Let's talk PDW's

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Not knowledgeable on this subject so I have to ask.
Seems like the magic spot for 300 is 9 inches? What length of barrel do you need to get comparable performance from 5.56?
And what is the shortest length you can go with 5.56 and get performance with readily available 5.56 ammo?

[Bratch]

I have a sick obsession with little guns. My go to right now is a Scorpion K. I have been debating building an AR pistol on my last lower but have never pulled the trigger. If I survive and stay employed over the next 6 months maybe I’ll finish it out, I’ve been planning on 5.56 since it is a caliber I already stock but may look at 300BO a little more.

[El Cid]

Not knowledgeable on this subject so I have to ask.
Seems like the magic spot for 300 is 9 inches? What length of barrel do you need to get comparable performance from 5.56?
And what is the shortest length you can go with 5.56 and get performance with readily available 5.56 ammo?

Some folks will say 10.3/10.5”. I agree with people like @DocGKR and Mike Pannone that 11.5” is as short as anyone should go. That’s for reliability reasons as well as ballistic reasons.

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Some folks will say 10.3/10.5”. I agree with people like @DocGKR and Mike Pannone that 11.5” is as short as anyone should go. That’s for reliability reasons as well as ballistic reasons.

So 11.5 vs 9. Thats only a two inch difference for comparable performance and the 5.56 is a lot more available in hd/sd/duty loadings. I am trying to figure out the draw for 300 BO. Can someone break it down for me?

[CleverNickname]

This is my road trip PDW, an 8" 300 BLK SBR with a Thunderbeast 30CB5 silencer.

[GearFondler]

So I had built myself a Scorpion exactly how I wanted it and I really liked how it turned out... It was fun as all get out at the range. But that's where it ended for me. I had built it as a PDW and when it was completed all I kept thinking was "This is as big and heavy as a rifle-caliber pistol but only fires 9mm... Where's the upside?
For cheap range fun, hell yes. For self defense, not so much."
I sold it and bought a 1301T.
For the record, it was dead on reliable with FMJ and HST.

[StraitR]

So 11.5 vs 9. Thats only a two inch difference for comparable performance and the 5.56 is a lot more available in hd/sd/duty loadings. I am trying to figure out the draw for 300 BO. Can someone break it down for me?

I don’t think he was saying comparable performance, just that some recognized experts stick with 11.5”+ barrels for 5.56mm.

Ill try to dig some comparisons up later, when not on my phone. Maybe some others can chime in sooner.

[TGS]

And for folks talking about a PCC, there is still a significant size advantage over even an 8.5” AR. It’s of course 300BLK because going shorter than 11.5” with 5.56 is just not smart.

I think the sub-11.5" 556 thing is overblown. People on the internet hear something and take it and run. We use Daniel Defense Mk18s at work without issue. I've never witnessed a malfunction that wasn't immediately identified as a magazine failure. ETA: Correction, I saw one go down on the line for a gas key issue, which isn't isolated to Mk18s.

Regardless of everything I've read on the internet, our Daniel Defense Mk18s just plain work. "11.5" has 40% more dwell time". Okay. But ours still work just fine, and our duty ammo is still reliable performance out to 110 yards.

Personally I'd go 12.5" if I was choosing an unsuppressed duty rifle, because it's pure sex....but I think the statement that "going shorter than 11.5" in 5.56 isn't smart" is a bit exaggerated.

With that said, this is a PDW thread, and CQBRs are not PDWs....so maybe we should save this conversation for elsewhere.

[Clusterfrack]

So 11.5 vs 9. Thats only a two inch difference for comparable performance and the 5.56 is a lot more available in hd/sd/duty loadings. I am trying to figure out the draw for 300 BO. Can someone break it down for me?

That's why I went with a 7.5" 300 BLK.

[UNK]

I think the sub-11.5" 556 thing is overblown. People on the internet hear something and take it and run. We use Daniel Defense Mk18s at work without issue. I've never witnessed a malfunction that wasn't immediately identified as a magazine failure. ETA: Correction, I saw one go down on the line for a gas key issue, which isn't isolated to Mk18s.

Regardless of everything I've read on the internet, our Daniel Defense Mk18s just plain work. "11.5" has 40% more dwell time". Okay. But ours still work just fine, and our duty ammo is still reliable performance out to 110 yards.

Personally I'd go 12.5" if I was choosing an unsuppressed duty rifle, because it's pure sex....but I think the statement that "going shorter than 11.5" in 5.56 isn't smart" is a bit exaggerated.

With that said, this is a PDW thread, and CQBRs are not PDWs....so maybe we should save this conversation for elsewhere.

Well what is the difference outside of the name? What I am seeing is this thread at least are AR Pistols with a short barrel. Is that not a PDW? So regardless if you put a pistol lower or a rifle lower its still a PDW designed to take up the least amount of space and be transportable. A hinged rifle lower would accomplish the same thing as a pistol braced lower wouldnt it?
I think I get the pistol lower because it not stamp required.