Is there something very wrong with my Faxon barrel?

[gofastman]

This gun has never been very accurate. 3-4" at 100 yards is usually the best it does.
I finally got around to measuring the lands and I was really surprised by this.
I pulled the bullet on a factory Hornady Black round.
You can see the factory seating depth versus how far it has to stick out to touch the rifling.

Is this normal?!?

[gofastman]

Additional information:
The barrel doesn't have very many rounds through it, I'd guess 250 at the absolute most, probably less.

[lazyengineer]

Some guns are OK with that round, some hate it. Try TNT 90s. If it won't shoot a TNT 90, some thing is wrong.

[gofastman]

Some guns are OK with that round, some hate it. Try TNT 90s. If it won't shoot a TNT 90, some thing is wrong.

I have some 90gn varmageddons or 95gn Vmax on hand, would those work, or is there something special about the TNT bullets?

[Klem]

Go fast,

Yes, that much jump for a short/light factory round is understandable.

Conventional wisdom for semi-auto ammo is to have at least the diameter of the bullet in shank length seating to prevent the bullet from shifting prior to being fired. So, at least 6.5mm of shank length in contact with the neck for this calibre. For the 95VMax this means the cartridge ends up short, and the jump long.

That said, 3-4 MOA is unusual even for a cheap barrel. Nowadays, if you are not shooting under MOA with a well-rested AR then you are not doing your time, effort, and money justice. Something is wrong with your setup.

[Snarf]

[montana]

What torque value did you use on the barrel nut?

Did you lap your upper receiver face?

Does your barrel crown look good?

Did you head space your barrel/bolt combination?

Is your optic and optic mount solid?

Is your hand guard free float?

Does the hand guard touch the gas block when pressure is applied to the end of it?

Does the firing pin strike the center of the primer or is it off set?

[gofastman]

What torque value did you use on the barrel nut?

Did you lap your upper receiver face?

Does your barrel crown look good?

Did you head space your barrel/bolt combination?

Is your optic and optic mount solid?

Is your hand guard free float?

Does the hand guard touch the gas block when pressure is applied to the end of it?

Does the firing pin strike the center of the primer or is it off set?

-Don't recall the torque off the top of my head, it's not super-ultra-mega tight. I think I remember putting it to the lower end of spec because I lubricated the receiver threads.
-Receiver was lapped and the barrel extension bedded in with sleeve retainer.
-Barrel crown looks new,/undamaged.
-I don't exactly know what your mean by headspacing the barrel/bolt. I had a bolt from a bear creek upper that I was using, recently replaced it with an Ultrabolt, didn't notice a significant accuracy change.
-optic mount is solid.
-Yes, free floating, no contact with gas block.
-slightly off center, pic attached.PXL_20231016_154357858.jpgPXL_20231016_154407717.MP.jpg

[gofastman]

I've always been pretty thorough when cleaning the bore, maybe a little copper left behind would help. That wouldn't affect it that much though, would it?
I use a guide and a lot of care when cleaning, so I don't think the chance of physical damage is very high.

[gofastman]

Go fast,

Yes, that much jump for a short/light factory round is understandable.

Conventional wisdom for semi-auto ammo is to have at least the diameter of the bullet in shank length seating to prevent the bullet from shifting prior to being fired. So, at least 6.5mm of shank length in contact with the neck for this calibre. For the 95VMax this means the cartridge ends up short, and the jump long.

That said, 3-4 MOA is unusual even for a cheap barrel. Nowadays, if you are not shooting under MOA with a well-rested AR then you are not doing your time, effort, and money justice. Something is wrong with your setup.

I was under the impression that .020" off the lands was an important number for accuracy. You mean to tell me it can be 6.5mm?!
That's a pretty wild difference, no?

[montana]

-
-I don't exactly know what your mean by headspacing the barrel/bolt. I had a bolt from a bear creek upper that I was using, recently replaced it with an Ultrabolt, didn't notice a significant accuracy change.
-

Every AR bolt and barrel should be checked for head space..Many don't understand the importance of a go, no go and field gauge..

IMO the go gauge is the most important because I have seen a lot of short chambered barrels in the AR platform..A short chamber can cause chamber pressure spikes, blown primers, reliability and accuracy issues..

People who think it is unnecessary to check new bolt/barrel combinations because of modern manufacturing are wrong..Replacing any new bolt and barrel combination on any AR should have the head space checked..Many get away with it or don't see the signs, so the rumor continues...I sort my bolts small, medium and large.. I have one new Grendel bolt that won't fit any of my barrels as it is too large..I keep it if I run into a longer chamber..

If a barrel has a tight chamber, the problems will magnify when the chamber gets hot..The chamber actually shrinks in on itself when it the chamber heats up, causing an even tighter chamber..

This is why a 5.56 chamber uses a different go gauge than a 223 commercial go gauge..The 5.56 minimum go gauge is .001 longer than a 223 commercial go gauge..

[biodsl]

I was under the impression that .020" off the lands was an important number for accuracy. You mean to tell me it can be 6.5mm?!
That's a pretty wild difference, no?

gofastman...re-read Klem's post.

[gofastman]

gofastman...re-read Klem's post.

Oh Derp....

seating depth

[Snarf]

[Klem]

Go fast,

Here are some readings showing seating relationships across a range of 6.5 bullets. The barrel is a Lilja and while yours will be different the trend will be the same.

Jump and shank contact - Copy.jpg

Measurements are in mm, and 0.5mm is the metric equivalent of a 0.02" jump.

First column is the OAL to ensure a 20-thou jump. As you know, different shaped bullets will have slightly different OALs.

Second column is for reference - it's the length of an ASC 6.5 Grendel stainless magazine. Rounds cannot be any longer than this for normal use in a semi-auto.

Third column shows how much shank will be in contact if bullets are seated to the max the magazine will allow.

Note the mag is the limiting factor in every case. Jump will always be further than preferred.

Even with mags limiting the OAL note how lighter bullets have progressively less shank in contact. You either have to crimp or have a lot of brass elasticity, or seat them even deeper (like in your case) to make sure they won't budge while being slammed home into battery.

Unfortunately 20-thou jumps are a luxury that only bolt gun users will enjoy. If you look after everything else however, longer jump-to-lands are not going to compromise your groups much, and maybe not at all - certainly not to 3-4MOA.

While it is convenient to blame the gun for large group sizes there are a number of factors that cause bullets to go where they do: gun, scope, rest, wind, ammunition, and firer. I remember a group of us shooting an old pencil barrel A1 AR with the handle upper. It had the barrel blown out by full-auto mag dumps yet still shot 3MOA with Milspec M193 ball ammo. And that was using iron sights. 3-4MOA means something is not right and it is not going to be the factory ammo, and for sure not the jump-to-lands.