AR15 Cycling Issues

[Shoebox]

I appreciate everyone not giving up on this rifle! Hopefully I come to a solution soon. I am going to try to reach out to Chad today and hopefully he is able to take this rifle in!

I missed it or forgot, but did you try the upper (new or old configuration) with a different lower?

 

[Evintos]

What is your interpretation of this data? Clearly you are far more qualified in these things than I am.

Those ranges don't seem to me to be enough to decisively cripple function like this. Maybe 0.262" to 0.2785", but even that doesn't seem like a huge variance. Isn't there some wiggle room in the tolerances? Or is that your point?

All honest questions.

So much wiggle room that still allows for function and have no drag that for the OP to have trigger hammer drag, the hammer height in the cocked position would have to be positioned so tall that the amount of pressure that the hammer and hammer spring would place on the bottom of the BCG would fall well outside of acceptable. Or that the bolt catch height is so tall it's constantly applying pressure to the BCG ramp. Or that the BCG ramp depth is shallow (but if that was the case, there would also likely be magazine feed lip drag that would be very noticeable, also not likely because different BCG was tried). Or hammer spring weight is like 4x USGI specs. Or the potential of hammer binding a bit on the disconnector.

So hypothetical scenarios for trigger height -

Scenario 1
Upper receiver to BCG ramp depth - 0.260",
Cocked trigger height - 0.383"
Depressed trigger height - 0.260".
The most amount of drag you can get, because if the trigger can't get out of the way of the ramp (like 0.261"), the BCG would never be able to move completely rearward since it would be wedged on the trigger hammer.

Scenario 2
Upper receiver to BCG ramp depth - 0.260"
Cocked trigger height - 0.373"
Depressed trigger height - 0.250"
Less theoretical drag than scenario 1 with about 0.010" extra room for the hammer to move

Scenario 3
Upper receiver to BCG ramp depth - 0.260"
Cocked trigger height - 0.363"
Depressed trigger height - 0.240"
Less theoretical drag than scenario 2 with about 0.020" extra room for the hammer to move.

----------------------------------------------------------------------------
So for the upper and lower combos I measured, I had as little as 0.027" to as much as 0.0745" difference between BCG ramp depth and depressed trigger height and all of those combos will function with each other without drag. OP would probably have to have less than 0.020" for there to be that much drag (maybe closer to 0.010"). To feel that drag, normally you press and hold trigger to the rear while pulling the charging handle all the way to the rear, if there is drag, you'll feel a lot of it through the trigger either throughout the travel or when you get towards the end of the travel.

So far OP has changed basically everything except the registered SBR lower, trigger, bolt catch and magazine catch and had no notable wear on various parts.

 

[Paradox]

What is your interpretation of this data? Clearly you are far more qualified in these things than I am.

Those ranges don't seem to me to be enough to decisively cripple function like this. Maybe 0.262" to 0.2785", but even that doesn't seem like a huge variance. Isn't there some wiggle room in the tolerances? Or is that your point?

All honest questions.

That's acceptable tolerances for a government standard, AR's are like motor oil, everyone's is the best and so on, for an AR i've built them from the most expensive parts on down to simply assembling a bunch of spare parts, and kits i acquired over the years, and have yet to have an issue nor notice a difference, especially with 5.56, their range is so limited, short of a completely shot out gun, at 300 yards, my $250 dollar shit boxes hit the steel just like a $1500 dollar gun, and for any home defense AR in the 11.5" and under it really doesn't matter, I really don't think you could ever get enough variance in a mil-spec piece to cause it to function improperly, just look at the M4, they're made by the thousands, under $600 a piece and built by many vendors, and so are the tolerances lol

 

[Evintos]

Some more references that @mkrem can use to measure the Aero lower.

 

[mkrem]

I missed it or forgot, but did you try the upper (new or old configuration) with a different lower?

Yes, I should have noted that I have tried the upper on two different lowers from working rifles.

Edit: This thread is getting so long I don’t remember what I have posted anymore haha!

 

[Shoebox]

Yes, I should have noted that I have tried the upper on two different lowers from working rifles.

Edit: This thread is getting so long I don’t remember what I have posted anymore haha!

Well I guess that rules out issues with the lower, then.

 

[Tiribulus]

So much wiggle room that still allows for function and have no drag that for the OP to have trigger hammer drag, the hammer height in the cocked position would have to be positioned so tall that the amount of pressure that the hammer and hammer spring would place on the bottom of the BCG would fall well outside of acceptable. Or that the bolt catch height is so tall it's constantly applying pressure to the BCG ramp. Or that the BCG ramp depth is shallow (but if that was the case, there would also likely be magazine feed lip drag that would be very noticeable, also not likely because different BCG was tried). Or hammer spring weight is like 4x USGI specs. Or the potential of hammer binding a bit on the disconnector.

So hypothetical scenarios for trigger height -

Scenario 1
BCG ramp height - 0.260",
Cocked trigger height - 0.383"
Depressed trigger height - 0.260".
The most amount of drag you can get, because if the trigger can't get out of the way of the ramp (like 0.261"), the BCG would never be able to move completely rearward since it would be wedged on the trigger hammer.

Scenario 2
BCG ramp height - 0.260"
Cocked trigger height - 0.373"
Depressed trigger height - 0.250"
Less theoretical drag than scenario 1 with about 0.010" extra room for the hammer to move

Scenario 3
BCG ramp height - 0.260"
Cocked trigger height - 0.363"
Depressed trigger height - 0.240"
Less theoretical drag than scenario 2 with about 0.020" extra room for the hammer to move.

----------------------------------------------------------------------------
So for the upper and lower combos I measured, I had as little as 0.027" to as much as 0.0745" difference between BCG ramp depth and depressed trigger height and all of those combos will function with each other without drag. OP would probably have to have less than 0.020" for there to be that much drag (maybe closer to 0.010"). To feel that drag, normally you press and hold trigger to the rear while pulling the charging handle all the way to the rear, if there is drag, you'll feel a lot of it through the trigger either throughout the travel or when you get towards the end of the travel.

So far OP has changed basically everything except the registered SBR lower, trigger, bolt catch and magazine catch and had no notable wear on various parts.

I haven't had the chance yet to properly study what you've said in this post. Just so I don't get off track, I'm not certain what you're calling the "BCG ramp?" I'm not sure I'm following that part. Are you referring to the bottom graded surface of the carrier that slides over the hammer?

 

[Evintos]

I haven't had the chance yet to properly study what you've said in this post. Just so I don't get off track, I'm not certain what you're calling the "BCG ramp?" I'm not sure I'm following that part. Are you referring to the bottom graded surface of the carrier that slides over the hammer?

Yup. You'll sometimes see it referred to as the BCG hammer ramp. Most people just call it the bottom of the carrier however, there are different sections of the "bottom." I just realized how confusing my post was, what I should've labeled it as was - "Upper receiver to BCG ramp depth" in reference to the measure taken between the red horizontal lines in the pic below which is basically the bottom of the upper receiver (edge/flat) to the bottom of the bcg flat (ramp/graded surface). I hope that made sense.

How trigger hammer stays in contact with the ramp during cycling.

Slightly off topic - https://www.snipershide.com/shootin...08-cycle-failure.7100361/page-2#post-10173628, reference post for how to check for potential issues with carrier drag on magazine feed lips and how a narrow feed lip gap can rub on the side of the ramp.

 

[mkrem]

Yup. You'll sometimes see it referred to as the BCG hammer ramp. Most people just call it the bottom of the carrier however, there are different sections of the "bottom." I just realized how confusing my post was, what I should've labeled it as was - "Upper receiver to BCG ramp depth" in reference to the measure taken between the red horizontal lines in the pic below which is basically the bottom of the upper receiver (edge/flat) to the bottom of the bcg flat (ramp/graded surface). I hope that made sense.

How trigger hammer stays in contact with the ramp during cycling.
View attachment 7861683
Slightly off topic - https://www.snipershide.com/shootin...08-cycle-failure.7100361/page-2#post-10173628, reference post for how to check for potential issues with carrier drag on magazine feed lips and how a narrow feed lip gap can rub on the side of the ramp.

View attachment 7861675
View attachment 7861682

Sorry about the long quote, doing this on my phone. This dimension for me was .265

There is no abnormal pressure/tension while holding the trigger in and cycling the bolt versus not holding the trigger in.

Edit: cocked trigger height: .359
Depressed trigger height: .263

 

[mkrem]

My takedown pins are a bitch to remove. Almost have to use a punch at times. Thoughts on that?

 

[mkrem]

Some more references that @mkrem can use to measure the Aero lower.

Do you have a view for the opposite side of the receiver?

 

[msgriff]

My takedown pins are a bitch to remove. Almost have to use a punch at times. Thoughts on that?

Blunt the tip of the detent. If you're concerned about losing the cad plating, KNS makes hardened nitrided stainless detents with a tip profile that helps. Kind of ridiculous to buy them alone due to shipping though.

 

[Evintos]

Sorry about the long quote, doing this on my phone. This dimension for me was .265

There is no abnormal pressure/tension while holding the trigger in and cycling the bolt versus not holding the trigger in.

Yeah, I figure this wouldn't be the case since you've mentioned you tried different working lowers. It's definitely an anomaly and I hope that Chad of SOTAR will be willing to look over everything.

My takedown pins are a bitch to remove. Almost have to use a punch at times. Thoughts on that?

For the tight pins, it could be anything from oversized diameter pins (from not machined correctly or too thick of a layer of cerakote or other coating), undersized takedown pin holes (machined diameter too small or could be from cerakote or other type of coating), misaligned takedown pin holes on the lower receiver (drilled crooked from one side to the other), bent pins, detent channel of the pins machined incorrectly, takedown pin detents do not have correct bevels, takedown pin springs too long (this usually happens if you have a set screw for the rear takedown pin and you forget to trim the spring, but normally doesn't happen for the front takedown pin), upper receiver tension screws adjusted too high (most lowers do not have these screws, the Aero M4E1 does have this), upper receiver rear lug dimensions too large, lower receiver pocket depth where the lug would seat too shallow.

In terms of whether tight pins (or tight pins due to upper tension screw) causing a short stroke; I can't imagine that it would cause that large of a misalignment between the BCG travel path and buffer tube and not have abnormal wear. Pic below of a friend's build that had the tension screw adjusted too high (high enough that it was really stiff but can be pushed out by hand with some effort) and showed accelerated wear within 100rds of adjusting it. Prior to this he said there was no wear whatsoever.

For it to be so tight that a punch might need to be used to take it apart, there would have to be some form of edge deformation on the buffer tube. I would first check to make sure you don't have that tension screw adjusted too high.

Do you have a view for the opposite side of the receiver?

If you're looking for the magazine catch slot specs, top left in pic below. The trigger pin and takedown pin holes will be the same on the opposite side.

 

[Milf Dots]

I would first check to make sure you don't have that tension screw adjusted too high.

This right here ^^^ could be a big deal.

 

[Tiribulus]

So much wiggle room that still allows for function and have no drag that for the OP to have trigger hammer drag, the hammer height in the cocked position would have to be positioned so tall that the amount of pressure that the hammer and hammer spring would place on the bottom of the BCG would fall well outside of acceptable. Or that the bolt catch height is so tall it's constantly applying pressure to the BCG ramp. Or that the BCG ramp depth is shallow (but if that was the case, there would also likely be magazine feed lip drag that would be very noticeable, also not likely because different BCG was tried). Or hammer spring weight is like 4x USGI specs. Or the potential of hammer binding a bit on the disconnector.

So hypothetical scenarios for trigger height -

Scenario 1
Upper receiver to BCG ramp depth - 0.260",
Cocked trigger height - 0.383"
Depressed trigger height - 0.260".
The most amount of drag you can get, because if the trigger can't get out of the way of the ramp (like 0.261"), the BCG would never be able to move completely rearward since it would be wedged on the trigger hammer.

Scenario 2
Upper receiver to BCG ramp depth - 0.260"
Cocked trigger height - 0.373"
Depressed trigger height - 0.250"
Less theoretical drag than scenario 1 with about 0.010" extra room for the hammer to move

Scenario 3
Upper receiver to BCG ramp depth - 0.260"
Cocked trigger height - 0.363"
Depressed trigger height - 0.240"
Less theoretical drag than scenario 2 with about 0.020" extra room for the hammer to move.

----------------------------------------------------------------------------
So for the upper and lower combos I measured, I had as little as 0.027" to as much as 0.0745" difference between BCG ramp depth and depressed trigger height and all of those combos will function with each other without drag. OP would probably have to have less than 0.020" for there to be that much drag (maybe closer to 0.010"). To feel that drag, normally you press and hold trigger to the rear while pulling the charging handle all the way to the rear, if there is drag, you'll feel a lot of it through the trigger either throughout the travel or when you get towards the end of the travel.

So far OP has changed basically everything except the registered SBR lower, trigger, bolt catch and magazine catch and had no notable wear on various parts.

Ok, I'm pretty sure I understand everything you're pointing out here. To sum up, it seems that your point is, that receivers that are far enough out of spec to actually cause serious functionality issues are relatively rare, but in light of the fact everything else has been eliminated through part swapping, something along these lines must be the explanation. Is that right?

 

[mkrem]

This right here ^^^ could be a big deal.

I don't use the tension screw because of the issues it caused with the takedown pins being super tight. I have come to the conclusion that slop in a forged upper is just part of it!

 

[mkrem]

For it to be so tight that a punch might need to be used to take it apart, there would have to be some form of edge deformation on the buffer tube. I would first check to make sure you don't have that tension screw adjusted too high.

I agree, but I am just throwing everything out there at this point. I will double check the tension screw this evening.

If you're looking for the magazine catch slot specs, top left in pic below. The trigger pin and takedown pin holes will be the same on the opposite side.

Thanks for the Schematic!

Are you sure you are not Chad from SOTAR? You sure seem knowledgeable enough to be! I really appreciate you and everyone elses continued help!!!

 

[Evintos]

Ok, I'm pretty sure I understand everything you're pointing out here. To sum up, it seems that your point is, that receivers that are far enough out of spec to actually cause serious functionality issues are relatively rare, but in light of the fact everything else has been eliminated through part swapping, something along these lines must be the explanation. Is that right?

Correct.

I agree, but I am just throwing everything out there at this point. I will double check the tension screw this evening.

Another part for you to check mainly because I just read the other thread of the individual who's dust cover won't stay close. The opposite would be dust cover that won't open (without a relatively large amount of force). This can happen to adjustable detent dust covers like Strike Industries or dust covers where the detent ball is stuck in the up position. This situation is also super rare.

Test is - remove bolt (+cam pin, firing pin, cotter pin), push bolt carrier all the way forward, close dust cover, tilt upper receiver back letting the bolt carrier slide rearwards so that the dust cover pops open. The weight of the carrier alone sliding with gravity should pop the dust cover open when the upper tilted rearwards at less than a 30* angle. (edited to add - this can only cause a short stroke for the first shot fired with the dust cover closed).

 

[mkrem]

No luck getting in touch with SOTAR yet. Haven’t really found a good avenue to do such.

 

[Tiribulus]

No luck getting in touch with SOTAR yet. Haven’t really found a good avenue to do such.

Phone number ( 443) 371-3057 ) is HERE

Just a couple things I would do if it were me.

Make clear that this is an ongoing issue for weeks on a well regarded forum site with detailed extensive input from many people, some of them quite experienced and it was suggested that you contact him to see if possibly he would like to make it one of his object lessons, which would be mutually beneficial to both of you.

I'm betting he gets a parade of folks who are just trying to get free gunsmithing out of him. I could be wrong, but I'm thinking that if he knows that a very significant amount of time and effort has been put into this rifle to no avail, it would be more attractive than if, in his mind, it's just some guy who doesn't know what he's doing.

I would also link him to this thread and pay for shipping both ways.

OR... I have no idea what I'm talking about

 

[mkrem]

Well, I left a message with SOTAR. Most likely, i'm going to wait for a call that will never come.

Cross your fingers for me.

 

[mkrem]

I'm writing off SOTAR as a no go.

Has anybody had any experience with these guys:

AR-15 Assembly, Inspection, and Tuning

Our full service AR-15 assembly and inspection service will give you the peace of mind that your rifle is ready for anything.

www.trajectoryarms.com

 

[Milf Dots]

I have no experience with them but have you looked at Midwest Gun Works?

AR-15 Gunsmithing

Midwest Gun Works is your one-stop-shop for all the expert gunsmithing, servicing, and repair you'll need for your AR-15 rifle or pistol. MGW has proven AR platform experience to fulfill any need you may have, whether it is general cleaning and repair or a full blown upgrade project, our...

www.midwestgunworks.com

 

[Milf Dots]

Perhaps contact the gunsmithing schools SDI Sonoran Desert Institute, or the Colorado School of Trades, which is a school that focuses exclusively on gunsmithing.

 

[mkrem]

I have no experience with them but have you looked at Midwest Gun Works?

AR-15 Gunsmithing

Midwest Gun Works is your one-stop-shop for all the expert gunsmithing, servicing, and repair you'll need for your AR-15 rifle or pistol. MGW has proven AR platform experience to fulfill any need you may have, whether it is general cleaning and repair or a full blown upgrade project, our...

www.midwestgunworks.com

I have not, but They look professional. I’ll give them a call and consult them.

 

[AMGtuned]

XXXXX

Nice way to say bye

Upgrade and move to the PX

@MarinePMI

 

[MarinePMI]

I need to read the forum rules about posting advertisements, before I get banned.

Next time there won't be a warning.