AR9 16" PCC with absolutely no accuracy.

[ajn1963]

You may have read my response in the "Is a PCC worth it".  I have a AR9 build with a 16" barrel.  It has no accuracy and best I can get is a scatter at 25 yards, and completely wild at 50 and 100 yards.  I have tried different ammo, reloads, and cannot get any accuracy to even get any sort of a zero.

 

I tried everything including a different 16" barrel.  And same results.  Before the brace ban it had a 10" barrel that shot anything with consistent accuracy out to 100 yards but would not feed reliably. 

 

For what I spent on this gun I could have bought a Sig MPX PCC. 

 

My last recourse and I don't know if it is worth the time and expense is to try to work up a load.  I typically load 9mm in 124g Hornady JRN with HS-6 or CFE which shot with great accuracy on the 10" barrel but at 50 yards on the 16" I got a scattering of a five shots all over about 24" wide. 

 

Would it be worth the additional aggravation to try to working and find a load?  I prefer 124 as that is what I shoot in my Glock 19 and Sig M17?  Otherwise I am already pricing out just scrapping this gun and buying a S&W Response. I am out of wit and money with this. 

 

 

[Joe4d]

well as your 10 " set up shot well, and 2 16's arnt,,, what else did you change ? Whats going on with the gas system ? Is it unlocking inconsistently ? What about the muzzle device ? Same on all 3 barrels ?  any sign of bullets hitting it ?
A taylored reload might take your groups down a bit, but if its that bad it isnt gonna help that much.. 
are the 2 16" barrels from the same source ? 

[ajn1963]

I forgot to mention I tried three different bolts.  The first barrel was a generic, I complained, they sent me another barrel, no luck I got a refund, then I bought a Spike's Tactical 16" barrel with the logic of spending more on a barrel it would be more accurate and no luck.  10" had no accuracy issues and could use different weights, manufacturers, loads ect.  It is blowback, so I can't see it being a gas issue.  I know 9mm is not know for accuracy and long range, but I have no other ideas as to what to do other than trying to workup and find a load.  9mm I usually pick a charge weight and dump seat and crimp.  But I am use to do that for my Highpower 77 and 80 grain match loads Audette method ladder testing, so I can do it if that is what it takes.

Edited December 29, 2023 by ajn1963
correction

[GrumpyOne]

You might not be pushing them fast enough to stabilize them. Worth a shot. Up the PF.

[Joe4d]

its blowback,, your bolt is opening before the bullet is leaving the barrel, and moving things around,, in the 10 set up bullet was gone before it opened... Go to a heavier buffer or stronger spring,, see what happens. 
 

[ajn1963]

I thought I would have to lower them I push about 1200 on my 9mm loads, but I have room to grow.  I will give that a shot.  Blazer 115,124 don't work, AE 124 don't work.  I think my 124s I load 5.1 or 5.6 of CFE.  I will have to check got my logs squirreled away.  I was thinking of laddering up a load to see what I get.  I am ready to just scrap this gun. 

[ajn1963]

1 minute ago, Joe4d said:

its blowback,, your bolt is opening before the bullet is leaving the barrel, and moving things around,, in the 10 set up bullet was gone before it opened... Go to a heavier buffer or stronger spring,, see what happens. 
 

Okay, I have a KAK heavy 9mm buffer.  I will have to look up the invoice to see what spring I got for it.

[ajn1963]

10 minutes ago, Joe4d said:

its blowback,, your bolt is opening before the bullet is leaving the barrel, and moving things around,, in the 10 set up bullet was gone before it opened... Go to a heavier buffer or stronger spring,, see what happens. 
 

I will inquire with KAK and see if a heavier spring is available.  This money pit of a gun runs very deep.

[Joe4d]

any way to add more weight ? maybe a stack of quarters ?

[ajn1963]

Just got back from the range with some even different ammo.  No luck, I tried 147g.  I am looking into a new spring as I know I have the heaviest buffer, I guess my option is to make some more potent 9mm.  

[mpeltier]

Are you running an optic? what optic? have you eliminated this as a problem by trying another sighting system?

[Runswithwood1]

I had a similar issue as well, tried numerous different loads and red dots and garbage was still around 5in groups at 25 yards off a rest. Swapped the brand new barrel out for a slightly used one and problem went away. Insane to me a brand new anything could be the issue but it sure was

[zzt]

Here are some things I would check before I scrapped the gun.  First, check your comp for bullet strikes.  Jacketed ammo is going to lead up your comp.  Bullets may hit the lead buildup.

 

Try different mags.  I had issues with Glock mags in my PCC.  ETS mags sit higher in my gun and feed 100%.  The rounds go straight into the chamber without hitting the chamfer surrounding the chamfer.  That's where bullets hit with Glock mags.

 

Try a different powder.  N320, AA2 or Sport Pistol should do the trick.  You will get a much better burn, and accuracy should improve.

 

Try a different brand of bullet.   I only use JHPs or plated bullets in my PCC.  No leading issues and accuracy is great.  Offhand I can put all the rounds in a 2" circle at 25 yards as fast as I can pull the trigger.

[ajn1963]

Thank you all for the replies.  So I will try to respond and address all the advice.

I have a Vortex Spitfire red dot, and I also swapped out for a cheap Aimsports 4x compact scope.  No difference.

I typically use HS-6, CFE Pistol or Bullseye for my 9mm loads.   I would say my loads are typically 1100-1200 fps.  I have not chrono'd them through this gun.  I am tempted not to do that as I don't want to shoot my Chrony if things are that off. 

I have a standard A2 birdcage for a flash hider.  I don't see any build up, I hardly have any residue and fired less than 200 rds through this barrel.  And just recently cleaned it.

 

I put my Magpul bipod on yesterday tried some completely different ammo I made with 147 grains/CFE Pistol and 124gr/Bullseye.  No groups all random scattered holes on the target at 50yds. 

 

As for the feed problem I fixed that by bending the LRBHO wire up and taking tension off the follower.  Gun always fired fine until the last round in the mag which got pushed straight into the chamber face smashing the round.  I used this gun in unsanctioned NRA ARC matches for both rifle and  2 gun variants we run which I use my G19 and liked having same cartridge and mags.  Two stages there is steel out a 100 yds which I rang perfectly with the 10" barrel, but sighing beyond 25 yards is not possible with the 16" barrel.   I have not used the gun with this new barrel in a competition yet but I know on the practice range that after sighting in best I could at 25 then using Strelok Pro to calc the come up to 100yds, I could not ring the steel plate and on paper the group size was scatter over 24". 

 

So I am going to ladder out some 9mm, I have No.2 Titegroup and Unique I have not tried yet.  The bullets I use are 124gr Hornady seconds I get from MidwayUSA,  in my Glock 19 and Sig M17 from a rest I easily put a three rd group in the X ring constently.  My Glock 19 is my ECW and I use it for Outlaw Steel Challenge and NRA ARC 2 gun competition along with my M17.  I know these bullets despite being seconds are dead on from my Glock and Sig that have respectively Trijicon and Leupold Delta Point Pro dots.  I bought some Berry's 115 RN to try also.  I have 124 Berry FP which do not feed at all in this gun to try.  

 

I use the Audette method to ladder my Highpower match loads for 69g, 77g and 80g 5.56 loads which I live and die by at Camp Perry,  so I can try to ladder out some new loads and see if that makes a difference.  The two barrels I sent back the vendor stated after receiving the barrel back he put five rounds under 2" at 50 yards, however he machined a lug off the BCG and the gun would not extract, after fighting with him he returned all my monies and sent me an unmachined replacement BCG.   I had two different people put the barrels on the upper, and I tried three different BCGs and no improvement in accuracy. 

 

If there is no other solution, my only hope is that the pistol brace ban gets killed and I go back to the 10" barrel which I liked better anyhow.   I spent way too much money on this gun that I tried to keep under $800 in total and sorry to keep repeating myself, could have bought the Sig MPX PCC, which I would have but was not available back in 2021 when I need a PCC for comp.  Seems like feed and accuracy problems are common and inherent is AR9 builds, and no clear cut answers or solutions.  I tried to sell this gun at our Flea Market at the club and absolutely no interest with a price to sell.

 

Edited December 30, 2023 by ajn1963
grammar correction

[caspian guy]

Is the barrel a good fit in the upper reciever. Is the barrel nut torqued ok? Is the crown of the barrel ok? Have you tried shooting it without the muzzle device?

 

Those are things I check with any AR type firearm that won't group.

[Nolan]

Find someone with a Lab Radar or Garmin radar chronograph.  Trying a bunch of different combinations without knowing the velocities is kinda just shooting in the dark.  What velocities were you getting with the 10 inch barrel versus your pistol barrels.   What brand/type of bullets are you shooting?  Plated, jacketed, coated?

 

Nolan

[ajn1963]

I have a Chrony F1.

 

Going over my load data from Hornady manual my loads are going out at 1100fps.  I used my own reloads, Blazer, American Eagle, Federal, I don't think it is the ammo. 

 

I think I am going to print a buffer spacer and try that.  There are a few on Thingiverse and I can easily print one.

 

I have a standard ar carbine buffer spring and a KAK Industries 8oz AR9 buffer.  I don't want to gamble another $60 and try their 10oz buffer yet unless I know that is the exact solution. 

 

I never messed with buffer spacers, my impression is that shorter buffer space would make the buffer constantly slam into the back of the buffer. 

[zzt]

3 hours ago, ajn1963 said:

Going over my load data from Hornady manual my loads are going out at 1100fps. 

 

If the load in the manual is for a pistol, you'll be getting a lot more velocity out of a 16" barrel with HS-6 or CFE.

 

If you like the 10" so much, spend the $200 for an SBR permit and put a stock on it.  You'd be firing the MPX from your shoulder.

[Dirty_J]

You haven’t chrono’d the load? In a handgun OR the pcc? Wow. 
 

With a slow(ish) powder… and a 16” barrel… are you just you’re not getting jacket separation?? What’s the max velocity for those projectiles? 

[ajn1963]

I chrono'd the load in the past from my Sig M17 it matches what the Hornady book states for 5.1g of CFE Pistol and a 124g JRN at 1100fps  The Hornady manual only goes up to 1200fps for those projectiles.  I shoot different Factory ammo and get the same results.  I cannot tell if the jackets separate, I am not able to retrieve them.  The holes in the target are round and no keyholes. 

 

From researching this online, I find that there is one school of thought that if there is not enough propellant in the ammo it will not clear the longer barrel and the other thought is a longer barrel is going to produce higher velocity which I know is true from loading rifle ammo.  I have not had a chance to setup the Chrony, but my peers with AR9s shoot Factory ammo and have no issues out to hundred yards.  They don't group great but they get 5-6" group and can hit the steel at 100yds. 

 

This is a Spikes Tactical barrel.  And is the third 16" barrel I put on the gun with no change in results.  I went through two barrels from an independent that did the same thing, I return those barrels as he machined the BCG to where it would not extract.  He did say that when he tested those barrel they printed a 2" group at 50, and I can get some semblance of a group at 25 but beyond that there is nothing. 

 

I had two different gunsmith capable people install the barrels, no change.  The one told me the most torque he could put on was just over 60 using a bar extension and could go any further.  The other told me that they tightened the barrel as tight as they could get it. 

 

I am going to call Spikes Tactical next week and see what they can offer.  Other than that with the availability of S&W Response's or FPC, I am probably going to scrap this gun and just go with one of those, probably the Response being it take AR parts and I can use a spare Geissele trigger I got laying around.   I searched around and seems others have the same feed problems and accuracy issues but nobody had any solutions.  Hopefully this pistol brace ban gets thrown out and I can go back to the 10" barrel. 

 

 

[WxGuy]

Could it be the upper?

[caspian guy]

3 hours ago, WxGuy said:

Could it be the upper?

Yea that's what I was wondering, if the shank of the barrel is a loose fit in the bore of the upper, the barrel can shift around in the upper regardless of the barrel nut being tight. But there can be other reasons for it.  But if you have tried 3 barrels if it's not the upper I'm not sure what to think.

[zzt]

Examine the 10" barrel breech end, chamber and chamfer and compare it to whatever 16" you still have.  What is the difference?  That's where you will find your answer.

[frankge]

IMO use a fast powder. Being a lefty I can tell when there not a complete burn… powder in the face. WSF did this, switched to w231 and e3 and now runs perfectly. Never had any problems with accuracy so can’t offer help there. My pcc is the most basic. PSA 16” upper with a spikes lower. 9oz buffer with carbine flat wire spring. Not pricey or fancy but runs 100%, me well that’s another subject.

[ajn1963]

Mine is basically the same build but I removed the 10" PSA barrel and replaced it with a Spike's Tactical 16" barrel.  I have a KAK 9MM Carbine Buffer Extended 8 oz and just a standard carbine spring.  I did not use a spacer, but I am going to print one and see if that helps.  My suspicion is the buffer might be too light, and I been googling "ar9 buffer accuracy" and from what I read it fixes reliability and FTE problems but few claims stated that it improved accuracy with the assumption the before accuracy was still at an acceptable grouping. 

 

At 25 yrds I get about a 6-7" group and best zero I could make from that group.  At 100 yards, I came up 5 clicks on my Spitfire and put on a bipod, the first shot was at 11 o'clock 21" from center, second shot 7 o'clock 5" from center, third shot 4 o'clock 18" from center.  That was with a 124gr JRN with 5.1g of CFE Pistol ≈ 1100 fps per Hornady Handbook of Reloading.  I don't have the targets/groups from before, but this last attempt I put up target backer and kept everything for analysis, before my groups were random anywhere upto 24" from the target at 100 yds, at 50 same thing but 8-14" from the target center. 

 

I am reluctant at this point to spend anymore money on this gun, and I may have said this before when there are problems it seems to be some common problem nobody has a clear cut answer to fix. 

 

I suspect maybe buying the KAK K-SPEC Enhanced AR15 PCC 9.5 oz Buffer with Flatwire spring, might be the solution.  But I know peers with similar configs and same or less buffers that shoot perfectly well.