XCR Forum banner
41 - 60 of 83 Posts

·
Registered
Joined
·
212 Posts
What xcr/barrel combos are considered low gas that you would want to move the piston?
Hell, I don't know. I've never designed moving parts before. I'm coming at this like a monkey with a rock.

I'm glad you brought this up though because I have been thinking about the XCR-P lately. RA seems to have made the XCR a long stroke and a short stroke piston system before, and I suspect they will try to make the XCR-P a long stroke piston gas system. The thing about the Sig MPX is that the placement of the short stroke piston basically makes it a direct impingement gas system kind of in the same way the AR-15 is, thus making the internals as gassy and dirty as it is. I was hoping RA would be able to do this with the gas block away from the chamber and not get gas into the upper, but what I'm seeing so far is that there isn't much difference in terms of gas port location between short- or long- stroke piston designs. I'm putting a lot of trust in Sig's engineering on this, and it seems the best place to get gas to cycle on a semi-auto 9mm cartridge is right on the damn barrel extension.

The gas port location on the .300 BLK Micro barrel is the shortest gas length that I know of on the XCR and I don't think that's short enough, it's like 5 inches from the chamber. I also don't know if the lugs on the XCR's bolt would create enough timing to allow for gas to build up in the barrel and produce enough pressure to push the piston to the system can cycle. I also don't know what kind of pressure would be coming out of that gas port and how much is needed to push the piston to cycle the system. My hope is that a good port location is about 1/2 inch in front of the taper on the barrel, just after the chamber ends; so a gas dial can be reasonably reachable and so there is enough length to put gas vents so less gas can get inside the upper.

What we really need is an engineer to figure out the math to find this stuff out; I wouldn't know where to begin. If I had to do it, it would be a lot of trial and error with a 5.56 bolt and extractor modified for 9mm, a 9mm barrel blank with XCR-L barrel extension, a welder and a machine to make lots of pistons. I'm reminded by the R&D work CMMG put into the Banshee before it came out: they went through several interations of a gas cycling system that became increasingly impractical before they went with the radial delay blowback system with the bolt. I'm taking that story to heart, as I'm seeing how challenging it could be to figure out a gas cycling system on a 9mm PCC. For that matter, I'm not sure if Robinson Arms knows or even has plans drawn. How long have we been waiting for an XCR-P? Since 2015? An engineer worth his salt would have had that figured out in a year or so and production could go on. I'm starting to suspect that it's an idea that isn't on any drawing board yet.
 

·
Registered
Joined
·
53 Posts
Monkey with a rock LOL I would go the delayed system somehow. Much simpler than a gas system. I have a few 9mm pcc and the only one that's smooth at all is the cmmg i put together with the barrel/bolt combo they used to have for sale. I'd say it's on par with the mpx or VERY close. Way close enough to justify saving almost half the cost.....
 

·
Registered
Joined
·
212 Posts
Monkey with a rock LOL I would go the delayed system somehow. Much simpler than a gas system. I have a few 9mm pcc and the only one that's smooth at all is the cmmg i put together with the barrel/bolt combo they used to have for sale. I'd say it's on par with the mpx or VERY close. Way close enough to justify saving almost half the cost.....
That's fascinating. I wish I knew someone who was a ballistics engineer, then I could have a better idea how a gas-operated PCC would work in more specific terms. It sounds like direct blowback, even for something like 10mm Auto, is smooth shooting in a PCC/subgun size-rifle. It's been awfully telling how large companies like CZ, CMMG and KRISS, with all their R&D budgets and time, have seen fit to come out with blowback guns for their 9 and 10mm guns, respectively. Considering the engineering and mechanical issues that Sig saw with the MPX, maybe going gas-operated with rounds that have such little gas volume isn't the best idea?
 

·
Registered
Joined
·
53 Posts
That's fascinating. I wish I knew someone who was a ballistics engineer, then I could have a better idea how a gas-operated PCC would work in more specific terms. It sounds like direct blowback, even for something like 10mm Auto, is smooth shooting in a PCC/subgun size-rifle. It's been awfully telling how large companies like CZ, CMMG and KRISS, with all their R&D budgets and time, have seen fit to come out with blowback guns for their 9 and 10mm guns, respectively. Considering the engineering and mechanical issues that Sig saw with the MPX, maybe going gas-operated with rounds that have such little gas volume isn't the best idea?
The gas system is exactly like the Mcx except the port is right off the chamber for the pressure needed to run the short strike piston. Same basic design as any short stroke piston system out there with some minor technical differences I assume because of the pressure difference.
 

·
Registered
Joined
·
212 Posts
I'm THIS level of giddy right now:


I was beginning to think that I was going to have to design the whole damn thing on my own, that's why I put so much head space on it.

Anyway, I hope that with metal construction, they can make the -P low profile and small. As I'm starting to see with the Scorpion and other blowback PCCs, they are pretty thick and are ballooning in size for something that fires a small pistol caliber. I hope it's something tactical and gives the MP5 a run for it's money.
 

·
Registered
Joined
·
564 Posts
It needs to be light AF and small AF to compete.

I’d love to see something like that Diamond back 5.7 size.

I’ve never understood those giant PCCs.


It better take an existing mag that magpul makes too. Glock or Scorpion

Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
23,125 Posts
It needs to be light AF and small AF to compete.

I’d love to see something like that Diamond back 5.7 size.

I’ve never understood those giant PCCs.


It better take an existing mag that magpul makes too. Glock or Scorpion

Sent from my iPhone using Tapatalk
Too bad they didn't go Scorpion for the 9mm. I get why they went Glock for the other calibers though....
 

·
Registered
Joined
·
564 Posts
Too bad they didn't go Scorpion for the 9mm. I get why they went Glock for the other calibers though....
Glock is convenient, so I also get it as well. It’s also nice to match your side arm.

Furthermore, it means less mags most potential buyers will have to buy. I’ve certainly not bought a gun before solely due to proprietary magazines.

Having said that, Glock mags are just not aesthetically pleasing in a PCC, and I’m tired of pretending aesthetics don’t matter.

If they didn’t matter the Nissan Leaf would have been the most popular car on the planet.

I just hope it’s light and compact though.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
23,125 Posts
Glock is convenient, so I also get it as well. It’s also nice to match your side arm.

Furthermore, it means less mags most potential buyers will have to buy. I’ve certainly not bought a gun before solely due to proprietary magazines.

Having said that, Glock mags are just not aesthetically pleasing in a PCC, and I’m tired of pretending aesthetics don’t matter.

If they didn’t matter the Nissan Leaf would have been the most popular car on the planet.

I just hope it’s light and compact though.


Sent from my iPhone using Tapatalk
Agreed on all points.

I'd wager 50% of 'gun guys' own at least one Glock....

Though with the price of PSA AK-V/Scorpion and Magpul Scorpion mags....it's hard to argue that people wouldn't buy in due to the price of mags.
 
  • Like
Reactions: willpgn

·
Super Moderator
Joined
·
296 Posts
So how will they handle 9mm/357sig/40 magazine dimensions vs 45/10mm? Magwell insert?

Personally I'd like to see something that could be changed between 9/10mm, those are my primary pistol rounds and other than something like 45 super/rowland are kind of min-max for semi auto pistols.
 

·
Registered
Joined
·
23,125 Posts
So how will they handle 9mm/357sig/40 magazine dimensions vs 45/10mm? Magwell insert?

Personally I'd like to see something that could be changed between 9/10mm, those are my primary pistol rounds and other than something like 45 super/rowland are kind of min-max for semi auto pistols.
I wonder the same.
 

·
Registered
Joined
·
564 Posts
Agreed on all points.

I'd wager 50% of 'gun guys' own at least one Glock....

Though with the price of PSA AK-V/Scorpion and Magpul Scorpion mags....it's hard to argue that people wouldn't buy in due to the price of mags.
The Scorpion has had such a huge following though. Even more so once Magpul adopted a pmag version. I think that’s what makes the difference. Once magpul enters the chat, it’s a go for folks on the fence.

But I digress.

I’m still adamant that what ever RA comes out with, it needs to be light and small.

That’s their biggest hindrance from wide spread adoption on the XCR if you ask me. Yes being a small company is a factor for parts availability. But if it was MCX weight, it would be a hard argument.

(Shakes fist in air) You hear me RA! Make it light!


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
23,125 Posts
The Scorpion has had such a huge following though. Even more so once Magpul adopted a pmag version. I think that’s what makes the difference. Once magpul enters the chat, it’s a go for folks on the fence.

But I digress.

I’m still adamant that what ever RA comes out with, it needs to be light and small.

That’s their biggest hindrance from wide spread adoption on the XCR if you ask me. Yes being a small company is a factor for parts availability. But if it was MCX weight, it would be a hard argument.

(Shakes fist in air) You hear me RA! Make it light!


Sent from my iPhone using Tapatalk
Agree. The weight is the biggest drawback to the XCR....but I'm not sure I'd want to give up durability for the lighter weight personally.

Since RA hates Magpul, I wonder if that would factor in as well.
 

·
Registered
Joined
·
564 Posts
I guess the new mlok upper on the L is lighter
I thought that as well but someone recently said that it’s not.

I don’t imagine the difference, if any, is by any means significant though.

MLOK seems to be the standard now wether RA likes it or not. It’s near impossible to find any new mount or grip that’s keymod now.


Sent from my iPad using Tapatalk
 

·
Registered
Joined
·
257 Posts
Regarding Scorpion mags, I believe the new S3 involved changes to the mag design, and the company will be phasing out the S1. Note that the positions for mag release and bolt catch/release on the S3 more closely resemble the XCR now. Anyhow, it’s seems that the future of scorpion magazines is now up in the air, but I do like the idea of using scorpion magazines since some may be drawn to upgrade to XCR-P if they can use the same magazines. My sense, though, is that RA will use Glock mags.

I’ll be happy if the XCR-P can readily swap between 9mm and 10mm, although .45 ACP could be fun as well.
 

·
Registered
Joined
·
23,125 Posts
I thought that as well but someone recently said that it’s not.

I don’t imagine the difference, if any, is by any means significant though.

MLOK seems to be the standard now wether RA likes it or not. It’s near impossible to find any new mount or grip that’s keymod now.


Sent from my iPad using Tapatalk
Yup....too bad too. MLok sux. KM needed bigger hardware (10-32 like MLok) and slightly thicker handguards. Once Crane picked it; it was over.
 

·
Registered
Joined
·
23,125 Posts
Regarding Scorpion mags, I believe the new S3 involved changes to the mag design, and the company will be phasing out the S1. Note that the positions for mag release and bolt catch/release on the S3 more closely resemble the XCR now. Anyhow, it’s seems that the future of scorpion magazines is now up in the air, but I do like the idea of using scorpion magazines since some may be drawn to upgrade to XCR-P if they can use the same magazines. My sense, though, is that RA will use Glock mags.

I’ll be happy if the XCR-P can readily swap between 9mm and 10mm, although .45 ACP could be fun as well.
RA has already said Glock mags....I doubt that's changed.
 
  • Like
Reactions: Northern

·
Registered
Joined
·
212 Posts
It needs to be light AF and small AF to compete.

I’d love to see something like that Diamond back 5.7 size.

I’ve never understood those giant PCCs.


It better take an existing mag that magpul makes too. Glock or Scorpion

Sent from my iPhone using Tapatalk
I feel like a long-stroke piston-operated PCC like the -P will be the last true innovation in civilian firearms for some time until directed energy weapons become a thing in the future. I mean, we can have our pick of just about anything with any form factor under the sun these days, what's left?

Anyway, considering RA's penchant for low-profile, all-metal designs, I'm imagining the -P to look like an Americanized Stribog SP9.


If they can make the gun as small as possible and make it completely ambi (looking at you, charging handle) I think the -P can be competitive with the glut of PCCs out there now. Not looking forward to waiting half a decade for two revisions of this gun to come out though.
 
41 - 60 of 83 Posts
Top