Over Gassed FTE?

[gdonley308]

I searched but didn’t find any topics covering this. I have an Armalite TAC18 in .308. I’ve been having FTE now very often. This rifle came with an adjustable gas block. I upgraded the extractor spring to the Springco extra power dual spring set up. This did not help. Now I’ve been reading that an over gassed rifle can have FTE? With this in mind I took off the handgard and tried to adjust the gas. The Allen head screw for the gas regulation was almost impossible to get out. I used heat and finally got it out. There was no locking screw as described in Armalites leaflet that came in the manual for the adjustable gas block. Has anyone heard of an over gassed rifle having failure to Extract? Stock photo shows the rifle in question. Thanks

[98Z5V]

You should see brass damage if that's the case.  If it's overgassed, it's cycling too fast, and begins the unlocking of the bolt/extraction process before the brass has slightly cooled and contracted - that will usually rip the rims on the brass.  Got any brass you can show us?

That's a damn nice looking rifle, by the way...

Edited May 6, 2018 by 98Z5V

[jtallen83]

Pictures of the gas block as well, Armalite doesn't make gas blocks so someone here will most likely be familiar with it. If it's over gassed there is no reason you shouldn't be able to adjust that issue away.

[gdonley308]

7 hours ago, jtallen83 said:

Pictures of the gas block as well, Armalite doesn't make gas blocks so someone here will most likely be familiar with it. If it's over gassed there is no reason you shouldn't be able to adjust that issue away.

First off I want to thank you and everyone else trying to help me diagnose this issue! Here’s the pictures. I included the Armalite litterateur for the adjustable gas block. There was no locking Allen screw, just the one shown. Even with allot of heat, threads were destroyed. Not happy about a new , relatively expensive, rifle coming through QC like this. As you can see, it happened with a variety of ammo. It also got worse with the Springco Dual extra power extractor Springs. 

[jtallen83]

16 minutes ago, gdonley308 said:

There was no locking Allen screw, just the one shown.

Was there no locking screw or no place for a locking screw? Sure looks like it was in there when the adjustment screw was turned out, could it be that it is a short one and sitting in there way deep?

Mt experience in the past with Armalite was that they take care of issues like this, call and insist. You shouldn't need to swap the springs unless they have seriously changed the specs, I find the springs I have bought from Armalite are better than most others.

[98Z5V]

30 minutes ago, gdonley308 said:

 

These two pictures are terrifying.  Maybe it's the angle of the camera, but there appears to be a HUGE difference in case length here.  Can you pull those same four rounds, and measure them with a digital vernier caliper?

I think you can clean that gas block up, with a tap. Get a different set screw, one that's not stainless steel, too - steel one, black oxide coated.  Ace Hardware will have one, just like that, on non-stainless.  I think JT is right, also, and there was a locking screw in there. If not, and there wasn't, that stainless galled up pretty bad coming out.  I also think Armalite would take care of you on this, and at least send you a new (same) gasblock to install.  Get your information in this thread to them. 

On a different note - your brass looks good. There are no cratered or flattened primers, no bulges at the base of the cases. It's not over-pressured ammo causing this.  It certainly does look like it's over-gassed, though, and you have some damage to the case rims, from the attempted extraction process.

[gdonley308]

44 minutes ago, jtallen83 said:

Was there no locking screw or no place for a locking screw? Sure looks like it was in there when the adjustment screw was turned out, could it be that it is a short one and sitting in there way deep?

Mt experience in the past with Armalite was that they take care of issues like this, call and insist. You shouldn't need to swap the springs unless they have seriously changed the specs, I find the springs I have bought from Armalite are better than most others.

No, just the one stripped Allen screw you see in the picture. No adjustment screw, or if this is the adjustment screw there was no locking screw? Either way, it took allot of heat ( most likely red loctite) and the screw is stripped. No answer to numerous emails and phone calls to Armalite? 

[gdonley308]

53 minutes ago, 98Z5V said:

These two pictures are terrifying.  Maybe it's the angle of the camera, but there appears to be a HUGE difference in case length here.  Can you pull those same four rounds, and measure them with a digital vernier caliper?

I think you can clean that gas block up, with a tap. Get a different set screw, one that's not stainless steel, too - steel one, black oxide coated.  Ace Hardware will have one, just like that, on non-stainless.  I think JT is right, also, and there was a locking screw in there. If not, and there wasn't, that stainless galled up pretty bad coming out.  I also think Armalite would take care of you on this, and at least send you a new (same) gasblock to install.  Get your information in this thread to them. 

On a different note - your brass looks good. There are no cratered or flattened primers, no bulges at the base of the cases. It's not over-pressured ammo causing this.  It certainly does look like it's over-gassed, though, and you have some damage to the case rims, from the attempted extraction process.

Yes I see that! Here’s some pics

[98Z5V]

Eh, that was camera angle or something - those are all within 0.002", which is alright.

[gdonley308]

I’m going to replace the gas block with a Superlative Arms .875” Bleed Off adjustable gas block. It costs $85 which, if Armalite ever answers me, is what it will cost me to ship it to them and back. Going to also polish the chamber although the brass looks fine, and go back to the factory extractor spring. Should I buy a “Go-No Go” gauge and check the chamber before polishing? This one has me baffled.  Of all my AR’s including my 6.8spc’s this is my first problem child.

[gdonley308]

LINk to the new gasblock

 

https://suparms.com/collections/adjustable-gas-blocks-direct-impingement/products/875-adjustable-gas-block-bleed-off-solid-melonited

[jtallen83]

46 minutes ago, gdonley308 said:

No adjustment screw, or if this is the adjustment screw there was no locking screw?

How about a picture of the front of the gas block, that is where the locking screw should have been. If there is no hole there then that is a defective block going by the directions. That screw should be the adjustment screw and should not have any loctite.

[jtallen83]

9 minutes ago, gdonley308 said:

LINk to the new gasblock

 

https://suparms.com/collections/adjustable-gas-blocks-direct-impingement/products/875-adjustable-gas-block-bleed-off-solid-melonited

Do a search here and read my review on this gas block if you haven't paid for it yet. The bleed of settings do not allow enough gas out to work properly, works fine in the restrictive setting but then you can get one lots cheaper that does that.

Edited May 6, 2018 by jtallen83

[gdonley308]

24 minutes ago, jtallen83 said:

Do a search here and read my review on this gas block if you haven't paid for it yet. The bleed of settings do not allow enough gas out to work properly, works fine in the restrictive setting but then you can get one lots cheaper that does that.

I haven’t paid for it yet. I want a forward adjustment on the next gas block, one that won’t work loose. What gas block would you recommend?

[jtallen83]

Just now, gdonley308 said:

What gas block would you recommend?

I love my SLR gas blocks. DVOR has some on sale right now;

https://www.dvor.com/weeklong-sale-on-slr-rifleworks-firearm-parts-65-2018-05-06.html

SLR is having a 15% off sale on their site;

http://slrrifleworks.com/index.php?route=common/home

For a cheaper route you can look here, Superlative and SLR are the only ones I have experience with so I'll let others chime in with recommendations.

http://www.primaryarms.com/MCategories+AR-15-Gas-Blocks

 

[Matt.Cross]

SLR's adjustable gas block is hard to beat performance wise.

[gdonley308]

2 hours ago, jtallen83 said:

How about a picture of the front of the gas block, that is where the locking screw should have been. If there is no hole there then that is a defective block going by the directions. That screw should be the adjustment screw and should not have any loctite.

Here’s where the locking screw should have been 

[jtallen83]

58 minutes ago, gdonley308 said:

Here’s where the locking screw should have been 

I’m betting that locking screw is in there just way deep. That would explain the galled threads. 

[gdonley308]

2 hours ago, jtallen83 said:

I’m betting that locking screw is in there just way deep. That would explain the galled threads. 

Nope, nothing in that hole but threads.

[308kiwi]

If I can add my 2c worth, don't go polishing your chamber unless there is a reason to, IE a visible burr etc.

On firing the brass expands and grips the chamber walls, a considerable amount of the rearward thrust created by the expanding gas and the equal/opposite reaction forces of the projectile being pushed down the barrel is counteracted by the case gripping the chamber, if you polish it mirror smooth you will increase the amount of thrust being applied to the bolt and locking lugs, not a good thing to be doing.

Whenever I chamber a barrel I always 'rough' the chamber surface with '0' steel wool wrapped around a small piece of dowel.

 

 

[gdonley308]

8 hours ago, 308kiwi said:

If I can add my 2c worth, don't go polishing your chamber unless there is a reason to, IE a visible burr etc.

On firing the brass expands and grips the chamber walls, a considerable amount of the rearward thrust created by the expanding gas and the equal/opposite reaction forces of the projectile being pushed down the barrel is counteracted by the case gripping the chamber, if you polish it mirror smooth you will increase the amount of thrust being applied to the bolt and locking lugs, not a good thing to be doing.

Whenever I chamber a barrel I always 'rough' the chamber surface with '0' steel wool wrapped around a small piece of dowel.

 

 

Ok, I’ll hold off on polishing. Could my extractor be out of spec? Ejector spring too strong? Buffer too light? Things definitely got worse with the Springco Extractor Springs. I have to go to work in Texas for the next 3 weeks so it’s going to be awhile before I get to shoot the rifle again. Can over gassing cause these FTE? Armalite states in their litterateur that the gas block is adjusted for full gas from the factory. Some people are telling me to throw in an H3 buffer? I run H3’s and Tubbs buffer springs on my 6.8spc’s for a 3 o’clocK Ejection pattern with 110-115gr loads.

[98Z5V]

1 hour ago, gdonley308 said:

Can over gassing cause these FTE? Armalite states in their litterateur that the gas block is adjusted for full gas from the factory. Some people are telling me to throw in an H3 buffer? I run H3’s and Tubbs buffer springs on my 6.8spc’s for a 3 o’clocK Ejection pattern with 110-115gr loads.

It could be the extractor itself, but that's doubtful. One way to check is to remove it from the bolt, and "clip" it onto the rim of a fired case - see if it's got full engagement on the case rim.

Yes, most definitely, overgassing can cause failure to extract.

If you have a full factory 308 rifle, from Armalite, and it's got the collapsible stock system in the pic above, then it's already got the H3 buffer in it. 

Edited May 7, 2018 by 98Z5V

[308kiwi]

Ditto to what 98Z5V said.

I would go as far as to say that unless some component involved in the initial extraction of the case from the chamber, eg extractor, has failed then your extraction issues are due to the bolt groups initial unlocking/extraction being too violent.

Adding extra weight into the system, heavy buffer, simply delays the rearward travel of the BCG by a few milliseconds allowing the case to relieve itself from the chamber a little more and the gas pressures to decrease ever so slightly, it is a solution but you need to fix the cause, not the symptom.

Sort your gas system first and you'll likely find your problems will go away.

Edited May 7, 2018 by 308kiwi

[COBrien]

17 hours ago, gdonley308 said:

Nope, nothing in that hole but threads.

Not trying to be a jerk, but did you stick an Allen wrench in there and try to hit a locking screw? Because I don't see any other way for the threads on that adjustment screw to be that FUBARed.

[gdonley308]

44 minutes ago, COBrien said:

Not trying to be a jerk, but did you stick an Allen wrench in there and try to hit a locking screw? Because I don't see any other way for the threads on that adjustment screw to be that FUBARed.

Yes, shone a light through and put a small screw driver through the locking screw hole until I could see it in the adjustment hole