Next month I am hoping to do a "ladder test" with the 500 ARNyati (freebore 0.255") using H4198 powder, WinLRMagnum primers, and 350 grain CEB raptor bullets. For comparison, 100grains of H322 and 350grain raptor does 2711fps.

I would like the ladder shots to be within 2500fps and 3000fps. My gut guess would be to shoot loads from 84.0 grains H4198 to 95.0 grains H4198, at intervals of 1.0 grain each.

Does that look about right with QuickLoad or from direct experience with anyone?

As a first group for testing the tips, I was thinking of loading up 3 rounds at 90.0 grain without the plastic tip and 3 rounds at 90.0 grains with the plastic tip (adding 10 grains weight to the bullet).

Ultimately, accuracy and the ladder test may dictate the best velocity and load for my 22" McGowen barrel. Anything between 2500 and 3000 should be devasting and usable out to 300 yards. If differences are imperceptible, then I may aim for about 2750-2850 fps with the 360 grain projectile.

Any thoughts, help, or suggestions?

Thanks,
the buffalo of Tanzania will appreciate your input.

Given the total powder weight, adding 1gr at a time makes for very small steps and would take like lots of time, powder and bullets. 2gr steps might give you plenty of usable data. The sweet spot will show up more quickly then you could go up or down 1gr. How many rounds of each load do shoot?

416Tanzan,

My 49-10/12.7x68mm Magnum (.500/.338 Lapua Magnum Improved 2.657") is nearly identical to your 500 AR Nyati except for your .510-caliber bullet instead of my .500-caliber.

My rifles also have 24" barrels instead of your 22", keep in mind.

My data should be safe to go right into your rifle.
You could even up my loads in your bigger bore, but it will be pretty close.
Ultimately you might get a little more velocity if barrels were same length, etc., etc.
Your primer (Winchester Large Rifle Magnum) is a little hotter than the F215 I used, but little matter there either.

I like H4198 for CEB .500/360-grain-tipped and 350-grain-no-tip Raptors.
But H322 is great too, just takes more powder to get up to pressure and speed, it being a slower burning powder.
I certainly favor that powder for 400-450 grainers

I have two rifles in 49-10, both 24"-barreled, 1:12" twist, .500-bore.

Here is how a limited "ladder test" worked for both H4198 and H322. Plotted points are actual velocity chronographed versus powder charge.
There were no pressure signs with brass or rifle.
My QuickLOAD showed 360-grainer (.500-caliber tipped Raptor, COL 3.609", 24" barrel) with
97.0 grains of H4198 giving 68,032 PSI and 2915 fps, 6793 ftlbsKE.
95.0 grains: 63,712 PSI and 2865 fps, 6562 ftlbsKE.
93.0 grains: 59,538 PSI and 2813 fps, 6325 ftlbsKE.

H322 gives much lower pressures for slightly higher velocity, all else same:
104.0 grains of H322 gave 59,019 PSI and 2922 fps, 6824 ftlbsKE
...
97.0 grains of H322: 46,159 PSI and 2732 fps, 5966 ftlbsKE

I consider 68,178 PSI (4700 bar, piezo) to be maximum, and 63K psi to be swell for the excellent .338 Lapua Magnum brass case heads.





Rifle No. 1 on left is an M70 with 24" barrel, McMillan stock, no brake.
Rifle No. 2 on right is a BRNO ZKK 602 with 24" barrel, has a brake, McMillan stock.

H4198 load comparison with non-tipped 350-grainers and tipped 360-grainers:

Day 1, 83 degrees F, 350-grainers:
Rifle No. 1 with 94.0 grains H4198 gave 2877 fps ave for 3 shots with only 3 fps extreme spread.
Rifle No. 2 with 95.0 grains H4198 gave 2905 fps ave for 3 shots with 11 fps extreme spread.

Day 2, 77 degrees F, 360-grainers:
Rifle No. 1 with 95.0 grains H4198 gave 2895 fps ave for 3 shots with 5 fps extreme spread.
Rifle No. 2 with 95.0 grains H4198 gave 2903 fps ave for 3 shots with 9 fps extreme spread (this load and rifle combo was shot at 300 yard target, with muzzle brake).





Adding the tip to make a 360-grainer, and shooting the 95.grain charge of H4198 out to 300 yards:



Above writing on target is busy but readable/obvious except for the 300-yard drop is nonverifiable due to POA being on an identical target stapled above the POI target for 300 yards. Measured and recorded best I could, may need re-checking.

350-grain (no tip) velocity was 2905 fps.
360-grain (with tip) velocity was 2903 fps.
Rifle No. 2 as detailed above.
Little difference, and chronographed on different days.
95-grains of H4198.
With your bigger bore you can get that or more by upping the charge.
H4198 would be my pick in the .510 bore 500 AR Nyati, for 350-360-grainers.
Good choice.

Then there is the 500 Bateleur (.510/.338 Lapua Magnum Improved 2.700") with either 24" or 25.5" barrels ...

Thanks for this headstart.

It is good data.

I'll probably still need to do a ladder test in order to see if there are any nodes or 'sweetspots' out there. Of course, I would call the .3 MOA so impressive that one wouldn't expect to find anything better.
Goodness, a 6750 ftlb bench rest rifle!

your numbers also look pretty close to my 'gut-guess' approximations. Of course, if 95 grains is an accuracy node, then I might want to move my ladder up to at least 86 gn to 96 grains. I had been thinking that 90grains was going to hit around 2800fps, which was my typical African hunting velocity.

Some update: I will be rebedding a new Boyd's stock after the fiascos last year and before. I'm thinking of something a little different this time. And I've learned to respect the ability of these rifles to bust stocks.

Setting "hidden" pieces of 1/4" allthread across the main recoil block behind the main action lug and also behind the "CZ" barrel lug, that hangs several inches (6"?) down the barrel. In addition, I saw that Larry Potterfield mentioned that Weatherby used the technique on their big boomers, they also embedded some kind of 'U' shaped bar just ahead of the trigger and cradling the action from below. Anyway, no shooting with the new stock until everything is in place. I might try the old Hogue stock for a first ladder test. After sanding off much of the pistol grip I got it to shoot without whacking my trigger finger.

PS: I think of H322 as about optimum with the 450 GSC bullet in the Nyati/Batteleur class 50.

But if I found a good load with H4198, it would simplify things for the 500. I could use one powder. The 500 will go through powder pretty fast at 70-75 rounds/lb.

quote:

Originally posted by 416Tanzan:
PS: I think of H322 as about optimum with the 450 GSC bullet in the Nyati/Batteleur class 50.

Agree, H322 also makes my .500/.338LM Improved 2.657" into a "benchrester" with the .500/430-grain CEB MTH.
It surely must be the cat's meow in the 500 AR Nyati with .510/450-grain GSC HV.
Just right for loading density and pressures with high velocity for that weight class of bullet.

But if I found a good load with H4198, it would simplify things for the 500. I could use one powder. The 500 will go through powder pretty fast at 70-75 rounds/lb.

It might be easier to find an H322 load for the lighter bullet, than to find an H4198 load for the heavier bullet.
Probably will be lower pressure with the former than the latter, mildly compressed H322 for the lighter bullet, but low pressure.

Stock reinforcement of Boyd's laminate stock: Yep it will work, but it is a lot of work.
Easier to just get a B&C medalist-type stock for your Ruger, full aluminum endoskeleton, if you can find one.
Or a McMillan with magnum fill for twice the money that the B&C costs, and a longer wait for delivery, but custom LOP, color, etc.
I would prefer a B&C with slip-on pad for my LOP and call it best, cheap and fast.
Can't beat it.
I hide allthread in McMillan stocks too.
No such compulsion with the aluminum bedding block of B&C.

How I had the Boyd's re-inforced for the 500 Mbogo:



B&C Medalist M98 Mauser from Cabela's mail order, fitted to FN Mauser 500 Bateleur with Wiebe bottom metal,
protruding proudly, just like Saeed does with his .375/404 M76 Dakota in a make-do synthetic stock.