Problem with first round loading

[spleify]

On one of my AR's I am having an an issue with the first round loading properly and seating fully.

I load a full mag with 20 rounds, bolt back. If I hit the bolt release button the bolt will close sliding forward and grabbing the round but will not seat fully and it jambs in the barrel. I have to grab the charging handle and bang it on the ground to release the round. It seems that with only 19 rounds in the mag it loads fine and every round after that there are no issues.

I am using C-Products mags and I use the same mags in both my AR's and I dont have this issue on my other rifle, just the one.

Any advice other than the obvious of short filling the mags with only 18 rounds?


Thanks

[FireMoth]

Does this happen with all your 20rnd mags? or just some? Are they marked and numbered, so you can segregate them?

Is the round actually making it into the chamber, or is it getting jammed up in the locking seat area?

Have you tried a full mag while applying pressure, or not, to the magazine body either from bottom, front or rear?

Are the magazines new, or worn?

How many rounds on the rifle? What is the condition of the action spring?

Does the gun have M4 feed ramps? Do the ramps on the barrel match those on the receiver?

Does this happen with full 30rd mags?

With a bit more information, I can probably help you work out whats going on, or you can just pop into the shop and we'll sort it out.

[spleify]

Does this happen with all your 20rnd mags? or just some? Are they marked and numbered, so you can segregate them? Yes this is happening with all of my 20 round mags, they are not numbered but I will load all 6 mags and then shoot an dit happens on everyone of them

Is the round actually making it into the chamber, or is it getting jammed up in the locking seat area? Yes, the round makes it into the chamber but falls about 1.4" short of of the bolt fully seating and even the forward assist doesnt help, the cartridge is jambed in and I need to slam the but of the rifle on the ground while pulling on the charging handle.

Have you tried a full mag while applying pressure, or not, to the magazine body either from bottom, front or rear? No, I have not tried this but next time I am out I will. I ALWAYS make sure my mags are seated and give them a couple of good whacks to assure they are seated fully, but never tried to keep pressure on them.

Are the magazines new, or worn? The mags are newish, I have only had them maybe a year and a half and each have been cycled probably 15-25 times.

How many rounds on the rifle? What is the condition of the action spring? This particular rifle I am having the issues with has somewhere around 800-1000 rounds through it and I have had this issues since day one.

Does the gun have M4 feed ramps? Do the ramps on the barrel match those on the receiver? Yes M4 feed ramps and they match up nicely

Does this happen with full 30rd mags? I dont own any 30 round mags(bullshit Denver high cap mag laws) but I did run one of my buddies 30 P-Mags through it this weekend and yes I did have the same issue.

With a bit more information, I can probably help you work out whats going on, or you can just pop into the shop and we'll sort it out.

As always, thanks so much Rob. Understandably so this is quite frustrating, and it always happens on a full mag. I'm a sucker and always load 20 rounds and always have an issue with the first round. I have not tried loading only 18 or 19 rounds to test that but after I cycle the first round out each round after that runs through fine with no issues.

[Blowby]

Sounds like the BCG is not returning properly with enough force with the most resistance of 20 rounds in that type of magazine. Check for any burr's or wear marks to show drag? Also make sure the alignment of the receiver extension tube to the rear threaded lower matches the upper's bolt path. To test this lock the bolt back and very slowly release it to see if any drag occurs. You might notice the BCG releases slow or hear a little drag. You have to release it so slow like you are trying to make it stick. This will happen at the rear most position.

I assume it's lubed properly but just wanted to throw that out. Maybe it just needs a squirt of Amsoil.

[legaleagle]

With one rifle and not the other, but all mags impacted, here is a thought. It may be thath te BCG is encountering impedence from the 2nd round pushing up hard, but if you load 19 rounds, there is enough room in the spring to allow the next round to push down enough to allow the BCG to go home all the way. This could be a few things. It could be that the mags sit higher into the mag well of that rifle. This would lend support to all mags having problem and thefact that you have to hard extract the round as described. It could also be that the spring has too many coils on it and it cannot flex downward enough to allow the BCG to slide over easily, kinda creating a bump for it to go over that makes things really tight.

Things to check:

After the 20th round (count them out to make sure you are not at 21 - many times you can get an extra round in and not realize it) can you push the round down still. About half the thickness of the round should be good. This will tell you if the spring is bottoming out and binding. If you want you could cut one coil of the spring and see if that helps. I would be leary to cut more than two coils as the spring may get too short. (Also, shortening a spring will make it stiffer or firmer, not softer). You could also try a new spring and see what happens.

On the spring again. If you can find a 20 round GI mag and it works, swap the spring and see if that works. Also count coils to copmare. You can also measure the diameter of each spring coil and add that together for the stack height. Do this with the problem mags and see if there is a difference to the GI mag. If the stack height is greater on the problem mag, your spring is taking up more room than the mag body has to allow the top round to push in a little bit.

Insert empty mag into reciver without upper on it. Measure the mag protrusion out of the top from the ledge of the receiver. You could caliperthis or put a tape line on it and visually measure on comparing receiver. Do the same for the bottom part of the mag from the bottom of the mag well. I would check this against other receivers to see if the results are the same. THe bottom measurement is not a likely to be determinative as the length of the magwell is not critical, it is the top ledge where it mates to the upper.

Again on the mage well. Remove the mag catch, spring and release button. Measure from the bottom of the catch cutout to the top of the receiver. (The bottom is thecritical measurement as the mag follower and round push up thus pushing the mag down agsint the mag catch which will rest on the bottom part of the cutout. If this is the culprit I would consult with Bowers Tactical on a fix. Machining on a reciever is a last resort to me and precision with a mill is a must. If the reciever is out of spec this is really the only true fix to make it work with other mags too.

Hope this helps. Let us know what you find out.



Look at feed lips to determine if the bolt is riding on them. I doubt this is the case as the remaining rounds 2-19 work fine.

[spleify]

Wow, absolutely great information here folks!

I will do some research and take some measurements over the next couple of days. I do have another rifle that this issue does not exist on, so I can make some comparisons.

I will post back with my findings.

Again, thanks so much!