375cal and 338cal scorpion projectiles

[groper]

Just a little sneak peak / teaser... more to follow soon along with range reports when we`ve sorted thru all the data etc...

The 375cals shown in the pic below, are stable from a 1:10twist at all velocities tested from 2950-3150fps - where pressure limits any further velocity from a 34in barreled 375 cheytac. yes, thats not a typo, 1:10twist!

There will be a separate thread on the 338cal appearing soon, as tested by the current Australian F-class long range champion, also 1:10 twist barreled 338LM and 338EDGE.

Futher down the track, 420grain 375cal ULD specially for the 375VM and some .416 and 50cals also.

Still a work in progress, but nearing completion... real world cumulative average BC`s are <span style="font-style: italic">very impressive</span> -not magical, and i have some videos shooting these past 2000yds that i need to tidy up before posting them for yas... The following image has been photoshop blurred to protect proprietary design features on the projectile, youll have to wait a bit longer for detailed images...

And of course the test rifle...

 

[McCrazy]

Re: 375cal and 338cal scorpion projectiles

Sounds very promising, and tag for followup info.

 

[vman]

Re: 375cal and 338cal scorpion projectiles

I think I just pee'd a little

Groper im interested in details... I dont know any fellow aussies with a .375.. guessing your rigs a Barnard Action Wild Dog 375 Cheytac?

PM me some info brother

 

[JTG]

Re: 375cal and 338cal scorpion projectiles

doesn't need to be magical just close, bc if you please for 338.

 

[groper]

Re: 375cal and 338cal scorpion projectiles

details on the 338 will follow in a separate thread, id like to focus on the 375 in this thread;

Required elevation for 2050yds from a 218yd zero = 16.7mils
velocity = 3030fps
atm pressure = 966mB
temp = 26deg C

required elevation for 1000yds from a 218yd zero = 5.1mils
velocity = 3030fps
atm pressure = 970mB
temp = 28deg C

Repeatable accuracy = 1min @ 1000yds 5 shots with a 6mph wind 4'clock, not much load development as testing many different designs, ES a bit erratic @ 40fps... accuracy will no doubt improve with proper ladder test load development, will come back to this after deciding which version is best- have 6 slightly different versions in each caliber.

Making good progress... Wind is 10mph full value from 9`clock;
<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/JcKX6W2XUhA"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/JcKX6W2XUhA" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>

More again soon, including paper target groupings etc

 

[Ragnarok]

Re: 375cal and 338cal scorpion projectiles

When will these bullets be available, it is 400gr?

thanks

 

[oregon]

Re: 375cal and 338cal scorpion projectiles

Will be fun to see your results and progress toward plans. The directions headed seem promising. Great job. Thank you for sharing. Asking myself which military contracts will you be part of first? It would be nice to see some government money for further research and development in the game if they want full benefit later. And it would help timeline.

 

[Wild_Bill]

Re: 375cal and 338cal scorpion projectiles

I will be testing the projectiles early next week the range is totaly booked this week and i am also competing in the Victorian Queens prise this weekend but i will have the testing all done early next week on the 338's for Nick and we will write another thread evaluating their performance Nick has supplied 4 different design variations

 

[groper]

Re: 375cal and 338cal scorpion projectiles

As an update on the .375`s...

So far i can get consistent sub-MOA 5 shot groupings at all distances out to +1000yds from my 10 twist barrel in the test rifle using a load of 135grains of H50BMG seated 40-50thou off the lands... i have <span style="text-decoration: underline">not</span> been able to get sub 0.5MOA 5 shot groupings- which is what i am really looking for, and is the only reason these projectiles are not on the market already. I have a few more things id like to try and improve the accuracy, but perhaps this is simply the best we can get from these bullets in this rifle...

 

[Longshotbill:)]

Re: 375cal and 338cal scorpion projectiles

Well start getting us some info on those 338 projos! It will make me happy

Seriously though I'm on the edge of my seat to see what you can come up with that can out do with a 300 grn+ in lapua.

I'm selfishly looking for a 9 twist design.

 

[mrjimsfc]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">As an update on the .375`s...

i have <span style="text-decoration: underline">not</span> been able to get sub 0.5MOA 5 shot groupings- which is what i am really looking for, and is the only reason these projectiles are not on the market already. </div></div>
Wow! Sub 0.5 MOA would yield truly impressive results! All 5 shots inside a large pizza (14") at 2,640 yards. That's 1.5 miles folks and the bullet is still supersonic! Even if you should manage to put together a combo of gun, glass, bullet and load to shoot 0.5 MOA at 2,640 yards, it would take an extraordinary person to shoot like that.

 

[groper]

Re: 375cal and 338cal scorpion projectiles

Its been a while since my last update, due to the fact we havnt been able to shoot anymore - our range has been closed until the range inspector has his requests rectified...

Anyway, some more CAD images showing the unique scorpion assymetric design.

So far the advantages are clear, these are;

- very low drag due to greatly reduced cross sectional area of the projectile base.

- Better stability due to drastically reduced magnus forces of the assymetric non-cylidrical boat tail. To clarify, The magnus force acts to destabilize a spin stabilized projectile and is very important in the transonic region.

-better stability allows for a longer projectile with higher SD per caliber AND/OR lower spin requirement for equal length/SD projectiles.

Problems/issues are;
- Can not get better than just under 1MOA accuracy.
- Loads are very sensitive to seating depth changes.
- May require a symmetric radial muzzle brake to achieve better accuracy, which isnt an option in a prone fired rifle.
- More expensive, although not by much.

 

[cega]

Re: 375cal and 338cal scorpion projectiles

Very interesting design and info. Any idea when the 338LM design info and testing posts will begin?

 

[mrjimsfc]

Re: 375cal and 338cal scorpion projectiles

I'm wondering if the bullet would work better out of a suppressor? The symetrical design of most suppressors might provide the stability you're looking for. More expensive for sure, but very desirable for noise and recoil control. Have you examined the results of cavitation under the "edges" of the flats on the asymetrical boattail? Increased rates of spin would cause more cavitation and more problems with stability. I've also noticed that the "real world" manufacture of the bullets does not exactly match with computer design. At the velocities and rates of spin you're dealing with, small differences from computer design result in large deviations from computed results. Just my thoughts....
Jim

 

[Jimmym40a2]

Re: 375cal and 338cal scorpion projectiles

Send me some 408 ones and I will shoot them with a suppressor.

 

[groper]

Re: 375cal and 338cal scorpion projectiles

Unfortunately suppressors are illegal/restricted in australia so its difficult to test this theory out. I do know however, that the increased lift from the flat surfaces on the tail can induce upto twice the initial yaw angle compared with a normal boat tail. The initial yaw angle is still incredibly small tho and damps quickly upon leaving the muzzle.

I wish i could tell you more about the .338 version, however the tester has not reported anymore info beyond the first few bullets he shot quite some time ago. His initial results were very similar to the 375cal. ie - Very good BC but poor accuracy... ill try to contaqct him again and find out more...

 

[mrjimsfc]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">I do know however, that the increased lift from the flat surfaces on the tail can induce upto twice the initial yaw angle compared with a normal boat tail. The initial yaw angle is still incredibly small tho and damps quickly upon leaving the muzzle. </div></div>
Unless the bullet engages (and leaves) the rifling in exactly the same position for each bullet of this particular design, the induced yaw will be directed in a different direction each time thereby afecting the acuracy of the projectile. I don't know how to overcome that problem.

 

[cowboywhorses]

Re: 375cal and 338cal scorpion projectiles

How to order this rad bullet

 

[mudvayne]

Re: 375cal and 338cal scorpion projectiles

The 338 projo has my attention in a huge way..I will be the first to buy some when they are available!!!

 

[cali_tz]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrjimsfc</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">I do know however, that the increased lift from the flat surfaces on the tail can induce upto twice the initial yaw angle compared with a normal boat tail. The initial yaw angle is still incredibly small tho and damps quickly upon leaving the muzzle. </div></div>
Unless the bullet engages (and leaves) the rifling in exactly the same position for each bullet of this particular design, the induced yaw will be directed in a different direction each time thereby afecting the acuracy of the projectile. I don't know how to overcome that problem.

</div></div>

excellent point. Maybe that's exactly the problem that the designer is having. It would explain a great BC, but poor groupings. I see how you could mark and seat bullets to an approximate alignment variation of a few degrees. But then how would the bolt pick it up and twist it randomly even if you try to feed marked brass the same way each time... interesting problem.

 

[mrjimsfc]

Re: 375cal and 338cal scorpion projectiles

I wonder if you were to use the same general configuration for the bullet but give it a "rebated" boat-tail if the yaw problem would go away? It seems like a pretty simple and inexpensive fix if it works.

 

[greentimber]

Re: 375cal and 338cal scorpion projectiles

Were the bullet not spinning rapidly in flight I'd say that's a great design (and it may yet be). Seems like those flat surfaces and three "fins" will be fighting with and breaking the flow of air over the base of the bullet as they spin, preventing a smooth transition. Will be curious to see further info, though. Kudos for thinking outside the box whether it works or not.

Just a note, too... Even with the most rigorous assembly/manufacturing of ammunition, maintaining a consistent 1/2 MOA performance at 1500m and beyond is going to be nearly impossible. Using the 300 gr .338 Scenar as a baseline, a mere 20fps extreme spread in muzzle velocity puts you nearly outside that window (0.4 moa difference) before you introduce any rifle or shooter inaccuracy whatsoever.

 

[cali_tz]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: greentimber</div><div class="ubbcode-body">
Just a note, too... Even with the most rigorous assembly/manufacturing of ammunition, maintaining a consistent 1/2 MOA performance at 1500m and beyond is going to be nearly impossible. Using the 300 gr .338 Scenar as a baseline, a mere 20fps extreme spread in muzzle velocity puts you nearly outside that window (0.4 moa difference) before you introduce any rifle or shooter inaccuracy whatsoever.
</div></div>

That's a great point... even if I handload to exactly 0.1 grain accuracy (as told by my RCBS digital scale), I still am totally unable to ever get 5 random rounds thusly loaded to stay within 40fps, let along 20fps. What is the cause of this variation spread? I was told from one source its because the true match ammo has powder loads that completely stuff the case, and my powder loads sit somewhat randomly inside the case and thus burn differently. Could it be that... ? Could it be case volume is slightly different ? I don't get it. Maybe the scales are inaccurate?

 

[jpmuscle]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrjimsfc</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">I do know however, that the increased lift from the flat surfaces on the tail can induce upto twice the initial yaw angle compared with a normal boat tail. The initial yaw angle is still incredibly small tho and damps quickly upon leaving the muzzle. </div></div>
Unless the bullet engages (and leaves) the rifling in exactly the same position for each bullet of this particular design, the induced yaw will be directed in a different direction each time thereby afecting the acuracy of the projectile. I don't know how to overcome that problem.

</div></div>

shot in the dark,

but how about adding more flats on the tail of the projectile but reducing the surface area of each flat? Say for example double the number of flats to 6 instead of 3 but reduce each of their surface areas to 50% of what they are now. The yaw issue would still be present but reduced in severity and you would have more repeatibility with the bullet entering and leaving the rifling perhaps?


john

 

[wadcutter]

Re: 375cal and 338cal scorpion projectiles

Groper,
How does your rifle shoot with bullets that do not have the flats?

e.g. Make up some with a traditional 8 degree, 0.6 calibre long boat tail with a square cut off base. Shoot them for accuracy in your rifle.
This will give you an accuracy baseline to go off. Then when you introduce the fins you will see how it effects accuracy.

By the way, when you sending some .338's down for me to try. I think Bill has given up on them.
Cheers Norm

 

[Wild_Bill]

Re: 375cal and 338cal scorpion projectiles

Hi Norm Better refrase what you have posted i have not given up on anything i am waiting for the modified design before we can progress We have spoken about some changes that have to be done to make them reliable and hopefuly they will make this a great projectile at this time there is a small area that is having a major influince that can be overcome with a slight change.

 

[wadcutter]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wild_Bill</div><div class="ubbcode-body">Hi Norm Better refrase what you have posted i have not given up on anything i am waiting for the modified design before we can progress We have spoken about some changes that have to be done to make them reliable and hopefuly they will make this a great projectile at this time there is a small area that is having a major influince that can be overcome with a slight change.

</div></div>
Hi Bill,
Good to hear that you are still working on these projectiles. Its been a while since we first heard of the test results, sorry if I had the bull by the horns. Be great for you to get them shooting accurate.Groper has done a heap of work on these pills and I wish him all success.

 

[bohem]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">
- Better stability due to drastically reduced magnus forces of the assymetric non-cylidrical boat tail. To clarify, The magnus force acts to destabilize a spin stabilized projectile and is very important in the transonic region.
</div></div>

How have you quantified this statement?

What is a "drastic reduction"? 10%, 50%, 100%, 1000%?

Can you get the bullet to transition and remain stable with the reduced magnus effects?

 

[Sebben]

Re: 375cal and 338cal scorpion projectiles

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mrjimsfc</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: groper</div><div class="ubbcode-body">I do know however, that the increased lift from the flat surfaces on the tail can induce upto twice the initial yaw angle compared with a normal boat tail. The initial yaw angle is still incredibly small tho and damps quickly upon leaving the muzzle. </div></div>
Unless the bullet engages (and leaves) the rifling in exactly the same position for each bullet of this particular design, the induced yaw will be directed in a different direction each time thereby afecting the acuracy of the projectile. I don't know how to overcome that problem.

</div></div>

Have you checked the effect of exiting muzzle gasses on the rear of that projectile? Just thinking outside the box but could you use a "semi sabot" one that just peels away protecting the flats on the bullet until it leaves the barrel? only down side is it would negate the use of traditional muzzle breaks and suppressors. you would have to use a ported barrel.

 

[Wild_Bill]

Re: 375cal and 338cal scorpion projectiles

The projectiles in 338 have been tested in a radial brake and side port brake the problem is not the exiting gasses it has even been fired without a muzzle breal and a deep hole crown 1" to allow the gasses to exit in harmony but the reason for the eratic performance we hope will be a small change to the rear fin section.

Also in 338 there is an issue with the hollow base design but the fin modification should also fix this issue. I know that there has been a lot of work done on them but there is the last change that will hopefuly fix the problems with regard to accuracy. i did have split groups where 3 would be touching and the other 2 touching but there was a 3" gap between the two groups. then there are just hollow groups and from recovered projectiles and lots of testing we think we have the reason tied down to one area.

Hopefuly when the next batch is done this will be fixed because they are a lot longer than any other projectile that will stabalise in a standard twist and also the BC is very high but this small issue is causing erattic BC variations and also deforming the fins in certain bore relationships.

 

[Noel Carlson]

Re: 375cal and 338cal scorpion projectiles

Bill,

In studying the four shot video, the group pattern looked random rather than vertically biased. I realize that you were fighting a 10 mph cross-wind, but are you saying that BC aberration is the sole source of dispersion attributable to the Scorpion design?

I would think that the moment the last band clears the crown, that blast wash over a randomly oriented asymetric tail, of large surface area greater than two calibers in length, would be a more tenable source of dispersion.

As for the BC itself, can you give a relative comparison of the Scorpion 338 with one of the jacketed standards?

 

[groper]

Re: 375cal and 338cal scorpion projectiles

its been a long while since ive posted anything... but i though i ought to give an update for those who are interested...

Ive been faced with many challenges, the most frustrating is with limited number of machine shops who have the right type of equipment to produce these bullets efficiently... I simply cant get things done in a timely fashion and ive been mucked around to my wits end.

I got the bullets to shoot reasonably accurate in my rifle but still not as good as i can achieve with jacketed bullets... so despite an incredible BC, theres no point producing/selling these unless you have accuracy with it for long range shooting.

For those that havnt figured things out yet, this projectile design has been tested extensively in the US military ballistic proving grounds... Bohem, the reduction in magnus and increased stability has been quantified <span style="text-decoration: underline">exactly</span> by the testing done there. Without going into long winded details, i can tell you that the stability of this boat tail design imparts more stability than no boat tail at all - ie, more stable than a flat base, actually it behaves like a slightly flared base whilst preserving the drag reductions of boat tailing.

With a boat tail 2 calibers in length, the base area is very small so the base area pressure drag is much less and thus we get a very high BC. Combined with very long, minimum wave drag nose cone design and heavy for caliber mass, the BC simply cannot be matched by any other design to date.

Until i can find a means of improving the accuracy, these bullets will not be available nor are they of any use to anyone who needs a good long range bullet.

Sorry guys, but who knows what the future holds...

 

[Noel Carlson]

Re: 375cal and 338cal scorpion projectiles

Nick,

If you think that your design would be capable of navigating a 30' diameter target at 2,000 yards, I would still be interested in verifying the BC at the end of November. Would you be willing to supply a dozen or so?

I seem to recall suggestions that a more conventional 375 might be forthcoming from Scorpion, in which case you may want to utilize this objectively supervised demonstration as a public debute.

 

[McCrazy]

Re: 375cal and 338cal scorpion projectiles

Groper, sorry to see you are such issues with these proprietary projos. Someone already mentioned it but I too think increasing the number of ”fins” may help decrease the dispersion. Using 6 or 9 fins would increase the odds of the round exiting the barrel with a consistent orientation compared to subsequent and preceeding shots.

Also, seems to me that the 3 fins allow a large amount of powder to settle underneath the projo while chambered. When fired this may cause uneven forces to act on the base of the bullet and lead to it being not true to the bore and inducing further instability. More fins would mediate this, as would cases filled to 100% capacity or slightly compressed loads.

Obviously I am not a ballistician nor projectile designer. Just an interested party trying to offer suggestions in hopes of getting these rounds to market.

Speaking of which, I think doing at least a limited production run would surprise you. If the BCs are so amazing, shooters may be willing to trade off some potential accuracy in order to have the benefits of a much better BC. Some of them may have setups that do much better accuracy-wise than your test rifle and they maybe be able to help you find what it takes to make these shoot accurately.

Best of luck, don't give up yet.