Failing to chamber.

[CavTrooper]

Allright, so Im having some problems. My grendel has issues chambering. Its not the ammo, Im using Lapua brass, all trimmed and sized consistently, bullets seated uniformly. I dont think its the magazines, I have 2 CProducts 10 rounders, one needed feedlip fixing, the other ran smooth right from the jump, both seem to feed fine. Im thinking it could be either a bolt lug problem. The reason I think this is because it also locks up pretty tight sometimes and is a pain in the a** to pull the charging handle back and extract a round. Im mostly concerned because I have been using this rifle for hunting and even though I havent come across the problem yet, Im worried about needing a quick second or third shot and having a round go off out of battery. This issues prevents me from taking my Grendel out more often and want to get it figured out now that Ive got some property thats overrun with hogs and free reign to hunt em.

Anyone else have a similar issue? Howd you fix it?

[LR1955]

Allright, so Im having some problems. My grendel has issues chambering. Its not the ammo, Im using Lapua brass, all trimmed and sized consistently, bullets seated uniformly. I dont think its the magazines, I have 2 CProducts 10 rounders, one needed feedlip fixing, the other ran smooth right from the jump, both seem to feed fine. Im thinking it could be either a bolt lug problem. The reason I think this is because it also locks up pretty tight sometimes and is a pain in the a** to pull the charging handle back and extract a round. Im mostly concerned because I have been using this rifle for hunting and even though I havent come across the problem yet, Im worried about needing a quick second or third shot and having a round go off out of battery. This issues prevents me from taking my Grendel out more often and want to get it figured out now that Ive got some property thats overrun with hogs and free reign to hunt em. Anyone else have a similar issue? Howd you fix it?

CT:

Only times this has happened is if I seated the bullets too long.

Try this. Clean the chamber using a M-16 chamber brush, hose it out with carb cleaner and dry. Put some lube on the extractor as well as through those two lube holes in the bolt carrier. No, lets not re-enact a Army range where guys squirt CLP all over the outside of the bolt carrier using a spray bottle. Get the stuff inside of the bolt carrier on to the bolt and gas rings.

BTW -- check your gas rings while you are at it. Grendels go through gas rings pretty quickly.

LR1955

[CavTrooper]

Thanks for the reply.

Ive cleaned the chamber very well, lubed and all that jazz, Im pretty anal when it comes to cleaning. Im wondering if theres a burr on the lugs in the chamber causing the lockup issues...

Anyhow, doing some searching, I found this fella describing similar issues and his resolution. Im not sure I want to take a sanding disk to my extractor but I do have an extra one laying around so I might give it a try.

Two issues plagued this barrel/bolt from the start. First was a failure to feed reliably from magazines. Second was intermittent failure to return to battery. Both of these issues I had addressed in the 7.62x39 chambering so it was not new discoveries. I'll cover the second issue first because sometimes that will also take care of the first. The bolt extractor has two sharp edges that tend to dig into the case rim preventing the bolt from obtaining full battery position. Remedy is too use Dremel tool with sanding disc to remove and polish these sharp edges that must slip over the case rim. Now rather than dig into the case rim the extractor will slip over the rim as the cartridge is chambered which will allow the bolt to obtain full battery position

Another thought I had was maybe the ejector was too tight/strong not allowing the bolt to fully close. Am I grasping at straws or does anyone think that its possible?

[LR1955]

Thanks for the reply.

Ive cleaned the chamber very well, lubed and all that jazz, Im pretty anal when it comes to cleaning. Im wondering if theres a burr on the lugs in the chamber causing the lockup issues...

Anyhow, doing some searching, I found this fella describing similar issues and his resolution. Im not sure I want to take a sanding disk to my extractor but I do have an extra one laying around so I might give it a try.

Two issues plagued this barrel/bolt from the start. First was a failure to feed reliably from magazines. Second was intermittent failure to return to battery. Both of these issues I had addressed in the 7.62x39 chambering so it was not new discoveries. I'll cover the second issue first because sometimes that will also take care of the first. The bolt extractor has two sharp edges that tend to dig into the case rim preventing the bolt from obtaining full battery position. Remedy is too use Dremel tool with sanding disc to remove and polish these sharp edges that must slip over the case rim. Now rather than dig into the case rim the extractor will slip over the rim as the cartridge is chambered which will allow the bolt to obtain full battery position

Another thought I had was maybe the ejector was too tight/strong not allowing the bolt to fully close. Am I grasping at straws or does anyone think that its possible?

CT:

This doesn't happen to concern the highly coveted 'Stoner' barrel, does it? You didn't.......

Well, others I know have done the extractor buffing thing without any issues. However, they did it because those sharp edges were cutting notches into the rim of the brass. I can't recall them doing it because the cartridge was failing to go completely into battery.

Yours sounds like it is not going completely into battery. Shoulder bumped enough? If the shoulder and cartridge overall length isn't the issue, I would look at the headspace.

An out of battery firing is a bad thing. No doubt you are a bit nervous.

I wouldn't blast with it until I found out the problem and had it fixed.

LR1955

[CavTrooper]

yup, its the AR Stoner barrel that produced these groups when I was doing some load testing.:



I figured that was "good enough" so I just went with that load until I get a chance to shoot a bit longer to really dial in a good load.

The problem doesnt present itself all that often, maybe once every 20-30 rounds, but its enough to give me pause for concern. I might have to go back and recheck all my brass and loaded rounds and look closer for inconsistencies.

Thanks.

[Rootshot]

I've had similar problems. Two root causes.
1. Headspace was set incorrectly on my die. Screw it down a bit further and use a Wilson case gauge to check the sized Grendel rounds. The amount the die will size the case will vary as the brass work hardens over multiple reloads, so pay attention to this.
2. The Ejector was too long. This resulted in the base of th cartridge not sliding properly into the bolt face. Cartridges would appear to be "wedged" 1/2 way into the chamber. I sanded a few hundreds of an inch off the ejector and everything has been fine. This one was a devil to troubleshoot.

--Rootshot

[bwaites]

I had this problem in the past with Wolf brass and a chamber that had ANY powder fouling at all. If the chamber was perfect clean, they would generally chamber, but any fouling and no way. My Lee dies would size AA/Lapua brass just fine, but the Wolf brass, either because it was thinner or because it had more springback, (or both!) or for some other reason, would not size correctly. I eventually had to shave .003" or so off the shell holder to get my Wolf brass to work. Until someone pointed that solution out, I just didn't use Wolf brass.

It looked perfect, but simply wouldn't chamber if there was ANY crud at all. (Which is one of the reasons I quit using BLC2).

The Lapua would do just fine.

Bump the shoulders another thousandth or two and see what happens.

[gunner69]

Rootshoot, Damn, your number 2, ejector too long sends chills up my spine. I have less than 100 rounds on a build. Alexander Arms Upper and barrel. The first 50 rounds or so O.K. Now the first round (sitting on the right side of the mag) feeds fine and shoots fine. The next round feeds about half way to chamber, but cocked to the side (where the case doesn't sit in the bolt). Different mags do the same thing. I installed a bolt "D-Fender" rubber gasket..... no change one shot then jam? Anyone have this problem?

[noone]

Here is what I would check:
1. Length to a datum line on the shoulder of a fired case
2. Compare that length to the length of your sized rounds at the same datum line
3. Check distance to ogive on the bullet you are using. You may be jamming the bullets into the throat, either because of a
short throat, or seating the bullets out too long for the ogive of the bullet you use.
4. Check extractor, and ejector to see if they both allow the cartridge to seat fully into the recess inside the bolt. Also insure
that the rounds aren't pressed too tightly to the opposite side of the bolt by an over powerful extractor, and that the
ejector works properly.
5. Insure that the chamber and throat are free from all carbon, and copper fouling.
6. Then I would smoke an unloaded dummy round with a candle, and see where the soot is removed by either the lands, or
by something pushing on the shoulder of the brass case. If you see clear signs of the rifling on the bullet's ogive, your
bullet may be jammed into the throat. This can cause difficulty chambering, and difficulty extracting unfired rounds.

[mgh33]

For gunner69: With AA barrel and bolt, you might want to check with Jacob at AA. They had a series of bad extractors, replaced mine. Sounds just like what I went through.

Mike

[rushmc]

I will reply to bwaites generally cause I dont know enough to help much here but, I did have a similar problem in a Armalite AR15. (I am almost embarased to say what it is but here I go to help others)
When I first got my black rifle about 4 years ago i was trying to learn all I could. The conflicting info out there is a swamp to wade through. But there is so much good info one dares not stop. Anyway, I kept reading the run it wet comments and so I was. What happened, either by screwing up or by acident, I got a lot of lube in the buffer tube. That oil acted like an o ring and kept the rifle short cycling. Alot. I finally got some help from someone who noticed this, we cleaned it up and the thing cycled great.

For what its worth

Now I will go back to lurking and learning

Marc

[1coyoteslayer]

i have a SAOD custom upper. It does not like to pick up rounds out of the magazine? Could this be a bullet seat depth problem? Sometimes it works perferct and sometimes not so much.

[glane5910]

i have a SAOD custom upper. It does not like to pick up rounds out of the magazine? Could this be a bullet seat depth problem? Sometimes it works perferct and sometimes not so much.

Shouldn't be a bullet depth problem unless the tips are hitting the inside of the mag. if so, try seating your bullets say 0.005" deeper and see what happens.