EXTREME .308 "Whiteout and Alpha 30 wins 1st & 2nd at EBR 200 yd event!

[rsterne]

Very KEWL, guys!.... The three of you are to be congratulated, you have done a fine job in a very short period of time.... Getting less than MOA accuracy out of a new bullet in a new gun the first time out is pretty astounding.... I couldn't be happier for you....

Bob

[Rizen 1]

Bob, we will have some bc numbers for you as well as some 200yd groups this weekend..   And THANK YOU FOR ALL YOUR HELP!!!

[C.ALLS]

Bob, we will have some bc numbers for you as well as some 200yd groups this weekend..

We shooting over your chrony or mine at 200 yards? Lol.....

Bob this bullets rocks! AM I mistaken or did you design a bullet exactly like the Whiteout but lighter? If so I think I'll get a mold coming so I can shoot this thing on air when I don't want to shoot off helium.

[Rizen 1]

WE ARE SHOOTING OVER YOURS AT 200 YDS!!!!  OF COURSE.....   LOL!

[rsterne]

C.ALLS.... Since designing the Whiteout bullet, I have done more research on the relationship between Meplat and Sectional Density, and have a series of bullets drawn in .257 cal from 65 gr. to 111 gr.... The heaviest is virtually a scaled down version of the Whiteout, but exactly 4 calibers long so a fraction lighter.... The series of bullets, all of which use the new 8* boattail like the Whiteout, can be seen in this thread....  http://www.gatewaytoairguns.org/GTA/index.php?topic=94920.0

If those bullets are scaled up to .308 cal, they would have the following weights.... 112 gr., 133 gr., 153 gr., 172 gr., and 191 gr.... They have the full bore-riding nose, but can easily be changed to the larger nose which engages the rifling like in the Whiteout bullet, with a slight increase in weight.... Other weights are also possible in between, but would mean a complete redesign of course.... Some of the lighter bullets could be made with existing patterns for the ogives that Veral has.... others, such as the 172 gr., would need a new ogive pattern, at additional cost of course.... If you let me know, here or in PM, what weight you want, I will have a look and advise my recommendation....

Bob

[rsterne]

What's the volume of the air reservoir?.... I'd like to calculate the efficiency....

Bob

[C.ALLS]

What's the volume of the air reservoir?.... I'd like to calculate the efficiency....

Bob

I'm  not sure. I know you've calculated the volume of their standard 24" tube as 300cc but this air tube is a cut down version at only 20".

I'll think about the bullet I'd be interested in and let you know. I'm  pretty sure it'd be under 150 grains. That 133 and 112 would most likely be perfect using regular air/nitrogen.

[Rizen 1]

 Chris must still be asleep...   the charge tube is 20 inches long.

[C.ALLS]

Chris must still be asleep...   the charge tube is 20 inches long.

Thanks  for the correction lol....

[rsterne]

That was what I remember, so the volume is 246 cc (15 CI).... At 450 psi (31 bar) per shot that is 466 CI of air to produce 420 FPE, or 0.90 FPE/CI.... For that amount of power in a .30 cal, I think that's pretty good efficiency....

Veral has a pattern for a 1.0" Ogive, which would be great for the 133 gr. bullet, and he also has a smaller pattern for the 112 gr.... To make the 153 gr. or 172 gr. bullets a longer ogive radius pattern would be reguired.... I would suggest you consider the 133 gr.... That would be 266 FPE at 950 fps, and 295 FPE at 1000 fps.... Let me know which nose style you would like and I'll draw it up for you to send to Veral....

Bob

[C.ALLS]

That was what I remember, so the volume is 246 cc (15 CI).... At 450 psi (31 bar) per shot that is 466 CI of air to produce 420 FPE, or 0.90 FPE/CI.... For that amount of power in a .30 cal, I think that's pretty good efficiency....

Veral has a pattern for a 1.0" Ogive, which would be great for the 133 gr. bullet, and he also has a smaller pattern for the 112 gr.... To make the 153 gr. or 172 gr. bullets a longer ogive radius pattern would be reguired.... I would suggest you consider the 133 gr.... That would be 266 FPE at 950 fps, and 295 FPE at 1000 fps.... Let me know which nose style you would like and I'll draw it up for you to send to Veral....

Bob

I was talking to Mike about the current Whiteout bullet and while we we're really excited about the bore riding we're also glad the bullet morphed into the finish product it is. We like the fact it can be sized so I think I want the 133 grain the same way. I figure after all the talk about not allowing Helium at future events we will need something we can shoot on air in the 1000fps range. Thanks for everything you've done for us Bob and I hope you know it's appreciated.

[Extreme Big Bore]

Bob the charge tube is 20 inches long but the fill end and valve each take up 1 inch and the bore on the white out is 1.018 inner diameter but the way the valve is designed you will want to use an inner diameter of 1.018 and a charge tube of 18.5 inches long for more exact calculations.

[rsterne]

HI Brent.... That gives me 15.05 CI of volume, which is 247 cc.... Close enough....

Chris, it figures they might change the rules to no Helium.... *LOL*.... Here is the design for the optimized 2.5 cal long bullet with the .308 cal nose.... It worked out to 132 gr.... 295 FPE at 1000 fps MV, and 250 FPE remaining at 200 yards.... The wind deflection should only be about 1/4" more at 200 yards than the Whiteout in a 10 mph wind.... A 14" twist would give a stability factor of 1.3 at 1000 fps, and higher below that.... but I think it should work fine in your faster twist barrel....



I know that Veral has a 1.00" radius Ogive pattern, and this uses the 8* Boattail pattern from the Whiteout, just shortened as appropriate.... so there should be no additional pattern charge.... The dotted line is where the ogive will start to engage the rifling, so the supported section is over 1 caliber long, which should certainly keep the bullet straight in the bore.... and it can, of course be sized.... The Meplat is a lot larger than on the Whiteout, but I spent a lot of time with the McDrag program optimizing the relationship between Meplat and Ogive, and that is what has the least drag and the flattest drag curve in the Transonic range for this length bullet.... Anyway, there you are.... If you need any changes, let me know, otherwise it's ready to send to Veral on your OK....

Bob

[C.ALLS]

The bullet looks great Bob! I'll talk with Veral after the shoot and we'll get the ball rolling on the new bullet. As far as the helium issue I don't understand what the problem is. They claim Helium is hard to source on the west coast but I know the last time I was in Colorado the local grocery stores had Helium balloons all over. That's the route I had to take after being told a 6500psi tank wasn't going to happen.

[rsterne]

I plan exactly the same route, I am building a pneumatic powered booster (130 psi shop air) to boost the 500-2000 psi Helium to 3.6K for my Hayabusa.... The 2K Helium tanks are readily available here, in several sizes, with or without the regulator for filling party balloons.... and we live in a town of only 3500 people (actually only 85, but that is the nearest shopping area).... The supplier has been told, however, they are rationed to only 90% of the previous year's supply each year, because of shortages....

Let me know if you want me to send Veral the drawing, and when.....

Bob

[C.ALLS]

I plan exactly the same route, I am building a pneumatic powered booster (130 psi shop air) to boost the 500-2000 psi Helium to 3.6K for my Hayabusa.... The 2K Helium tanks are readily available here, in several sizes, with or without the regulator for filling party balloons.... and we live in a town of only 3500 people (actually only 85, but that is the nearest shopping area).... The supplier has been told, however, they are rationed to only 90% of the previous year's supply each year, because of shortages....

Let me know if you want me to send Veral the drawing, and when.....

Bob

I use my Shoebox compressor to boost the helium. That allows me to pretty much deplete the tank and fill all my other tanks to 4500psi. I've also used my booster and that worked well and those booster pumps are super reliable.

[rualert]

     That's one wicked rifle! Very nice work, and great results. Have you considered trying Nitrogen instead of the Helium? Nice and dry, and available at any gas supply or welding supply.

Casey

[rsterne]

Nitrogen is nearly as heavy as air, and would show almost no gains.... Helium works because it is less massive, wasting less energy accelerating itself.... plus the velocity of the atoms/molecules and the speed of sound is much higher in Helium....

Bob

[C.ALLS]

     That's one wicked rifle! Very nice work, and great results. Have you considered trying Nitrogen instead of the Helium? Nice and dry, and available at any gas supply or welding supply.

Casey

The gun will be using air and or nitrogen after the shoot. I'll most likely only use Helium for long range shooting.

[jimreed1948]

Has the rifle been tested for accuracy using air?