AR-15 short stroking? (Or just not working)

LeeEnfieldNo.4_mk1

LeeEnfieldNo.4_mk1

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So I went out with my AR build today for some shooting and had a few issues. It appears the action is short stroking. It seems to cycle enough to #### the action, but not enough to pick up another round which also results in the empty mag not locking the bolt back. I had similar issues last time I fired it (which was the first time as well). It seems to function fine for a bit then starts to act up.

Its a home build, 20" barrel, rifle length gas system, with an Armalite A2 stock/buffer set. Magazines used were 10 round pistol mags with AE 55g black box ammo. Temp wise, it was about -5 I would have to say.

Any Ideas in the issue? I am thinking either cold temps effecting the lube or the buffer spring to too strong.

Thanks.
 
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Could be lube. I've heard of people having problems because of over-lubing in the winter.

I had similar issues last time I fired it (which was the first time as well). It seems to function fine for a bit then starts to act up.
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Weather the same or warm(er)?

I would check the gas port diameter.

Doubt highly it's the spring.
 
The list below seem to be the main causes of short stroking.

Try different mag?
Ammo?
correct spring, buffer?
lube?
gas key tight?
gas rings still there?
gas tube kinked?
gas block lined up tightened down properly?
 
6gm6 said:
The list below seem to be the main causes of short stroking.

Try different mag?
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Mags have nothing to do with short stroking.

6gm6 said:
Ammo?
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A possibility, but a good gun should work with nearly any reasonable ammo.

6gm6 said:
correct spring, buffer?
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These questions are relevant only to carbines. Rifle length systems only come with one type of spring and buffer. Using carbine components in a rifle system will result in something quite the opposite of a short stroke.

6gm6 said:
lube?
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The best guess.

6gm6 said:
gas key tight?
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Worth checking.

6gm6 said:
gas rings still there?
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Worth checking. Kind of.

6gm6 said:
gas tube kinked?
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Possible, I guess.

6gm6 said:
gas block lined up tightened down properly?
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Now we're really grasping at straws.


The most likely issue is simply a new gun and inadequate lube. Clean it thoroughly, oil the hell out of it and shoot 200 through it. If at the end of that the problem still isn't resolved you need to start disassembling the gun looking for defective components.
 
Ill give it a few more goes with the oil and see what happens. I only have maybe 200 rounds through the pretty lady so maybe it does need a little more break in for the parts to mate and smooth out a little.

Just a note, I am using Castrol Syntec full synthetic 5w30 for lube as I had about a liter left sitting in the garage, I feel if it can handle the exponentially worse (yet similar) conditions of an engine, it should be able to handle the conditions of a firearm right?
 
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Let the rifle get cold.
Any thickening of the oil?
Or leave the oil outside overnight. See if there is any change in viscosity.
 
Yeah, I've had rifles freeze up on me. On a really cold day where shooting is not generating enough heat to over come the cold.
Cold weather is where a carbine shines.

Ammo powder can freeze up too and general less gas pressure. It's a stretch but I know MFS won't cycle my 20" rifle in cold weather.
AE has more kahonas then MFS tho'.

I lighter weight oil might be worth a try to see.
Too much oil can also slow things down if it's getting cold. If you are over oiling it kind of thing. I "precision" oil my AR's. My BCG is pretty much dry except for the slide points, the bolt lugs, and the gas rings. Runs like a top with my reloaded ammo.
 
Clean it thoroughly, oil the hell out of it and shoot 200 through it.
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In cold weather, putting too much oil on can cause the carrier to 'frost up'. And it kind of sounds like what is happening if it works at first and then stops.

Just a note, I am using Castrol Syntec full synthetic 5w30 for lube
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Likely way too thick.

I lighter weight oil might be worth a try to see.
Too much oil can also slow things down if it's getting cold. If you are over oiling it kind of thing. I "precision" oil my AR's. My BCG is pretty much dry except for the slide points, the bolt lugs, and the gas rings. Runs like a top with my reloaded ammo.
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More or less how I lube mine and I never have an issue.

You shouldn't need to dip your AR in a bucket of oil to make it run ;)
 
In some cases where there is a fixed stock the length of the bolt that attaches the stock to the tube can be too long. I had a time finding the short bolt for the early stock. There is a longer bolt for the Canadian C7 stock with the spacer.
Just an issue I had with one of my guns.
 
Leave the 5w30 in your engine where it is meant to be and use a GUN specific product like G96 spray lube which will NOT freeze or even thicken unless it is 100 below.

Why is that guys always want to use products designed for a car in a gun? Good thing women cook.
 
alberta tactical rifle said:
Leave the 5w30 in your engine where it is meant to be and use a GUN specific product like G96 spray lube which will NOT freeze or even thicken unless it is 100 below.

Why is that guys always want to use products designed for a car in a gun? Good thing women cook.
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Best advice yet! I don't get why people try to cheap out on their lube. Motor oil is for use in a motor and gun oil is for use in a gun. When you operate a gun in extreme conditions ( cold, hot, dusty, ect) lube becomes critical for reliable operation. Clean your gun well use proper gun lube and try again, report back.
 
You should have an experienced AR Armourer look at the gas port / gas system to ensure it is un obstructed and the gas port is the appropriate size. Just a thought based on experience. Cheers Wolfgang.
 
LeeEnfieldNo.4_mk1 said:
So I went out with my AR build today for some shooting and had a few issues. It appears the action is short stroking. It seems to cycle enough to #### the action, but not enough to pick up another round which also results in the empty mag not locking the bolt back. I had similar issues last time I fired it (which was the first time as well). It seems to function fine for a bit then starts to act up.

Its a home build, 20" barrel, rifle length gas system, with an Armalite A2 stock/buffer set. Magazines used were 10 round pistol mags with AE 55g black box ammo. Temp wise, it was about -5 I would have to say.

Any Ideas in the issue? I am thinking either cold temps effecting the lube or the buffer spring to too strong.

Thanks.
Click to expand...

I would take just the upper assembly and check the following,

- check the gas key & gas tube, and make sure they line up ok
- clean the chamber, polish it if its not chrome lined
- check for worn or damaged gas rings

Happy New Years!
 
IDPACONVERT said:
I would take just the upper assembly and check the following,

- check the gas key & gas tube, and make sure they line up ok
- clean the chamber, polish it if its not chrome lined
- check for worn or damaged gas rings

Happy New Years!
Click to expand...

If the gun is new then the gas rings should not be worn (could be damaged but highly unlikely). They might, however, not be lined up properly. Each of the three rings needs about a one third overlap with the adjacent one to prevent gas blow by.
 
ted_dent said:
.... They might, however, not be lined up properly. Each of the three rings needs about a one third overlap with the adjacent one to prevent gas blow by.
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Oh really. Can I interest you in my latest invention then, the gas ring position optimizer? They are on sale all this week! ;)
 
Guns will work with one gas ring, the alignment issue is a old wives tale taught by morons.

With home built guns its harder to diagnose as you did not list who made what parts.

Colder Climates need a lighter lube than warmer, however if its working then stops - that tends to rule out lube, as it would (provided the weapon is cool/cold to begin with) get thinner while being shot.

But -5C is not cold (relatively) and your weapon should not be having issues like that, however your ammo may be on the weak side, and colder climates affect powder burb rates, so it may just not have enough ass - and your getting lucky on the first few rounds that it is running on the jagged edge of function
 
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