BA5 6.5CM Build - Behaves Undergassed

[EdgeReady]

3 minutes ago, 98Z5V said:

That buffer will be fine, man.  I searched all the usual places that I get the EA1095s from, and everyone is out of stock.  I have a spare EA1095, if things really get bad...   The Sprinco Red spring is a good alternate, and was designed for this application.  You could pick up a Red spring, run it until the EA1095s come back in stock, and swap it out.  If you don't like the Red spring, I'll but it from you for whatever you had to pay for it, plus shipping to me, regardless of round-count that you'd rack up on it.  I can always find a use for it around here somewhere. 

Here it is:

https://www.primaryarms.com/sprinco-m4-ar15-carbine-red-extra-power-carbine-buffer-spring

Thanks for the compatibility tip, that's just what I needed to scratch my itch to make progress here.  I'll gladly purchase a reasonable substitute until the real deal comes in, which will permit me to verify my progress thus far and get some other things sorted out.  If you're looking for SpringCo Red, I'll be happy to send it your way.  I'm only holding one 308AR system at present so you'll probably need it before I do again. 

[EdgeReady]

On 4/25/2020 at 8:49 AM, Magwa said:

How well are you lubing your BCG? you are going to want it almost dripping wet with a good oil until the parts have married you can even leave your BCG soaking in something like Mobile one synthetic it is awesome stuff as the oil binds to the metal after a couple of weeks the BCG will always feel lubed

I lube all my weapon systems with a mixture I learned from the armors at Blackwater which they referred to as "monkey cum". It's a mixture of MIlitec grease thinned by Militec oil to lower it's viscosity.  I only place it on mating surfaces or wear points, nowhere else.  It stays put even under extreme heat and use, but is thin enough to lubricate well.  It lubes well, lasts long, and does not tend to collect debris.  I use it in all my rifle and handgun systems, except when in extreme cold conditions when I switch back to a lighter lube.  It's always worked well for me, especially once I learned where and how much to use.

[EdgeReady]

Gents,

Clint's Armalite spring was shipped most rikitik.  I installed the spring with the 5.6oz buffer and I achieved functionality.  However, after drilling the gas port out to 0.094, it was highly gassed at max gas setting.  I had ripped case rims, base marking, and stovepipes until I dialed the gas down.  I had to go about 1 full turn from CLOSED to achieve reliable function, bolt lock, with strong 4pm ejection.  After single round function testing, I performed multi-round reliability testing.  Slow fire or mag dumps, the gun is running well.  I retested everything suppressed and the gas block setting end up being only 1 click down for best suppressed function.

I'm happy with the way the gun is running now, but I'm concerned that the functional "window" of gas block settings is very small.  1 click more gas brings overgassing with a 1pm ejection or and 1 click less gas brings failure to lock back.  There are settings on the gas block that are in-between the detents and provide even more optimal function, but I'm not comfortable adjusting between a detent as it probably won't stay there.  I learned long ago never to underestimate the ability of gun fire vibrations to screw stuff up. 

Question: I filed and polished ramps to eliminate the scarring I was seeing on the casings. Now it does not scar when I load and eject a round, but the scarring is still there when I fire and eject an empty casing.  The scarring is two lines on the case neck about 1/4" apart.  I thought I would ask before I do anything else with ramps.

Thank you all kindly for your assistance with this project.  Had I not invested the time in joining this group, I would not be where I'm at with this.  I hope that I'll be able to repay the favor in some way.

Edge

[EdgeReady]

On 4/26/2020 at 2:20 PM, 98Z5V said:

That buffer will be fine, man.  I searched all the usual places that I get the EA1095s from, and everyone is out of stock.  I have a spare EA1095, if things really get bad...   The Sprinco Red spring is a good alternate, and was designed for this application.  You could pick up a Red spring, run it until the EA1095s come back in stock, and swap it out.  If you don't like the Red spring, I'll but it from you for whatever you had to pay for it, plus shipping to me, regardless of round-count that you'd rack up on it.  I can always find a use for it around here somewhere. 

Here it is:

https://www.primaryarms.com/sprinco-m4-ar15-carbine-red-extra-power-carbine-buffer-spring

After boring out gas port, I got everything running, gas tuned, and function tested.  I picked up some better ammo (American Gunner) to see what kind of accuracy I get achieve.  The American Gunner shot better than the FMJ was using for function testing, but I was underwhelmed with the accuracy to say the least.  At 200yds I could only squeeze 2MOA groups from it.  The rifle was bagged front and rear, using a Nightforce 3-15NXS for testing.  I did have some gusty tailwinds, but I honestly think I could have shot better groups with any AR from my fleet.  I'm prepared to just ditch this Hanson barrel and invest in a Criterion, but I think I owe it a bit more effort before going to the nuclear option.  After all I've been through with this build, I just don't have confidence in this barrel.  Any thoughts?

[98Z5V]

3 hours ago, EdgeReady said:

After boring out gas port, I got everything running, gas tuned, and function tested.  I picked up some better ammo (American Gunner) to see what kind of accuracy I get achieve.  The American Gunner shot better than the FMJ was using for function testing, but I was underwhelmed with the accuracy to say the least.  At 200yds I could only squeeze 2MOA groups from it.  The rifle was bagged front and rear, using a Nightforce 3-15NXS for testing.  I did have some gusty tailwinds, but I honestly think I could have shot better groups with any AR from my fleet.  I'm prepared to just ditch this Hanson barrel and invest in a Criterion, but I think I owe it a bit more effort before going to the nuclear option.  After all I've been through with this build, I just don't have confidence in this barrel.  Any thoughts?

It's a good barrel, from a great company,as far as barrels go.  It's not bad.  Every barrel likes a certain load more than others, though.  Finding the ammo is just a search for what the barrel likes.  That's why I load my own, honestly.  Tune the load for that barrel, and it's on, after that.  The the .260 Rem, I only have one, so it gets that handload. For .308, I find a load that works in the 18" Mk11 and the 20" Rem 700 - and I stick with that load.  It would suck if the same load didn't work for both.  I have some 5.56 guns like that. Certain load for these 3, but that other little bastard...   gets it's own load.  Luckily, for Grendel, the same load works for all of them, quite well. 

It's just trial and error, man - finding what your barrel likes.  Tell you what - if that barrel doesn't like Federal Gold Medal Match, then it might have issues.  Excellent ammunition.  Try both 168gr FGMM and 175gr FGMM through it.  At 100 yards, I doubt you could tell the difference between the two.   At 600 yards, there would be a slight difference, with the 175s winning out.  At 800 yards, there's a very real difference in the two, with the 175s smoking the 168s.  

Glad that thing is running - that's fantastic news!  

FWIW - Hornady American Gunner in the Grendel load - doesn't shoot for shiit through my Grendel family.  It's not bad - but it's not what I'd call accurate, either. 

Edited May 9, 2020 by 98Z5V

[EdgeReady]

2 hours ago, 98Z5V said:

It's a good barrel, from a great company,as far as barrels go.  It's not bad.  Every barrel likes a certain load more than others, though.  Finding the ammo is just a search for what the barrel likes.  That's why I load my own, honestly.  Tune the load for that barrel, and it's on, after that.  The the .260 Rem, I only have one, so it gets that handload. For .308, I find a load that works in the 18" Mk11 and the 20" Rem 700 - and I stick with that load.  It would suck if the same load didn't work for both.  I have some 5.56 guns like that. Certain load for these 3, but that other little bastard...   gets it's own load.  Luckily, for Grendel, the same load works for all of them, quite well. 

It's just trial and error, man - finding what your barrel likes.  Tell you what - if that barrel doesn't like Federal Gold Medal Match, then it might have issues.  Excellent ammunition.  Try both 168gr FGMM and 175gr FGMM through it.  At 100 yards, I doubt you could tell the difference between the two.   At 600 yards, there would be a slight difference, with the 175s winning out.  At 800 yards, there's a very real difference in the two, with the 175s smoking the 168s.  

Glad that thing is running - that's fantastic news!  

FWIW - Hornady American Gunner in the Grendel load - doesn't shoot for shiit through my Grendel family.  It's not bad - but it's not what I'd call accurate, either. 

I run the FGMM 168/175 in my .308 precision guns and they do run just like you said.  This build is a 6.5CM, so Federal offers a 140 Sierra and a 130 Berger in FGMM.  I'll try the 140 BTHP. 

[98Z5V]

5 hours ago, EdgeReady said:

I run the FGMM 168/175 in my .308 precision guns and they do run just like you said.  This build is a 6.5CM, so Federal offers a 140 Sierra and a 130 Berger in FGMM.  I'll try the 140 BTHP. 

Yeah, that was me screwing up the Creed build you have, and the common FGMM .308 ammo.  With the 1:8" twist in your barrel, try the heaviest projectile that you can find, in quality loaded ammo.  Black Hills might end up being the source.  The 147gr Hornady ELD-M projectile has worked miracles in my .260 Rem, and would do well in your 6.5C gun.  I'm playing around with Hornady 143gr ELD-X projectiles now, but will have some info up on them in the future.  I've heard that the 130 Bergers are pretty good in the 6.5C.  I'll tell you, that Berger 185gr Juggernaut projo in the new .308 Win FGMM ammo is a BADASS round!... 

[EdgeReady]

On 5/10/2020 at 3:37 AM, 98Z5V said:

Yeah, that was me screwing up the Creed build you have, and the common FGMM .308 ammo.  With the 1:8" twist in your barrel, try the heaviest projectile that you can find, in quality loaded ammo.  Black Hills might end up being the source.  The 147gr Hornady ELD-M projectile has worked miracles in my .260 Rem, and would do well in your 6.5C gun.  I'm playing around with Hornady 143gr ELD-X projectiles now, but will have some info up on them in the future.  I've heard that the 130 Bergers are pretty good in the 6.5C.  I'll tell you, that Berger 185gr Juggernaut projo in the new .308 Win FGMM ammo is a BADASS round!... 

I just hit the range to run more tests on the 6.5 CM BA Rifle w/14.1 Hanson bbl.  Here's what I did since we last messaged...

• Thoroughly cleaned chamber/bore and lubed BCG
• Checked scope & mount torques
• Re-torqued flash hider using formula to compensate for wrench extension
• Shot comparison test groups using American Gunner 140gr and FGMM 140gr
  • 200yds
  • Rifle bagged fore & aft
  • 85 degree F
  • Light variable breezes, tree cover either side of range
  • I also chrono-graphed and the velocities seemed low to me

Here's a pic of the American Gunner 140gr group, my control group...

 

Here's a pic of the Federal Gold Medal Match 140gr group, my test group...

 

My conclusion remains the same at this point...something is up with this barrel.  Thoughts?

 

 

[shooterrex]

Velocities should be at least 500-700 fps more unless they were measured right in front of the target. Tht barrel should do better than 2-3MOA.

[EdgeReady]

14 minutes ago, shooterrex said:

Velocities should be at least 500-700 fps more unless they were measured right in front of the target. Tht barrel should do better than 2-3MOA.

No doubt on the velocities.  The highest velocity measured was measured after this test at 2330fps.  It was measured at the muzzle.  This barrel is consistently printing those groups with three types of 140gr ammo.  Unless I become aware of some new sorcery, I'm headed for a different barrel.  BA won't honor this one because I've modified it.  It's looking like I've got a very short Tomato stake.

 

[EdgeReady]

43 minutes ago, shooterrex said:

Velocities should be at least 500-700 fps more unless they were measured right in front of the target. Tht barrel should do better than 2-3MOA.

Are you aware of any reason that a particular system would run lower than expected velocities?  The short barrel length is the only factor I'm aware of if you rule out the ammo.  The ammo I'm using is well established.  The performance of that 14.1 Hanson barrel is also established by others who have used it.  I did drill out the gas port, but the gas pressure is controlled with an adjustable block and there appears to be plenty of gas available in the system.  The block is only 1 turn from off, which is 75% closure.  What other system factors could cause this ammo to be low velocity?

[98Z5V]

40 minutes ago, EdgeReady said:

Are you aware of any reason that a particular system would run lower than expected velocities?  The short barrel length is the only factor I'm aware of if you rule out the ammo.  The ammo I'm using is well established.  The performance of that 14.1 Hanson barrel is also established by others who have used it.  I did drill out the gas port, but the gas pressure is controlled with an adjustable block and there appears to be plenty of gas available in the system.  The block is only 1 turn from off, which is 75% closure.  What other system factors could cause this ammo to be low velocity?

These cartridges (.260 Rem and 6.5C) only lose about 25fps per inch of barrel.  I'm right at 2650fps on my 20" .260 Rem gun.  Even for a 16", that should be about 100fps less, and come in somewhere around 2550fps, with a 14" at 150fps less, around 2500fps.

I've never seen anything else, system-wise, that would affect muzzle velocity, other than barrel length differences, given a particular load.  Even if that thing is rough, internally,that only affects cycling, not firing.

Can you try these 3 types of ammo at 100 yards, and see if the group sizes drop to half of what you're getting now, at 200?  That 140 FGMM was looking promising, except for that lower left shot, at least as far as height of group, under 2" (minus that lower left shot).  Windage was wide, but group height looked decent.

I have almost 600 rounds of NEXUS match .260 Rem ammo to test out, loaded with 130gr Bergers.  It's the only factory ammo this gun has ever digested.  I shot a box of 20 already, and it's impressive, but wouldn't cycle the gun.  After that, the gas port diameter went from 0.070" up to 0.081".  Retest coming, now, along with several of my other handloads that were good, but didn't cycle it, either.

Edited May 17, 2020 by 98Z5V

[shooterrex]

That's just plain weird. I'm getting 2200+ fps out of a 12"  6.5 Grendel w/123 gr factory ammo. Have you slugged the barrel? Maybe bore is oversized and letting gas around the bullet. If the bore diameter is off they should take the barrel back. Just a thought.

[EdgeReady]

On 5/17/2020 at 3:55 PM, 98Z5V said:

These cartridges (.260 Rem and 6.5C) only lose about 25fps per inch of barrel.  I'm right at 2650fps on my 20" .260 Rem gun.  Even for a 16", that should be about 100fps less, and come in somewhere around 2550fps, with a 14" at 150fps less, around 2500fps.

I've never seen anything else, system-wise, that would affect muzzle velocity, other than barrel length differences, given a particular load.  Even if that thing is rough, internally,that only affects cycling, not firing.

Can you try these 3 types of ammo at 100 yards, and see if the group sizes drop to half of what you're getting now, at 200?  That 140 FGMM was looking promising, except for that lower left shot, at least as far as height of group, under 2" (minus that lower left shot).  Windage was wide, but group height looked decent.

I have almost 600 rounds of NEXUS match .260 Rem ammo to test out, loaded with 130gr Bergers.  It's the only factory ammo this gun has ever digested.  I shot a box of 20 already, and it's impressive, but wouldn't cycle the gun.  After that, the gas port diameter went from 0.070" up to 0.081".  Retest coming, now, along with several of my other handloads that were good, but didn't cycle it, either.

I will retest again and attempt to remove some variables.  At this point I don't trust the chronograph readings.  I did some research and apparently there's some sorcery regarding chronograph setup and lighting conditions.  I probably had it too close to the muzzle and the sunlight conditions were extremely bright. 

Also, I'm going to ground the rifle next test.  I've been shooting from a carpeted platform installed on a Polaris Ranger for that purpose.  It permits me to keep my kit mobile and quickly change shooting locations.  I'm standing when I shoot, but can base out, lean over the platform, and get onto and into the rifle.  While it's pretty stable, especially with a bag and GI socks, it's not like being grounded.  I will also shoot from 100yds.

If this next test brings results consistent with those to date, I'm going to move on a different barrel.  My build goal was portable, accurate, suppressor host.  3 or so MOA is thus far failing in the accuracy category.  I had a POF308 with 20" bbl for years, and it consistently shot sub-MOA with FGMM from the same shooting platform.   

[billymagg]

On 4/24/2020 at 10:43 AM, Matt.Cross said:

You have an adjustable gas block, drill the gas port up just once to the appropriate diameter and use the adjustable gas block to regulate it to whatever extent you wish. You're defeating the usefulness of the gas block by trying to upsize the gas port incrementally. Technically you could go as high as .125" in a gas port and still regulate it as needed, but you don't need to be that drastic. I'd drill it up to a 3/32" (.094") and use the gas block as it was intended.

That's very helpful Matt, I may end up here as well, bought some bits tonight.

[shooterrex]

I bought a new(better) barrel for my creedmoor. When I went to switch the barrels I found where the gas block was touching the rail. That could be why it didn't shoot well. I might have to put that barrel in a different upper and give it a try.

[98Z5V]

On 5/17/2020 at 12:55 PM, 98Z5V said:

I have almost 600 rounds of NEXUS match .260 Rem ammo to test out, loaded with 130gr Bergers.  It's the only factory ammo this gun has ever digested.  I shot a box of 20 already, and it's impressive, but wouldn't cycle the gun.  After that, the gas port diameter went from 0.070" up to 0.081".  Retest coming, now, along with several of my other handloads that were good, but didn't cycle it, either.

^^^  Update on this aspect of it - I punched that gas port up to where it should have been - 0.080~0.081" - and it eats that NEXUS Match ammo like a champ.  MISTAKE on my labeling of it, though - it wasn't 130 Bergers loaded in that ammo - NEXUS loads it with 139gr Lapua Scenars.  It's damn near right on par with my 147gr handloads out to 600 yards, and a slight edge going to the 147s at 850 yards. 

2 hours ago, shooterrex said:

I bought a new(better) barrel for my creedmoor. When I went to switch the barrels I found where the gas block was touching the rail. That could be why it didn't shoot well. I might have to put that barrel in a different upper and give it a try.

^^^  Found out something like that on my .224 Valk, when I tore it down to rebuild/rebarrel it into a 6 ARC.  Two screws for a piece of pic rail attachment were too long, and both those bastards were touching the Valk barrel.  No wonder I didn't like that thing...