Feeding issues

[jambau]

So I've been running the same load in my Grendel upper for a couple years. All of a sudden it doesn't want to fully chamber the rounds. Pulling back on the charging handle to get the round out is almost impossible. If I manually feed the round and then let the bolt slam home I am able to fire the round (not slam fire) I've tried numerus other loads with no success. What do y'all think? Why won't it chamber anymore? Trim length is fine too

[mv1arms]

How dirty is your chamber? Is your sizing die set up correctly or get bumped out of whack? Do you have an ammo chamber checker? I use a lyman to drop rounds into before running them. Gas block/tube still aligned correctly?

[Klem]

Jam,

Are you talking factory or hand-loads?

Do you pull your BCG apart when you clean?

[Rosecrans1]

As above......................plus, if you do reload, do you full length or just neck size? Do you double check your finished loads? As Klem states but if you don't have a caliber chamber checker like the Lyman, (i use mine all the time), did you measure what the case length, OAL, etc is of the original verses what you are making now that doesn't feed? If these are factory rounds, look no further than a dirty chamber, BCG or a very out of spec factory lot number!

[A5BLASTER]

Clean the chamber good, possible a carbon ring is forming.

Clean the bcg real good, strip it down and clean it out fully.

Also if you dont have them get the hornady comparator tools and make sure you are sizing your brass down enough.

[jambau]

BCG is fine. Have not rechecked my dies in 5 years. Hmm. I Full length size all the time. The OAL of current loads are identical. I did have to tighten the gas block a while back. Never bothered to check alignment. Oh and the dreaded carbon ring. Well, at least I have three things to look at. Thanks guys

[Klem]

Jam,

In mean no disrespect as I don't know your experience. With each post it is becoming clearer.

The difference between normal loading and the manual loading into the chamber is telling. So, with the less friction of manual loading it is going into battery and firing, but not if precious momentum is being robbed as it strips from a mag and is pushed up on an angle. This is why I asked if the (1) BCG is functioning nomally (being cleaned). How hard is it to push the bolt fully back into the carrier, simulating going into battery? Or (2) maybe there is an obstruction somewhere, something compressible like a blade of grass in the chamber. (3) Or, the ammunition headspace is so close to being too short/tight that only the full energy of the spring will get it into battery. (4) Or the bullets are seated too long and it takes the full recoil spring energy to push them in, allowing the bolt into battery.

[jambau]

No disrespect taken. I appreciate any help. I've had this upper for years. It's always shot great with several loads. Then one day, about two years ago, it started to not go fully into battery. One round here, one there, but it got progressively worse. I've cleaned, stripped, lubed, even bought a different set of dies. It got to the point that I stopped taking it to the range. I haven't bothered with it in so long I almost forgot about it. It has recently occurred to me that I haven't tried changing the spring yet either but that would not explain why the rounds that don't fire are so difficult to extract. The more I research it the more it sounds like I let a carbon ring form. I can't see anything with the naked eye. Are there any special techniques to removing the carbon ring?

[Redraider]

I may be completely out in right field, but, I thought manually loading a live round in the chamber, and letting the bolt slam home, was an out and out no-no with any weapon with a floating firing pin!

Redraider

[Redraider]

Sorry, the above post had nothing to do with your original question, just seemed like no one else felt like it should be mentioned.

Redraider

[jambau]

It is a no no but was done out of frustration with the gun pointed at one of my buddy's shooting berms. Just had to know ya know.

[Lemonaid]

Jambau, it's unclear from your posts if you are having this problem with factory rounds. If it dose not then it's a reloading problem, likely not enough sizing of the base.
If it has the same problem with factory rounds then it is a firearm problem, rough chamber or such.
What does the brass look like after it comes out of the chamber unfired? Does the bullet jump forward a large amount out of the case when it chambers? Land marks on the bullet?
Take the upper off the lower and place a round by hand in the chamber, use the charging handle to close the bolt and extract. It should be fairly easy to chamber and extract in this manner. If it dose not then you have ruled out a number of things and can concentrate on the chamber.

[jambau]

Lemonaid,

All Handloads. I did get a small base die but have not tried it yet. I'll do the chambering experiment tonight. You guys have been great thanks.

[Klem]

jambau,

Releasing the bolt with a live round already in the chamber in an AR is the most momentum you can have against the primer - but it is still unlikely to go off. Pointing it in a safe direction whenever it goes into battery with a live round is common sense but on top of that we have the luxury of deciding what our 'Rules' are as civilian shooters. If you are using thick-cupped primers like CCI450 then that is added protection against something that is almost an urban myth. My point is there is no imperative in borrowing dogma from a large institution like the military without making your own informed decision.

I have no issues releasing the bolt on a hand-loaded round when it is pointing in a safe direction and no one in the vicinity is going to get upset. If a shot going off at your home is going to bring the Police running then save it for the Range. In your case of needing to figure out what is wrong with the gun versus the likelihood of a slam fire in a safe direction, where no one else is going to get upset, is an easy decision to make.

My understanding is when you release the bolt on a live hand-load that is already in the chamber it goes into battery, but when you then try and manually pull it back out it is sticky. And this has not always been the case. So, the hand-loads or chamber have changed dimensions, or both. The most likely is your hand-loads.

What gear do you use to measure your loads?

[A5BLASTER]

When is the last time you trimmed your brass?

[achristian8]

Mine did this after about the fifth firing on Hornady brass. Trimmed, full length sized and go to go.

[tdbru]

Jambau,
i think A5BLASTER and achristian8 have hit the nail on the head. please check your case length after you full length resize. i suspect, based upon your description, that the case is too long, mostly in the neck and when the round is slammed into the chamber by a full speed BCG it drives the neck into the bullet (like a super crimp) hard enough that the bolt can close. but that is also why it's so darn hard to extract. please look at the primers of the rounds that you chamber like that and shoot. i'll bet they show signs of pressure as the case is not releasing the bullet easily when the powder ignites. i suspect it's that the case neck is too long after full length sizing and needs to be trimmed.
-tdbru