Optimum Caliber for an AR based PDW.

[nortac]

@OkieStubble , do you think that the recoil from a 7.5 in. 5.56/.223 barrel would be much different than that of an 11.5 in. barrel? Muzzle blast certainly would be increased. The weapon would be somewhat lighter due to the shorter barrel and perhaps recoil a bit more, but would it be that significant? While I have some learning to do to get the level of control that I want with my longer barreled AR pistol, I feel that can be reasonably achieved.

As far as getting a P 90 or a Rattler or some other non-AR, if you find you don't like it, you're stuck selling it at a loss. If your AR build doesn't please you, you can rebuild it/swap components until it does.

 

[OkieStubble]

@OkieStubble , do you think that the recoil from a 7.5 in. 5.56/.223 barrel would be much different than that of an 11.5 in. barrel? Muzzle blast certainly would be increased.

I don’t think there is that much of a huge difference in recoil of a 7.5 versus a 11.5 in a .556 shouldered AR pistol.

And since we are speaking on it being cheek welded and not shouldered fired, let’s just consider these next few questions from only a ‘shouldered’ fired perspective.

1. I’ve shot in the past shorter and longer barreled AR’s in .556 and other calibers many times. The differences in recoil were all manageable. Yes, muzzle blast is much more obvious with shorter barrels, but also, muzzle rise and flip. All muzzles rise when fired, but the muzzle flip of shorter barrels are faster and much more aggressive then longer barrels.

These are things that most who will read this thread or post, already know. Yes, one can train to manage any one of these things.

But the challenge isn’t going to be training to manage any one of these things. The challenge is going to be training to manage all three of these things 1. Recoil 2. Muzzle Flip 3. Muzzle Blast and 4. Getting the barrel back on target effectively and speedily.

I know you know this already also. I’m not trying to debate not trying it with a .556 or 9mm, again, not from a shoulder but from the cheek.

But this thread’s title was what we thought the best caliber would be? Just because you can reload .556, 9mm, or .300 BO might make them the most obvious to choose from caliber’s, still doesn’t negate the consideration of the 5.7. Just saying.

Think about it…. A .300 BO from a 7.5 or less is being considered running & gunning from ‘the cheek’ over a 5.7 because it can be reloaded?

If one can be serious enough to stock up on hard to find reloading components, one can get serious enough to stock up on 5.7 ammunition?

This project sounds like it is going to be a very specialized, ‘niche pistol’ with a ‘niche set up’ and used for a specialized ‘niche purposes and ‘niche skill set.

Why not load it with ‘niche ammo’? Which will make your ‘niche AR pistol’ come alive? Rock & Roll? Separate itself from “all the other “typical calibered” AR rifles, SBR’s and pistols you already own?

Who cares you can’t reload 5.7? It’s a ‘niche’ pistol? For a specific ‘niche purpose?’

If ever used in ‘real life’ one can consider in the big picture of things, this niche pistol could be a throw away gun? If it ever was needed to pull you out of the fire only once over the course of your 5.7 supply? Throw it away and consider it an valuable investment and it served its purposes admirably.

If you don’t never need to deploy it? Have fun shooting it with the freedom to always acquire more 5.7 ammo for the store closet.

All I’m attempting to point out here, is, this is an exciting new build and training venture you are setting out upon. And I’m here ready to read it all regardless of what caliber you choose and decide.

I just see an opportunity to not be redundant with calibers and rifles and SBR’s and AR Pistols you already have and own. If someone already has ATF paperwork on any particular build? Or muzzle device? What’s one more form? They only ever needed one to find you?
But they like redundancy.

If you already have lots of builds you can ‘reload’ for? What’s one more build that you can’t reload for?

You only need one? Why be redundant? You can’t own one because you can’t reload for it?

As far as getting a P 90 or a Rattler or some other non-AR, if you find you don't like it, you're stuck selling it at a loss. If your AR build doesn't please you, you can rebuild it/swap components until it does.

Have a hard time selling a P90 or Rattler? Really?

 

[nortac]

@OkieStubble, you make some very valid points. If and when I build this compact PDW AR pistol, overtime I will probably have a few uppers in different calibers to go on it. So, if I have an upper in a caliber that's easy to reload for, I'll probably train with it more. You are absolutely correct that I could have the 5.7x28 and just not reload for it. Why the hell not, it's only money. But my income post-retirement is much more limited than it was during the past couple of years of my AR building spree. I've pretty much decided to initially build a .223 upper. Of course, that is subject to change.

I've never fired a 6.8 SPC, but I assume its recoil is similar to .223? What do you, or anyone else, think of that round in a short barrel?

As for selling a P90 or Rattler, no, I don't think that they would be hard to sell, but I imagine that you would sell them at a loss? Besides, I don't want one of them, can't afford them, and as previously mentioned, don't want any SBR nonsense going on, at least during the current administration. As for already having a tax stamp on record, mine are only for suppressors and SO FAR, they aren't making any efforts to take them at the moment. All of my AR pistols were built by me and all the 4473 says is that I purchased a stripped lower.

 

[OkieStubble]

I’m not here to debate your common sense post of what you want, think or need for your individual goals for this thread. Your OP title said ‘Optimum Caliber’.

5.7 isn’t ‘practical’. But ‘Practical’ wasn’t in the thread title? . But if you really meant the word ‘Optimum’?

Well, my perception of the word Optimum, relates to pure performance in ‘purpose of use’ (POU’s) you intended, not the practicalities of switching parts or ease of reloading?

Why? Well, simply because practical mess of caliber wasn’t mentioned in the title.

However, when considering POU’s? I would even argue or suggest the 5.7 would be more effective and practical in the purpose of use rolls over all other calibers mentioned. Small barrel? Shooting from the cheek? Short distances? Fast target acquisition, follow ups and moving and engaging with speed and surgical accuracy?

My vote is the 5.7x28 over all others mentioned and I’m sticking to that opinion.

Regardless of the practicalities of switching uppers, parts or reloading be dammed. But you know me, I’m an odd individual.

If you would like to reconsider a title change to practical instead of optimal?

I will change my answer to 9mm. Still considering the exact same POU’s.

 

[nortac]

@OkieStubble, While I can concede your argument of "optimal" vs. "practical", practicality still plays a large role for me. But even if the thread title were to change, what does a 9mm, short-barreled AR that can't be shouldered have over a conventional 9mm pistol? You can buy a damn nice hi-cap 9mm conventional pistol for what the AR PDW would cost. As usual, these threads tend to veer off track as new options are considered. And that's a good thing.

 

[OkieStubble]

@OkieStubble, While I can concede your argument of "optimal" vs. "practical", practicality still plays a large role for me.

I don't know if I would call it "my argument" Since I was simply responding to the optimal thread title, I have garnered that your optimal, possibly meant practical. That's why it makes me curious as the reasons of the use of the word optimal and not practical in your thread title. Your posts covered 'practical' quite a bit, inspite of the 'optimal' description in your title. Definitely can throw a loop in the responses from others you might expect?

Just in case you didn't realize; I was expecting to talk optimum... Hence the 5.7X28... Surprise!

But even if the thread title were to change, what does a 9mm, short-barreled AR that can't be shouldered have over a conventional 9mm pistol? You can buy a damn nice hi-cap 9mm conventional pistol for what the AR PDW would cost. As usual, these threads tend to veer off track as new options are considered. And that's a good thing.

Well, while I have never cheek fired a 9mm AR pistol, Common sense would tell me,

1. There would be a velocity advantage with a 7.5 inch barrel vs. a 4 inch 9mm barrel.

2. There would be a greater consistency in the expansion of 9mm HP bullets because of the increased velocity from a longer AR pistol's barrel over a 4" handgun.

3. Greater accuracy and handling would be achieved or at least assumed, because of:

A. Increased sight radius if using iron sights.
B. Increased stability due to 4 points of contact with an AR pistol ie; two hands, cheek and sling vs. only two points of contact with a handgun.
C. Greater firepower and magazine capacity, unless both AR & handgun are accepting Glock 30 round magazines.

 

[OkieStubble]

Thread Title:

Optimum Caliber for an AR based PDW.​

Original Post:

If you were going to build the most compact PDW based on the AR platform, what do you think the most practical caliber would be for SD/HD use, vehicle defense, etc. Not just a range toy, but for serious purposes. Would you consider a binary trigger?

I love you like a brother... But you really got to stop moving the goalposts?

 

[nortac]

Mea culpa, I guess I did move the goal post. My original intent in asking for opinions on the optimal caliber was more a question of terminal performance available from a short barrel that also is controllable in a small form factor. A secondary consideration would be the availability of ammo.

 

[nortac]

Just the CMMG barrel and BCG combo in 5.7x28 is a bit pricy, almost twice the cost of a .223 barrel and BCG. But the rave reviews can't be denied. Assuming I do build this PDW, which is almost a foregone conclusion, a 5.7x28 upper will be the second upper that I build for it as soon as I can afford to do so. Initially it will be a .223 project. That in itself will be a slow process of accumulating parts.

 

[HDSledge]

I have a Ballistic Advantage 8" barrel with a flash can. I've only shot 40 rounds through it because there wasn't a lot of ammo available when I put it together.

View attachment 1621251

I also have a 4.5" Faxon 9mm barrel. I bought it as a BCG, barrel set. It would be very compact if I didn't have a 12" suppressor hanging off the end of it.

Have you thought about a 458 Socom? I worked with Tony Rumore (Tromix) about 20 years ago and he fixt me up with a 10.5" barrel when they first came out. Back then it was hard to find ammo and I didn't want to reload so I traded it off. That's a pretty hard hitting round.

I see the bullet hose mark for the selector. You have a rdias?

 

[Mlee]

I see the bullet hose mark for the selector. You have a rdias?

No, I wish I did, although with ammo prices, I probably wouldn't use it. It's a Spikes Tactical lower that I picked up at a gun show about 10 years ago.

I had an opportunity to buy a rdias about 20 years ago for $3000. I hate to ask but what are they going for now?

 

[OkieStubble]

Just the CMMG barrel and BCG combo in 5.7x28 is a bit pricy, almost twice the cost of a .223 barrel and BCG. But the rave reviews can't be denied. Assuming I do build this PDW, which is almost a foregone conclusion, a 5.7x28 upper will be the second upper that I build for it as soon as I can afford to do so. Initially it will be a .223 project. That in itself will be a slow process of accumulating parts.

Lol’d! Waaaa! Quit crying. . I too Am on a retirement budget and saving for thermal to put on top of a bolt action in 6.5 Grendel at around a 8K price tag!

Go big or go home! We are gun guys? It’s what we do?

 

[OkieStubble]

Just the CMMG barrel and BCG combo in 5.7x28 is a bit pricy, almost twice the cost of a .223 barrel and BCG. But the rave reviews can’t be denied.

See? You do get it…. This is what we always hunt, seek and chase after.

It’s just money after all. It’s not like we can take it with us.

 

[nortac]

Lol’d! Waaaa! Quit crying. . I too Am on a retirement budget and saving for thermal to put on top of a bolt action in 6.5 Grendel at around a 8K price tag!

Go big or go home! We are gun guys? It’s what we do?

See? You do get it…. This is what we always hunt, seek and chase after.

It’s just money after all. It’s not like we can take it with us.

Just trying to maintain marital harmony and avoid being put to the curb by SWMBO! Incremental spending under the radar. Once the basic .223 PDW is completed, then splurge for the 5.7 kit! Still paying off my last upper build and buffer tubes, optics, etc. A few months to go before I can buy new stuff. Might start hording some 5.7x28 ammo in the meantime. I have a few extra pieces parts on hand, got to put them to use eventually.

 

[OkieStubble]

Just trying to maintain marital harmony and avoid being put to the curb by SWMBO! Incremental spending under the radar. Once the basic .223 PDW is completed, then splurge for the 5.7 kit! Still paying off my last upper build and buffer tubes, optics, etc. A few months to go before I can buy new stuff. Might start hording some 5.7x28 ammo in the meantime. I have a few extra pieces parts on hand, got to put them to use eventually.

And you’ll need a sidearm in matching caliber…. Don’t forget.

Man I love this place.

 

[nortac]

I won't spend the money on an FN 5.7 pistol, other guns I want way more and I'm not thrilled with the thought of any Ruger semiauto pistol other than their .22LRs.

 

[OkieStubble]

I won't spend the money on an FN 5.7 pistol, other guns I want way more and I'm not thrilled with the thought of any Ruger semiauto pistol other than their .22LRs.

I bet if you went and rented a FN 5.7 and tried it out, you would change your mind and at least consider it long enough the pause would be noticeable….

 

[nortac]

I bet if you went and rented a FN 5.7 and tried it out, you would change your mind and at least consider it long enough the pause would be noticeable….

You buy one and give us a write up, then I might consider it, maybe... Reading a review on the Ruger 57 showed poor accuracy and a mushy trigger with a slow reset...kinda defeats the whole purpose of shooting the 5.7

 

[nortac]

Back to reality, sort of...while I was considering a LaRue trigger for the PDW build, I was thinking that a TriggerTech Adaptable might be appropriate given it's zero creep and rapid reset, it would be very conducive to rapid follow up shots. It is also adjustable up to a safe defensive trigger pull weight. If for some reason it seemed too light, I wouldn't have any problem putting it in another AR that I already have.

 

[HDSledge]

No, I wish I did, although with ammo prices, I probably wouldn't use it. It's a Spikes Tactical lower that I picked up at a gun show about 10 years ago.

I had an opportunity to buy a rdias about 20 years ago for $3000. I hate to ask but what are they going for now?

>$40,000. Have not seen one for sale in a while. Could be more.