Not ejecting properly

[Sinster]

Ok, so I am the new guy, but yes, I did use the search function! Anyways, I have a Grendel upper I put together myself using an AA 18" barrel and bolt combo, MI lo pro gas block, AA receiver, and LMT carrier. I am running it on my existing M4 lower with collapsible stock, standard carbine length spring, and Spike's ST-T2 buffer. The problem I am having is the majority of my spent brass barely makes it out of the rifle and lands right next to me on the bench. A few will actually eject and make it about 5ft in the 2:00 position. There are 2 heavy gouges in the rims of the casings from the edges of the extractor claw, but when I place a case in the bolt face manually and let go it drops freely from the bolt so I don't think it is hanging up. I am having no issues with short stroking and the bolt always locks back on a dry mag. Any thoughts?

[warped]

Ejecting randomly is a case of several things going on, were these reloads?

The brass ejecting two feet is not a problem, ejecting random distances says that there is a possibility your gas block is leaking or loose, the rim gouges are a combination of the extractor needing a bit of tuning and the chamber pressures being possibly high making the brass stick as the bolt travels rearwards.

If you have an H3 buffer, swap it in and see if there is a difference, also look for carbon stains at the gas block. I just looked up your buffer and it is too light for the Grendel and at the lower end of function weight for the 5.56mm.

AA Stakes their gas key so that is not a problem.

Also the weight in a buffer is supposed to move in order to give an effect like a dead blow hammer, no bolt bounce.

[Drifter]

It might be overgassed if it's a midlength system. My suggestion is to try an adjustable gas block.

I've used the PRI gas block on two different 18" midlength barrels. I shut the system off, then backed the screw out one quarter of one turn. Both run great now.

Buffers, springs, different weight carriers, etc work fine for tuning a setup that's already close to ideal. But they simply treat the symptoms if the problems are severe.

[LRRPF52]

I just measured my ST-T2 buffer from Spike's, and it is 3.9 ounces, which is on the heavier side for carbine buffers in 5.56mm. I have been using it in the Grendel, and it works great for me on a mid-length 16" barrel with M16 carrier weight, and a standard AR15/M4 carbine spring from Brownell's. I'm also using a VLTOR low-profile clamp-on gas block. I unitized the carrier key to the bolt after checking gas tube alignment.

The standard carbine buffer weights for 5.56 that are on the market are 2.9 ounces, which is often too light in systems with a lot of gas flow. Understanding the system in context of a balance between buffers, recoil springs, gas port diameters, gas system lengths, bolt carrier weights, brass or case surface smoothness, propellant charge, bullet length/weight, chamber dimensions, chamber smoothness, and rifling twist helps understand how many variables are in play.

I have had problems with MI and bad QC on their gas blocks for my last AR10 build, where we discovered that the gas tube roll pin hole was cut way off of 90 degrees. If you're having inconsistent ejection patterns, something is awry. I would make sure your gas block is secured well, that the port hole is aligned with the gas block hole, and work my way back from there. One issue the bad gas block would have caused is that it torqued the gas tube out of alignment, which could have caused binding if we would have used it. (We didn't, of course.)

Another thing to consider is lubrication. If you're running dry, you will have inconsistent bolt carrier velocity, leading up to failures to chamber. Use some SLIP 2000 on your bolt carrier raceways, cam pin, and bolt band generously.

With buffers, it isn't the total weight of the buffer assembly that equals success, but the independent weights of the buffer body and internal buffer weights. Their combined weight resists the inertia induced on the reciprocating parts to prevent an excessively fast unlocking sequence (dangerous), but when the buffer body reaches the rearward point of the cycle, the internal weights continue rearward until hitting the back of the buffer.

Then the recoil spring drives the buffer and bolt carrier group forward until the parts strip a new round off the mag, feeding into the chamber, and coming to a stop against the barrel extension, then bounces off it often when the cycle is fast. The internal buffer weights continue to move forward until they hit the front of the buffer body to counteract this "bolt bounce" characteristic.

This is why internal buffer weights are more important than external buffer weight in a high power rifle caliber in the AR15. Here are a list of some different buffer weights, keeping in mind that this is the combined weight of the buffer and internal weights:

CMT (Continental Machine & Tool) standard carbine buffer: 2.9 oz.
CMT H Buffer 3.8 oz.
CMT H2 Buffer 4.1 oz.
Spike's ST-T2 4.3 oz. (listed) mine weighs 3.9 oz.
Armalite H3 4.7 oz.
Rifle buffer 5.2 oz.
9mm SMG buffer 5.4-5.5 oz. (but low weight internals-not for high power rifles)

Most buffers are made from Aluminum, with a combination of steel and tungsten internal weights. I think the 2.9 oz. has 3 steel, the H has 1 Tungsten and 2 steel, the H2 has 2 tungsten and 1 steel, and the H3 has 3 Tungsten weights. I'm not sure what's inside the rifle buffer, but it seems to work the best. The Spike's has High Density Tungsten Powder in it, so you don't have the impact of the internal weights rattling around, but you still have the dampening effect of the internal tungsten flying back and forth.

Here are some great high-speed camera videos of different buffer/ammo/gas system length comparisons:

http://www.youtube.com/watch?v=575Q0O41u5s

[Sinster]

Thanks for the responses guys!

First off, yes I am shooting reloads. I do all my own loading and my rifle has never seen a factory round. I am running 123gr Amaxes over 26gr of 8208 with CCI 450 primers for a COL of 2.250. Shouldn't be overpressure as it's towards the low end of the data according to Hodgdon, and the primers are reading good. I weigh each charge individually on a Redding No. 2 beam so shouldn't be much inconsistency.

As far as the buffer goes, I was also under the impression that the Spike's buffer would be plenty for the Grendel mid length.

I have not seen any signs of leakage around the gas block, but what I did notice upon further inspection is that all three of my gas rings were in perfect alignment. Doh! Don't know if that's the whole problem, but is certainly a good start.

The gouges on the rims of my cases are being caused by what I think is a couple of sharp points at the ends of the radius. It is indeed in need of a little tuning. Is it acceptable to smooth these out with a file of some type or will I run into issues with the extractor not properly gripping the rim of the case?

Thanks again for all of your help guys! I will try to make it to the range this weekend and see if there is any improvement after the gas ring fix. Should've been something I caught right away, but you know how it is, we often tend to overlook the simple things.

[warped]

Jewelers file and then a light polishing.

[LRRPF52]

I think the aligned gas rings on the bolt is a well-debunked myth, since the rings collapse when the bolt is forced into its slot in the bolt carrier. It's something that barracks lawyers have passed-on from Drill Sergeants and who knows who else.

While on the subject, your gas rings should be replaced every 2,000-4,000 rounds in a 5.56 gun if you shoot high-volume. You can test the serviceability of your gas rings and BCG by extending the bolt all the way in its most forward position, and place the BCG vertically on a flat surface, with the bolt face down, so the whole unit stands on the bolt face. If the bolt rotates and pushes into its recess from the weight of the bolt carrier, you need new gas rings.

[Sinster]

Ok, so I took the Grendel to the range saturday to try it out. Ran my upper on my lower with my Spike's buffer, a lower with a standard carbine buffer, and another lower with an A2 stock and buffer. Nothing seemed to affect my ejection issues. Tore into the rifle on sunday. Checked my gas block alignment. It was slightly too far back, but I could tell from the carbon staining around the gas port that none of the port was blocked by the gas block. I did properly align it while I was there though. Also, checked into my extractor a little closer. Found that it seemed to hang on to a case a little too well after the ejector had done it's part. I filed and reshaped a couple of burrs on the outer edges of the radius of the extractor. Another trip to the range showed a marked improvement. All of the brass is now clearing the bench and headed in the 2:00 direction. I have a new Wolff extra power buffer spring on the way from Midway, so we will see if I can possibly move that more towards 3:00. Making progress at least.

[wolverine]

Sinster

Did you ever figure out whats going on with your rifle??.............I am having the same problems........I was dealing with Jacob @ AA who was awesome............He sent me a new extractor spring, he claimed there was some issues with a batch of them............this did not help at all...........I even sent the upper to AA and they claimed it looked great and ran awesome on the range with factory ammo...........I'm thinking it may be something with my reloads...........I am using Hornady brass with lee dies..............I am going to buy a Redding die and Lapua brass and see if this helps................Anyway hats off to Jacob and AA for AWESOME customer service!................Roger

[LR1955]

Sinster

Did you ever figure out whats going on with your rifle??.............I am having the same problems........I was dealing with Jacob @ AA who was awesome............He sent me a new extractor spring, he claimed there was some issues with a batch of them............this did not help at all...........I even sent the upper to AA and they claimed it looked great and ran awesome on the range with factory ammo...........I'm thinking it may be something with my reloads...........I am using Hornady brass with lee dies..............I am going to buy a Redding die and Lapua brass and see if this helps................Anyway hats off to Jacob and AA for AWESOME customer service!................Roger

Wolverine / Guys:

I ought to start a psych forum.

'Awesome' customer service yet your rifle was returned and still doesn't work?

Everyone was 'awesome' yet no one has offered you a solution that has corrected what ever problem you are having?

Seriously -- this is something like the Stockholm syndrome.



OK -- what is the rifle not doing and why do you think your handloads are the problem?

LR1955

[davidj]

Wolverine / Guys:

I ought to start a psych forum.

'Awesome' customer service yet your rifle was returned and still doesn't work?

Everyone was 'awesome' yet no one has offered you a solution that has corrected what ever problem you are having?

Seriously -- this is something like the Stockholm syndrome.





LR1955

More of the same: On July 26 AA acknowledged receipt of my recently acquired upper. It was returned for similar problems(short stroking). I haven't heard a word since.

[wolverine]

Wolverine / Guys:

I ought to start a psych forum.

'Awesome' customer service yet your rifle was returned and still doesn't work?

Everyone was 'awesome' yet no one has offered you a solution that has corrected what ever problem you are having?

Seriously -- this is something like the Stockholm syndrome.



OK -- what is the rifle not doing and why do you think your handloads are the problem?

LR1955

[LR1955]

Isn't “customer service” sort of subjective? Or in other words what I feel is good customer service others may not. In this case, I do feel like Jacob at AA was earnestly trying to help me and still is. Yes, point-in-fact the rifle is still malfunctioning, however it is still very shootable. I know though the process of elimination I will eventually figure it out.

I’m thinking it may be my hand loads because AA claimed they fired with no malfunctions on factory-loaded ammo. I am using Lee dies and Hornady brass and have read where guys were have issues with both of these products. If you put the Hornady brass next to the Lapua there is a difference in the shoulders.

What the rifle is doing is “stove piping” every 4 or 5 round and the last case in the magazine never ejects, it does a complete 180 in the chamber and stays in there. The casing eject in the 1 or 2 a clock position and only about 3feet, very similar to what Spinster’s rifle does. if fact to me it sounds like both rifles are malfunctioning in the exact same manner.

Another thing that bothers me is the way it tears up the brass. I have heavy gouges from what looks like the feed ramps just under the shoulder as well as extractor marks. Some of these gouges are so deep I will not reload them. I have plans to do some polishing on both these areas to see if this helps…………………….Thanks Roger

Roger:

Did the brass that AA fired also show the gouges in the shoulder and extractor marks? There is no reason why yours would show these marks and not factory loads.

Size a piece of your brass and put it in the chamber. Ride the bolt forward about half way and let the bolt go. It should go into battery. Then, pull the charging handle back and extract the brass. It should come out without effort on your part. If it sticks while coming out, my guess is that you didn't bump the shoulder back enough when sizing. This appears to be the most common problem guys have when loading for the Grendel. If it does come out easily but hangs up on ejection -- most likely your extractor is holding the brass too firmly. Polishing and rounding off the edges of the extractor normally fixes this problem.

I am not fan of the Lee Grendel dies and do not recommend them. The Lee sizing die is hard on the brass but that doesn't mean it won't size the brass down enough for it to chamber and extract easily.

If you are using a mid range load and your overall length is such that the bullet itself isn't getting jammed into the rifling, your rifle should function as perfectly as if you were using factory loads.

One more thing to understand is that AA uses a powder that is not available to hand loaders. And my bet is that they test fired the rifle using a heavier bullet -- probably a 123 grain bullet. A heavy bullet with the loads used by AA will offer more inertia so the bolt may well travel back far enough for sufficient function. Go to a lighter bullet and the rifle may not function. What this means is that something is wrong and it isn't your handloads.

The only way you will find out is to isolate variables. Start with the brass check I mentioned. Then check your extractor that it isn't jamming the brass. Then look at your magazines to see if the follower and feed lips are orienting a dummy round so that it enters the chamber as efficiently as possible. Use five dummy rounds because the magazine is staggered. Then check the alignment of the gas port with the gas block. If you find problems, fix each as you go along and check again. When everything seems to work with a couple of dummy rounds, load some ammo, lube the Bolt / Bolt Carrier liberally, and go to the range and shoot. If it still stovepipes most likely your buffer and recoil spring is the culprit.

That is what I would do. Remember to lube the bolt and bolt carrier liberally.

LR1955

[bwaites]

LR1955 gives a good process to follow.

I've seen similar issues and they were always related to the extractor holding the brass to strongly, a MILD smoothing with a dremel flex wheel and the issue disappeared.

Using 123's, as LR1955 mentions, will often give you enough inertia to overcome that strong hold by the extractor, but not always.

See if you can cause it manually cycling as LR1955 suggests, if so, its not the gas or buffer system, but something easily rectified.

[wolverine]

So what is the ideal buffer and recoil spring? I'm using a Magpul UBR stock and unknown spring and buffer. I have used this lower on other uppers and it functioned perfectly so it never occurred that this could be the issue...............Roger