If I wanted to put a 9mm upper on a regular AR lower---

tbs

tbs

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I have this Griffith Armament lower that's been sitting in my safe for a few years. If I wanted to add a 9mm complete upper is there anything that has to be done to lower to get it to except the 9mm magazines?
 
tbs said:
complete ... 9mm upper on a regular AR lower ... is there anything that has to be done to lower to get it to [accept] 9mm magazines?
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You will need to use H3 (5.4 oz) or heavier buffer as lighter H1 (3.8 oz)/H2 (4.6 oz) buffers will produce sharper/harsher recoil (Combined bolt/buffer weight needs to be around 19-22 oz ... FYI, PSA 9mm bolt weighs 14.7 oz) - https://www.thehighroad.org/index.p...back-recoil-impulse-9mm.924171/#post-12740825

Depending on the magazine used, you have three options:

1. Colt/Uzi pattern stick magazine - These magazines require using mag well block that installs from the top or bottom of mag well and comes with last round bolt hold open or not. I recommend metal block (Got mine from PSA) that has locking screws for best secure reliable feeding. I do not recommend plastic blocks like Pro Mag as thin side panels could warp and prevent reliable feeding. This would be my last option.

2. Mean Arms Endo Mag - 9mm insert kit for Magpul PMag. Good thing about Endo Mag is there is no mag well modification as you simply insert converted PMag to use with 9mm upper and last round bolt hold open is retained. Downside is each Endo Mag kit requires a PMag for conversion and plastic ejectors are built into the mag lips (They have been 99% reliable feeding for me) so I would only recommend for range blasting/practice use (3 kit pack is $79 with free shipping and 5% off with THRFORUM code on $50+ orders) - https://www.opticsplanet.com/mean-arms-endomag-9mm-pmag-30-magazine-conversion-adapter.html

Jim Watson said:
Exomag for magazines not requiring adapter.
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Yes, Exomag does not require PMag shell donor and they are $22 each or $58 for 3 (Order "Ejector Version") - https://www.meanarms.com/products/detail/exomag-15-round

3. Glock/M&P/Beretta 92 pattern magazine - If you already have Glock/M&P/Beretta 92 pattern magazines, mag well insert block for these magazines is what I recommend as feed angle positions nose of 9mm round straight into the chamber for best reliable feeding (I decided to use dedicated Glock mag receiver but they work the same). You need to use "Hybrid" 9mm bolt cut for Glock magazines (Instead of Colt) but these days, most 9mm bolts are compatible with both Glock/Colt magazines. Down side is due to pistol mag lock slot being on opposite side, instead of using magazine release on the receiver, you use repositioned mag release depending on the manufacture.
 
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We used the Stern Defense adapter for my Daughter's build-
IMG_20200628_174243_0.jpg

We went with the Beretta pattern as I had a ton on hand and wasn't into Glocks then. I would go Glock-style now just because they are cheaper and more available these days, especially the 30+ rounders.

The adapter is high quality and works fine once you get it properly adjusted- there are two little levelling/ tension set screws. The downsides are it's a bit pricey and the release lever is in a unique spot, so if you have muscle memory from training on regular ARs, you'll find youself mashing the wrong button alot.

I also have a PSA-9 with a Glock-mag lower and it is a much simpler and more elegant solution. If I were to do it again, I would just get a dedicated lower.
 
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Colt and CMMG still use a 5.5 ounce buffer. 5.5 ounces is the minimum buffer weight. Most people run a 7.5 to 8.5 ounce buffer. I'm still running a 5.5 ounce buffer in my CMMG dedicated lower but am thinking about adding more weight to it.

It is a personal choice when it comes to choosing what types of magazines to use and going with a dedicated lower or magazine adaptor. If you plan on using different caliber uppers on your lower then magazine adaptors are the way to go. I ended up going with the CMMG dedicated Colt lower since I got a pretty good deal on it.

I have seen many discussions about Colt versus Glock magazines. They both have their pro's and con's. Both are pretty much standard for 9mm AR setups.
 
9mm buffers are usually longer to prevent over travel. Over travel allows more room for acceleration after last round to slam into your bolt catch causing breakage.

If yhe buffer you go with is not longer, you will need a spacer. You can buy one, or make one for $2.25-$2.50. 9 or 10 quarters in the bottom of your buffer tube, secured in place by the recoil spring does the trick.
 
12Bravo20 said:
Colt and CMMG still use a 5.5 ounce buffer. 5.5 ounces is the minimum buffer weight.
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While it has always worked fine, I've considered a heavier buffer for a turnkey Colt 9. How can you determine the weight of the buffer?
Thanks,
Moon
 
halfmoonclip said:
12Bravo20 said:
Colt and CMMG still use a 5.5 ounce buffer. 5.5 ounces is the minimum buffer weight. Most people run a 7.5 to 8.5 ounce buffer. I'm still running a 5.5 ounce buffer in my CMMG dedicated lower but am thinking about adding more weight to it.
Click to expand...
considered a heavier buffer for a turnkey Colt 9. How can you determine the weight of the buffer?
Click to expand...
Combined bolt/buffer weight should fall within 19-22 oz range using carbine length spring. If you go heavier, you may run into cycling issues and may "short-stroke" the bolt to not actuate last round bolt hold open (For match shooting to keep front sight flat without bolt/buffer slapping the back of buffer tube, this is actually desired by some shooters who don't need LRBHO ... See below for more discussion on short-stroking).

Let's use PSA 9mm bolt weight of 14.7 oz as an example:

22 oz - 14.7 oz = 7.3 oz​
​
So, you start out with 5.4 oz H3 buffer and increase buffer weight until you have recoil impulse you are happy with while still reliably cycling the bolt/buffer. (Some companies sell adjustable buffer weight set or variable recoil buffer systems)

BTW, if you are shooting matches/3-gun, milder recoil impulse is important as it will hold the front sight more steady (Less bouncing around) for faster follow up shots/lining up next target. We discussed evolution of fine tuning of bolt/buffer weight cycling to keep front sight flat for match shooting to include magnetic delayed milder buffer system that short-stroke - https://www.thehighroad.org/index.p...back-recoil-impulse-9mm.924171/#post-12740825

Here's a video example of very flat shooting PCC setup - https://www.facebook.com/watch/?v=3526785537439787
 
i did the 9mm ar15 2 ways:

1) 9mm glock lower, heavy buffer blowback upper. it worked fine. recoil was greater than a 223.
2) regular AR lower, mean arms endomag, and a cmmg radial delayed upper. uses a standard buffer, so converting from 223 to 9mm is and upper and mag sway only. The ejector is in the bolt face, so the plastic mean arms ejectors aren't needed. recoil was cut in half, and it was a lot quieter with a suppressor.

I immediately sold the blowback 9mm. I don't really care what system you use, radially delayed, roller delayed, whatever, there are a half dozen companies out there doing something now (cmmg, jp, mean arms, maxim to name a few) but using a delayed system is vastly superior to straight blowback.
 
greyling22 said:
i did the 9mm ar15 2 ways:

1) 9mm glock lower, heavy buffer blowback upper. it worked fine. recoil was greater than a 223.
2) regular AR lower, mean arms endomag, and a cmmg radial delayed upper. uses a standard buffer, so converting from 223 to 9mm is and upper and mag sway only. The ejector is in the bolt face, so the plastic mean arms ejectors aren't needed. recoil was cut in half, and it was a lot quieter with a suppressor.

I immediately sold the blowback 9mm. I don't really care what system you use, radially delayed, roller delayed, whatever, there are a half dozen companies out there doing something now (cmmg, jp, mean arms, maxim to name a few) but using a delayed system is vastly superior to straight blowback.
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How many rounds do you have on it? I am looking at those too. Only thing kinda holding me back is seeing lot of failures in low round counts.
 
Mot45acp said:
How many rounds do you have on it? I am looking at those too. Only thing kinda holding me back is seeing lot of failures in low round counts.
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So, I got an early one, and it killed the ejector spring pretty early on. Cmmg sent me a shorter stiffer spring that seems to be doing the trick. The original died at maybe 300 rounds. The 2nd is going strong at about 800 or so so far.

I'll be honest though, I shoot the suppressed 38 lever gun a lot more than the cmmg. It's a better host.
 
LiveLife said:
Combined bolt/buffer weight should fall within 19-22 oz range using carbine length spring. If you go heavier, you may run into cycling issues and may "short-stroke" the bolt to not actuate last round bolt hold open
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Hmm, busy morning, I'll need a longer look at my Colt. IIRC, in addition to the buffer, there is a tungsten weight in the bolt itself. It has always run flawlessly (with the exception of one of the mag brands, that doesn't like HPs), and the recoil and 'cheek slap' has always been moderate.
I'll have to check on bolt travel as well; don't want to lose the bolt stop boss on an SBR lower.
I'm not a high speed/low drag guy; just like PCCs.
Thanks,
Moon
 
halfmoonclip said:
Hmm, busy morning, I'll need a longer look at my Colt. IIRC, in addition to the buffer, there is a tungsten weight in the bolt itself. It has always run flawlessly (with the exception of one of the mag brands, that doesn't like HPs), and the recoil and 'cheek slap' has always been moderate.
I'll have to check on bolt travel as well; don't want to lose the bolt stop boss on an SBR lower.
Click to expand...
If you reload, you can make small tweaks to the load to not over drive the bolt instead of going with heavier buffer weight.

I use 5.4 oz H3 buffer weight with 14.7 oz PSA bolt but adjust my powder charges. Since I do not need last round bolt hold open, I adjust powder charge to "short stroke" the bolt to reduce bolt slap of buffer tube, depending on powder.

FYI, match/3-gun shooters prefer faster burning than W231/HP-38 powders for quicker seal with case neck/chamber wall and longer "dwell time" before bolt moves back and starts leaking gas for more consistent powder burn (Less soot on case) and greater accuracy - https://www.thehighroad.org/index.php?threads/9mm-target-load.927857/page-5#post-12846195
 
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LiveLife said:
If you reload, you can make small tweaks to the load to not over drive the bolt instead of going with heavier buffer weight.

I use 5.4 oz H3 buffer weight with 14.7 oz PSA bolt but adjust my powder charges. Since I do not need last round bolt hold open, I adjust powder charge to "short stroke" the bolt to reduce bolt slap of buffer tube, depending on powder.

FYI, match/3-gun shooters prefer faster burning than W231/HP-38 powders for quicker seal with case neck/chamber wall and longer "dwell time" before bolt moves back and starts leaking gas for more consistent powder burn (Less soot on case) and greater accuracy - https://www.thehighroad.org/index.php?threads/9mm-target-load.927857/page-5#post-12846195
Click to expand...
Again, thanks. My concern is more avoiding excess wear and tear on my SBR Colt, though, frankly, as little as I shoot it, it probably isn't an issue. I do have a ramped bolt, and a Geissele trigger; even in its 16" form, it never was common. It started life with A1 carry handle and sights; scored a flattop 10" Colt upper, and do like it with an optic.
I have a standard reload that works in everything; currently using Blazer Brass, same velocity as my standard.
It's dazzling the extent gamers will go to cut their times; I applaud your cleverness. :)
Best,
Moon
 
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