AR build is short stroking

[BMF JK]

Figure I may as well include a picture . FDE is my latest creation and my problem child ! Decided featureless since I have a couple fixed mag rifles already !
Ok guys looking for trouble shooting suggestions. Rifle will not eject unless I manually eject spent cartridge with charging handle .

Build list of what I’d believe to be pertinent, anything I leave out lemme know.

-Aero m4e1 enhanced builders set
-16”crowned match barrel with carbine length gas port chambered in 5.56
- seekins low pro adjustable gas block with aero carbine length gas tube
- aero nickel boron BCG
- spikes tactical t2 heavy buffer and spring

What I’ve done so far

-Gas block full open
-Tried different ammo
- attached a little surgical hose to gas tube inside the upper , blew through and could feel air at muzzle and chamber ends of the barrel.
-tried different BCG from another rifle , thinking maybe a blockage in the gas key or beyond . Same short stroking occurs
- swapped out buffer and spring with a regular 3oz carbine buffer .

I’m by no means a master builder , however have built a few rifles before . I dimpled the barrel myself with a ring type jig . I’m wondering if I messed up the alignment of the gas block somehow.
I’m really frustrated at the moment! I sunk some good money into this build for essentially a bolt action AR ! Lol

Any suggestions would be greatly appreciated! Before I say eff it and take it to a gun smith . THANKS

 

[Bushmaster]

I'm starting at bottom of my list questions... once you manually eject, what does the second round do? And do you see any marks on the casing? Does it try to double feed next round or just stop?

 

[dsdmmat]

Open the gas port in the barrel a few thousands wider.

 

[Bushmaster]

And are you using the same mag each test?

 

[ArmedCorgi]

Is your gas block covering the port some?

 

[BMF JK]

I'm starting at bottom of my list questions... once you manually eject, what does the second round do? And do you see any marks on the casing? Does it try to double feed next round or just stop?

Case looks fine , I assume your thinking a bur in the chamber ? No double feed just stops

 

[Bushmaster]

Open the gas port in the barrel a few thousands wider.

THIS above with out further info.... !!

 

[Bushmaster]

Open the gas port in the barrel a few thousands wider.

...........................................!!!!!!!!!!!!!!!!!

 

[BMF JK]

Open the gas port in the barrel a few thousands wider.

Ok now you making me nervous lol
I’ll give that a shot thanks !

 

[BMF JK]

And are you using the same mag each test?

Nope 4 different mags

 

[Bushmaster]

Ok now you making me nervous lol
I’ll give that a shot thanks !

I bet he is CORRECT !!!!! Had a pred unit did same thing.

 

[BMF JK]

Is your gas block covering the port some?

I’ll pull it apart and check

 

[Bushmaster]

Nope 4 different mags

I bet DSDMMAT is correct....

 

[Bushmaster]

By the way, nice looking units. !!!

 

[BMF JK]

I bet DSDMMAT is correct....

I’m thinkin , the gas port looked tiny compared to the gas block port . Figured it allows tolerance with alignment. I’ve never done a gas block install myself, figure I’d give a whirl this go around.

 

[BMF JK]

By the way, nice looking units. !!!

Thank you

 

[dsdmmat]

Ok now you making me nervous lol
I’ll give that a shot thanks !

Your gas block is wide open and you are still not getting enough gas. You should be able to have your gas block in the middle and have the rifle operate properly with a wide variety of ammo.

Open it up with the next size up drill bit.

 

[Bushmaster]

How to Fix Common AR-15 Malfunctions and Stoppages

 

[BMF JK]

Your gas block is wide open and you are still not getting enough gas. You should be able to have your gas block in the middle and have the rifle operate properly with a wide variety of ammo.

Yes wide open . I have the same gas block on my other rifle and I run it half open .

 

[BMF JK]

How to Fix Common AR-15 Malfunctions and Stoppages

Thanks for the link !

 

[BMF JK]

Wow guys I musta earned some street cred with this thread I’m a 22lr now
Guess I’ve lurked far too long .

 

[Bushmaster]

Wow guys I musta earned some street cred with this thread I’m a 22lr now
Guess I’ve lurked far too long .

Thats a basic newbie link trouble shoot LOL....

 

[BMF JK]

I’ll try to open the barrel port a bit .

 

[Bushmaster]

I/m out a here LOL, dsdmmat already jumped ahead on what I think is correct on info given, Let us know... I bet he is correct, I had one like that also.

 

[BMF JK]

Thank you guys , I’ll keep ya updated

 

[Bushmaster]

I HATE NYS FUAC AR,S but your quality scope mount and upper pulls the eye away from it... Nice build, good job !!

 

[BMF JK]

I HATE NYS FUAC AR,S but your quality scope mount and upper pulls the eye away from it... Nice build, good job !!

Thanks I took my time and did some research.

 

[meketrefe]

Follow the process end to end....

-It starts with the right port size.
-Also don't assume the bolt closes and opens freely. When you headspace the rifle w/o the ejector plunger make sure the bolt
rotates and opens+closes w/o any resistance.
- Don't assume the adjustable block is full open when it says full open. The fact that blows air it says nothing other than there
is no obstruction but you need to be able to achieve a certain amount of pressure in a fraction of a second so any constrictions
will impact that.
- Make sure there is no bleeding anywhere and the block and barrel ports are correctly position both in the X and Y axis. Don't
assume the any witness mark is in the right place as barrels and parts makers make mistakes too.
- The tube should not have any obstructions.
- The end of the gas tube should be properly flared and deburred. It should make with the gas key snug but w/o getting stuck.
-The bolt body should be snug but move freely.
-The cam should be snug but also free of burrs and provide reasonable tolerances to rotate w/o problems. This will loose with
use as everything else.
-The gas rings should be stacked accordingly.
-The carrier should move freely and fall into battery and out by gravity. If you take the buffer spring and weight off you should be
able to feel the opening of the carrier w/o any resistance other than the hammer.
-By the same token and still w/o the buffer spring the carrier should move forward when pointing down and fall w/o resistance
and close into battery just by inertia. Then you can add the buffer and spring back.
-The hammer spring should be tuned to avoid excessive pressure (common problem) as well as the hammer itself that should be free of burrs
and with the right angle.
- make sure the magazines do not drag with the carrier. If necessary adjust the lips with proper pliers.
- do not start with excessive pressure like a fully loaded magazine that might be or not in spec. First you want to make sure the
system cycles and stops by simply single feeding.
- you might want to close the gas block and then remove the spring but leave the buffer (to stop) to see if by opening the port
progressively and single feeding can get enough reaction to the carrier to the back
-Lastly if everything checks above and you continue to have issuse you most likely need a wider port or check for burrs but
also consider the ammo you are using. for example between a PMC bronze (rather mild) and a NATO LC plant there is about
10K PSI difference and 300-400fps speed.
This is the bitch with the carbine ported barrels that they are harder to balance. The AR doesn't need a heavier buffer unless
one wants to delay the group that is more important in selective fire for reliability. But also consider that if you do nothing
the milder ammo might not have enough pressure while the hottest ammo will slam the group hard. Because of the dwell time
the carbines are harder to adjust for balance and that is why I believe the carbine porting shoud have never existed. It was a
design mistake of the M4.
In any case measure the port and if needed run a cobalt bit with the next size up and as I said make sure the adjustable block
is not interfering.
Follow this steps and slowly paying attention to detail. Everything that happens in the cycling can be reproduced and almost insulated
and you will find the root cause that might well be the port itself or some burr in there or something.
Everything happens for a reason and one step has an impact in the next so follow the GAS flow.

Good luck brother.

 

[Bushmaster]

Well he is correct AGAIN!!! But he always gives the FULLLLLL info. If ya ask the time of day MEK will tell you how the watch was built LOL.... But ya, he know's his stuff.... !!! trust him !!

 

[BMF JK]

Follow the process end to end....

-It starts with the right port size.
-Also don't assume the bolt closes and opens freely. When you headspace the rifle w/o the ejector plunger make sure the bolt
rotates and opens+closes w/o any resistance.
- Don't assume the adjustable block is full open when it says full open. The fact that blows air it says nothing other than there
is no obstruction but you need to be able to achieve a certain amount of pressure in a fraction of a second so any constrictions
will impact that.
- Make sure there is no bleeding anywhere and the block and barrel ports are correctly position both in the X and Y axis. Don't
assume the any witness mark is in the right place as barrels and parts makers make mistakes too.
- The tube should not have any obstructions.
- The end of the gas tube should be properly flared and deburred. It should make with the gas key snug but w/o getting stuck.
-The bolt body should be snug but move freely.
-The cam should be snug but also free of burrs and provide reasonable tolerances to rotate w/o problems. This will loose with
use as everything else.
-The gas rings should be stacked accordingly.
-The carrier should move freely and fall into battery and out by gravity. If you take the buffer spring and weight off you should be
able to feel the opening of the carrier w/o any resistance other than the hammer.
-By the same token and still w/o the buffer spring the carrier should move forward when pointing down and fall w/o resistance
and close into battery just by inertia. Then you can add the buffer and spring back.
-The hammer spring should be tuned to avoid excessive pressure (common problem) as well as the hammer itself that should be free of burrs
and with the right angle.
- make sure the magazines do not drag with the carrier. If necessary adjust the lips with proper pliers.
- do not start with excessive pressure like a fully loaded magazine that might be or not in spec. First you want to make sure the
system cycles and stops by simply single feeding.
- you might want to close the gas block and then remove the spring but leave the buffer (to stop) to see if by opening the port
progressively and single feeding can get enough reaction to the carrier to the back
-Lastly if everything checks above and you continue to have issuse you most likely need a wider port or check for burrs but
also consider the ammo you are using. for example between a PMC bronze (rather mild) and a NATO LC plant there is about
10K PSI difference and 300-400fps speed.
This is the bitch with the carbine ported barrels that they are harder to balance. The AR doesn't need a heavier buffer unless
one wants to delay the group that is more important in selective fire for reliability. But also consider that if you do nothing
the milder ammo might not have enough pressure while the hottest ammo will slam the group hard. Because of the dwell time
the carbines are harder to adjust for balance and that is why I believe the carbine porting shoud have never existed. It was a
design mistake of the M4.
In any case measure the port and if needed run a cobalt bit with the next size up and as I said make sure the adjustable block
is not interfering.
Follow this steps and slowly paying attention to detail. Everything that happens in the cycling can be reproduced and almost insulated
and you will find the root cause that might well be the port itself or some burr in there or something.
Everything happens for a reason and one step has an impact in the next so follow the GAS flow.

Good luck brother.

Thank you for the info ! Well looks like I’m not hunting this weekend. Lol no really that all makes sense divide and conquer I will .