Is there something very wrong with my Faxon barrel?

[gofastman]

Woaah! Got a live one!

Every time I have mentioned this over the last fifteen years, the guy who posted their problems got his panties in a knot.

Can you call your shots? If so, what is your call area and did the shots go into it?

If you have no idea what shot calls are, then I would bet you are the problem.

Using a Sierra 120 Match King will eliminate two variables. Powder charge and overall length. Seems like any powder listed for the 120 and used to about 80% the listed charge weight, with a standard overall length, will shoot that bullet to right around one minute plus or minus a bit.

LR55

Lol! I've learned the fastest way to fix a problem you're asking for help with is to listen to the answer someone gives you, even if it's not what you want to hear.

I'm not sure what you mean by shot calls, so I'm probably not doing that. Can you explain it a bit?

I do not have 20" blades on my Impala.
(Old rap song reference, probably not the right audience)


Additionally, do I need all 3 headspace gauges?

[stonehog]

just go/no-go gauges.

[gofastman]

just go/no-go gauges.

If it closes on factory ammo, doesn't that negate the need for a GO gauge?

[montana]

If it closes on factory ammo, doesn't that negate the need for a GO gauge?

You need to re-read what I posted..No, a factory cartridge will close on a short chamber..

A go gauge is the industry or military standard (depending on which need is being used) the minimum length a chamber should be for safety and reliability reasons.

A no go gauge is a guild line, not an industry standard of the maximum length to maximize accuracy and case life.

A field gauge is the industry or military standard (depending on which need is being used) to determine if the chamber is too long for safety reasons..

For most people a go and no go is enough.. If the no go fits in a chamber it does not necessarily mean the chamber is unsafe, it means the chamber is not optimum for case life and accuracy. It would take a field gauge to see if the chamber is unsafe..Most people will reject a barrel that a no go gauge will pass for obvious reasons (case life and accuracy) as it is expected that any decent factory commercial rifle barrel should pass a go and no go..

[LR1955]

Lol! I've learned the fastest way to fix a problem you're asking for help with is to listen to the answer someone gives you, even if it's not what you want to hear.

I'm not sure what you mean by shot calls, so I'm probably not doing that. Can you explain it a bit?

I do not have 20" blades on my Impala.
(Old rap song reference, probably not the right audience)


Additionally, do I need all 3 headspace gauges?

Do the Go, No Go, and Field Gauge test that Montana recommends.

You can run a search on 'calling the shot' or 'shot calls' on the forum or run a internet search. Probably the most elemental and important feedback skill a marksman must learn if he is to become a better shot.

LR55

[gofastman]

Update:
The bolt does NOT fully close on a GO gauge (1.2201")
It's really, really close. I can see the bolt lugs start sliding under the barrel lugs, but it won't close completely.
What's the play here? Is this something that requires modification (by someone qualified)of the bolt or barrel?

[Klem]

Gofast,

Sounds like you've got a tight chamber - tighter than the industry standard SAAMI.

This gives you the option to complain and get a replacement. Given it is grouping 3-4MOA I would suggest you do (regardless that the groups might not be the barrel's fault).

The other thing to consider is safety. As long as whatever ammo you cycle through it is less than SAAMI then you are fine. The lugs will go fully into battery and everything is safe. In fact the brass will thank you for it because the stretch will be minimal on first firing. BUT, if you ever load ammo that is exactly SAAMI (unlikely) then it will be like loading the GO gauge with the bolt only partially closed. Then, as long as the gun cannot fire with the lugs partially closed, again, that is fine. The safe way to test all this is to load that GO gauge and see if you can fire the action. If it won't fire - all good.

Factory ammo is almost always less than SAAMI, so it can be fired from any chamber right up to those exactly machined at SAAMI. Your chamber is less than SAAMI, but as long as the ammo is always shorter than SAAMI and the bolt closes fully (and any hand-load is within safe pressures) you are fine.

Once you have spent cases from that action you can bump them .003" like we all do and it will close properly and fire properly. If you want to keep that barrel then you can even weigh the water capacity of spent cases to know how much less than normal it is. Case capacity affects pressure and if you ever load on the raggedy edge using other people's recipes then be aware their larger case capacities will be more forgiving - you need to be more careful here.

I'd send it back for a replacement, to be safe and sure.

[gofastman]

Gofast,

Sounds like you've got a tight chamber - tighter than the industry standard SAAMI.

This gives you the option to complain and get a replacement. Given it is grouping 3-4MOA I would suggest you do (regardless that the groups might not be the barrel's fault).

The other thing to consider is safety. As long as whatever ammo you cycle through it is less than SAAMI then you are fine. The lugs will go fully into battery and everything is safe. In fact the brass will thank you for it because the stretch will be minimal on first firing. BUT, if you ever load ammo that is exactly SAAMI (unlikely) then it will be like loading the GO gauge with the bolt only partially closed. Then, as long as the gun cannot fire with the lugs partially closed, again, that is fine. The safe way to test all this is to load that GO gauge and see if you can fire the action. If it won't fire - all good.

Factory ammo is almost always less than SAAMI, so it can be fired from any chamber right up to those exactly machined at SAAMI. Your chamber is less than SAAMI, but as long as the ammo is always shorter than SAAMI and the bolt closes fully (and any hand-load is within safe pressures) you are fine.

Once you have spent cases from that action you can bump them .003" like we all do and it will close properly and fire properly. If you want to keep that barrel then you can even weigh the water capacity of spent cases to know how much less than normal it is. Case capacity affects pressure and if you ever load on the raggedy edge using other people's recipes then be aware their larger case capacities will be more forgiving - you need to be more careful here.

I'd send it back for a replacement, to be safe and sure.

Good info, thanks. I'll contact Faxon and see what they say.
I dug the old 6.5 Grendel bolt out of the parts drawer I have.
Closes fine on the GO gauge, doesn't close on the NO GO.
Guessing there's some stacking of tolerances going on, tight chamber + new bolt with "tight" specs = won't close.
Wonder if it's worth a try to get a new Ultrabolt and see what happens.

[montana]

If it takes more than 8 to 9 pounds of pressure on the back of the carrier for the bolt to close on a go gauge, then the chamber is too short..

Chambers can also be cut to narrow that can be identified with a function gauge. Most gunsmiths and armorers don't carry these... I have a 5.56 Faxon barrel with this problem that I keep as an example..

Lapping the bolt lugs can sometimes correct a short chamber that is near the edge of passing, but if the bolt and barrel were sold as one unit then it is best to send it back to the manufacturer..

I will (respectfully) disagree with Klem's statement about the chamber being shorter than SAMMI is OK, but it isn't the first time we have disagreed lol..
Best to have the chamber meet the minimum go gauge set by SAMMI so there is zero chance of pressure spikes with any types of ammunition that may be on the edge of size or pressure..The other factor is when a chamber heats up, the chamber gets tighter compounding the problem..
Tight chambers can create accuracy problems (erratic pressures), popped primers and reliability problems..