There seems to be alot of suggestions about the 75gr A-max driven around the 3500 fps range. I recall reading some where that this bullet has a hard time taking a fast spin at those speeds and blowing up. Are any of you actually running this bullet at that velocity? Have you experienced any of this? or is this all paper velocities? No flames intented just an honest question.

Belle's Dad, in case of the Hornady number I quoted, that's straight from their manual. I HOPE those are actual, not simulated, numbers!

There would be a crucial difference in twist. A 7 twist barrel might be too fast, but a 9 twist was fine for Hornady (IF IRC). HTH, Dutch.

Dutch, Having owned a host of .224 centrefires, I have been keeping a close eye on the hype and claims previewing the release of the .223 WSSM.

You mention that the case capacity of the .223 WSSM is 54 grains, and I will be interested to see if this is correct, as I have seen about 5 "official" figures, ranging from 52.4 up to 58.5.

The Hornady claim of 3,500 fps from the 75 Amax should be achievable if the case capacity is around 54 grains, but marginal if the case capacity is around 52.

I previously owned a .220 Swift, and a .220 Swift AI, the Swift cases I used had a capacity of 50.5 grains, and when fireformed to the AI version had a capacity of 55.5 grains.

In the late 1980s, using a Rem 700 with 25.25 inch Shilen ss barrel, the 220 Swift AI achieved 3,900 fps with the 60 grain Nosler, and 3,700 fps with the 69 grain Sierra. The Hornady 75 Amax was not tested, as it had not been released at that stage in Australia.

However, judging on the velocity achieved with the 69 grain Sierra, I believe it would have achieved 3,550-3,600 fps with the 75 grain Amax, which judging from the experiences of many is around the limit to which it can be reliably driven without starting to come apart.

Regarding barrel life, if you follow the "Howell line" and use a full case of slow burning powder (Re25, H1000 etc)at normal pressure with 75 Amax, I believe that you should get at least 1500 rounds of useful life.

As I alluded to in my earlier post, I have been getting around 1500 rounds with about .220 - .250 inches of throat erosion from a range of calibres and case sizes. My field loads are usually about 1.0 to 1.5 grains below maximum.

Good luck with the .223 WSSM, and I will be interested to hear your progress. Brian.

Just to be different, I built a 22-243AI on a 40X action with a 28", 8 twist, Hart barrel.
I intended on shooting JLK and Sierra 80gr bullets. However, my rifle prefers the Hornady 75gr A-Max bullet.
75gr A-Max bullets fired @ 3,668ft/sec do unbelievable things to big fat groundhogs. Bullet fragments often penetrate right through, blowing fur all over the place. And that's at 450 yards. They would probably kill whitetails as well.
Barrel life, well, who knows???????????????????
VH

Brian, I have about 200 cases of WSM (once fired, from the Browning test range). I measured the 54 grains on my trusty little powder scale: it's pretty close.

For grins, I ran the two velocities through the Powell calculator (winload version). According to it, 3291 fps gives 45,000 cup, and going to 3500 fps requires going to 51,000 cup. That's probably pretty close to the limit that the Hornady folks are using. Interestingly, the Hornady manual achieved that with I4350, while the Powell Calculator predicts best velocities with I4831.

If Redding would get their act together, and get me my bushing die set, I could find out for myself..... LOL! Dutch.

Dutch, I am glad that it is at least 54 grains, as it would make it little sense if it were less with their .220 Swift case being around 50.5-51.0 grains.

Using my experience with 220 Swift AI (55.5 grains), as guide I would expect the best powders for 75 grain Amax in the 223 WSSM would be considerably slower than the IMR 4350 listed by Hornady, and a little slower than the IMR 4831 listed by the Powell Calculator.

To give you some practical idea of the capacities with the various powder types, I have listed what applied in my .220 Swift AI, and you could probably subtract about 1 grain from that. To fill the case to the base of the neck with:
long cut powders (IMR4350,IMR4831,etc)-48.5 grains
short cut powders (H4831sc, Re 22,etc)-50.0 grains
ball powders (Win WMR, H870, etc) - 52.5 grains

In my 220 Swift AI, 49.0 grains IMR 4831 gave the highest velocity (4,100 fps)and also good accuracy with the Sierra 55 grain bullet, and 47.0 grains of IMR 4831 & 49.0 grains IMR 7828 both achieved 3900 fps with the 60 grain Nosler bullet.

However with the 69 grain Sierra 45.0 grains IMR 4831 gave 3,591 fps, but 48.5 grains of the slower IMR 7828 gave 3691 fps, which was the highest.

Although I couldn't try the 75 Amax, I did chronograph the 74 grain RWS Conepoint, and 47.5 grains IMR 7828 achieved 3542 fps at maximum pressure, and 53.0 grains H870 achieved 3294 fps at mild pressure.

Judging from my results above, I believe you will find that powders such as IMR 7828, H4831sc, Re 22, V165, will probably be best with the 75 grain Amax. Also with the ball powders, around 51 grains of WIN WMR (if you can find it), and the slowest of the Ramshot powders will probably give you a competitive velocity at near 100% loading density. Good luck, Brian.

My .240 Incinerator with a 70 grain ballistic tip (it'll get up to 4,400 fps, but works best around 4,100). I've taken a couple of ground hogs at 500+ yards with the cartridge. Though I love the .22 calibers, I prefer the 6mm's for long-distance varmitting.

Lee Martin
www.singleactions.com

Experiments by a couple of bench-rest barrel-makers showed that the Hornady 75-grain A-Max came apart in the air when it was spinning about 330,000 revolutions per minute (rev/min) but was accurate when spinning about 290,000 rev/min. Here's how fast two velocities and three rates of twist spin a bullet:

9-inch twist, 3,600 ft/sec --- 288,000 rev/min
9-inch twist, 3,500 fr/sec --- 280,000 rev/min

8-inch twist, 3,600 ft/sec --- 324,000 rev/min
8-inch twist, 3,500 ft/sec --- 315,000 rev/min

7-inch twist, 3,600 ft/sec --- 370,300 rev/min
7-inch twist, 3,500 ft/sec --- 360,000 rev/min

How fast this bullet can spin without coming apart also seems related to how much the rifling scores the jacket -- fewer lands and a smoother surface with consistent diameter along the entire bore apparently weaken the jacket less than more lands and a rougher bore that varies in diameter.

Some of my sources have reported driving the Hornady 75-grain A-Max as fast as 3,800 ft/sec but didn't mention the twist, which would have to be slow to keep the spin down.

I've learned a whole lot from this string of posts and was wondering if anyone knew a site on the net where case capacities of standard and wildcat cases are located?

Thanks

The spin from a nine-inch twist at 3,800 ft/sec would be marginal -- 304,000 rev/min (I just checked it in Mathcad). My last .220 Howell barrel (three grooves, very smooth, very uniform bore) would probably handle it all right, but I'm not interested enough to check it out.

I'm well satisfied with 3,500 to 3,600 ft/sec at peak pressures well below the 60,000 lb/sq in. that SAAMI likes for safety but which isn't as barrel-friendly as my preferred 50,000 to 55,000 lb/sq in.

If I remember right the 224 Clark came out in 1964 and yes it was a necked downed 257 Roberts.
Redding still list the dies for it. At the time it came out the powders were still a little too fast to get the most out of it.

I would try some of the new powders like N550 or N560 in a 224tth which is the 6mm necked downed to 224 cal, it'll get you what you want.

As the proud pappy of the .220 Howell, I guess I owe you all some explanation of the rationale behind the design and some data on how well it satisfies my criteria.

I'd wanted a long-range .224 cartridge, superior to my beloved .22-.250 and the classic Swift, since the early 1950s. But until very recently, we didn't have either (a) the bullets with the necessary ballistic efficiency or (b) the powders slow enough to give the heavier bullets (even if we'd had 'em) enough velocity to take full advantage of the necessarily bigger case.

To drive any bullet faster than Cartridge A can push it, you need to be able to burn more powder behind it. This means a bigger case for Cartridge B. If you make the case enough bigger, you don't have to run its loads up to maximum pressures or velocities to get that increase in velocity.

So I started with the 75-grain Hornady .224 A-Max and IMR-7828 and designed a cartridge that I hoped would give me substantially better DOWN-RANGE performance than the Swift, with significantly lower pressures than the Swift MUST HAVE to do its best. And it does.

It is PRESSURE and the high temperature associated with it that "erodes" (actually heat-wears) chamber throats. If velocity were the culprit, barrels would erode worst near the muzzle. If heat ALONE were to blame, the barrel wear would be fairly even all along the bore. But erosion occurs first and worst in the throat -- where the hot powder gas outside the case and behind the bullet is at its highest pressure. So it's the pressure that we want to reduce if we want to increase the accuracy life of the barrel.

It's imperative, if you want your barrel to last significantly longer, to load to pressures a good bit lower than the SAFETY limit specified by SAAMI (usually around 60,000 lb/sq in.). Keep your pressure peaks down to 50,000--55,000 lb/sq in., and you automatically extend the life of your barrel.

So I made the .220 Howell case big enough to use a lot more slow powder than I ever plan to use. I could fill the case about 99% full with 53--54 grains of MRP and get about 3,750--3,800 ft/sec if I wanted to load it to the maximum 60,000 lb/sq in. that SAAMI regards as the upper limit of SAFE pressure.

But I don't need to. I can fill the case 100% full with about 56 grains of Ramshot Magnum and get about 3,700 ft/sec at about 56,000 lb/sq in.

But I don't want to load that hot, either, and I can get a very satisfactory 3,500--3,600 ft/sec at peak pressures around 50,000--55,000 lb/sq in.

What counts is what happens out there where the A-Max pops the prairie dog. Using the classic .220 Swift factory load (50-grain bullet, 3,780 ft/sec, SAAMI maximum pressure) as a comparison, the 75-grain A-Max at 3,500 gt/sec MUZZLE velocity from the .220 Howell reaches the same DOWN-RANGE velocity as the Swift's 50-grain bullet at a bit more or less than 100 yards (I forget the exact distance).

It also (a) stays supersonic out to 1,500 yards or beyond, (b) travels increasingly faster than the 50-grain Swift bullet after it overtakes it, (c) takes about 1/2 to 2/3 as long to go 500 or 1,000 yards, (d) travels a demonstrably flatter trajectory than the Swift, and (e) is deflected only 1/2 to 2/3 as far by a cross-wind. And of course, being 50% heavier to start with, it delivers significantly more foot-pounds of energy than the Swift at all points beyond the muzzle.

The point-blank range for a hit zone three inches in diameter, with the .220 Howell zeroed at 250--255 yards, is 290--300 yards.

This cartridge works as it was designed to work, because I did NOT go into its design armed with only popular folk-lore ballistics, but based my design, from the beginning, on scientifically proven interior-ballistics principles. So no one should be either surprised at or mystified by its performance -- nor skeptical.

Ken Howell, Your information regarding spin rates of bullets spinning at 3,500 -3,600, and the relationship with the Hornady 75 Amax was both welcome and interesting.

It appears that about 330,000 revolutions per minute (depending on barrel condition, etc) will cause the 75 grain Amax to begin to disintegrate in flight.

However, my experience with this bullet raises the following question. Has anyone evaluated how many revolutions per minute are required to stabilise the 75 grain Amax?

First the history! In South Australia in 1988, I had a rifle chambered for the .224 Clark. On my gunsmith's advice, I had installed a 25.25 inch Shilen SS 1 in 10 inch twist barrel. The 1 in 10 twist was chosen because the heaviest suitable bullet available in Australia at the time was the 69 grain Sierra HPBT.

In September 1997,when the Hornady 75 grain Amax became available in Australia, and despite the warning on the box regarding the required twist, I purchased several boxes, as I was interested to see what velocity it would achieve in the Clark, and also if a 1 in 10 twist would stabilise it.

Despite achieving 3,800 fps, all (or at least 95%)
bullets keyholed into the target, so there was a mixture of elation and disappointment.

However, a few moments ago I did the sums on velocities of 3,600 - 3,800 fps with a 1 in 10 twist and was quite surprised.
3,800 fps - 273,709 revolutions per minute
3,600 fps - 259,303 revolutions per minute

The 273,709 revs/min from my 1 in 10 twist barel, is remarkably close to the 280,000 in a 1 in 9 inch twist barrel at 3,500 fps.

If 280,000 rev/min is the theoretical minimum, and 330,000 rev/min is the theoretical maximum, then it certainly constitutes a narrow band of use.

My chronograph data for 21/9/97 on the 75 Amax is listed hereunder using Winchester cases, Fed 215 primer, and bullets seated .020 from the lands.
52.0 grains WW785- 3,652 fps
53.0 grains WW785- 3,722 fps
53.5 grains WW785- 3,783 fps (Max)

51.0 grains Re 22- 3,590 fps
52.0 grains Re 22- 3,674 fps
53.0 grains Re 22- 3,770 fps (Max)

52.0 grains IMR 7828- 3,698 fps
53.0 grains IMR 7828- 3,781 fps
53.5 grains IMR 7828- 3,832 fps (Max)

54.0 grains H1000- 3,598 fps
55.0 grains H1000- 3,660 fps
56.0 grains H1000- 3,745 fps
57.0 grains H1000- 3,796 fps (Near Max, slightly compressed load)

60.0 grains H870- 3565 fps
61.0 grains H870- 3631 fps
61.5 grains H870- 3663 fps Normal pressure, compressed load

Ps. In 1972,my interest in large 224 Centrefires,heavy bullets, and slow powders began when I had a 22/284 built. Since then I have been devouring any information that I can find, and have followed with great interest the development of the .220 Howell, and read many of your articles in the various forums. Regards, Brian.

To save you the trouble of scrolling back up and reading my post again, here's the answer to your question, in this copy-and-paste from that post:

Experiments by a couple of bench-rest barrel-makers showed that the Hornady 75-grain A-Max came apart in the air when it was spinning about 330,000 revolutions per minute (rev/min) but was accurate when spinning about 290,000 rev/min.

Brian, one thing to keep in mind is that Mr. Howell lives in view of God's Country in the Bitterroot valley in Montana. The elevation is somewhere upwards of 4,000 feet (1100 M.). At those elevations, air is about 88% as dense as it is at sea level, and bullets stabilize easier, the thinner the air is.

Although I'd love to find out the exact relationship between required twist and air density, it has so far eluded me......... FWIW, Dutch.

Dutch, Thank you for the information. I assumed that the figures supplied by Don Howell would be at or near sea level.

However, I also realised that the figures are only to be used as a useful guide, and that because of the numerous variables that can have an effect, you still have to test your rifle to find out how well the 75 Amax will work.

I do my chronograph testing at a property which is about 250 feet above sea level. The highest mountain (you would probably call them hills) in our state is 4,200 feet, and is situated about 1300 kilometres (800 miles) away in an aboriginal reserve, so my chances of testing at that elevation are next to zero.

I intend to build up another rifle for the .224 Clark using a long action M700 Remington action. However, next time I hope to use bullets of 80 grains and heavier, so I will have to confront the issue of whether to use a 1 in 8, or 1in 7 inch twist to obtain the necessary revolutions per minute to stabilise the bullets.

I agree that the relationship between air density and rifle twist can appear perplexing, and although I don't have a degree in higher mathematics, my belief is that there are too many variables involved to be able to construct a formula that would adequately cover each rifle.

I also own a .17/222 magnum improved, and use 30 grain bullets, and there has been considerable debate on another forum, over what twist is required to stabilise some of the longer VLD style 30 grain bullets. Again, it appears that those shooting at altitude have an advantage. Regards, Brian

Brian, if you do not already have this in your favorites, the JBM ballistics site is top notch, with regard to predicting stability:

http://www.eskimo.com/~jbm/

HTH, Dutch.

Dutch, Thanks for the site reference. I agree it is very comprehensive, and it will be interesting to see if the calculations appear realistic.

The downside for making the calculations is the amount of data that you have to supply. It appears that you would need a mobile weather station, to be able to supply relative humidity, etc, figures for your testing site. Regards, Brian

Fjold,

A practical and very inexpensive solution to your problem is to just buy a Savage 10fp in 223 with the new Accutrigger. It has a 1:9" twist. They run from $450-$475 on www.gunbroker.com

Shoot nothing but the Sierra 69gr Match King bullet. It has an excellent ballistic coefficient and note that Sierra Manual #5 shows that you can load up to 27gr of Varget behind it which pushes you WAY over 3,000fps.

If you let your barrel cool so it doesn't get hot to the touch you can shoot thousands and thousands of rounds through it with this "heavy bullet".

Or... If that's not enough horsepower for you....Pick up a used Savage for cheap and buy one of Fred Moreo's 22-250 Ackley Improved 1:8" twist barrels for it and shoot the 80gr SMK or 75gr Amax. You can buy the barrel for $235 and with $40 worth of tools (or make your own tools) you can rebarrel it yourself for free. The barrels are air gauged Douglas XX Stainless.

Fred can be reached at www.varminthunters.com/sshooter which is Sharp Shooter's Supply. He also has triggers for the older Savages (pre Accutrigger models). Be sure to ask for his catalog.

You can own a Savage for just a little more than half of the cost of a Remington and never need a gunsmith again which can save you a small fortune if you shoot a lot and cook a lot of barrels like I do.

The Savage Accutrigger which comes on all their fat barreled 2003 model rifles will adjust right down to 1.5lbs and is EXCELLENT!!! You get a special tool to make the adjustment and it's very easy to do with no need to know how to adjust for overtravel etc.

Remember... Let your barrels cool!!! Most throat damage happens when people let their barrels get hot. I rotate out my varmint rifles and always have a couple cooling in the shade when the action get's hot and heavy.

$bob$

The new Savage with the AccuTrigger will shoot and stablize 75 grain AMax and 75 Grain HPs with no problems right out of the box.

If you know anyone who uses these 75 grainers, they double the range on a 223.

27.5 Grains of H 380 has give me Chronographed speeds in the Neighborhood of 3250 fps. out of a 24 inch barrel with a One in 8 twist. Rem 7 1/2 primers.

Remember the more powder you shoot the more barrel erosion you will get. This load should easily give you 4,000 to 5,000+ rounds of Minute of Prairie Dog. This combo is used commonly on 600 yd competition courses and at speeds in the 2700 fps range.

My PacNor Barreled Ruger from Noveske Rifleworks in Grants Pass Oregon, has given me several One hole groups at 200 yds with the 75 hornady HP.

The rifle also wears a Hogue Rubber Stock, and makes a great Varmint Rifle for long distances.
It also blows the crap out of a ground hog, rockchuck or prairie dog, regardless of distances I have hit them with.

Thanks guys. The gun I'm building will be on the Montana LH short action that I have on order already. I shoot a 223 and a Savage in 243 for varmints now so I wanted something different.
I'm still on the fence here but leaning toward a 22-250 AI or 22-243 throated for 70-75 grain bullets and loaded to 3200-3400 fps.

[ 06-05-2003, 18:50: Message edited by: Fjold ]