.220 Howell — reamer dimensions

[Ken Howell]

Several shooters with new .220 Howell rifles have been having trouble getting decent varmint accuracy from these rifles.

Trouble-shooting by a top-level bench-rest barrel-maker and rifle-maker revealed that (a) the rifles weren't properly bedded and (b) the chamber throats were so long that a 75-grain or 80-grain bullet properly seated in the neck had to jump too far to reach the rifling, and a bullet seated to reach within a few thousandths of the rifling was barely seated in the neck (1/8 inch isn't enough!).

So this barrel-maker and I put our heads together (takes two to make a wit sometimes!) and developed the optimum reamer dimensions for this cartridge — a chambering reamer with no throat (which works for some bullets and some seating depths) and a separate throating reamer for extending the throat if necessary. These dimensions then allow a 'smith to chamber a rifle for the bullet intended for it.

I bought the first of these "authorized" reamers from Pacific Precision Grinding (P O Box 2549; White City, OR 97503; [541] 826-5808), and it's in the custody of Richards Rifle Company (10501 N Monarch Street; Hobbs, NM 88241; [505] 392-1515; http://www.rifle-barrels.com).

 

[danr55]

Ken, Let me be one of the first to welcome you to Moosies Board. We have a pretty good time here and we discuss some interesting topics. Stop by the Who Am I thread and put yourself on board. Anyway, now that you're here, I need to ask. Is it a coincidence that the .220 Howell has the same name as you? Tell us a little bit about the round.

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Dan AZ www.huntandlodge.com

 

[Ken Howell]

Thanks, Dan! It's good to be here. I "cruised" the place a long time before I posted the above — not because I was being cautious, but because I didn't have anything to add to what I saw asked and answered here.

Yes, the .220 Howell is one of the cartridges I've designed. Over two hundred by now, I'd guess. Over a hundred I know. The .220 Howell is my current favorite, since at my age (70) and financial status (typical meal: shadow soup made with dehydrated water), I'll probably never hunt big game again. Varmint-shooting has always been one of my favorite shooting pastimes anyway.

I designed the .220 Howell after a long wait for the appropriate bullets (high-BC 75-grain and heavier) and powders (IMR-7828, Ramshot Big Boy, and their near-kin) to be available. I wanted a long-range cartridge that would out-shoot the .220 Swift and my beloved .22-.250 at long prairie-dog ranges on the windy plains, yet not burn barrels up in a day or two of shooting. And that's just what I got. This cartridge makes the Swift look a lot poorer than it actually is.

The rationale or philosophy behind the design takes a little explanation.

• First, it is the high heat that accompanies high peak pressures that rapidly erodes chamber throats. Since the temperature and the pressure are essentially Siamese twins, and pressure is what we "measure" and talk about, the usual (and correct) way of saying this is that "throat erosion is a function of high peak pressures."

• Second, the wise and proper industry concern for shooters' safety has led the industry to establish two "official" pressure levels — (a) proof level, which is for one-time industry use, not for handloaders, and (b) maximum SAFE level, which is for the maximum SAFE use, no matter what effects it may have on accuracy, barrel life, or anything else but S, A, F, E, T, Y.

• Third, it's well established ancient knowledge that a significantly lower peak pressure (and its lower peak temperature, of course) allows the rifle to shoot a heck of a lot more rounds without cooking the throat out.

• Fourth, it's also solid, ancient knowledge that a more aerodynamic bullet (which almost always means a heavier bullet) retains its velocity, energy, trajectory, and cross-wind resistance a lot longer than a less aerodynamic bullet that starts out faster but also slows down faster.

So what I did was school-boy simple. I designed a cartridge with about 25% to 30% more capacity than the .220 Swift, but intended to be loaded (a) to significantly less than its SAAMI-safe potential but (b) to more-moderate pressures with slower powders and higher-BC bullets.

The result is a cartridge that starts heavier bullets on their way a bit slower (3,450 to 3,600 ft/sec) than the factory .220 Swift's 3,800 ft/sec, at peak pressures of 45,000 to 50,000 lb/sq in. instead of the Swift's over 60,000 lb/sq in.

The 75-grain Hornady in the Howell slows to the same velocity as the Remington factory .220 Swift bullet at about 180 to 190 yards and rapidly increases its velocity advantage (and related advantages) from that point on out.

A 10-mi/hr, 90º cross-wind at 1,000 yards blows the 75-grain Hornady (from a .220 Howell) about 70 inches off-course, and the Remington .220 Swift bullet about 170 inches off-course.

The brass is available unloaded or loaded. I have a small supply, but not enough for a dedicated, determined prairie-dogger, and I can't afford to buy the factory .220 Howell brass by the thousand, so I'll be re-forming a bucket of new Winchester .25-06 cases.

The .220 Howell case is a .25-06 shortened to 2.400 inches, with a neck 0.375 inch long and a 25º shoulder. Its gross capacity (full to the mouth) is about 61 or more grains of water, depending on the make of the brass and its internal dimensions.

As I said, I could load the cartridge a lot hotter — higher velocities, and even higher peak pressures — and some shooters will, no doubt, being obsessed with the highest possible muzzle velocities and to Hell with barrel life and accuracy. But that isn't what I designed this cartridge for. Throttled back to barrel-coddling pressures, it still out-shoots the superb .220 Swift out where the bullet hits the 'dog.

If I were as smart as the rest of you guys here, I'd be happy to post a JPEG copy of my original AutoCAD dimensioned drawing of this cartridge — but I don't know how to do that.

 

[danr55]

YOu know Ken, that sound very interesting. The one thing that I see that could be a down side is the shoulder angle. Don't you get a lot of case stretch with such a slight angle? I really like the idea of the 1.5 caliber neck. That will contain most of the burn so that all that escapes to the throat would be gas. Most of the powder particles with burn before they exit. Sounds like a great round. If you ever figure our how to do it, I would like to look at the chamber dimensions. What twist ratio do you use? With bullets that long, it would seem that you would need something in the 1:7.5 range. Thanks for the information.

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Dan AZ www.huntandlodge.com

 

[WDSWIFT]

Ken, good to have you on the board with us and don't be so bashful. I have seen the 220 Howell listed and discussed in the Varmint Hunter magazine a time or two that I remember. Like Dan, I'd be curious as to the recommended twist rate for this round. Also, can I ask which barrel maker you worked with on this? And while I'm asking quesions, is there any concern for bullet break up due to the muzzle velocity on this round?WD.

 

[Ken Howell]

Dan, I designed the .220 Howell and all the other cartridges in this family of '06-based cartridges with a 25º shoulder because they were to be (and some are) factory cartridges — and the manufacturers of cartridge cases have trouble making cases with steeper angles.

The case should stretch a good bit less (if at all) with the level of pressure I designed this cartridge for. Time and use will tell.

WD, the Greenhill equation indicates a 6.9-inch twist for the 75-grain Hornady A-Max and other bullets of the same length. So one of my .220 Howell rifles has a 7-inch twist.

But the Greenhill equation is flexible. Sir George's nominal constant in the equation is 150 — but a constant as high as 200 also works well — sometimes better. So my other .220 Howell rifle has a nine-inch twist, which seems to stabilize these long bullets just as well.

Also, the longer twist is less prone to make these bullets blow-up in flight, since it's the rate of spin (x,000 revolutions per second) that makes 'em go to pieces — another reason not to go all-out for the maximum attainable velocities and maximum safe pressures. Load 'er down and get the best over-all performance at long ranges.

The barrel-maker best-acquainted with all this — whom I recommend most highly — is Greg Richards, whom I listed in my first post on this thread (above).

 

[Ken Howell]

Nominal case dimensions, .220 Howell
------------------------------------

head — same as .30-06 case

shoulder — 0.4450 in. diameter, 1.829 inches from breech reference line (BRL)

base of neck — 0.2540 in. diameter, 2.025 inches from BRL

mouth — 0.2540 in. diameter, 2.400 inches from BRL

capacity, full of water to the mouth — about 61 grains of water with Bertram brass head-stamped "220 Howell"

 

[danr55]

Ken, This sounds like a very interesting critter. Have you measured any appreciable differences in velcoities with the 7 vs. 9 inch twist? How about differences in pressure? I would also be interested in your best performing loads with the same heavy bullet in both rifles. If this isn't proprietary info?

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Dan AZ www.huntandlodge.com

 

[Ken Howell]

Dan, the rate of twist in any rifle affects the pressure, therefore the velocity, far too little to be detectible. The usual, familiar variations from round to round in a group are greater than any variation that one could blame on twist rates.

The problems with the screwed-up reamer dimensions (mentioned above) have, as far as I'm concerned, just about junked all the load data so far developed. I'm having one of my .220 Howells' barrel set back a couple of threads and rechambered and the other replaced with a new Richards barrel before I do any more testing with this cartridge.

I'm also having them chambered to seat the bullets with the base of the shank about 0.050 above the base of the neck and the ogive into the rifling far enough to make the lands leave marks about as long as they are wide. This means that all the loads I develop with this arrangement will have significantly lighter powder charges but equivalent or higher velocities than loads developed with the bullets seated to allow some bullet jump before engagement with the rifling.

Bottom line: my data will not apply to anybody else's rifles chambered and throated on the basis of the usual sporting-rifle criteria. But I fully expect the accuracy to improve, from good enough for ordinary shooting to good enough for long-range varmint-shooting and probably good enough for entry-level or junior-grade bench-rest shooting.

[This message has been edited by Ken Howell (edited 02-06-2001).]

 

[danr55]

Well Ken, I'll agree with most of what you've said. The one issue that I have is the opinion on twist rate not effecting chamber pressures. I had 2 22-250s for a while. Since they were both built guns and I did the chamber work of both of them, I am pretty certain that the chambers were very similar. As a matter of fact, I cast both chambers and compared them on a comparitor. One was about .001 longer than the other. Other than that, they were the same. The difference was one had a 14:1 barrel the other had a 9:1 twist barrel. The 14 inch twist would shoot rounds that the 9 inch twist would blow primers on. Loads built a random and consistantly blowing primers, tight bolt, hard to extract in one rifle only and always the same rifle. So, I don't know. It sounds to me as though the barrel twist made the difference.

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Dan AZ www.huntandlodge.com

 

[WDSWIFT]

Ken & Dan, While we are somewhat on the topic of wildcat cartidges here, what are your opinions on the 17-223, and the 6mm-284? WD.

 

[Calif. Hunter]

We should make the above question a new topic so no one misses it! There may be a lot of people with feedback on those two wildcats.

 

[Ken Howell]

My opinion of the .17 Anything will upset .17 fans, but none of 'em can dispute my reasons — they and I just come to different conclusions based on different personal values and criteria. As far as I'm concerned, all cartridges smaller than .22 are imaginative solutions to imaginary problems. One reason is that they introduce problems that larger calibers so easily avoid.

This is just my take on the .17s, and I have no animosity toward 'em, nor any desire to argue against 'em — they're just not for me, so I'll leave it at that.

I also don't want anything to do with a case as drastically rebated as the .284 case. The minor problem with rebated rims is that they often skip right into the chamber without any engagement with the extractor. Not a life-threatening problem, perhaps, but not worth putting-up with (as far as I'm concerned) since it's so easy to avoid. (Just use a better case. There are plenty of 'em out there, just begging for your attention.)

The major problem with the rebated case is that it weakens the case precisely where it needs to be the strongest it can be — exposed, not tightly enclosed, between the chamber and the face of the bolt or block. Add to this the fact that most reloaders tend to load the .284 case until it strains the seams, and the problem gets even worse.

I'm obviously not the bird to chirp sweet songs of praise for either a .17 on any case or any caliber on the .284 case. There are enough of the .17 and .284 birds out there who can tell you why they like 'em. Great. They're just not for me.

[This message has been edited by Ken Howell (edited 02-07-2001).]

 

[Mike375]

Ken,

One area where the 17 Remingtom ruled supreme was for professional fox shooting in Australia.

Mike

 

[WDSWIFT]

Califhntr---OOOOOPPPPS my bad.

Ken, Thanks for the reply. I have no stake in either, but have some previous experience with the 6mm 284. I am getting in the mood to have another varmint rifle built and this time I was considering going the wildcat route but haven't decided on what to go with yet.

WD.

 

[Calif. Hunter]

No, WDSWIFT, you're great.

I just remembered some other guys talking somewhere on here about the .17 calibers...I think Fatman may have been one in one of his .22 Hornet posts.

 

[danr55]

There are lots of reasons to build wildcat caliber guns. The best one is because you want to. The worst one is because there is a wildcat that will do something that a factory round won't do. I con't claim to be as familiar with wildcats as anyone, but I have been building and reading about them for years. All of the wildcats that offered something that is not available in a factory round are now factory rounds themselves. i.e. 25-06 and 22-250 and 17 Remington. That being said, I am fond of the little 17s from the perspective of little bullets moving very very fast. That same thing that I find facinating is the thing that makes them so impracticle. I build wildcats because I like them. Making them shoot well gives me great satisfaction. Perhaps some day I will have one with my name on it. One of my favorite wildcats is the 6.5-284. It doens't do anything that the 6.5-06 won't do as well, it just does it in a shorter case. So...Do it because you want to, not because you think you can get something you can't already find.

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Dan AZ www.huntandlodge.com