I couldn't get my 16" Faxon match barrel in 6.5 Grendel to shoot well. Graciously Faxon sent me another barrel to try. This new barrel has OAL (case head to lands) difference of 50 thousands. Is this normal? I figured same barrel, same twist, same manufacturer, same caliber it should be dam close to the old one. It seems to me like this can get someone hurt.
-
Having trouble using the site?
Contact support
Same barrel, same Manufacturer, Different throats ?
- Thread starter doubleduck
- Start date
How did you determine it was longer than the other? Did you ask the barrel manufacturer if there was a change?
I chose faxon because my brother had a faxon barrel that shot very well and he offered to build me an AR15 if I paid for parts.
I determined the difference in depth with a Hornady OAL gauge. Using a 120g eld-m, my old barrel measured 1.755 to ogive, my new barrel measures 1.705 to ogive
I determined the difference in depth with a Hornady OAL gauge. Using a 120g eld-m, my old barrel measured 1.755 to ogive, my new barrel measures 1.705 to ogive
Quality control is a thing of the past.
The old saying "Close enough for government work comes to mind".
Adapt, Overcome and Survive.
It's not just weapon parts.
The old saying "Close enough for government work comes to mind".
Adapt, Overcome and Survive.
It's not just weapon parts.
There are several different freebore specs for the 6.5CM other than SAAMI .199".
Are you sure you used the exact same bullet that you used for the previous barrel.
How many rounds did you have through your old barrel when you obtained that measurement? How many rounds through the new barrel when you obtained the measurement? Did you use the EXACT same bullet with the new barrel that you did with the old barrel?
...
A difference in throat length will not get anyone hurt. What will is if the headspace is out of spec.
I have to disagree with that, modern cartridge designs like the 6.5CM with factory ammo running up near max SAAMI pressure specs that get jammed into the lands on a chamber with a shorter throat could very well be dangerous.
Modern bolt action designs can obviously handle overpressure events fairly well by design but an AR platform not as much.
If I read the SAAMI 6.5 Creedmoor chamber drawing correctly, a factory chamber should have 0.1992" freebore (0.2645" dia.) and 0.162" leade. The two combined create the throat. These dimensions should be the minimum dimensions and maximum would be +0.015". Anything shorter would not meet SAAMI spec and would be considered a custom chamber. Unless the barrel maker specifies this fact it would open them to a liability as factory ammo either would not chamber or cause unsafe pressures.
If a reamer is worn then the leade taper could be larger and possibly explain the 0.050" difference in the two barrels.
If a reamer is worn then the leade taper could be larger and possibly explain the 0.050" difference in the two barrels.
Thats correct there are several shorter freebore specs optomized for specific factory ammo and a worn reamer could aslo cause issue or someone inadvertently using a different reamer.
In this case it is most likely poor QC or lack of it.
I remember a thread on here or maybe the bench rest site someone was having issues with overpressure signs with factory ammo and turned out to be a shorter than SAAMI spec freebore but was actually engraved on the barrel so user error.
In this case it is most likely poor QC or lack of it.
I remember a thread on here or maybe the bench rest site someone was having issues with overpressure signs with factory ammo and turned out to be a shorter than SAAMI spec freebore but was actually engraved on the barrel so user error.
I had about 250 rounds thru the old barrel that I couldn't get to shoot and yes I used the exact same bullet, the 120g eld-m
In my latest development I tried to get the brass from my old faxon barrel to load into my new AR15 faxon barrel. No way! So, I started pushing the shoulder back measuring with my Hornady Cartridge Headspace Bushing B350. I had to push the shoulder back 5 thousands before it would chamber. I went from 1.219 (worked in old barrel) to 1.214. I looked on line and I believe the spec for this measurement is 1.22 + or - .007 (for the Grendel). It makes me wonder if factory ammunition will even shoot in this barrel. I am throwing all this out there in order to learn something. Is Faxon FUBAR, is this semi normal or something in between?
To be honest I am not able to translate all that information into something I can get my head around. My game isn't there yet.
Thank you. It certainly looks like I am well below the min headspace of 1.221. Again, I dont get why this barrel is so different from the last one and I haven't heard back from Faxon
Did you use your comparator on an actual Go headspace gauge? If you didn't don't trust your figures as to being below. The reason is because your comparator will not give you the exact dimension of the headspace gauge. If you have any Federal Gold Medal Match ammo measure it with your comparator. I've always seen that FGMM in .308 Win measured 0.002" less than my Forester Go gauge.
Just assuming you have the type II bolt ?
Yeah im fully aware of that
Was just using the Creedmoor as an example.
Last edited:
When talking headspace I am not using a comparator at all. I am using my Hornady Headspace gauge and the B350 insert
This is an AR15 semi autoJust assuming you have the type II bolt ?
Yeah im fully aware of that
Was just using the Creedmoor as an example.
Hornady
"The five bushings that come with the Lock-N-Load® Headspace Comparator provide the ability to check most bottleneck cases, from .17 Rem through belted magnums."
I think I found the problem and I think it is me 
. The brass I am using was shot in my other barrel and although it is the same manufacturer, length, caliber etc etc, my understanding is once the brass is fire formed 'that don't work'. Apparently I am starting over and I might as well throw out all that brass and buy a new bag. Probably obvious to all of you but ya don't know what ya don't know. Thank You for all the advice.
. The brass I am using was shot in my other barrel and although it is the same manufacturer, length, caliber etc etc, my understanding is once the brass is fire formed 'that don't work'. Apparently I am starting over and I might as well throw out all that brass and buy a new bag. Probably obvious to all of you but ya don't know what ya don't know. Thank You for all the advice.To add further insult to my self inflicted injury I didn't realize some of my fired primers had raised lips that threw my numbers off by 5 thousandths. Thanks again for the tolerance :/I think I found the problem and I think it is me
Thank You Byron, Now that I realize some of the rookie mistakes I was making that seems very feesable.
Yes, you are using a comparator; that's what the Hornady headspace gauge is. The Hornady headspace gauge does not measure the actual headspace of your brass. It's used to give you a comparative measurement between fired brass and resized brass.
...
