| I have a pair of AR's with 18 inch barrels and rifle length gas systems that won't run. 1st gun: 18" White Oak 1-8 rifle length with a .100 port. A5 buffer system running a sprinco green and an H1 buffer. Won't run anything but American Eagle 55 grain. Everything else is short stroking. 2nd gun: BA 18" 1-8 rifle length with a .094 port. Carbine length buffer system with a sprinco Yellow and a standard 3.0 oz buffer. Same situation It is cold here at about 20 degrees. I'm loading Hornady 75 gr BTHP with 24.0 grains of TAC hoping the hive mind can produce some suggestions before I launch one of these POS' off a cliff. | |
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Ar's that won't function
- Thread starter owtlaw
- Start date
Those both sound like guns that should work great. So... gas block/port alignment?
Rifle #1 has a very strong spring and light buffer...gas port seems pretty big too.
Rifle #2 has the lightest spring Sprinco makes, designed for SIM rounds, etc.
Rifle #2 has the lightest spring Sprinco makes, designed for SIM rounds, etc.
My suggestion is that since the gas rings are good, the gas blocks are reportedly aligned, and gas ports are what you say they are, ditch the current spring/buffer combo and try something more traditional. Also, besides a handload recipe and American Eagle 55gr FMJ, what other ammunition have you tried through the rifle?
In the case of Rifle #1 a rifle length buffer spring with a BCM MkII T2 buffer
bravocompanyusa.com
bravocompanyusa.com
I run this combo in my SPR and it cycles everything from 50gr to 77gr .223 and 5.56.
Rifle #2 a carbine length spring with a H2 or H3 buffer
ar15discounts.com
bravocompanyusa.com
bravocompanyusa.com
In the case of Rifle #1 a rifle length buffer spring with a BCM MkII T2 buffer
BCM MK2 Buffer Mod 1 - T2
The BCM MK2 Mod1 T2 AR15 buffer (5.6oz) is built for the BCM MK2 receiver extension to reduce felt recoil and provide consistent carrier velocity.
bravocompanyusa.com
Rifle M16 Action Spring
Action spring for M16, M16A1, M16A2, M16A3, M16A4. For use with a full size M16 Rifle buffer and full size rifle M16 receiver extension.
bravocompanyusa.com
I run this combo in my SPR and it cycles everything from 50gr to 77gr .223 and 5.56.
Rifle #2 a carbine length spring with a H2 or H3 buffer
Aero Precision AR-15 H2 Buffer
Aero Precision AR-15 H2A Buffer.A The H2 Buffer is a heavy buffer designed to reduce felt recoil as well as reduce the cycling rate on full-auto rifles. It is designed to be used with a carbine receiver extension (buffer tube) and spring.This true mil-spec buffer is AMERICA Made and features...
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H3 Carbine Buffer
The H3 (Heavy) carbine AR15 buffer is designed to significantly reduce felt recoil and is weighted with 3 tungsten weights to 5.4oz.
bravocompanyusa.com
Carbine Action Spring
The BCM AR15 carbine action spring is made for AR and M4 adjustable stocks to M4A1 Mil-Spec specifications. Made in the USA.
bravocompanyusa.com
Can you verify alignment of the gas block? Are you sure it’s short stroking and not over running? You said It cycles with 55 factory ammo. But you running 75gr hand load. 24 grains of tac. I don’t know your rifle or if it can run that charge. But per the Hornady manual your over charging the cartridge. Are you seeing pressure signs?
That T2 is heavier than what I have in the rifle now. I do have a Cobalt A5 H2 on hand I can try. That H3 buffer is the one I'm running now. I'll see if I have a standard carbine spring.My suggestion is that since the gas rings are good, the gas blocks are reportedly aligned, and gas ports are what you say they are, ditch the current spring/buffer combo and try something more traditional.
In the case of Rifle #1 a rifle length buffer spring with a BCM MkII T2 buffer
BCM MK2 Buffer Mod 1 - T2
The BCM MK2 Mod1 T2 AR15 buffer (5.6oz) is built for the BCM MK2 receiver extension to reduce felt recoil and provide consistent carrier velocity.Rifle M16 Action Spring
Action spring for M16, M16A1, M16A2, M16A3, M16A4. For use with a full size M16 Rifle buffer and full size rifle M16 receiver extension.
Rifle #2 a carbine length spring with a H2 or H3 buffer
Aero Precision AR-15 H2 Buffer
Aero Precision AR-15 H2A Buffer.A The H2 Buffer is a heavy buffer designed to reduce felt recoil as well as reduce the cycling rate on full-auto rifles. It is designed to be used with a carbine receiver extension (buffer tube) and spring.This true mil-spec buffer is AMERICA Made and features...H3 Carbine Buffer
The H3 (Heavy) carbine AR15 buffer is designed to significantly reduce felt recoil and is weighted with 3 tungsten weights to 5.4oz.Carbine Action Spring
The BCM AR15 carbine action spring is made for AR and M4 adjustable stocks to M4A1 Mil-Spec specifications. Made in the USA.
I realize that the T2 is heavier but what you're using isn't working so why not try a "weaker" rifle length spring with a heavier buffer to see if it balances out? I'm running a 18" RLGS WOA barrel too using a standard milspec spring and heavy A5H2 buffer with no issues.
Also, you said you were running a 3 oz buffer (a standard carbine buffer) not a H3 buffer in Rifle #2.
Also, you said you were running a 3 oz buffer (a standard carbine buffer) not a H3 buffer in Rifle #2.
Did the issues start only after the weather got cold? What's your lube/oil routine?
Has it turned into toothpaste yet? I got a bunch of Lucas samples at matches years ago, used it all summer, then it turned pasty below 20 degrees and I threw it away.
I'll have to look at it. Possible. Perhaps I should try a thinner oil.
That's the first thing that I would do, after thoroughly removing all of the Lucas ED. Including the buffer/spring/RE if it's in there.
Since your problem started once the temperature dropped, a couple other things to consider:
- some ammunition is temperature sensitive.
- are the buffer tube, buffer and spring clean? Oil, grease or some other debris in the buffer tube can slow the buffer.
At colder temps, very thin oils/grease work best. I typically use:
- ALG Go-Juice 0000 Very Thin Grease on the bolt carrier bearing surfaces.
- Hornady One-Shot Gun Cleaner & Lube in the upper receiver.
Hornady One-Shot works really well at cleaning the carbon and lubrication out of the upper receiver. It's also a leaves a very slick non-tacky surface once it is allowed to dry. It's also less likely to attract debris.
I have nearly the exact setup as rifle #1 which should run anything you feed it. If you've verified visually the gas port alignment I would suspect BCG.
What BCG are you using in each gun? Have you done a reverse torque check on the key screws and inspected it for leaking around the key?
What BCG are you using in each gun? Have you done a reverse torque check on the key screws and inspected it for leaking around the key?
As some above posters said. Strip all surfaces of sticky Lucas. Lube with CLP or similar. Rock and roll.
Concur.
Try a standard weight buffer and spring. Maybe an H1 but you have rifle-length gas in your favor. You should get normal function back.
Yup.
Try a standard carbine spring and buffer. At the "Meh" top end of .223 and low-mid of 5.56 pressure but with a rifle-length gas system and 18-inch barrel.
You can push them a little faster than 24, especially in the cold. Try 24.5. From Western Powders 8.0:
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You list @2 as having a Sprinco Yellow, those are a light spring for simunition etc.
Update: Starting with rifle no.2 18" rifle gas system carbine buffer system. I pulled it completely down and did a thorough cleaning. I actually took the buffer out and weighed it. It came in at 4 oz. which is odd considering it is marked as 3. I pulled the buffer and spring and replaced them with a brand new set from Aero Precision. That gun seems to run fine now.
gun number 1 still seems to be a mystery. I pulled an A5 H1 buffer apart and changed out the weights. I got it down to 3.35 oz. I ran that on top of the Green spring and it ran fine at first. Once it got cold though, it would not hold the bolt open. I also added some other loads to the test. I used some H4895 under both a Hornady 75 BTHP and the 73 ELDM. I had a lot more issues with the 4895 loads. My hottest were loaded to 24.4 grains under a 69 grn match burner. Again those shot and loaded ok but would not hold the bolt open. Someone with more knowledge can certainly correct me if I'm wrong but I believe that the 4895 must be just a bit too slow.
for this outing I added gun no.3
An AR 10 6.5 cr. this one has a 20" proof barrel with a rifle length plus 2". This gun has been a complete pain in the ass since I got it. I am running a Sprinco green spring in it as well with a buffer that is lightened to 4 oz. It was working fine in warmer temps but now is giving me all sorts of problems. I finally took the green spring out and put a standard AR 15 rifle length spring in it from Brownells. I was able to get it to moderately function with that but it is on the ragged edge. I'm running 41 grains of H4350 under a 147 ELDM in it. The more I try to get these Ar's to shoot the more I like my Robinsons.
gun number 1 still seems to be a mystery. I pulled an A5 H1 buffer apart and changed out the weights. I got it down to 3.35 oz. I ran that on top of the Green spring and it ran fine at first. Once it got cold though, it would not hold the bolt open. I also added some other loads to the test. I used some H4895 under both a Hornady 75 BTHP and the 73 ELDM. I had a lot more issues with the 4895 loads. My hottest were loaded to 24.4 grains under a 69 grn match burner. Again those shot and loaded ok but would not hold the bolt open. Someone with more knowledge can certainly correct me if I'm wrong but I believe that the 4895 must be just a bit too slow.
for this outing I added gun no.3
An AR 10 6.5 cr. this one has a 20" proof barrel with a rifle length plus 2". This gun has been a complete pain in the ass since I got it. I am running a Sprinco green spring in it as well with a buffer that is lightened to 4 oz. It was working fine in warmer temps but now is giving me all sorts of problems. I finally took the green spring out and put a standard AR 15 rifle length spring in it from Brownells. I was able to get it to moderately function with that but it is on the ragged edge. I'm running 41 grains of H4350 under a 147 ELDM in it. The more I try to get these Ar's to shoot the more I like my Robinsons.
given what we know;
regular buffer and springs, no need for spingco etc
I use 10w mobil 1 down to zero and 0w below with light application
you really should not have any issues
that said, surprised at the lucas as I've used the lucas extreme at 0 temps with no issue but as said, i prefer mobil1
regular buffer and springs, no need for spingco etc
I use 10w mobil 1 down to zero and 0w below with light application
you really should not have any issues
that said, surprised at the lucas as I've used the lucas extreme at 0 temps with no issue but as said, i prefer mobil1
My vote is a weird gas issue. Maybe a gas tube with a hole drilled in the wrong spot. a gas tube that is misaligned to the gas key. I had one rifle where the gas key wore down the gas tube severly and would not provide enough gas to operate. Gas key hole maybe too large. Double check anywhere that might be prohibiting flow or bleeding flow.
On gun #1 try a standard-weight (5.2-ish ounces) A5 with a GI or Tubb spring.
How did you pick the components you have? What was your starting base line (out-of-the-box or original build)?
H4895 is a middle burn rate powder and should be fine around 24 to 24.5 pushing 73 to 77. 24.4 to 24.7 pushing a 69 Sierra or Nosler.
Looks like you attacked a lot of problems that weren't problems if the gun was working -- until temperatures dropped. Fighting in sub-freezing climes changes lots of stuff (including how viscous petroleum products act) -- why NATO and DOD test ammo under EPVAT protocols (extreme hot and cold included).
How did you pick the components you have? What was your starting base line (out-of-the-box or original build)?
H4895 is a middle burn rate powder and should be fine around 24 to 24.5 pushing 73 to 77. 24.4 to 24.7 pushing a 69 Sierra or Nosler.
Looks like you attacked a lot of problems that weren't problems if the gun was working -- until temperatures dropped. Fighting in sub-freezing climes changes lots of stuff (including how viscous petroleum products act) -- why NATO and DOD test ammo under EPVAT protocols (extreme hot and cold included).
In gun #1, you have a GREEN spring with is 2 steps stiffer than standard which is WHITE. YELLOW is one step down from standard.
In all the rifle gas guns that I have built, I have never used anything but WHITE or YELLOW with a 3 or a 4 oz buffer; the only time I have ever gone stiffer is to go one step stiffer, which is BLUE, is on some mid-gas guns.
Try your fully cleaned # 1 gun with your YELLOW spring & both a 3 oz & a 4 0z buffer & I think your problems will go away. Personally, I'd ditch the A5 too.
Even though it worked when warm, you were probably on the edge of not working.
And start at the start..................one round in the mag to see if it locks back.
I've had cold weather problems with weak 223 ammo in a KAC, of all guns, when weather got cold & had to got to full powder NATO equivalent loads so temp impact is real.
Your 24 gr of TAC should be OK; if in doubt about ammo, IMO, IMI full powder NATO ammo is the best test standard to measure against,
Any good synthetic 0-20 oil use sparingly should be fine. Lube your locking lugs, rings & all the right places on the BCG.................do not over do it. g
MM
In all the rifle gas guns that I have built, I have never used anything but WHITE or YELLOW with a 3 or a 4 oz buffer; the only time I have ever gone stiffer is to go one step stiffer, which is BLUE, is on some mid-gas guns.
Try your fully cleaned # 1 gun with your YELLOW spring & both a 3 oz & a 4 0z buffer & I think your problems will go away. Personally, I'd ditch the A5 too.
Even though it worked when warm, you were probably on the edge of not working.
And start at the start..................one round in the mag to see if it locks back.
I've had cold weather problems with weak 223 ammo in a KAC, of all guns, when weather got cold & had to got to full powder NATO equivalent loads so temp impact is real.
Your 24 gr of TAC should be OK; if in doubt about ammo, IMO, IMI full powder NATO ammo is the best test standard to measure against,
Any good synthetic 0-20 oil use sparingly should be fine. Lube your locking lugs, rings & all the right places on the BCG.................do not over do it. g
MM
Ar15s are supposed to be idiot proof to assemble, and here I am with a 16” 308 “AR-10” with mid length gas, a rifle receiver extension, carbine buffer, and suppressor; that shoots, ejects, and locks back once the gas block is adjusted.
I agree with the above posters that suggest the cold weather issue is a result of temp sensitive ammo and/or lubrication.
The only thing I’ll add is that anytime troubleshooting is involved, eliminating handloaded ammunition from the equation is my first step. Get it running with known good factory ammo. That’s your “ground truth.” Adjust from there.
I agree with the above posters that suggest the cold weather issue is a result of temp sensitive ammo and/or lubrication.
The only thing I’ll add is that anytime troubleshooting is involved, eliminating handloaded ammunition from the equation is my first step. Get it running with known good factory ammo. That’s your “ground truth.” Adjust from there.
The answer is any correctly put together AR with correct parts will run under all conditions. If not something is wrong with parts or installed wrong
1. Take apart upper. Take off gas block to install with correct alignment as you move gas block to spot you feel least resistance to air blowing in. That will make sure it’s installed correctly
2. Take bolt out of carrier and Aline gas tube to carrier key do it smoothly goes into key with no up, down or side to side movement. Use wide screwdriver to slightly bend if needed
3. Examine bolt gas rings to make sure the gaps Aline
4. Put the BCG back together clean. Stand on bolt. If it goes down with weight of carrier rings are shot
5. Just oil with light oil and go shoot and see if it works. If it does not try a bolt carrier assembly from working AR. There are a bunch of bad bolts out there out of spec that won’t work period dot and pass the typical DIY tests these usually show as out of round in the firing pin tube area
6. If that does not work change to standard springs and buffers and try again
If that does not work it’s time for opening gas holes but that’s last resort
1. Take apart upper. Take off gas block to install with correct alignment as you move gas block to spot you feel least resistance to air blowing in. That will make sure it’s installed correctly
2. Take bolt out of carrier and Aline gas tube to carrier key do it smoothly goes into key with no up, down or side to side movement. Use wide screwdriver to slightly bend if needed
3. Examine bolt gas rings to make sure the gaps Aline
4. Put the BCG back together clean. Stand on bolt. If it goes down with weight of carrier rings are shot
5. Just oil with light oil and go shoot and see if it works. If it does not try a bolt carrier assembly from working AR. There are a bunch of bad bolts out there out of spec that won’t work period dot and pass the typical DIY tests these usually show as out of round in the firing pin tube area
6. If that does not work change to standard springs and buffers and try again
If that does not work it’s time for opening gas holes but that’s last resort
It's interesting that all three rifles are having issues in the cold but not when warmer... After a thorough cleaning with a metal cleaner to strip away any sticky buildup, use a light synthetic oil.
That’s a band aide fix because it should work dirty or clean or it’s a safe queen not a weapon. lol. It might work temporarily but in the end It’s a gas system issue that needs to be addressed. Too many guys just read on net “ What’s best” then throw parts at things and hope
Your loads should be fine. Ran thousands of 75’s in front of 24.0 Tac
On the 6.5. Creedmoor. That round has terrorized many a rifle builder KAC and LMT have solved the gas problems. If I am putting together one I use an adjustable gas system because I run both suppressed and without all the time. The slower powders needed for the 6.5 are harder to get gas perfect without adjustments for the difference between suppressed
The 1 factory ammo shot fine.
All your reloads have issues. 20 degrees isnt even really THAT cold.
Im not a reloader so forgive me, but is it possible to try some other factory ammo and see if it works?
If it does, maybe there is an issue with weak loads. Sounds stupid, but maybe your powder scale is off or something else in your reloading process?
All your reloads have issues. 20 degrees isnt even really THAT cold.
Im not a reloader so forgive me, but is it possible to try some other factory ammo and see if it works?
If it does, maybe there is an issue with weak loads. Sounds stupid, but maybe your powder scale is off or something else in your reloading process?
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