Trouble chambering first 2 rounds of my AR Build:

[VariableRecall]

I have a fairly newly put together AR build, that started from a stripped lower that I had filled in. It's an Anderson Lower, with an A2 Buttstock and a 20 inch government profile 5.56 Upper with a 1:9 Twist. I have less than 200 rounds through this upper.

I first had an issue of light primer strikes, but that was fixed easily by getting an extra power trigger spring.
Most likely this next issue was unable to be seen due to my previous issues, or I had not noticed the problem before, but I now can try and diagnose this other problem.

I am having a lot of trouble getting the first round of a 20 or 30 round magazine chambered in my rifle. The 30 rounder is an Okay Industries magazine, and the 20 rounder is an unknown aluminum magazine. I have Pmags but from my previous experience, I believe that they had the same issues too.

Usually I lock the bolt back and let it ride, but even that gives it a fight. The first cartridge fails to get into battery, leaving the rounded lip on the side of the BCG visible. Extraction then needs to be quite forceful, to get the partially in battery case out of the chamber.
This same issue continues often for the second round in the magazine, but after that point chambering and firing the next rounds is completely smooth and painless.

Any idea on what may be going on in there? When I had inspected my BCG, there was some brass debris from the manufacturer that was likely left from testing, but otherwise I don't think there's anything dangerous going on in there. My suspicion is that I've left the chamber a little grimy or the BCG less lubed than it really should.

Can any of you provide some insights into how I can solve this problem? Under-loading my magazines would likely help but that doesn't seem to be the right thing to leave a problem unsolved.

[Winger Ed.]

Provided its clean and there isn't something obvious causing the bolt carrier to drag or hang up--
Just a guess, but the magazine spring might be so strong it pushes up the top round hard enough to drag on the bolt carrier
enough to slow it down.

Mags. & springs are cheap, I'd try another (Known good) or a high end mag.
Or, clip a coil off the spring of one you have if there is a lot of pressure on the follower when its empty.

If that doesn't fix it- the solution might get a little more involved.

[DDriller]

The first thing I would try is to over lube the BCG. AR's don't mind being wet but hate being dry.

[VariableRecall]

I had noticed that the BCG occasionally leaves quite prominent scratches on the brass when it's traveling rearward. Another guess to the issue is that there's grime or a burr, perhaps a bit of brass, stuck in the chamber and causing problems, but considering that the next 18 or 28 respective rounds chamber and fire just fine, maybe that's not the issue...

From what I've heard, Okay Industries mags are pretty reliable, but that one's the only one of its kind that I have. I'll certainly need to go and test my Pmags to see if they have the same issues.

Not to mention, if I need to modify my magazines or download them for reliable use, I may be ignoring a problem that my rifle may have to begin with.

[VariableRecall]

The first thing I would try is to over lube the BCG. AR's don't mind being wet but hate being dry.

I would like to add that when I was at the range my rifle was quite dry. I had used Tetra-Gun Lubricant wiped from a cotton cloth onto the respective parts in a thin film. For next time, I have directly glopped the lubricant onto the BCG and charging handle, and spread them evenly with a cotton cloth. Here's hoping that does the trick for next time!

[kr54]

If you load the magazine 2 short of capacity, does it load the first round ok?

[Gtek]

Just asking and please take no offense, Are you confident of the A2 RIFLE spring length and buffer? I assume these are factory rounds? Open top up and look at extractor, any rub marks on back/outside? Have you tried with only two rounds?

[VariableRecall]

Just asking and please take no offense, Are you confident of the A2 RIFLE spring length and buffer? I assume these are factory rounds? Open top up and look at extractor, any rub marks on back/outside? Have you tried with only two rounds?

My A2 Buttstock came from UTG. It was a complete kit with a Rifle length buffer tube, spring, and plunger.

I'll be able to run some tests next time I visit the range, including under-loading my magazines.
The ammunition that I was using were some Golden Tiger steel cased rounds, and some 55gn soft point reloads with Lake City brass. When the ammunition was fired, it burned clean, ejected just fine, and was satisfactorily accurate, it just seems that the first couple of rounds are causing me a heap of trouble.

So, this next range trip I make, I plan to double check how lubed up my rifle is, and experiment with all magazine types that I have in my collection to figure things out.

Thankfully I have a Maglula StripLula so getting the ammo into and out of those magazines is going to be quite a bit easier than smashing them in by hand.

[kerplode]

Is your carrier well lubed? The bolt should be wet, and the gas rings should also get a drop of oil through the vent holes.

Does the carrier assembly pass the tilt test? Unload the rifle and engage the safety. Hinge the upper open and point the muzzle down at about a 45 degree angle, Stick your finger into the back of the BCG and pull it out the back of the upper about half way, then let it go. It should fall smoothly back into the upper and lock into battery.

I suspect the bit of additional drag on the carrier from the extra-power hammer spring coupled with the probably dodgy action spring might reducing carrier velocity just enough to prevent the bolt from locking after forcing the top rounds out of the mag. The top two from a full mag take the most force for the carrier to strip.

I don't mean to be critical, but parts are not parts, and UTG stuff is airsoft grade junk. Throw that action spring in the trash and buy one from Brownells or BCM.
https://bravocompanyusa.com/rifle-m16-action-spring/

Who made your LPK? In my experience, you shouldn't need an extra power hammer spring to set off Russian or commercial primers.

[Moleman-]

If you sharpie up a cartridge and let it jam as described where it need forcefull extraction, where is the sharpie removed or worn thin on the cartridge? How does it do with factory new brass cased ammo? Is the chamber on the tighter side and you need to use a small base die or polish the chamber? For the case scratches it can be the BCG, mags and very often if you're getting brass glitter with gouges/dings on the shoulders and necks, the locking lugs on either side of the extractor need dehorned. Just dull the sharp inside front corners that are acting like chisels. Don't go crazy removing metal.

[VariableRecall]

Is your carrier well lubed? The bolt should be wet, and the gas rings should also get a drop of oil through the vent holes.

Does the carrier assembly pass the tilt test? Unload the rifle and engage the safety. Hinge the upper open and point the muzzle down at about a 45 degree angle, Stick your finger into the back of the BCG and pull it out the back of the upper about half way, then let it go. It should fall smoothly back into the upper and lock into battery.

I suspect the bit of additional drag on the carrier from the extra-power hammer spring coupled with the probably dodgy action spring might reducing carrier velocity just enough to prevent the bolt from locking after forcing the top rounds out of the mag. The top two from a full mag take the most force for the carrier to strip.

I don't mean to be critical, but parts are not parts, and UTG stuff is airsoft grade junk. Throw that action spring in the trash and buy one from Brownells or BCM.
https://bravocompanyusa.com/rifle-m16-action-spring/

Who made your LPK? In my experience, you shouldn't need an extra power hammer spring to set off Russian or commercial primers.

My Lower Parts kit was from Tom's Tactical, with their premium nickel teflon trigger kit and the rest of the parts provided from the same source. The trigger is great for the price, and has a nice break to it. I'd say it's about 5lbs. I did have to replace the hammer spring cause it were apparently not strong enough. A Wolff extra power spring solved the problem but i can barely tell the difference between the two of them by finger.

I'll try the tilt test when I get the chance. Thanks for the tip regarding that check! When I actually get the chance to make a range trip.
Also, thanks for the tip on a good value rifle spring!

[Gtek]

Extension lugs/ramps and fit into upper. M4 upper, rifle upper? if not already confirmed gut upper and from underneath take a toothpick and from bottom feel transition from into ramps.

[VariableRecall]

Extension lugs/ramps and fit into upper. M4 upper, rifle upper? if not already confirmed gut upper and from underneath take a toothpick and from bottom feel transition from into ramps.

What exactly do you mean by that? the ramps on my upper look fine and don't show any prominent wear. One thing that I did notice is that through my familiarizing with snap caps I had zero issues with feeding rounds. Other than the BCG scratching the anodized coating of my snap caps as it traveled backward, I had no issues. The barrel/chamber seems to be quite the tricky spot to clean! Any tips/tricks to ream it clean of grime when the contours of the barrel lugs and chamber make cleaning awkward?

[Gtek]

Sometimes the grooves (right and left feed ramp area) cut in the barrel extension are narrower or misaligned with the cuts (ramps) in M4 upper, old rifle has a flat ramp in upper. This can create high spot ridges that the nose of bullet can hang on and cause problems with feed. Google M4 verses Rifle feed ramp, there are some great pictures online. A whole bunch of people made parts, I have had instances where maker A's part does not exactly line up with maker B's part. Just helping you chase your problem and not knowing where you are at on build knowledge, no disrespect intended. In regard to cleaning, pop rear and remove guts, I have a link to hold weapon open in rifle vise with muzzle pointed down. I use carb cleaner and spray in gas tube and into extension with all running down out muzzle. Then push a couple to clean/dry, the carb cleaner helps remove carbon, then bore solvent as needed and done.

[Rcmaveric]

I had some issue once in my Grendel. I pollished my feed ramps. I have to two part feed ramp and they didnt line up well. I ground it down to make better angle and pollished to make it look professional and not bubba.

I noticed my cast bullets had dings in them and would catch causing a stove pipe. The lomg 6.5m would catch in the mag while riding up the feed ramps.

If i remember correct you had the match the feed ramp of the barrel to the feed ramp of the upper. No m4 ramps or with m4 ramps. I am not sure what a miss match would cause. All it is the feed ramps extending into the upper or not. Hind site i think it was M4 ramps causing my long bullets to jam. Had i had a shorter ramps the bullets would clear the mag before tilting up i think. But i fixed it with pollished and a slight angle adjustment.

Sent from my SM-G991U using Tapatalk

[VariableRecall]

Sometimes the grooves (right and left feed ramp area) cut in the barrel extension are narrower or misaligned with the cuts (ramps) in M4 upper, old rifle has a flat ramp in upper. This can create high spot ridges that the nose of bullet can hang on and cause problems with feed. Google M4 verses Rifle feed ramp, there are some great pictures online. A whole bunch of people made parts, I have had instances where maker A's part does not exactly line up with maker B's part. Just helping you chase your problem and not knowing where you are at on build knowledge, no disrespect intended. In regard to cleaning, pop rear and remove guts, I have a link to hold weapon open in rifle vise with muzzle pointed down. I use carb cleaner and spray in gas tube and into extension with all running down out muzzle. Then push a couple to clean/dry, the carb cleaner helps remove carbon, then bore solvent as needed and done.

Thanks for the clarification. I can see how different barrel profiles may cause some conflict with other BCGs. The BCG I have came with my rifle as a complete upper kit, so i doubt they would have given me a BCG that was out of spec for that thing. As far as I'm aware, it's a generic mil-spec BCG with no real distinguishing features other than given a standard black nitride finish.

Unfortunately I don't have a vice, but I'm pretty sure I've got carb cleaner handy. That sounds like a very stinky and human unfriendly, but effective method of cleaning. I doubt I could have put much grime into an upper that new, but when the time comes when it gets truly filthy, that sounds like a solid way to clean things out.
Would Brake Cleaner do a similar job? I'm pretty certain that both of them are quite nasty pressurized liquids that evaporate quickly and tear through whatever fouling it comes across.

[VariableRecall]

I had some issue once in my Grendel. I pollished my feed ramps. I have to two part feed ramp and they didnt line up well. I ground it down to make better angle and pollished to make it look professional and not bubba.

I noticed my cast bullets had dings in them and would catch causing a stove pipe. The lomg 6.5m would catch in the mag while riding up the feed ramps.

If i remember correct you had the match the feed ramp of the barrel to the feed ramp of the upper. No m4 ramps or with m4 ramps. I am not sure what a miss match would cause. All it is the feed ramps extending into the upper or not. Hind site i think it was M4 ramps causing my long bullets to jam. Had i had a shorter ramps the bullets would clear the mag before tilting up i think. But i fixed it with pollished and a slight angle adjustment.

Sent from my SM-G991U using Tapatalk

So far I have not tried loading excessively long projectiles in my rifle. The highest I've gone was 56gn Golden Tiger. A 1:9 twist means that I can go pretty light in terms of projectiles down to 40gn, up to about the edge of 65gn or so, as far as I'm aware. My projectiles had been sticking between 40 and 55 grains.

I'm not really sure if it would be worth polishing my feed ramps if it means removing the finish that keeps my bits in tip top shape.

[JimB..]

Just to clarify. Fully loaded magazine, release bcg from lock, rounds fails to fully chamber.
Drop the magazine.
Extraction of the round is difficult, correct?

Now strip a few rounds from the mag. And reinsert.
Feeds fine? If yes, does a round extract easily by hand?
If it doesn’t feed fine in this test, when does it feed fine?
Whenever you get it to feed fine, can you then easily extract a round by hand?

[VariableRecall]

Just to clarify. Fully loaded magazine, release bcg from lock, rounds fails to fully chamber.
Drop the magazine.
Extraction of the round is difficult, correct?

Now strip a few rounds from the mag. And reinsert.
Feeds fine? If yes, does a round extract easily by hand?
If it doesn’t feed fine in this test, when does it feed fine?
Whenever you get it to feed fine, can you then easily extract a round by hand?

At the time, I was more worried about staying safe at the range and ensuring I would get my money's worth for the reservation. I didn't directly troubleshoot the mags like so since I had only brought their contents to the range, besides the rifle and ear/eye protection.
From my recollection, when the round had failed to go into battery, with the rounded lip of the BCG visible at the ejection port, ejection was stiff. I had to mortar it on a table to ensure vigorous ejection. I didn't try the forward assist, but I think that could have helped. I'd assume a forceful series of strikes to the forward assist would inch the BCG towards its destination?

When I was at the range, I had not attempted to see if a down-loaded mag would improve reliability. However, I can assume that down-loading the magazines will help as the rest of the magazine worked just fine after the first two caused a lot of trouble.

When I had the issue with light primer strikes, I was able to eject rounds just fine when the issues occurred. If anything, a light primer strike would be far more dangerous for myself and others than a failure to feed.

[JimB..]

I’m hung up on the ejection issue. If it fails to feed and can’t be ejected easily when the mag is removed then there is a more serious issue than the mag spring being too strong.

None of the troubleshooting requires firing a round. Keep the gun pointed in a safe direction, as always, and see what will or won't feed. Can likely get this figured out before you head back to the range.