Grendel Question

[writerman]

I have built a few Grendels and a new problem has come up in my last two builds. I know they can be finnicky, but I have those problems ironed out except this one. It does not want to reload. I contacted the barrel maker, and upon their recommendation opened up the gas port one drill size, and it seems to be healthier, but still when I shoot it, it doesn't want to load the next round, or if it does, somehow the round becomes jammed forward, not enough to shoot, but just enough to be stuck. I use a small base die, so I thought that would cure the sticking problem but no. I have an adjustable gas block, it's about all the way open now. It's like the magazines don't have a strong enough spring at time, to push the round up, so I used an Alexander new magazine, and still the same problem. When I got to the range this morning, one was working fine, loading fine, but after twenty rounds, bam, stuck and had to pry open the bolt. I use a standard spring and buffer weight, same as my other builds. Different barrel manufactuers between the two rifles. I use my gold standard 25GR XBR 8208 so I know it isn't the powder. Things seem bit stiff, because they are new rifles, but again, never had this problem before on many other rifles I've built. Any ideas? Suggestions?

 

[280ai]

25 grs 8208 could be tooo hot for that set up 8208 is known to potentialy spike pressures way before any kind of max is reached. Try ar comp or win 6.5 staball I have had great success with both using up to 123 gr bullets.

 

[ZenArchery]

What die are you using? I've discovered with my Hornady Die I have to quarter turn the die so it doesn't bell at the web of the case.

 

[writerman]

What die are you using? I've discovered with my Hornady Die I have to quarter turn the die so it doesn't bell at the web of the case.

It's a brand new, RCBS die. I was told they were the best. However, the decapping pin was broken in the package and they had to send me a new one. Now, when using the bullet seater, if you don't hold the bullet EXACTLY straight up into the press, it bends the base over making it unusuable. Sometimes happens? I don't know about that. 10 out of a 100 seems excessive. Never happened with my Hornady die set, which I now have to use in conjunction with the small base die set from RCBS. Now I know why guys I know own some much stuff......

 

[Lone Hunter]

Sounds like a gas problem to me.. I ( built ),first one I ever put together, that would fire but not eject. Would have bet a lot of money the gas port was lined up correctly but upon closer examination it was off. Bought a better quality gas block, non adjustable, made sure everything was lined up properly and have never had that issue again. Also check and make sure the gas tube is lined up correctly and not dragging on the bolt. I run 8208 in the 120-123 class bullets and H335 in the lighter class 100gr and down bullets.

 

[Kevin1990]

Too late now but if a barrel manufacturer recommended to me to open up the gas port on a barrel I bought from them, I'd be telling them to pound salt, and sending it to them to do and test it.

By the way I'm of no help. Good luck though.

 

[Bat Rastard]

Is it possible you have a rifle length buffer spring crammed into a carbine buffer tube?

 

[DHD]

Are you using cases from the other rifles you mentioned building? I ask because I have tried to use Lapua (AA) cases fired from one barrel I've since pulled, in a new barrel. Those cases were not going into battery. Some measurements later and I knew why. I now had over 500 once fired Lapua cases I couldn't use as the last .200" at the casehead was too fat. After some time I found the Sergeant of Arms belt buster die (whatever they call it) and every case is now usable. The Satern cut-rifled barrel had a fatter chamber than my new Proofs did.

Measure a few of your fired cases you are reloading (if that is what you are using) and compare them to new cases. I had my issues with cases that were .442" or larger. They had to be mortared out and I really don't like to do that. .441" and under dropped in and caused me no issues.

I use a lot of 8208 in the Grendel but only for 107/108 grain bullets. Slower powders get used for 120/123 grain bullets but that is what I do. I do not see this as your problem.

IMO, without having your new rifle in front of me, I suspect you have a magazine issue or possibly your cases have a fat bottom. Have you fired any fresh factory ammo or used brand new cases to try? I now either fire new cases or some factory ammo for the initial break-in so I can get good honest measurements. I didn't see whether you did this or not.

I have a few different brands of magazines and lowers and they do not always play nice with each other.

 

[writerman]

Okay, so I changed the buffer spring to a standard AR one, from a stiffer spring, and put in a regular buffer, whereas I had a Kynshot hydraulic buffer in there before when it would only shoot one round and then jam the reload in the chamber, and I opened up the gas block a bit. Now it will shoot four rounds, but then the fourth gets stuck as I loads. Have to use a flathead screwdriver to get it out and reload the next rounds. This is consistent. I also noticed that the ejector has serious gouge marks on it, like it's scraping heavily on the barrel extension. They are both Odin works matched, so I don't understand why this is happening, or why I can't shoot more than four rounds. Any ideas?

 

[jelenko]

ejector has serious gouge marks

The ejector? Gouge marks? The ejector is a pretty hard piece of metal.

 

[writerman]

The ejector? Gouge marks? The ejector is a pretty hard piece of metal.

I would say so. It's a good one too, an Odin works bolt. Has to be running against the barrel extention somehow, but I have not figured out how yet. I would guess a manufacturing defect? Barrel and bolt are both Odin works.

 

[jelenko]

I'm not seeing how an ejector possibly could engage the barrel extension.

 

[writerman]

I'm not seeing how an ejector possibly could engage the barrel extension.

Neither am I. But the huge gouges are still there. I'm perplexed.

 

[jelenko]

I had an ejector spring go soft that caused what you're seeing now.
The extractor would hold onto the case after firing, the ejector spring was weak enough that fired case stayed on the bolt, then the BCG slammed the fired case back into the chamber. We had to use force to get the case out. A Marine armorer found and fixed the issue.

If it were me, with those gouges I'd also get a new ejector.

 

[DLT]

Not read whole thread. If a sized empty case will not fall out of the chamber when muzzle is pointed up it’s not sized enough

 

[writerman]

I had an ejector spring go soft that caused what you're seeing now.
The extractor would hold onto the case after firing, the ejector spring was weak enough that fired case stayed on the bolt, then the BCG slammed the fired case back into the chamber. We had to use force to get the case out. A Marine armorer found and fixed the issue.

If it were me, with those gouges I'd also get a new ejector.

I think that's the most plausible explanation I have ever heard. Will replace the spring and ejector. Will do. Sounds right. Some issues are just beyond me, and I am not exactly a novice. Love to learn. Thanks.

 

[jelenko]

I think that's the most plausible explanation I have ever heard. Will replace the spring and ejector. Will do. Sounds right. Some issues are just beyond me, and I am not exactly a novice. Love to learn. Thanks.

Thanks!
But, from my experience, the gas operated ar platform can do a lot of non intuitive things => I wouldn't put more than 40% chance that what I mentioned is the actual issue.

The ejector spring should NOT be easy to push in.

 

[writerman]

Thanks!
But, from my experience, the gas operated ar platform can do a lot of non intuitive things => I wouldn't put more than 40% chance that what I mentioned is the actual issue.

The ejector spring should NOT be easy to push in.

My bad. It was on a .223 the marks were. Haven't been to the range lately because of the cold, so I took two rifles. So I switched the spring to a new one anyway. It was working fine, but the marks! I am still having the loading issue with my 6.5 Grendel. New barrel and bolt, Odin works. 26GR Xbr 8208 123 GR Hornady EldMatch. Four rounds, then jams. Don't get it. I just mixed up thinking about the marks because I cleaned them both at the same time when I got home.

 

[S3silver]

Too late now but if a barrel manufacturer recommended to me to open up the gas port on a barrel I bought from them, I'd be telling them to pound salt, and sending it to them to do and test it.

Sneaky way for them to void any sort of warranty.

 

[Oso]

Few things more frustrating than a AR that is having issues. There are a number of potential culprits. Based on your initial post this AR is a DIY Build. You can do everything right assembling parts and still have an issue because of the component. I’ve done a few of these “Guess my problem“ and fix it on friends AR’s. I have found that best approach is a structured process of elimination. My checklist goes something like this

1). Gas Issue (too little or too much)
> check gas block alignment and port hole, also check for burs
> check that gas key on BCG is properly staked
> check buffer setup (spring and buffer: weight & length)

2). Cartridge / Chamber fit interference
> does your rifle operate with factory store bought ammunition
> do your handloaded cartridges freely drop in the chamber (pull off upper and remove BCG)
> insert BCG into upper and manually push it forward. Does it fully close on your cartridge
> are there signs of pressure on spent cases (ejector swipe or exterior of case looking like scoured with fine sand paper)
> any bent case rims from hard ejection
> if possible run a bore scope down barrel and into chamber to see if any obstructions

3). Component Fit Issue
> fit between upper & lower receiver (swap upper and lower with second rifle and make sure each rifle operates properly)… don’t just swap over some of components. Need to isolate where the problem is occuring
> is buffer retainer pin bent or appear damaged (too light of a buffer spring or the pin location was machined out of spec)
> inspect the rear portion of lower receiver where buffer tube attaches for potential damage from BCG impact (if upper and lower don’t properly align … machining is off on upper receiver Or even something as minor as takedown pin holes on lower receiver are not perfectly square)

I no longer take these “Can you take a look at this?” requests from brother-in-law…