6.5 Grendel Upper

[BIg_John]

I recently added a 6.5 Grendel Upper to my 7.62 AR Mutant.

Took it to the range and the very first round, stuck hard in the barrel after firing. The pick below is my gun, but wondering what I need to do for it to cycle.

 

[Zuzudaddy]

Question, are you saying the round itself stuck in the barrel ? like a squib round. Or the fired casing was stuck in the chamber ? Also was it factory ammo or reloads ?

 

[Biggie1976]

Also you used an AR10 lower on an AR15 upper as in the grendel?

 

[JohnCarter17]

6.5 Grendel use small frame lowers.

 

[cornhusker86]

Port is to scale w/ magwell. Grendel in a creedmoor chamber?

 

[JohnCarter17]

What is engraved on the top end of the barrel?

 

[diggler1833]

Thats a small frame lower. Unfortunately there isn't enough additional information in the OP's post yet to narrow it down.

Looks like a budget friendly upper from the photo...perhaps the chamber is off significantly.

 

[supercorndogs]

 

[BIg_John]

Fired case stuck in the chamber. Like an idiot, I didn't take my cleaning kit to the range, so I couldn't pop out the case until I got home.

I am shooting Wolf Steel Case with 100 grainer's. I am guessing I will get some comments.... that I should be shooting brass, but I simply don't have any now and I am not buying any until the prices come down. Brass Grendel is really pricey right now.

During the break-in period of this barrel... I wonder if I should simply lube the steel cases. When this gun was a full Russian, it cycled 7.62x39 like butter. It has never jammed, every round a steel case.



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[drewthebrave]

If I'm not mistaken, the Mutant MK47 is a modified AR15 platform designed around 7.62x39 and differs slightly from a standard AR15 to accept AK magazines.

According to https://www.thetruthaboutguns.com/gun-review-cmmg-mk47-mutant-ar-15-7-62x39/:

"The Mk47 is longer, which precludes the ability to swap out the upper for any standard AR-15 size replacements — you’re stuck with the gun you got."

While I don't have any experience with the Mutant myself, I suspect you need to put that Grendel upper on a standard AR15 lower receiver for it to function properly.

 

[BIg_John]

My mags are specific for 7.62x39 (steel mags) for the AR platform.... and I made the assumption they would work perfectly with the Grendel cartridge. I am puzzled why you would raise the concern of magazines, when the issue is the case sticking in the chamber.


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[trdjohn]

most grendel chambers now uses 0.136 depth bolt face, there were few years ago that used 0.125 but that is not the norm - believe the 7.62x39 uses 0.125 bolt face depth - which is yours?

 

[TonyTheTiger]

Are the bolt and barrel from the same manufacturer? Sounds like a type 1/type 2 mismatch.

 

[drewthebrave]

Reread the quote I pulled from the article:

"The Mk47 Mutant is longer, which precludes the ability to swap out the upper for any standard AR-15 size replacements — you’re stuck with the gun you got."

The Mutant isn't a milspec AR15, and may not be compatible with the Grendel upper you put on it.

 

[BIg_John]

Are the bolt and barrel from the same manufacturer? Sounds like a type 1/type 2 mismatch.

Yes, the whole upper came as a complete kit.

Reread the quote I pulled from the article:

"The Mk47 Mutant is longer, which precludes the ability to swap out the upper for any standard AR-15 size replacements — you’re stuck with the gun you got."

The Mutant isn't a milspec AR15, and may not be compatible with the Grendel upper you put on it.

I'm confused about this... I mean if I was trying to go from 7.62 to 2.23... that makes sense. But I am going from 7.62 to Grendel, nearly the same case.


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[r.tenorio671]

Yes, the whole upper came as a complete kit.




I'm confused about this... I mean if I was trying to go from 7.62 to 2.23... that makes sense. But I am going from 7.62 to Grendel, nearly the same case.


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...easy to answer, put the 6.5Grendel upper on a standard AR15 lower and see what happens...

 

[bmash]

Yes, the whole upper came as a complete kit.




I'm confused about this... I mean if I was trying to go from 7.62 to 2.23... that makes sense. But I am going from 7.62 to Grendel, nearly the same case.


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Respectfully you need to do some research…the grendel was designed to fit in a 223/AR15 lower. the 308 does not fit an AR15 - it uses an AR10 lower.

 

[blackblue]

Where are you getting calling it a mutant from?

Also was it a complete upper and purchased from where?

 

[TxWelder35]

Respectfully you need to do some research…the grendel was designed to fit in a 223/AR15 lower. the 308 does not fit an AR15 - it uses an AR10 lower.

He has a 7.62x39 which is AK ammo, not x51 which is 308.

 

[bmash]

He has a 7.62x39 which is AK ammo, not x51 which is 308.

Ok, got it. just Confused over the not 223, since grendel is designed for that platform. Sounds confused to me…

 

[drewthebrave]

I recently added a 6.5 Grendel Upper to my 7.62 AR Mutant.

Where are you getting calling it a mutant from?

This is what I was focusing on. The Mutant is not a standard AR15. If that's the lower the OP is using, then it may not be compatible with the standard AR15 upper.

...easy to answer, put the 6.5Grendel upper on a standard AR15 lower and see what happens...

This should be the solution. A standard AR15 lower should work with the 6.5 Grendel upper the OP owns.

 

[blackblue]

That's why I was asking why mutant was referenced vs the picture that was used.

 

[EMorr]

Maybe have a gunsmith check the chamber, there could be a burr or something else that caused the case to stick.

Another possibility - The steel case will not spring back as much as a brass case, so if the gun has a tight and or rough chamber and the action timing is just slightly off, the case may still be contacting the chamber walls as the bolt starts to unlock and move reward, causing the extractor to pull off of the case rim. Again take it to a gunsmith and make sure the chamber is to spec and mirror smooth.

edit: 10000% No don't lube your ammo prior to loading it in you rifle!

 

[JohnCarter17]

Maybe have a gunsmith check the chamber, there could be a burr or something else that caused the case to stick.

Another possibility - The steel case will not spring back as much as a brass case, so if the gun has a tight and or rough chamber and the action timing is just slightly off, the case may still be contacting the chamber walls as the bolt starts to unlock and move reward, causing the extractor to pull off of the case rim. Again take it to a gunsmith and make sure the chamber is to spec and mirror smooth.

edit: 10000% No don't lube your ammo prior to loading it in you rifle!

That is not uncommon.

Some poorly finished chambers have been seen and they need to be polished/deburred/smoothened out. By default I take some honing oil on a dremel polishing bit and hit the chamber and lugs. Mind you that is undoubtedly overkill on Lilja barrels, but hey.