9MM AR Lightweight Barrel/Muzzle Device Options

[MikeRush]

I am throwing together a PCC and trying to figure out a light weight barrel setup. I live in a non SBR state so I need to keep OAL to 16+ inches, but I will keep it as close to that length as possible.

I want a 13" handguard so I don't want to dump gas before that length. It seems like there isn't much pressure left for ports or comps at that point.

1. 16" barrel turned down to .625 or so. Could always drill ports if I wanted to.

2. 10.5" (or shorter?) barrel and aluminum sleeve permanently attached to get to 16" oal. I am not currently set up to weld aluminum, so I would probably need to use silver solder.

3. Cut back to 13.x" or 14.x", thread to .685x40, permanently install pistol comp, or thread 5/8x24 and run AR10 comp reamed to appropriate diameter. This is a heavier option, and it doesn't seem likely to provide much benefit. Could also cut/thread, and pin the JP 9mm brake as well.

Thoughts? Ideas? Planning on getting the JP bolt and SCS. Regardless of PCC's future I think it would make a good trainer for my 3 gun carbine- will set it up with same furniture.

[jrswanson1]

You know, 9mm ARs aren't gas operated, they're blow back operated.

[MikeRush]

You know, 9mm ARs aren't gas operated, they're blow back operated.

Yes, I know this.

The dumping gas comment is in reference to having any form of compensation under the handguards. Barrel ports in open guns can work because the pressure is relatively high closer to the chamber.

I found a lightweight profile 16" barrel for $109 that weighs 19 oz so that is on the way- I can always have my AR guy chop and rethread should I decide I want to run a pinned comp at 16" OAL. For now it will get a thread protector and loctite.

[bmiller]

I machined this one last night. It is just a prototype, not the final version. I live in a sbr friendly state, but I like having the 15" handguard. For now I am sticking with a 16" barrel. The brake seems to cut muzzle climb well. I did not get a chance to run that many rounds today. Had some residual tapping fluid in it when I fired it. Most of the smoke was going up and out the sides. Not much straight out.

[Southpaw]

I found a lightweight profile 16" barrel for $109 that weighs 19 oz so that is on the way- I can always have my AR guy chop and rethread should I decide I want to run a pinned comp at 16" OAL. For now it will get a thread protector and loctite.

I'm guessing this is the one you ordered? http://www.joeboboutfitters.com/Kaw_Valley_Precision_16_9MM_4150_QPQ_AR_15_Barrel_p/kvp-9mm-bbl-16-laser.htm

I just put together a PCC with this barrel. I also wanted it as light as possible, but didn't want to deal with NFA stuff. This was the only lightweight profile 16" barrel I could find and I looked pretty hard because they were sold out for a few weeks, but I waited for it to come back in stock since I couldn't find anything else. I haven't shot it yet, but did notice that the chamber is really tight. Rounds that will easily pass my EGW gauge (which is pretty tight) aren't all plunking completely freely into the barrel, but it I think they'll still chamber fine.

[shooterDrew]

I picked up a palmetto state complete upper and added their comp. The gun is very light weight with the 13" rail that it shipped with, but to be honest I barely noticed a difference between the a2 hider and the comp with my production minor loads. The gun is a great shooter

Sent from my iPhone using Tapatalk

[bmiller]

That is the rifle I picked up. So far mine has been accurate and reliable. There is a thread on arf.com talking about the gas key shearing off. It has one bolt vs two compared to others. They said it is attributed to the barrel being chambered too deep and the bolt smashing into the barrel. Mine has some light marks on the barrel where they are contacting. Does anyone have any insight?

[peterthefish]

I picked up a palmetto state complete upper and added their comp. The gun is very light weight with the 13" rail that it shipped with, but to be honest I barely noticed a difference between the a2 hider and the comp with my production minor loads. The gun is a great shooter

That's the upper I have. I was going back and forth on getting a comp, but without it and using my minor loads (more like 140+ PF out of this) it recoils about the same as my compensated .223 - barely. I can't imagine the comp making a big difference.

[MikeRush]

I machined this one last night. It is just a prototype, not the final version. I live in a sbr friendly state, but I like having the 15" handguard. For now I am sticking with a 16" barrel. The brake seems to cut muzzle climb well. I did not get a chance to run that many rounds today. Had some residual tapping fluid in it when I fired it. Most of the smoke was going up and out the sides. Not much straight out.

I like the comp prototype! There are certainly not a lot of "off the shelf" options in 1/2"-36. Always great to be able to problem solve at home.

I found a lightweight profile 16" barrel for $109 that weighs 19 oz so that is on the way- I can always have my AR guy chop and rethread should I decide I want to run a pinned comp at 16" OAL. For now it will get a thread protector and loctite.

I'm guessing this is the one you ordered? http://www.joeboboutfitters.com/Kaw_Valley_Precision_16_9MM_4150_QPQ_AR_15_Barrel_p/kvp-9mm-bbl-16-laser.htm

I just put together a PCC with this barrel. I also wanted it as light as possible, but didn't want to deal with NFA stuff. This was the only lightweight profile 16" barrel I could find and I looked pretty hard because they were sold out for a few weeks, but I waited for it to come back in stock since I couldn't find anything else. I haven't shot it yet, but did notice that the chamber is really tight. Rounds that will easily pass my EGW gauge (which is pretty tight) aren't all plunking completely freely into the barrel, but it I think they'll still chamber fine.

That is indeed the barrel I ordered. I should have it in hand tomorrow, I will drop test some factory and the typical coated lead loads that will be used in it.

That is the rifle I picked up. So far mine has been accurate and reliable. There is a thread on arf.com talking about the gas key shearing off. It has one bolt vs two compared to others. They said it is attributed to the barrel being chambered too deep and the bolt smashing into the barrel. Mine has some light marks on the barrel where they are contacting. Does anyone have any insight?

Does your PSA upper use the colt pattern mags or the Glock ones? Curious if this issue is with the older style or newer "hybrid G9" bolt.

I picked up a palmetto state complete upper and added their comp. The gun is very light weight with the 13" rail that it shipped with, but to be honest I barely noticed a difference between the a2 hider and the comp with my production minor loads. The gun is a great shooter

That's the upper I have. I was going back and forth on getting a comp, but without it and using my minor loads (more like 140+ PF out of this) it recoils about the same as my compensated .223 - barely. I can't imagine the comp making a big difference.

If you don't mind me asking- what buffer are you using with it? In most of the blowback guns I have tried the bolt traveling back and forth seems to account for most of the disruption to the dot or sights. Either way if it feels comparable that is a good thing for those of us using ARs- we haven't really seen yet if the gas or roller guns will prove to be as advantageous as the HK/SIG fans suggest.

After browsing a few of the NFA heavy forums it seems some people feel that a shorter barrel, even with a permanent muzzle device, is preferable to the longer barrels due to pressure in the barrel being released earlier and less gas finding its way into the action and out the ejection port. The problem there in light of the ATF's flip flopping on muzzle devices is coming up with a way to achieve this that isn't excessively heavy or suppressor-like.

I have a friend looking for an upper, so assuming the 16" chamber is in spec I may use that for his build and play with a shorter barrel and permanent muzzle device for comparison. I have a feeling I will probably end up with another 16" anyway (the idea of getting involved with the NFA over a misunderstanding does not appeal to me, perhaps my muzzle device can incorporate lots of holes forward of the handguards?) but I can slap on another barrel in the garage for cheap. If that proves fruitful I may have a smith recreate it in a more professional manner. I appreciate the input- it will be interesting to see how setups might evolve as more people start shooting PCC.

[peterthefish]

I picked up a palmetto state complete upper and added their comp. The gun is very light weight with the 13" rail that it shipped with, but to be honest I barely noticed a difference between the a2 hider and the comp with my production minor loads. The gun is a great shooter

That's the upper I have. I was going back and forth on getting a comp, but without it and using my minor loads (more like 140+ PF out of this) it recoils about the same as my compensated .223 - barely. I can't imagine the comp making a big difference.

If you don't mind me asking- what buffer are you using with it? In most of the blowback guns I have tried the bolt traveling back and forth seems to account for most of the disruption to the dot or sights. Either way if it feels comparable that is a good thing for those of us using ARs- we haven't really seen yet if the gas or roller guns will prove to be as advantageous as the HK/SIG fans suggest.

After browsing a few of the NFA heavy forums it seems some people feel that a shorter barrel, even with a permanent muzzle device, is preferable to the longer barrels due to pressure in the barrel being released earlier and less gas finding its way into the action and out the ejection port. The problem there in light of the ATF's flip flopping on muzzle devices is coming up with a way to achieve this that isn't excessively heavy or suppressor-like.

I have a friend looking for an upper, so assuming the 16" chamber is in spec I may use that for his build and play with a shorter barrel and permanent muzzle device for comparison.

Whatever PSA included in their lower build kit - I think it weighs 4.9 or 5 oz. I have a pistol build too and the 16" recoils softer. I think partly with the extra weight up front. However, when I was first loading for the pistol I used 115s and 124s with slower powders - I was worried about a squib running a faster powder like N320 in a blowback gun. Running 147s w N320 takes away all muzzle blast which just makes it a much more pleasant round to shoot. On the timer my splits are the same at 25 yards with the 9mm and the .223.

[Southpaw]

I found a lightweight profile 16" barrel for $109 that weighs 19 oz so that is on the way- I can always have my AR guy chop and rethread should I decide I want to run a pinned comp at 16" OAL. For now it will get a thread protector and loctite.

I'm guessing this is the one you ordered? http://www.joeboboutfitters.com/Kaw_Valley_Precision_16_9MM_4150_QPQ_AR_15_Barrel_p/kvp-9mm-bbl-16-laser.htm

I just put together a PCC with this barrel. I also wanted it as light as possible, but didn't want to deal with NFA stuff. This was the only lightweight profile 16" barrel I could find and I looked pretty hard because they were sold out for a few weeks, but I waited for it to come back in stock since I couldn't find anything else. I haven't shot it yet, but did notice that the chamber is really tight. Rounds that will easily pass my EGW gauge (which is pretty tight) aren't all plunking completely freely into the barrel, but it I think they'll still chamber fine.

That is indeed the barrel I ordered. I should have it in hand tomorrow, I will drop test some factory and the typical coated lead loads that will be used in it.

When you get it check case protrusion before assembling - drop a round or piece of brass in the chamber and measure how far it sticks out. It should be .135" to get proper headspace. I didn't think to check this before assembling mine and now am having headspacing issues. I'm going to pull the barrel and measure mine; I think the chamber is cut too deep.

[T Bacus]

I found a lightweight profile 16" barrel for $109 that weighs 19 oz so that is on the way- I can always have my AR guy chop and rethread should I decide I want to run a pinned comp at 16" OAL. For now it will get a thread protector and loctite.

I'm guessing this is the one you ordered? http://www.joeboboutfitters.com/Kaw_Valley_Precision_16_9MM_4150_QPQ_AR_15_Barrel_p/kvp-9mm-bbl-16-laser.htm

I just put together a PCC with this barrel. I also wanted it as light as possible, but didn't want to deal with NFA stuff. This was the only lightweight profile 16" barrel I could find and I looked pretty hard because they were sold out for a few weeks, but I waited for it to come back in stock since I couldn't find anything else. I haven't shot it yet, but did notice that the chamber is really tight. Rounds that will easily pass my EGW gauge (which is pretty tight) aren't all plunking completely freely into the barrel, but it I think they'll still chamber fine.

That is indeed the barrel I ordered. I should have it in hand tomorrow, I will drop test some factory and the typical coated lead loads that will be used in it.

When you get it check case protrusion before assembling - drop a round or piece of brass in the chamber and measure how far it sticks out. It should be .135" to get proper headspace. I didn't think to check this before assembling mine and now am having headspacing issues. I'm going to pull the barrel and measure mine; I think the chamber is cut too deep.

Assembled an upper for a friend with this barrel and had lots (like 90%) of lite strike problems because of excessive headspace. I fixed the issue but it would have been nice to not have too. If I recall correctly, case protrusion was around .118. Other than that, it is a really nice barrel and my friend really likes the lightweight profile. The gun handles great with a very light feeling front end.

Edited April 19, 2016 by T Bacus

[T Bacus]

This is the gun. We couldn't send the barrel back because it was cut to 13.5" and had a brake permanently installed. The brake is an Armalite 5.56 opened up to 9mm.

Brake detail

Edited April 19, 2016 by T Bacus

[MikeRush]

I found a lightweight profile 16" barrel for $109 that weighs 19 oz so that is on the way- I can always have my AR guy chop and rethread should I decide I want to run a pinned comp at 16" OAL. For now it will get a thread protector and loctite.

I'm guessing this is the one you ordered? http://www.joeboboutfitters.com/Kaw_Valley_Precision_16_9MM_4150_QPQ_AR_15_Barrel_p/kvp-9mm-bbl-16-laser.htm

I just put together a PCC with this barrel. I also wanted it as light as possible, but didn't want to deal with NFA stuff. This was the only lightweight profile 16" barrel I could find and I looked pretty hard because they were sold out for a few weeks, but I waited for it to come back in stock since I couldn't find anything else. I haven't shot it yet, but did notice that the chamber is really tight. Rounds that will easily pass my EGW gauge (which is pretty tight) aren't all plunking completely freely into the barrel, but it I think they'll still chamber fine.

That is indeed the barrel I ordered. I should have it in hand tomorrow, I will drop test some factory and the typical coated lead loads that will be used in it.

When you get it check case protrusion before assembling - drop a round or piece of brass in the chamber and measure how far it sticks out. It should be .135" to get proper headspace. I didn't think to check this before assembling mine and now am having headspacing issues. I'm going to pull the barrel and measure mine; I think the chamber is cut too deep.

Assembled an upper for a friend with this barrel and had lots (like 90%) of lite strike problems because of excessive headspace. I fixed the issue but it would have been nice to not have too. If I recall correctly, case protrusion was around .118. Other than that, it is a really nice barrel and my friend really likes the lightweight profile. The gun handles great with a very light feeling front end.

Carbine looks great- how did you end up fixing the light strikes? Bolt/firing pin mods, or ?

I will measure protrusion on mine tonight.

[MarkCO]

You can make a comp work, but you will be looking at 140PF, slower powders and some tweaking. Not sure if it off with the effort or not. I do like my 90s at 1950 and a comp helps.

[bmiller]

1950? Holy crap, I thought I was on the edge at 1580 with 105 grain bullets. What powder are you using?

Edited April 19, 2016 by bmiller

[MikeRush]

I suppose the other limiting factor is the proposed ruleset's 1600 fps limit. I was thinking more along the lines of a 124 or 135 loaded to around 135 PF with fast powders. It would be great to be able to take advantage of the pressure near the chamber but I don't like the idea of having body parts forward of ports.

I have some 115s, 124s, 135s, 147s and 158s on hand that I can test. Will have to run those with timer and chrono once I get my PCC running.

[T Bacus]

I milled .011" off the front of the bolt. Headspace is still a little deep but it ignites 100% now. Not the best way to fix it, but the best way I had with the tools at hand.

[MarkCO]

1950? Holy crap, I thought I was on the edge at 1580 with 105 grain bullets. What powder are you using?

WAP, AA#7, 800x. I am loading in the +P range with new +P+ stamped brass and pressure transducers, so I am not providing load data.

The DoubleTap 115+P runs right at 1600 in my 16".

[bmiller]

No problem, want to stay under 1600 for USPSA anyways. Is the recoil sharp and heavier?

[MarkCO]

No problem, want to stay under 1600 for USPSA anyways. Is the recoil sharp and heavier?

You know it is not 140PF, which is where I plan to run for USPSA. I would not call it sharp, but it is more recoil.

[bmiller]

I thought uspsa has a 1600 fps ceiling on velocity for pcc?

[MarkCO]

I thought uspsa has a 1600 fps ceiling on velocity for pcc?

I believe that is correct. There are however other uses for a PCC than just competition, even if we are not allowed to talk about them.

[MikeRush]

I milled .011" off the front of the bolt. Headspace is still a little deep but it ignites 100% now. Not the best way to fix it, but the best way I had with the tools at hand.

I tried a couple of makes of factory ammo- looks like .125 to .1285. I have a bolt coming, I will go ahead and assemble it and see what it looks like from underneath with the bolt forward and a cartridge in the chamber.

[T Bacus]

I milled .011" off the front of the bolt. Headspace is still a little deep but it ignites 100% now. Not the best way to fix it, but the best way I had with the tools at hand.

I tried a couple of makes of factory ammo- looks like .125 to .1285. I have a bolt coming, I will go ahead and assemble it and see what it looks like from underneath with the bolt forward and a cartridge in the chamber.

Holding the barrel vertical with a case in the chamber, slowly press the bolt down against the barrel. If the case snaps under the extractor you should be alright.