Headspace failure - need advice

[kwshoop]

This is a brand new build with brand new parts. Faxon bcg and bolt, faxon 18” heavy fluted barrel. Removed extractor and ejector from the bolt. Will not close on go gauge or no go gauge. Gauges are from Manson. I did not purchase a field gauge. Bcg is about an 1/8” from closing. The bolt will close with no gauge in. Is there something I should check or contact faxon or Manson?

[kwshoop]

I have added a pic showing the bcg position with a go gauge

[montana]

Call Faxon and explain your problem, looks like a short chamber. Faxon has been very cooperative with me in the past with the problem barrels I had and replaced them...

[kwshoop]

Thanks for the advice. I sent them an email describing my problem. I also included measurements of each gauge and measurement of bolt face depth. Hopefully they will be as helpful to me as they were to you

[Old Bob]

I had a BCG that wouldn't close on a PTG go-gauge but would close on a Manson go-gauge. Using a different bolt, the BCG would close on both go-gauges. I took all-sorts of measurements of both gauges, both bolts & the bolt carrier. I really didn't see much difference between any of those items. The biggest difference I found was in the bolt-face depth. The bolt that wouldn't close on the PTG go-gauge has a depth of .135" while the bolt that did close has a depth of .1355" That .0005" was all the difference that was needed for the bolt not functioning as required. The headspace difference between the two go-gauges is under .0001". The PTG gauge is perceptibly longer than the Manson, but just barely.

I have no problem using either bolt in my AR. The bolt with the shallower face-depth chambers & ejects factory ammo without any problems. My rifle functions like a Swiss watch. Cases fired from that rifle have nearly identical case-base to datum line measurements regardless of bolt used.

[kwshoop]

I did measure bolt depth as best as I could which measured out to .1365. I used the hornady b350 comparator to measure the gauges with the go at 1.2160 and no go at 1.2220. I have not tried loading a live round to see if the bolt will fully close. I only have the one bolt. Hopefully faxon will help since the bolt and barrel are both from them.

[VASCAR2]

I’m curious if a loaded cartridge will fall out of the chamber when the muzzle is raised? If the cartridge won’t fall out it might be the bullet is stuck in the lands. If you have to push the cartridge out with a cleaning rod you probably have an out of spec chamber. If a cutter is used to long and is worn it can lead to a short chamber during manufacture.

[kwshoop]

I did try this. I loaded a live round by hand then raised the muzzle. The round fell right out. Never had to use a cleaning rod to remove the round.

[Happy2Shoot]

Did you try loading a commercial round from a magazine with the BCG assembled, and then eject it?

[kwshoop]

I have not loaded a commercial round from the magazine. Once the go gauge failed I pretty much stopped and posted here as well as emailed Faxon. I am hoping to hear back today. If not I will call them in the morning.

[LRRPF52]

Gas guns need some slop in the chamber to reliably function.

What are your bolt lug lengths?

If it chambers and fires live factory ammunition without issue, I would move on.

I measure headspace with fired cases after pre-checking the chamber with various dummy cartridges I have for that purpose.

I use a spare, stripped bolt for that, which has .136” face depth and the same lug lengths as my others.

I use that bolt to test my die set-up as well. Loaded cartridges need to be able to chamber and allow clear bolt closure.

I’ve never used any chamber gauges on 6.5 Grendel for that reason.

The loaded cartridges and spent brass don’t lie.

[kwshoop]

Bolt lug length measured to .2865.

So there is no issue with reassembling the bolt with the extractor and ejector then loading a live round from the magazine. I haven't had an ar fail a go gauge so I have been more cautious in proceeding with loading live rounds.

This is my only ar in 6.5 grendel so right now I don't have spare parts to swap in and out.

[montana]

As you will see on this or other forums, people will have differing opinions.. I do use go gauges to set the minimum standard for the chambers I use. I believe tolerances were set for a reason..If I hand one of my rifles to someone, they will know that my rifle will meet the tolerances set for that caliber..I separate my bolts by short medium and long..Bolts can effect head space when it comes to chamber tolerances. I have swapped bolts to fit the chamber.. I have one Grendel bolt that will not meet tolerance on any of my barrels, I would never use it, but that is just me..I also use a function gauge to verify the chamber was cut correctly..Some use comparative gauges, some will put rounds through their rifle and consider it good to go if it functions reliably and the brass looks good, while others will size their brass to fit their chambers..I have seen out of spec chamber gauges, which is why I test all of my chamber gauges...I also don't believe a rifle needs to be broken in to run correctly,I consider a rifle that needs to be broken in as a rifle that is out of spec..When I work on troubled AR rifles, I can many times find the culprit in a poorly cut chamber or manufactured bolt and carrier..Properly made chambers are very important to me..There is a reason some rifles will eat steel case ammunition and others will choke on them...

[kwshoop]

I appreciate all of the advice and the help I am getting. I would say this is by far the best forum I have been on for information and for people treating each other with respect. This is only my 3rd AR build so I am quite the novice especially when I run into problems. That is one reason I am more cautious since I am still learning. I did call Faxon today and their automated system said to hang up if you had already sent an email because you were already in the queue. Hopefully I should get a call from them.

I would hope that Faxon will either send a replacement bolt or want to look at the barrel and pay to have it shipped back to them. This is why I haven’t done much more.

[kwshoop]

Talked with Faxon today and they said to send them the bolt and barrel and they would determine which part was the problem and fix it. Sent me a prepaid shipping label. Send the parts out tomorrow.

[kwshoop]

Ended up being an out of spec bolt. Faxon is replacing the bolt.

[montana]

Ended up being an out of spec bolt. Faxon is replacing the bolt.

Happy it was taken care of..Was it head space, bolt face or something else with the bolt??

[kwshoop]

They were not specific. Just said the bolt was out of spec. Guess I was happy it was being taken care of I didn’t think to ask.