and if so, is that enough to mitigate overgassing troubles seen in the shorter barrel AR pistols? I read the mostly positive reviews of the 10.5 inch kit builds, and haven't seen overgassing listed as a problem. Is the longer barrel the reason for fewer troubles?
Thanks friends. I appreciate the patience shown my questions. I've googled my questions until my eyes are googly. Don.

 

[badkarmamib]

I built a pistol similar to that, with a Radical Firearms barrel in the same profile. I didn't feel like it was overgassed. If you and your brass aren't getting beaten up, and your face isn't getting excessive gas blown around the charging handle, and your brass is getting ejected at 2-4 o'clock, I would suspect you are fine. With a carbine gas, 10.5" barrel, you won't see a lot of dwell time. i.e., before the pressure can get too high, the projectile has left the barrel, and given the expanding gas an easier path to escape.

 

[railroader]

I recently got a nitrided 10.5" pistol from PSA. It runs very well and is a hoot to shoot. The only thing I have done is too change the buffer to a slightly heavier H2 buffer. The only issue I got when I first shot it was some stuck steel case shells. I cleaned the chamber really well and it hasn't been an issue since. Here's the upper I have. https://palmettostatearmory.com/psa...-slick-side-upper-with-bcg-ch-5165448560.html

 

[Tallbald]

Thanks. Here's the kit I chose. Not snazzy to some, but reminiscent of the appearance I saw growing up in the 60's and 70's, when only a few People of the Gun were AR enthusiasts:
https://palmettostatearmory.com/psa...ve-pistol-kit-flat-dark-earth-5165449194.html
It's a wait and see thing it appears. Do loads create variables that affect overgassing? I mean, does bullet weight from 55 grain to 72 grain, and from light charges to heavier charges also impact overgassing? Or is it a situation wherein you sort of have a "range" of loads that do well in a given gun once it's balanced? I'm a reloader and these are things I don't know about the AR platform. I'm wondering if I should have chosen 300AAC instead of 5.56 NATO (all sold out at the time) because I also am a bullet caster (a cheapskate) and if I get sucked into the AR platform pistol scene I can see myself casting and loading for my new range gun.
Don.

 

[badkarmamib]

I'm wondering if I should have chosen 300AAC instead of 5.56 NATO (all sold out at the time) because I also am a bullet caster (a cheapskate) and if I get sucked into the AR platform pistol scene I can see myself casting and loading for my new range gun.

Now that's funny! You appear to actually believe that you will be able to stop with just one AR.

But, in all seriousness, you could easily get another upper in .300AAC, and swap back and forth. Even better, your mags, bolt carrier group, and charging handle will all swap over. BUT, if you do, make ABSOLUTELY CERTAIN which rounds are loaded before inserting the magazine. A Blackout round can have the bullet jammed back and "chamber" in a 5.56 upper, but the bullet won't exit the barrel. At least, not out the muzzle end...

This upper is $260, with BCG and CH:
https://palmettostatearmory.com/psa...-with-fluted-flash-can-bcg-ch-5165447685.html

 

[Tallbald]

Yeesh. Hadn't considered the potential for chambering 300AAC in 5.56 NATO. My beloved wife is a Cricut vinyl cutting enthusiast. May be that I can have her create a bold chambering warning. Don.

 

[badkarmamib]

Yeesh. Hadn't considered the potential for chambering 300AAC in 5.56 NATO. My beloved wife is a Cricut vinyl cutting enthusiast. May be that I can have her create a bold chambering warning. Don.

I have AR uppers chambered in 5.56 and 6.8SPC. My method is simple: if the magazine is polymer, it is loaded with 5.56. If the magazine is metal, it is loaded with 6.8SPC. A buddy of mine differentiates by using windowed and non-windowed Pmags for his 5.56 and Blackout.

 

[GunnyUSMC]

I have the same 10.5 upper on my SBR and have never had an issue. It runs great.

 

[Tallbald]

GunnyUSMC. Would you share which weight slugs you find do best in your "arrangement" please? 55 to 72 grain? I need to order some rounds. Accuracy is my goal. internet search suggests heavier slugs do better.....Thanks. Don.

 

[GunnyUSMC]

GunnyUSMC. Would you share which weight slugs you find do best in your "arrangement" please? 55 to 72 grain? I need to order some rounds. Accuracy is my goal. internet search suggests heavier slugs do better.....Thanks. Don.

The 1/7 barrels shoot the heaver bullets better. I have only fired 55 and 62gr ammo in mine so far out to 50 yards. It does a little better with the 62gr but not by much. I need to mount a scope on it to see what it can do.

 

[Tallbald]

Excellent. I have a Weaver 2X32 scope in the safe waiting for my calling. Long eye relief, it's been a favorite for a number of years. "Only accurate rifles interest me..." I've read. I'm hoping this build fulfills that interest. Again, I thank you.Don.

 

[[email protected]]

I had a 7.5 inch barrel in 223 a few years ago. It was fun to shoot , but the percussion from the muzzle blast was nerve racking. It had numerous failure to extract cases at first. The extractor would rip the case rim off. I determined that he bolt was unlocking and trying to extract the case form the chamber before the chamber pressure dropped off enough. I ended up putting an O ring between the extractor spring and extractor to give the extractor more tension. No problems after that. With a 10.5 inch barrel you still may want to look into a linear flash hider instead of the bird cage. It directs more of the muzzle blast forward.

 

[Tallbald]

Hmm. I'll look into the linear flash hider. May just whip one out on my lathe. Only need a tap for the threads. Hope this whole thing is as fun as I mean for it to be. Thanks. Don.

 

[railroader]

Hmm. I'll look into the linear flash hider. May just whip one out on my lathe. Only need a tap for the threads. Hope this whole thing is as fun as I mean for it to be. Thanks. Don.

Here a low concussion brake I put on my pistol. The price is right and it works ok. It's short too like an a2 flash hider.
https://www.ebay.com/itm/Low-Concussion-Muzzle-Compensator-Knurled-Compact-Brake-1-2x28-TPI-223-223/263663420593?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

 

[FL-NC]

10" is the length of the barrels used in the SOCOM issued uppers (MK18). Issues with reliability for specific rounds were addressed by using the correct buffer weight. We fired mostly 62 grain SS109 or && grain MK 262. Don't ask me what buffer was recommended because I don't remember, we just got the ones the armorer said to use, put them in our guns, and handed back the other ones.

 

[Tallbald]

Thank you all so much for the replies. FL_NC is your compensator crafted of aluminum or steel? Don.