9mm AR discussion

[mustangfreek]

Good stuff guys..I have been thinking a while about one..

Barrel length I'm thinking 5-8" somewhere, not sure how much velocity is gained past like a 5" barrel.

The QC 10 stuff looks nice and they say the LRBHO works but snooping around many have problems, so not a real 100% reliable hold open model I know of.

The joe job lower is one I've been looking at,,
Also

So any particular bolt catch, trigger, buffer idea seems s few different ways..just need a somewhat list of what I might need

Also what parts work together good and dont

[RiverRat]

Barrel length I'm thinking 5-8" somewhere, not sure how much velocity is gained past like a 5" barrel.

Source: ballsticsbytheinch.com

If you're most concerned about being subsonic with (relatively hot) 147s, here are the isolated data for Federal 147 HSTs. Right click and open in a new window to see the axes labeled correclty:

Source: ballisticsbytheinch.com

he QC 10 stuff looks nice and they say the LRBHO works but snooping around many have problems, so not a real 100% reliable hold open model I know of.

True statement, this has been a problem area. QC10 changed the transfer bar design a couple of months ago and it seems that might have helped - and they have some hand-fitting instructions to tweak performance if needed. It's also important to limit bolt travel so it doesn't have as much forward momentum when the bolt catch engages. There are plugs that fit in the receiver extension (back end of the spring) to limit buffer travel, or you can just dial it in by sticking a few quarters in the extension as spacers. I'll post results when I get to this part of the tuning on my lower.

If you go JBO/NFA lower and you want a bolt hold, you'll have to wait until NFA gets the new upper design to market. I expect JBO will get a branded copy, like they have with the lowers. Without that (currently unreleased) upper, I don't think there's any option for LRBHO with the Spartan lowers.

Just a note, which I assume you've already addressed in your plans: you'll want a ramped, glock-cut bolt.

[JHoward]

No safety or is that an optical illusion? Do you wish you went longer or shorter barrel? Or is the 7.5" just right?

As of now there is no safety. The Shockwave just came in the mail today. It's definitely ,"in progress", I had a Shockwave but I swapped from FDE to black. The trigger is actually just in progress as of now as well. I'm planning on an SD3G to go in it. I'm so excited to get it working properly, but the holidays are not conducive to builds at all. I will check back in when it's complete and I can get more than 5 test rounds through it.

[JHoward]

Sorry. I didn't answer the question about barrel length. I feel like 7.5" was perfect. I was going to go with 5.5 and a "flash can" but felt like that was a little too "tacticool" for me. The 7.5 and flash hider feel just right. My only regret is that I didn't go with the Wilson 7.5, but I did not because it's an HBAR. I wanted lightweight. But the whole damn thing is pretty hefty. I'm waiting for a BAD safety and BAD clamp for the MATECH sight I have here. So yes. It looks very incomplete.

[mustangfreek]

So special parts for glock model jbo/NFA lower with a normal upper and pistol tube/Kak blade probably
-bolt carrier..so glock cut..good options ?

What about
-trigger?
-Bolt catch?
- buffer and spring option ?
-barrel selection/ company for a 7-8" barrel?

Don't want to get to deep into this for a blaster but if o do it if like it to run reliably..lol...

[JHoward]

I have almost given up on a reliable LRBHO option. I'm thinking I may just focus on making it function more smoothly. I'm thinking the Q9 buffer is going to be a big ticket item in that area. Q9 and the extra power Wolff spring and the added tension of the Q9 head should go a long way toward holding the chamber closed.

[RiverRat]

Ramped bolt = almost any AR15 trigger works. If your bolt isn't ramped, you'll either need to modify a standard hammer or purchase a 9mm specific trigger package. So it's pretty easy to extrapolate that you'll want a ramped bolt.........

[RiverRat]

I have almost given up on a reliable LRBHO option.

I'm confused....I thought you had a New Frontier lower - and I didn't think LRBHO was an option with any of their current lowers?

[mustangfreek]

I'm confused...lol...should I go for it or what ..just after a range toy

So build me a 9mm pistol with a jbo lower...cost wise upper, barrel, comp or FH and barrel?

[JHoward]

It's an option with their upcoming upper, but I don't really like the way they're doing it. Unless it proves to be uber reliable, I'll just run it without any hope of LRBHO.

[mustangfreek]

So std trigger with a glock ramped bolt..so is the NFA the best option with a different Lin it was that just the modular one?

Good spot for barrel ?

Not sure what buffer to look at? That Q9 how much? spikes 9mm buffer, Kak?

Help..or not too many out there yet playing with these ?

[JHoward]

I would have to say, I started this build to be a cheap alternative to practice with a 5.56, but I don't think it's going to end up that way. I wish I would have gone with a Wilson barrel at 7.5" and a QC10 bolt. I am not disappointed with my New Frontier lower, but I am not sure how close QC10 is to having a reliable LRBHO.

[mustangfreek]

Quick thinking and rough numbers after looking around, just using a normal upper and budget buying here and there

Lower- jbo/nfa - $150-$180 with tax/ transfer
Ballistic adv Barrel- $115-$120
Bolt $150
Upper-50-100
Rail - 100
Buffer 50
Pistol tube, fh or Kak can, LPK, misc pieces 100

So 750'ish right there if you were starting with nothing but most of us have some extra parts laying around...So as is , more then your budget 566 build but not to bad unless you went all out.. but I'm just looking for a new build idea and something different then the std 556 builds .This would be a slow build if I decide to..

Plus Sights/RDS/ mags..Humm ..looks and sounds fun with the bonus of taking glock mags .but want it reliable or enough to where I can shoot it without hiccups every mag

Pyzik.. I thought you were in the process of building a 9mm..if so how's the process and why are you not in here....lol

[RiverRat]

Mustang,

I think at least 3 of are doing the 9mm thing, some maybe a step further along the path but without enough practical use to make specific recommendations.

I'll offer what I've found in looking for my own pieces.....again without a single round downrange yet.

I think there are 4 off the shelf glock cut, ramped bolts available: New Frontier, JP Enterprises, Splinta Precision and QuarterCircle 10. I know Macon Armory also makes a version, but it's not listed on their web site. I've not seen unfavorable reports on any of them other than the NFA modular variant, so I suspect you can pretty much buy any of the one-piece bolts and be OK. Splinta is in stock on their site, NFA is in stock at JBO, the others may be harder to find.

ETA: Looks like there is a 5th glock-compatible ramped bolt option: Armil-Spec (also in stock).

Those BA barrels are probably the 5.5" and 10.5" versions. It's much easier to find rails for the 10.5" and it's generally a more practical length (not that much is practical about an AR in 9mm. ) FWIW, I've considered getting one to build a 2nd upper (or in case the TROS delivery doesn't pan out). JBO also just received a shipment of 8.5" Kaw Valley Precision lightweight barrels - price is good ($110) and it would mesh well with 9" rails but I know nothing of their quality.

JBO has a Spartan slick side upper that would match the lines of your lower, if you were so inclined. NFA sells the same design, but without the text engraving (if you want a cleaner look). If you're after a more typical forged upper, I've used a couple of Aero slick sides and they're good if you can catch a sale. And the Rainer slab side is priced to move at $50 - might be the value play if you're OK with the overt branding.

Buffer and springs are likely build and ammo sensitive - but you have the advantage of not having to tune around LRBHO. As long as you start with at least a 5.6 oz 9mm buffer, it should have a decent chance of running. Heavier buffers, stiffer springs and/or a buffer spacer might let you reduce felt recoil and still remain reliable - I look forward to both tweaking my own build and hearing your progression in this area (it seems like this is the voodoo/art with these carbines).

I recently picked up one of the KAK flash cans for a 300 BO. I don't think an aluminum muzzle device is a good permanent choice, but I'm using it as a short-term placeholder for a suppressor. It is really light and decently fabricated though.

ETS looks like the mag of choice.

[JHoward]

Have you heard of specific issues with the NFA modular other than mine? If so, what were they?