What 9mm PCC Barrel Length Did You Choose (OR would you choose if you buy/build)

[seb5]

With a 5.5 or shorter you will need to use a mag well grip to keep from burning your off hand. I have a 5.5 and am awaiting a suppressor approval. If I was just going to use it unsuppressed I would go 8.5

[everready73]

So I called PA and talked to them about this FM AR9. I would really like to get a range report from you on how well it runs, any cycling issues etc. And also down the road after you have a 1000 or so pills down range.

Feedback I got from PA was that it was a solid running pistol and that they sell A LOT of Foxtrot Mike AR9's and have had very few returned for malfunctions. But I'd rather hear that from an actual owner/shooter. You mind posting up a range report and some follow-on feedback?

Thx
RTX

They have an industry section on TOS if you want to contact them. Rep is pretty active. There is a decent amount of info on these over there. Mostly good. The only issues I remember seeing where with their .45 upper, and they really worked with the guy to get it fixed. 9mm seems gtg.

[boomer223]

So I called PA and talked to them about this FM AR9. I would really like to get a range report from you on how well it runs, any cycling issues etc. And also down the road after you have a 1000 or so pills down range.

Feedback I got from PA was that it was a solid running pistol and that they sell A LOT of Foxtrot Mike AR9's and have had very few returned for malfunctions. But I'd rather hear that from an actual owner/shooter. You mind posting up a range report and some follow-on feedback?

Thx
RTX

I have 600 flawless rounds so far. It basically runs like a scalded dog...

[boomer223]

With a 5.5 or shorter you will need to use a mag well grip to keep from burning your off hand. I have a 5.5 and am awaiting a suppressor approval. If I was just going to use it unsuppressed I would go 8.5

I have the 5" barrel, 5" hand guard version of the FM9 and it's surprisingly forgiving as far as hand position. I was surprised with what I could do with 5" (That's what she said.....)

[Clint]

There are a couple points here.

In general 115-124 grain round nose feed perfectly, even if the feed cone of the barrel is not right.

Hollow point and heavier flat nose ammo needs the barrel feed cone and chamber radius to be correct in order to run reliably.


Ballistically, there's no "issue" with 147gr, other than it feels lame and has noticeably more drop at range.

Whereas with a pistol, the consistently lower velocity and shorter expected engagement ranges often tips the tables in favor of the lower energy, more consistent terminal performance of the 147gr ammo.

However with an 8.5" barreled PCC, the ease of making hits tends to stretch out the useful engagement distances up to 100 yards.

This in turn points to flatter shooting, high energy ammo in the 115-124gr class.

Full strength 124gr NATO ammo delivers velocity around 1300 fps and muzzle energy ~450 ft-lbs.

Most 147gr ammo doesn't gain enough extra velocity to be interesting.

In fact, it does just the opposite.

Ideal velocity for subsonic is ~950 fps for reduced flight noise when suppressed.

The longer barrel just pushes most ammo up into the transonic range ~1050 fps, negating much of the signature benefit of the heavier projectile.

This may not be the best approach for competition, but the more potent ammo feels more appropriate for general purpose carbine use.

Thank you Clint. This is some great intel and really got me to really think through the ammo application for this project. As I think through this idea from purpose to execution, I believe the bulk of my ammo will not be subsonic ammo, but primarily 115gr which is my primary HD/SD load (Barnes Tac/XP) and I do have some heavier round in the 147gr variety, but by and large my stock is 115-124.

Have you seen any issue with heavier ammo like 147gr in the longer 8.5" barrels?

Thanks again

Rob

[gaijin]

^^This.

We run 124 Zero or PD handloads that perform to 100+ yds. for range ammo.
The drop is 4”+- at 100 with a 50 yd. zero, accuracy is A zone at 100 with RD and braced/prone position.

[Bang4Buck]

^^This.

We run 124 Zero or PD handloads that perform to 100+ yds. for range ammo.
The drop is 4”+- at 100 with a 50 yd. zero, accuracy is A zone at 100 with RD and braced/prone position.

So I just ordered this FM a couple days ago and waiting to take delivery: https://www.primaryarms.com/foxtrot-...ith-sba3-brace

You brought up a question I was thinking about, and that is the best distance to zero. Sounds like you prefer 50 yard vs. 25 yard as there is flatter trajectory. Anyone else have thoughts about best distance to zero one of these?

[1168]

I'm going to build a 14.5 pinned upper and peddle the 8.5. I'll probably end up using a 15" ALG Rail because LaRue doesn't make their $10.00 an incher in 15 inch.

Is there enough meat under the threads to do a P/W on a 9mm?

I only own one 9mm AR, and its fun and cheap to shoot, but I can’t figure out what its good for compared to my proper rifles. So it doesn’t get shot much.

Blowback barrels are a bit shorter than rifle barrels when installed. So consider your handguard length. You really have to consider what you want the gun to do.

For full time suppressed use under a handguard, I would go as short as reasonably possible, so you can shoot cheap 147. As Clint pointed out, the heavy bullets don’t gain much from barrel length, but factory 147 will go transonic, given enough barrel.

For a general screwing around SBR or pistol, I would choose a 8.5” to 10.5”, depending on handguard and muzzle device. You don’t need a flash hider or brake. Unless you want to use a cheap, oversized A2, I would suggest using the cheapest linear comp available. I went with a KVP on a 8.5”.

If you want a real stock and no stamp, 16” barrels are very appealing. They are easy on the ears, and only a little longer than a 14.5” P/W 5.56 gun. So perhaps a useful training analog. If you plan on shooting PCC matches with USPSA or IDPA, I would add that you may want a brake to louden it up a bit for the shot timer.

On ammo selection:
147’s make cheap subs in a short enough barrel. Otherwise, they really don’t take advantage of additional barrel length. The only real reason to use 147 gr is if you have piles of it (like I do) and want to streamline logistics. With a longer barrel, you might be able to use the heavier stuff that is marketed for subsonic use, but they cost more and I’ve not been pleased with any that I’ve tried.

In longer barrels, 124 NATO ball makes the most sense, as Clint pointed out. Lighter bullets gain more in longer barrels, and if the gun doubles for home D, 124 grain NATO is close enough in weapon function and POI to 124+p. If not considering the weapon for home defense, there are 115gr +p ball loads available such as Aguila that you can use for general screwing around cheaply. While we’re talking about home defense, I would suggest a +p loading of a bullet that is known to penetrate deeply and hold together at pistol velocity. The added velocity will result in greater expansion. My top choice would be XTP 124+p, with Critical Duty 135 +p as runner up.