A 22-284 Build....The Baboon Slayer...Done Now With Pics

So.........spent the afternoon at the bench........5 hrs non stop shooting groups and chronographing. The 22-284 Baboon slayer was top of the list, like I promised Suther...........I have only this to say.................It was an abysmal and absolute failure. No bullets on the targets at 100 mtrs.......got a box and set it up at 50 mtrs after dumping some rounds at clay pigeon bits on the hillside and figured that it was hitting in about a 1 foot circle at that range.

This is what I found................



The only bright side was that I was able to achieve my velocity goal and reached 3950 fps, but alas it did not matter..........no stability

I WAS WRONG..........apparently the 80 grn Sierras and 80 gn Amaxs I tried need more than 250,000 RPM..........they weren't even moderately stable.........they weren't even stable enough to put a hole in the entire target set at 100 mtrs, likely didn't even hit the backboard.......

So off comes that barrel and I either look for a 1-10 barrel or go to a tougher bullet or heavier bullet in the 1-8 barrel I already have for this action. I may try 70 or even 60 grn bullets with this barrel if I can find some with a decent BC........

Such is the fun with experimenting, the wins are great but the failures are informative and enhance the learning curve as well as helping to keep me somewhat humble, when I have to admit that despite all my math and calculations to the contrary..........I WAS WRONG !!!!! Anybody got a 32" heavy varmint barrel in 22 cal with a 1-10 twist in stainless? Back to the calculator and drawing board as they say...............
 
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c-fbmi said:
Okay gents, you're not thinking about this correctly, let me explain.
The goal is not to develop a better bullet to withstand the rotational stress at extreme RPM, the goal is to calculate the rotational stability requirements of a given bullet and then match the barrel twist and velocity to that requirement. Every bullet will have a rotational stability range where it will fly well and maintain it's structural integrity. Which is why TBs statement lacks any logic at all. A 90 gn 22 cal bullet can be stabilized in any twist barrel, provided one can drive it fast enough to attain it's rotational stability rpm range. As I said previously, velocity does not destroy bullets, it is the centrifugal forces of exceeding the rotational limits of the structural integrity of the bullet.
Now, the 90 gn Berger can obviously be stabilized at an rpm below it's structural limits. People do shoot them, and they shoot well at SOME given rpm. All I have to do is peruse loading manuals and Bergers data to see at what twist and velocity this bullet functions normally and then recalculate the twist required for my projected velocity range. However I have done this with the Sierra and have 500 of them, so I think I'll just forge ahead and see if I can't achieve my goals with the Sierras. I'm not here to reinvent the wheel (bullet), so all I have to do is rethink my project and work it around the wheels we already have.

I was unable to get up to my shop and get into my project yesterday as I was "re-tasked/re-prioritized" by the wife and had to go to town, we'll see what today brings, but I have great intentions at this point.
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I have calculated the RPM that worked in one caliber and then used it to calculate twist required in caliber of different velocity.

In theory this should get us close. The other variable is the increase in air density at higher velocities. Higher air density requires more RPM. I have no id how significant this variable is. Probably as significant as density altitude.
 
I ran tests for Savage after they agreed to make the 223 in a faster twist. The objective was a stable 80 Sierra MK. I reported than in the winter a 1:9 would work, so long as velocity was max. That is about 232,000 RPM

I estimate you would need about 235,000 RPM to handle the colder air and higher velocity (increased air density due to compression)
 
Apparently not Ganderite, as I had very close to 240,000 rpm at 3950 fps but to no avail.........still broadside through the box. I think this bullet would need somewhere in the 270,000 to 300,000 rpm range at 3900+ fps to overcome the forces acting upon it. There is absolutely no sign of stability at 240,000 rpm......none, no point on holes at all, so it obviously is not even close. By my calculations a 1-10 twist would give me just shy of 285,000 rpm at 3950 fps or 281,000 rpm at 3900 fps. This may give me what I want and still be within the structural integrity of the bullet, I was getting bullet disintegration at around 335,000 rpm with the 80 gn SMK.

The other option I have is to screw the 1-8 barrel back on and try the 90 Berger VLD at whatever velocity I can get..............3600-3700 fps and see how it does at 330,000 rpm. If it hangs together then I'll have to see if the improved BC makes up for the loss of velocity over the 80 gn SMK out to 600 mtrs. My goal is to be able to consistently hit a baboon, hopefully in the head out to 600 mtrs. For this I need a consistent 1/2 MOA load at extreme velocity with a great BC in order to deal with the winds and mirage that I have experienced in southern Africa.
I'm not sure that a 90 gn 22 cal bullet holds any advantage at 3650 fps over an 80 gn match bullet at 3950 fps, I'm pretty sure the 80 wins out over 600 mtrs by quite a margin..........
 
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c-fbmi said:
The only bright side was that I was able to achieve my velocity goal and reached 3950 fps, but alas it did not matter..........no stability
Click to expand...

I gotta thank you for doing this as your first thing to test, the anticipation has been killing me. And its not all bad. Think of it this way, you hit your velocity goals. Now if you can only get a barrel with the right twist you might be able to do it with some semblance of accuracy.

Alternatively, if you need to switch bullets, 3650 is less than 10% slower than 3950, so they would still be going pretty darn fast, and better BCs should help mitigate the effects of wind drift and velocity loss, so at 600yds they might be pretty comparable. I was tempted to google a ballistic calculator and run some numbers, but its late and I'm going to bed. If nobody else does it before then, I might do it in the morning...
 
Pretty neat how you got them bullets laying down regardless there Douglas.
Maybe more horsepower would get them bullet tips landing with them
pointing at the Bullzs-eye.
Wouldn't that be an achievemint.

The Pengwin be call'in.
 
The berger 90gr bt match @2650 shows less drift at 600m than the 80gr mk @2950. 10kph wind shows 2.6moa for the berger, 2.8moa for the sierra. The berger has a slightly longer flight time, .640s vs .608 for the 80gr.

It was a good experiment anyway. Thanks for sharing it here. Before you take that barrel off it would be cool to see what bullets in the 70gr range do.
 
cdn shooter said:
The berger 90gr bt match @2650 shows less drift at 600m than the 80gr mk @2950. 10kph wind shows 2.6moa for the berger, 2.8moa for the sierra. The berger has a slightly longer flight time, .640s vs .608 for the 80gr.

It was a good experiment anyway. Thanks for sharing it here. Before you take that barrel off it would be cool to see what bullets in the 70gr range do.
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CS..........I fully intend to do just that, I have some 69 and 70 gn bullets which I will try before breaking it down........might even try some slippery 60 grnrs......I'll have to see what's out there and available.
 
c-fbmi said:
CS..........I fully intend to do just that, I have some 69 and 70 gn bullets which I will try before breaking it down........might even try some slippery 60 grnrs......I'll have to see what's out there and available.
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If you can push the 80s at 3950, whatcha think a 70gr is capable of? 4200+?
 
SS..........I can't see a 69 gn bullet being any better from a 1-12 twist @ 3700 fps than the 80 gn @ 3950..........I doubt it will make it to it's stability RPM with the 1-12 barrel...........now it may make it at 4100 fps, which should be about what is possible with this rifle and barrel.
I'm seriously thinking that a 90 gn Sierra or Berger at 3700 fps from the 1-8 barrel I have, may be the way to go..........or find a 32" stainless barrel with a 1-10 twist and try again. Of course it's cheaper to buy enough bullets to shoot this barrel out than it is to buy another barrel....
Anyway, I have some 69 gn Sierra match and some 70 gn Hornady match I will try before I yank this barrel off.........
 
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Yeah, I'm leaning more in the 1-8 to 1-9 area for the heavier bullets you want to use in .22-284, especially after sifting through info on it. Lots of folks go with 1-9 but your 1-8 should do good with a 90 gr.
 
80 smk 3950fps = .742 stability
69 smk 3700fps = 1.022 stability

Just for fun
80 gn smk 4500fps = .774 stability
Going faster gets the rpm up but as you go faster the air pressure forces go up as well.
 
Purple shoulder said:
80 smk 3950fps = .742 stability
69 smk 3700fps = 1.022 stability

Just for fun
80 gn smk 4500fps = .774 stability
Going faster gets the rpm up but as you go faster the air pressure forces go up as well.
Click to expand...


What is your basis/formula for these numbers............I somehow do not think that a 69 gn SMK will work at 3700 in a 1-12 twist............using your formula, where does the 69 SMK end up, stability wise at 4100 fps? So you are saying that the 80 gn SMK won't stabilize at even 270,000 rpm @ 4500 fps, but I know for a fact it will stabilize at 240,000 rpm at 3400 fps. What RPM does the 80-90 gn SMK need to be stable at 4000 fps?

My goal is the highest possible BC at the shortest possible ToF over 600 mtrs. So going to a lighter bullet goes against my goal, but then so does dropping velocity with the 80-90 gn class of bullets, that have the .5+ BCs.

1-12 @ 4000 = 240,000 rpm

1-10 @ 4000 = 288,000 rpm

1-9.5 @ 4000 = 303,000 rpm

1-9 @ 4000 = 320,000 rpm

1-8 @4000 = 360,000 rpm

Now I know for a fact that the 80 gn SMK loses bullet integrity at around 330,000 rpm...........so according to your calculations where do I go with twist rate to achieve my goal?
 
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So I'm assuming that 1.0 is stable............so the 80 and 90s are just barely stable in the twists you quoted? Meaning if I can't get 4000 fps I won't be able to get stability.........
 
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