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First post here and unfortunately it's a troubleshoot.
I just recently built my first 6.5 Grendel and am having issues with the bolt going into battery. I finished the build and took it to the range and had zero issues with it for about 20 rounds. Then I began getting the dreaded click from the trigger and there was a round chambered but the bolt was not fully closed and I had to mortar it to get it back open. I figured it was a gas or mag issue but it even does it when I handload a cartridge into the chamber and slam the bolt closed. It only goes about 75 to 80% in and then I have to practically mortar it to get it out. I've tried removing the o-ring from the extractor and it does not help. Head spacing is good checked with gauges. I've switched the barrel to a different upper to check if that got twisted on barrel install but no luck. I've used two different bolts and got the same results. When there is no round in the chamber the bolt closes fine and moves freely with no issues. I'm stumped!!!
Atheris barrel and bolt
Faxon bolt carrier
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Typically - this is headspace issue. Confirm this by seeing if it'll close on factory ammo. Wolf Steel in particular has the shortest headspace you can get.
If it's still not closing on a live round of Wolf Steel, then it's likely an obstruction in your star-chamber, such as a blown primer, or debris from a broken extractor (i.e. the end "hook").
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Deano6183 Wrote:First post here and unfortunately it's a troubleshoot.
I just recently built my first 6.5 Grendel and am having issues with the bolt going into battery. I finished the build and took it to the range and had zero issues with it for about 20 rounds. Then I began getting the dreaded click from the trigger and there was a round chambered but the bolt was not fully closed and I had to mortar it to get it back open. I figured it was a gas or mag issue but it even does it when I handload a cartridge into the chamber and slam the bolt closed. It only goes about 75 to 80% in and then I have to practically mortar it to get it out. I've tried removing the o-ring from the extractor and it does not help. Head spacing is good checked with gauges. I've switched the barrel to a different upper to check if that got twisted on barrel install but no luck. I've used two different bolts and got the same results. When there is no round in the chamber the bolt closes fine and moves freely with no issues. I'm stumped!!!
Atheris barrel and bolt
Faxon bolt carrier
My bet is your brass isn't bumped enough. Like LE said, headspace issue but with the brass, not the chamber.
LR-55
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Sorry I should have mentioned I am using Hornady Black 123 grain.
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The hornady black factory 123 is typically seated short enough to chamber IIRC.
If you're mortaring the round back loose, are there land marks on the side of the bullet, like bullet was stuck up into the lands?
If so, then the chamber might be too short, or you possibly have a 0.125" depth bolt face bolt but a 0.139"-type cut barrel chamber.
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09-15-2021, 12:34 AM
(This post was last modified: 09-15-2021, 12:45 AM by Klem.)
Dean,
Welcome to the Forum.
I am with 55' on this one. If you have checked the chamber with GO/NOGO gauges and yet you have to mortar out a round because it is sticking in the chamber then it is ammunition, not the gun. Confirmed further by you trying different bolts and even a different upper. One thing to note, the gun will fire without a gas system however that normally results in a sticky case in the chamber when manually extracting. You are using a gas system however and if the gun does not load a round into battery manually then it is a not a gas issue.
If it functioned for 20 rds but then started sticking the difference is the build up of carbon. So, the ammunition was barely in spec to start with but then as carbon builds up the chamber becomes unforgiving. The ammunition is either too long in headspace, and/or too wide. Headspace is not just in length from base to shoulder, it is also the clearance around the case (diameter).
On the issue of the two types of Grendel chambers, can you confirm you used GO and NOGO gauges and both passed. What type of chamber are the gauges for?
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grayfox Wrote:The hornady black factory 123 is typically seated short enough to chamber IIRC.
If you're mortaring the round back loose, are there land marks on the side of the bullet, like bullet was stuck up into the lands?
If so, then the chamber might be too short, or you possibly have a 0.125" depth bolt face bolt but a 0.139"-type cut barrel chamber.
There are no markings other than scrape marks on the casing.
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Klem Wrote:Dean,
Welcome to the Forum.
I am with 55' on this one. If you have checked the chamber with GO/NOGO gauges and yet you have to mortar out a round because it is sticking in the chamber then it is ammunition, not the gun. Confirmed further by you trying different bolts and even a different upper. One thing to note, the gun will fire without a gas system however that normally results in a sticky case in the chamber when manually extracting. You are using a gas system however and if the gun does not load a round into battery manually then it is a not a gas issue.
If it functioned for 20 rds but then started sticking the difference is the build up of carbon. So, the ammunition was barely in spec to start with but then as carbon builds up the chamber becomes unforgiving. The ammunition is either too long in headspace, and/or too wide. Headspace is not just in length from base to shoulder, it is also the clearance around the case (diameter).
On the issue of the two types of Grendel chambers, can you confirm you used GO and NOGO gauges, and both passed. What type of chamber are the gauges for?
Thank you! I'll try to grab some different ammo up if I can find it and check that out. I appreciate all the feedback from everyone. This build has me flustered.
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Klem Wrote:Dean,
Welcome to the Forum.
I am with 55' on this one. If you have checked the chamber with GO/NOGO gauges and yet you have to mortar out a round because it is sticking in the chamber then it is ammunition, not the gun. Confirmed further by you trying different bolts and even a different upper. One thing to note, the gun will fire without a gas system however that normally results in a sticky case in the chamber when manually extracting. You are using a gas system however and if the gun does not load a round into battery manually then it is a not a gas issue.
If it functioned for 20 rds but then started sticking the difference is the build up of carbon. So, the ammunition was barely in spec to start with but then as carbon builds up the chamber becomes unforgiving. The ammunition is either too long in headspace, and/or too wide. Headspace is not just in length from base to shoulder, it is also the clearance around the case (diameter).
On the issue of the two types of Grendel chambers, can you confirm you used GO and NOGO gauges and both passed. What type of chamber are the gauges for?
Sorry didn't see the chamber question. These are brothers gauges and I believe they are PTG Type II gauges. He checked the headspace for me.
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Sure sounds like a short chamber issue , had that with my 24" upper .
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sundowner Wrote:Sure sounds like a short chamber issue , had that with my 24" upper .
How can that be the case if the chamber has passed GO/NOGO gauges?
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Isn't PTG the one with some faulty gauges? IIRC this has been an issue with some of their stuff.
"Down the floor, out the door, Go Brandon Go!!!!!"
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09-15-2021, 08:11 AM
(This post was last modified: 09-15-2021, 08:14 AM by Klem.)
grayfox Wrote:Isn't PTG the one with some faulty gauges? IIRC this has been an issue with some of their stuff.
...But what are the chances this guy gets stuck cases AND both his gauges are faulty?
...and wasn't the PTG issue related to reamers, specifically the lack of a compound throat. Surely their headspace gauges will be within spec.
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09-15-2021, 12:23 PM
(This post was last modified: 09-15-2021, 01:53 PM by montana.)
Remove your upper from the lower and remove the BCG. The chamber and throat needs to be cleaned thoroughly before this test. After the chamber and throat have been cleaned, put a factory cartridge in the chamber and lightly tap the back of the cartridge into the chamber with your finger. Tip the end of the barrel up and the cartridge should fall out. If it sticks, it could be a tight chamber. A function gauge works in the same manor..I would try different factory cartridges to remove any possible defective ammunition from the equation.If you have access to a case gauge, it would help eliminate the cartridges as the problem..
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09-15-2021, 03:07 PM
(This post was last modified: 09-15-2021, 03:45 PM by jasper2408.)
Do you save your fired cases or do you just leave them? The reason I ask is if you did not check all of the fired cases then maybe a neck separated from one of the cases and part of it is lodged down inside the chamber neck. A Go gauge would show good because they do not go down into the neck area.
Do you know anyone that has a bore scope. This is just the type of situation that one is needed. At least you can see if there is anything inside the chamber/neck/throat area that is causing trouble.
Just my .02.
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So, an update is I went to the local GS and bought the last box of 6.5 Grendel they had which was Barnes Vortx 115 grain I believe. Although I have not shot it yet the bolt closes 100% now and I can cycle rounds through the mag with 100% ejection without the bolt staying in the locked position. Ill update again after I shoot it tomorrow. Hopefully, it was just the ammo and my nightmare has ended. Appreciate all the feedback.
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09-15-2021, 07:41 PM
(This post was last modified: 09-15-2021, 07:44 PM by Old Bob.)
I'm also thinking it's a head space issue. Too shallow a bolt face or too short a chamber... IDK...
I have a PTG Grendel go gauge that might be about .0005" too long. That half a thousandth won't let my bolt close that has a .135" deep bolt-face. However, the bolt from my 6mm ARC will close on that gauge when installed in my Grendel. It takes a little bit more pressure on the carrier to get it to close though. That bolt is .1355" deep. Both bolts easily close on a Manson go gauge in the Grendel. If I would have had the second bolt in the Grendel first, I wouldn't have known the gauge was a bit long.
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Jasper,
The most likely place a case splits into two pieces is half way down the body, at the natural weakest point between where the front end is sealed against the walls of the chamber and the thicker base which is not. The times I have seen cases separate half the case is left in the chamber, not just the neck. Neck splits are less dramatic and more longitudinal along the axis of the bore.
Any part of a case left in the chamber will be obvious. The next round goes nowhere near being able to close and there will be an unusual amount of smoke coming out of the action.
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Klem,
You are 100% correct, but so am I.
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jasper2408 Wrote:Klem,
You are 100% correct, but so am I.
Genuinely curious here - have you seen a neck separate from the shoulder/body? For a while I neck turned in 6.5x47 [bolt gun] to a smaller neck diameter than SAAMI. It was sold on the promise it would be more accurate, but required all cases to be neck turned. I worried at the time about neck splitting or separation. Never happened however and for all that effort it was a less accurate than a normal ream. Probably the quality of the barrel swamped any efforts with the tight neck.
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