6.5 Creedmoor short stroking

[98Z5V]

31 minutes ago, Rougaroux22 said:

Small update:

I measured the gas port this evening and it is at .082.

IMHO, I think that gas port is too small - and that fits what is happening with the gun.  I think my setup should be at that size, minimum, and I'll be drilling mine to 0.081" to start, soon, and going up from there if I have to.  The gun is coming apart for Cerakote anyway.  I honestly think - with that gas system of yours that's 2" less than what I'm running - needs to be in the 0.090"~0.100" range, with 0.090" being the minimum for your setup. 

As far as cartridges go, you and I are shooting virtual twins, here - there's so little difference between 6.5 Creed and .260 it's not even funny.  We've got big differences in gas systems, though.  I think my 0.070"-ish is too small, and you're two inches less on gas system length/dwell time, and only another 10-thou up - so you'd be under-gassed as well. 

[RAM2940]

98Z5V,

Have you shot your .260 yet.  Ive got a Wilson combat 6.5 Creedmoor barrel, 20"  just got gun assembled and it might be a couple weeks before I can test fire and shoot.  Mine also has a .073 gas port.

[98Z5V]

4 hours ago, RAM2940 said:

98Z5V,

Have you shot your .260 yet.  Ive got a Wilson combat 6.5 Creedmoor barrel, 20"  just got gun assembled and it might be a couple weeks before I can test fire and shoot.  Mine also has a .073 gas port.

Shot the piss out of it so far.  It's scary accurate.  Heads up on Wilson Combat barrels - you need Armalite AR-10 gas tubes in them.  Even the gas tubes that Wilson Combat sells/sends out are DPMS-lengthed, and too short.  You'll need the Armalite AR-10 Rifle length gas tube. 

I'm 100% handloading for this rifle, no store-bought ammo at all through it.  The only load I have right now that functions 100% of the time is a 147gr Hornady ELD-M projo, 43.0 grains of RL-22 powder (it's a magnum powder that I use for .338 LM loads and 300 Win Mag loads), CCI 200 primers, at 2.785" COL.  Perfect load.  The 140s I had loaded up (Hornady ELD-Ms and a different powder) won't even extract the brass from the chamber, and it's not a weak load.  There's just not enough gas in there, and that load is suffering. 

So, do I think you should up your gas port?  Hell yeah, start off with 0.081".  When mine comes apart for paint, it's going to 0.081", and might go up from there.

[RAM2940]

I took your advice and got a Armalite AR-10 gas tube, Ordered couple boxes of different 140 grain ammo, after testing will let you know how it went.

[98Z5V]

2 hours ago, RAM2940 said:

I took your advice and got a Armalite AR-10 gas tube, Ordered couple boxes of different 140 grain ammo, after testing will let you know how it went.

Let me know how your 140s do through it - are you going to drill the gas port first?  Reason I ask is - if you don't, and your 140s DO work, something is terribly wrong with my own 140 load...  

[RAM2940]

Im going to try it first as is, I had a slr gasblock laying around so I put that on and we will see what happens.  But it might take a week or two before I can shoot.  Also I looked at Ballistic Advantage gas port sizes and they seem to be close to same size.

[RAM2940]

Okay, got out and fired a few rounds of federal non typical 140.  Bolt will not lock back on empty mag, and will not pick up a round with round in mag.  Shells eject to the 4 o clock .

I have AP m5 upper and lower

AP M5 rifle extension buffer and spring

Armalite AR10 gas tube. verified

Toolcraft BCG double ejector small pin

SSA-e trigger

20" Wilson combat tactical hunter

Going to pull the gas block and check alignment, but thinking it might be time to drill larger gas port.  

Any comments and suggestions.

Edited February 3, 2019 by RAM2940

[edgecrusher]

5 minutes ago, RAM2940 said:

 

Going to pull the gas block and check alignment, but thinking it might be time to drill larger gas port.  

Any comments and suggestions.

 

This, measure it and let us know!

[98Z5V]

3 hours ago, RAM2940 said:

AP M5 rifle extension buffer and spring
 

You need to look at this junk before anything else.  Gas port size is a bonus, and you need to know that - but you really need to check out that recoil system, to inlude the internal depth - INTERNAL DEPTH - on that receiver extension.  The one and only Aero I had for the M5-specific shiit ended up at 7.100" internal.  Dumpstered that thing.  It was worthless on any platform.

Aero's buffer is fucked, at 2.500" long, but 3.8oz, and the spring is weird.  Run a Sprinco Orange spring in there, and it might work - and you might need a heavier buffer anyway, WITH that spring. I'm telling you this firsthand. The buffer is worth something, though - it has two tungsten weights in it, that are worth saving, and the bumper on the end of the buffer is worth keeping.

Get your gas port diameter, first. There's lots of places/companies that are "compensating" for a weak recoil system with a "too-small" gas port - that's a balancing game that never works...  That math that they're using doesn't always work out, when you only need a functional weapon.  It's fucked up logic, and too many manufacturers are trying to use it.

Edited February 3, 2019 by 98Z5V

[RAM2940]

This is the AP m5 rifle buffer kit I have:

https://www.aeroprecisionusa.com/m5-308-rifle-buffer-kit

 

Edited February 3, 2019 by RAM2940

[98Z5V]

I figured that was the one.  It's a 3.8oz buffer, aluminum body, two tungsten weights, and 2.5" long.  The internal depth of the receiver extension is the big part. It needs to be 7.000" internal depth and not any more than that.  The one I received from them was 7.100" internal depth, and it took quite awhile to identify that as the source of my weird issues.  I chucked it and went Armalite AR-10 Carbine recoil system for the first time.  Went that route every other time, too, minus the experimentation with this last gun.

Everything I stated previously about the barrel is still pertinent.  I think my gas port in the .260 is too small, and it won't even think about trying to extract a 140gr-load casing from the chamber, every single shot.  The 147s run like a champ, though, zero functional issues.  I'm on a 20" barrel, rifle gas as well.  Our barrels are identical,minus the chamber.  I'll bet your gas port diameter is the same as mine, 0.071".  I am going to take mine up to 0.080" minimum.

[RAM2940]

I just pulled the gas block and  only had half the hole open, readjusted and going to give it another try but it might be another 2 weeks.    My rifle buffer is alittle over 5" and says it weighs 5.6oz.  And the gas port is .071.  The brass seemed to eject good but the neck was getting a flat spot.

Edited February 3, 2019 by RAM2940

[98Z5V]

Damn, see what I get for being impatient?  I went to the link you posted above, and the page was loading slow - I scrolled down until I got to pictures...  

I saw this, and thought you did the carbine kit:

 

You won't have any issues with a rifle recoil system.      I figured that's what you'd have for a gas port diameter... 

[Rougaroux22]

**UPDATE***

After a lot of back and forth, I sent the rifle to Proof Research. To make a long story short, they widened the gas port to .088 and they say it runs like a champ now. After reading around it would appear that I am not the first person to have a 20" barrel not cycle the rifle with the gas port length/size they ship their barrels with. Seems to work okay with their 22" and 24", but I guess the 20" barrel gas port needs to be wider or be at rifle length?

Looking to run the rifle this weekend to verify. Hopefully this post will serve someone well in the future that has the same problem and save them a lot of time and $. 

Thanks again everyone for their help. Look forward to being a part of the forum.

[98Z5V]

2 hours ago, Rougaroux22 said:

After reading around it would appear that I am not the first person to have a 20" barrel not cycle the rifle with the gas port length/size they ship their barrels with. Seems to work okay with their 22" and 24", but I guess the 20" barrel gas port needs to be wider or be at rifle length?
 

Way less dwell time, with that long gas tube.  It's enough on the 22s and 24s...

 

Good job, man. 

[Pilgar]

Great discussion on getting the 6.5 creed to function properly as a AR10.  My name is James and I manage a gunshop and build all our custom AR variant rifles/pistols.  

I am amazed at how many times I have had to open a gas port to get a rifle to function properly.   I came across a problem I have not seen before last week and I am still trying to wrap my head around it.   Guy brought in a AR10 in 6.5creed it was not able to pick up the next round or lock back on an empty mag.  The shell ejected at between  3 and 4 oclock.  The primers on the ejected shells had a rebound dome inside  what looks like a normal depth firing pin dimple.  The rebound dome extended beyond the end of the case head enough to feel it raised with your finger, there is also a ring around this dome that is sharp.   So far no adjusting the gas block or changing buffers and springs has made much difference.  Our two gunsmiths think it is overgassed and the bolt is opening to soon causing space where the pressure can pop out that primer dome.  I am not so sure.   It is a 20 inch barrel, standard rifle length gas port.  

This is the first one I have not just been able to fix directly.  I have not seen primers like that before.  

If anyone here has any ideas I would love to hear them, this is the best discussion I have read yet on this subject and that is why I am asking here.

 

[98Z5V]

13 hours ago, Pilgar said:

 It is a 20 inch barrel, standard rifle length gas port.  

 

Gas port diameter on that should be 0.080"~0.085", for that round, and that barrel config.  I'm betting it's around 0.070" right now - it's not overgassed - it doesn't have enough gas.  Get that gas block off there and lemme know what that gas port diameter is. 

If you get a chance, check out all the recoil system parts, and post up what it's got.  Recoil system and gas system have to be balanced, or that thing won't run. Not locking the bolt back on an empty mag points me to gas, first.  If gas is good, we go to recoil.

Edited October 28, 2019 by 98Z5V

[Pilgar]

I got a chance to take this apart this morning.  It is a PSA upper 20" barrel the gas port diameter is .073"   The Lower is PSA the buffer is a 3.25" H the spring I don't know it is 11.25 inches long.  The buffer tube is 7.75" long.   This is the first I have had a chance to look at it.  I think the gas port enlarging is going to fix it.

 

 

[Pilgar]

I opened up the gas port to .096   It had an adjustable gas block.  The gun functions correctly now but the primers still are looking weird.  There is a reverse dome inside the firing pin depression.  I will try and take a photo and post it.  

[shooterrex]

There are creadmore bolts with smaller diameter firing pins w/a corsponding smaller hole in the bolt face. That will likely solve your problem. PSA really doesnt have this larger platform quite right yet.

[98Z5V]

7 hours ago, Pilgar said:

I got a chance to take this apart this morning.  It is a PSA upper 20" barrel the gas port diameter is .073"   The Lower is PSA the buffer is a 3.25" H the spring I don't know it is 11.25 inches long.  The buffer tube is 7.75" long.   This is the first I have had a chance to look at it.  I think the gas port enlarging is going to fix it.

Big issues here - I didn't see you mention where this was a PSA, before this post I'm quoting here - but that explains everything.

7.75" internal depth is too much, so they still haven't figured that out.  Internal depth, when running a 3.250" buffer, needs to be 7 5/8.  You're at 7 6/8", comparing fractions and all.  That's 0.125" too deep.  Quarters are 0.069" thou thick, so that thing is gonna need two quarters down the extension before the spring and buffer go in there.  Sounds backyard-tech, but it works, and it makes the gun work as designed.

Next: H Buffer = 3.8oz.  Not enough Ass to control the Mass - a 3.8oz buffer isn't gonna control that heavy .308-based BCG.  Hell, we went to an H buffer in the M4A1 Carbine as the "reliability upgrade" to get the thing to run properly on full-auto.  It's not enough for a .308-based BCG, never will be unless you're building some tricked-out Race Gun.  You need an H3 buffer (5.4oz).  This setup runs AR15 Carbine buffers (actually, AR15 Carbines run AR-10 Carbine buffers...).  Any AR15 Carbine H3 buffer that's properly made is what you're after. 

Spring - don't trust what was shipped in that rifle, it's jacked.  You need the genuine (not a copy) Armalite EA1095 spring.

^^^  That list above will straighten out the recoil system, completely, forever.  Punch that gas port diameter up, and that thing will run like a sewing machine. 

I think above I told you that you needed 0.080"~0.085" on that barrel - that's my numbers for an 18" midlength PSA barrel - and all other 18" midlength .308/Creed/.260 barrels. That will work on a 20" rifle gas barrel, even though the 20" rifle gas barrel has different dwell time.  Don't be surprised if you need 0.090", though.  My 20" rifle gas .260 Rem gun is 0.081", after being punched up from a shipped-port diameter of 0.070". 

Edited October 29, 2019 by 98Z5V

[Pilgar]

When the gun doesn't cycle the primers look like on the right.  

when it does it looks like on the left  (Domed in the depression.

 

 

[98Z5V]

Small amount of cratering on the primer - slightly flattened primer.  That's up there in the charge-weight.  I think I see an ejector smear in that right one, about 4 o'clock, but it's minor. 

Bottom line - your recoil system isn't up to task here.  It's too light, with too little spring pressure - that's making the gun cycle (gas system), but that fucker is trying to unlock too early - because that weak recoil system isn't keeping it locked long enough.  

That 0.073" gas port diameter is still too small - but make changes one at a time.  THEN you pinpoint the differences your changes make.  Don't modify it all at once - change recoil system, drill gas port, mess with the gas block adjustments...   You never know what change made what happen.  Fix the recoil system first...  After that, we drill gas port diameters up. This can be a tedious process, but it's what you have to do when dealing with a fucked up gas gun.

Make absolutely SURE that the adjustable gas block is WIDE OPEN for all testing.  If it's not, you're wasting your time.  Test them wide-open  - then you adjust down, as necessary.  If it's not wide-open - you'll never know if that gas port diameter is large enough to begin with, because you've restricted it... 

Edited October 30, 2019 by 98Z5V

[Armed Eye Doc]

On 10/28/2019 at 5:33 PM, Pilgar said:

I opened up the gas port to .096   It had an adjustable gas block.

 

8 hours ago, 98Z5V said:

That 0.073" gas port diameter is still too small - but make changes one at a time.

He has already opened it up.

[98Z5V]

18 hours ago, Armed Eye Doc said:

 

He has already opened it up.

NOW I see it!     Time to address the recoil system...