One quarter of a ten-thousandth of an inch!
I didn't know he could measure runout that small.
"The Gun Tailor" is on his break from med school.
Kevin just put a Pac-Nor on a CZ action for me.
Being the "precision freak" that he is, he was most impressed with the PAC-NOR barrel.
That is a No.6 Sporter contour with 1:9" twist stainless, "Super SS," .510" 8-groove, 28", a standard offering at Pac-Nor, for $280 USD.
Ordered from the web site, and arrived in 8 weeks, new-made.

I just wanted to brag about PAC-NOR.

Yeah, +1, they supplied my A-2 barrel, precisely to my dimensions.

quote:

I didn't know he could measure runout that small.

Easy stuff .... laser micrometer

RIP

Every single B&M and MDM all wear Pac-Nor barrels, each and every one of 'em! I could not be more pleased with them, nor ask anything else of them.

Hats off to Pac-Nor, I am with you 110%

Cheers

Michael

quote:

Originally posted by RIP:

One quarter of a ten-thousandth of an inch!
I didn't know he could measure runout that small.

That is a No.6 Sporter contour with 1:9" twist stainless,
"Super SS," .510" 8-groove, 28", a standard offering at Pac-Nor, for $280 USD.

Eeeeek! That much runout is terrible!!
You better send that barrel and reamer
up to Dave.
He'll find a way to live with it.


That is a damn fine job.
Is that button rifled?

PAC-NOR barrels are button rifled.
Must be some spiffy CNC on the contouring too.
This 500 Mbogo CZ will deserve a spiff-up by AHR.

quote:

Ordered from the web site, and arrived in 8 weeks, new-made.

Pretty fast!

Another quick turnaround: 3 week gunsmith turn around from parts to shootable.
Just waiting for the NECG "moon bead" and large windowed hood for the front sight, back ordered.
NECG Rear sight has one fixed and 3 fold-down leaves.
Talley barrel band sling base.
Recoil lug on the barrel.
Matte black Gunkote blends the stainless and chrome-moly.
It has a hogback Lux stock, pillared, cross bolted, glass bedded.
Another project rifle is born, the second 500 Mbogo, no muzzle brake allowed on this one.
It will go in a CZ Kevlar drop-in stock next:



Bottom metal and "manly" cartridges in next pic, below.
It is a 4 shooter.
Easily holds 3.75 cartridges in the box.
So about 3/4 of the fourth cartidge is pressed down into the box, then the bolt is closed,
and she is then loaded for bear.
One in the chamber, three in the box.
It will handle any 500A2 or 500 Jeffery load, and then some, more efficiently than either.









Yikes! Gunkote in the muzzle rifling.
I guess I will have to shoot it to clean it!





I hear that NECG has a new part to be found on the "Toy Chest" page of their web site.
It is a "ring base sight," a long barrel band with an express sight base on top and a recoil lug on the bottom.
Wish I could have gotten one of those.
Maybe next time.

Unfortunately, the 500 Jeffery rifle, even that from CZ, cannot be simply rechambered to 500 Mbogo. It requires a re-barrel.

He's dreamin' or living in adream world if he really believes that. I know it can be measured but what was he measuring, runout? Where? Bore to chamber? Did he measure it in the lathe? Out of round?

Whew, I am diminished, but mostly skeptical.

Jim,
That's classified.
Super Cosmic Top Squirrel Secret.
Need to know basis only.
Kevin builds sniper rifles for a U.S. government agency.
He has capabilities, machinery, instruments far beyond yours, I reckon.

quote:

Originally posted by Jim Kobe:
He's dreamin' or living in adream world if he really believes that. I know it can be measured but what was he measuring, runout? Where? Bore to chamber? Did he measure it in the lathe? Out of round?

Whew, I am diminished, but mostly skeptical.

Measured what roundness?
Deviation from specified diameter with an air guage?
Variation in groove diameter after lapping?

If it does not shoot so what?

I doubt that he has the facilities to measure that close. It would have to be in an enclosed lab. with strict temp controls with multi thousand dollar equip. I will raise the BS flag. I bet the barrel will shoot and that is what matters.
Butch

I agree with Butch that not many labs can measure in Microns without very exacting equipment and climate controlled facilities.
I am sure the barrel is very exact in dimension but have to raise issue with stating that kind of tolerance.
Great looking work.

Are you sure on the 9 twist? Most barrel makers use 15-17 twist on 50 cals and 18-21 on black powder 50's. You may have trouble with that twist rate.
Butch

quote:

Originally posted by butchlambert:
Are you sure on the 9 twist? Most barrel makers use 15-17 twist on 50 cals and 18-21 on black powder 50's. You may have trouble with that twist rate.
Butch

What kind of trouble would one have with a faster twist ..??

You did know that you can overstabilize a bullet. If not they would only offer 1 twist that is faster than any bullet that you could use. It ain't good for accuracy either. I guess accuracy is not needed with this cartridge.
Butch

No way you're gonna overstabilize a .510" bullet in any known platform.

quote:

Originally posted by Macifej:
No way you're gonna overstabilize a .510" bullet in any known platform.

Only if you have a 510 shooting at 3500fps or so.
Hey! There's an idea, any volunteers to pull the trigger?

John

butchlambert,
The overstabilization problem is ugly for target rifles used at long range. Yes, in that case you want to make the bullet long axis follow the trajectory and also eliminate the nutation-gyration-heebie-jeebies of imperfect bullets, way out there, by using "just enough twist."

Have you not followed the "Twist Wars" here? Try a search on twist. Old hat.

Some adventurous souls like fast twist for big game rifle used at close range. I won't go into that now. Guilty!

All,
O.K. maybe the smith imagined the runout of the exterior of the Pac-Nor barrel. At least one point along the barrel's length showed all exterior radii to be dang close to equal.
It remains to be seen how well the bore was centered, and how well the threading and chambering were too.

It will take some good bullets to give a hint of that. Testing has just begun:

Hornady DGX .510/570-grain softs: They are soft!

I fired 12 of them today.
Started filing in the sights.
At 50 yards got on paper with the first five shots,
however the paper was an array of four 16"-square targets.
I was aiming at the four-corners center, of a 32" square.
first shots were about 9" high and 3" to the left:





Then I filed the fixed-standing rear leaf a bit, drifted the rear sight about 1/64" to the right and shot and filed some more.

By the 10th shot I had a bullseye, then I flailed the last two shots, ran out of time and ammo:




Three slugs were recovered from the superficial dirt of the berm of red clay, sand, and some small gravel.

Only three of 12 fired were found. The empty jackets were lying in the surface dirt, 183.6 grains and 187.8 grains, just over 32% retained each.
The third slug buried itself a few inches deeper, and retained most of the core: 402.9 grains or 70.7% of the 570-grain initial weight.
You can guess the expansion fromm the one-inch grid on the target. Does anyone care?

The rest of the load components:

Quality Cartridge brass
GM215M primer.
100.0 grains of Varget
5.0 grains of Dacron filler
COL = 3.705"
25" barrel 1:9" TWIST

Velocity at 5 yards = 2216 fps average for 5 shots
at 80 degrees F
1. 2216
2. 2210
3. 2214
4. 2223
5. 2219

QuickLoad predicted 2197 fps MV.
I am not sure of the BC.
Actual MV I am guessing was about 2225 fps.
50 yard velocity was probably about 2100 fps.

The DGX into dirt at 2100 fps was ... how shall I say ... uncertain?

The rifle itself was a pleasure to shoot.
It is so well balanced that it felt lighter.
Exactly 10 pounds dry weight.
Recoil: 89.35 ft-lbs @ 23.97 fps

This load should work well in the 500 Jeffery at these low velocity levels,
and give about the same velocity.

105 grains of Varget with 6 grains of Dacron and the 535 grain bullet is a documented accuracy load in the 500 Jeffery.
Moderate

I will stick with my slow twist barrels and real life measuring. I do not doubt that your rifle will shoot minute of dangerous game. Pac Nor makes good barrels. No sense getting into the twist wars as neither side will go with the others thoughts.
Butch

no doubt its approaching zero runout .. anything past .000 is really just braggin, probably of no importance.

butchlambert,
I accept slow twist for special purpose, long range rifles, and limited bullet weight selection.

I acknowledge both sides.

I prefer more than enough twist.

I have only been disappointed in real life by too slow twist.

This makes a rifle would shoot well with a light/short bullet, but not the heavier/longer bullets.

Never will that happen with faster twist.
Inside of 500 yards no accuracy problems will occur.

Oh, do you reckon the centrifugal forces of 1:9" TWIST at 2225 fps simply shredded the DGX by centrifugal force?

Maybe I better stick with monometal expanding bullets.
That is a thing of the future anyway.