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Boosting BC of commerical bullets.....

 
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Old 03-17-2013, 05:20 PM
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Boosting BC of commerical bullets.....

Well, this is an idea that popped into my head several years ago when I was working with the old Wildcat Bullet company. My work load grew to the point that I really just put it on the backburner until I found out that Corbin started selling these aluminum tips. That really got the ball rolling.

Well, Over the past several weeks, I have machined up several collet fixtures to allow me to precisely mount bullets in my lathe at the shop and do the needed work to convert them for these tips in a precise and repeatable manner.

Was able to take a couple hours this afternoon and put all the theory into reality. The main reason for wanting to try this is mainly the fact that the 375 cal, 350 gr SMK bullet is really a pretty poor performer as far as expansion at long range. The reason is because its jacket is massively thick. I figured one of these aluminum tips would not only boost BC but it would also make BC more consistant and aid in expansion at long range. Anyway, just starting out working on this but the theory worked very well and here are some examples.



Both of these are 375 cal, 350 gr SMK bullets, one on left modified for the aluminum tip. This added 0.137" to the OAL of the 350 gr SMK and should make a significant boost in BC as well as expansion performance at long range.



This one also intereted me. I have always liked the Nosler Accubond but they tend to run a bit low in BC, especially in 375 cal. This is the 300 gr Accubond in 375 caliber. Modifying this bullet for the aluminum tip added nearly 0.200" in bullet length. This bonded core bullet with a much better BC will make it a viable option for the larger 375 magnums for long range use including in my 375 Allen Magnum loaded to +3400 fps.



Perhaps the one that interests me the most is the Barnes 375 cal 300 gr TSX. By modifying this bullet with the aluminum tip, it gains a massive 0.333" in OAL. The BC increase for this bullet should be huge by removing the massive meplat of the standard bullet. Plus, Barnes bullets tend to be poor expanders at true long range distances, this tip may eliminate that issue.

Next up I tried a couple 338 caliber bullets.



Here is the old war horse, the 338 cal, 300 gr SMK. Adding the aluminum top took the OAL of this bullet from 1.720" up to 1.840" and should help to boost BC a bit and also make BC more consistant from shot to shot. Expansion has never been a HUGE issue with this bullet in the larger magnums but this tip may allow the smaller 338 magnums to get better performance at that +1000 range.



Another Barnes bullet that really impressed me. The 285 gr, 338 cal TSX-TAC. This one modified with the aluminum tip made it the longest bullet made of all the ones I tried so far. The tip added 0.165" to the standard bullet with an OAL of 1.962" making this one, one of the more interesting ones for me to test at long range out of my 338 Allen Magnum loaded to 3400 fps or a bit more. Again, should get a good boost in BC as well as better expansion at +1000 yard ranges.

These were the first bullets I have made so far with my new collet system. Again, these bullets are machined to accept these tips, not swaged formed. I will be working on the following bullets as well to see what improvements can be made on them ballistically:

6.5mm
123 gr SMK
142 gr SMK
130 gr Accubond
140 gr Accubond

7mm
160 gr Accubond
175 gr SMK
180 gr SMK

30 cal
180 gr Accubond
200 gr Accubond
210 gr SMK
220 gr SMK
240 gr SMK

I will also be working on some Barnes bullets in all of these calibers as well to see what they can turn out. You may notice that there are no berger bullets listed. The reason why is because their ogive design is a bit more aggressive then the ogive on these tips. The result would likely be a wash in BC with the smaller ogive but slightly blunter meplat. I may test them. The 300 gr Hybrid may benefit from a tip as far as expansion at long range from chamberings such as the 338 Edge, 338 Lapua an even my 338 AX where there have been some examples of pencil holing through big game at ranges past 1000 yards. This tip would certainly solve that problem.

Again, just starting, no bullets in the air yet. I have made up 25 of each of the above bullets for testing. When that will happen, not sure. Still lots of customer project rifles to get out the door but hopefully with spring here and longer evening day light hours, I can spend some after hours time on the range doing some more ballistic testing.

I am also going to test these tips in the Barnes TSX bullets in 416, 458 and 50 caliber. The tips used in these larger calibers will be a much larger tip design.

Should be interesting, stay tuned. It can be scary what a curious mind and a precision metal lathe can produce with a few sleepless nights!!!
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Kirby Allen(50)

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Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

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Old 03-17-2013, 05:42 PM
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Re: Boosting BC of commerical bullets.....

Should be interesting. How are you attaching them
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Old 03-17-2013, 05:50 PM
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Re: Boosting BC of commerical bullets.....

Those things look Awesome ! Meat Darts
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Old 03-17-2013, 05:59 PM
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Re: Boosting BC of commerical bullets.....

those are pretty cool, they look similar to elkaholic's bullets.
would you ever sell these to people who dont have a lathe? namely me?
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Old 03-17-2013, 06:29 PM
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Re: Boosting BC of commerical bullets.....

Kirby

Iím impressed that you could make such a mod to so many different bullets without tearing them up let alone have them turn out looking like factory new. It will be interesting to hear what you discover when testing them.

Are not the 30 cal and under bullets you mentioned a little less interesting given that Nosler is coming out with their Accubond Long Range line?
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Old 03-17-2013, 07:47 PM
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Re: Boosting BC of commerical bullets.....

Kirby,

You and I seem to be a lot alike when it comes to getting all of the bc possible,

The differences between you and I are that you have skill, experience, talent, equipment and an uncanny knack for bringing these together with near magical results. However, I do think that I have it on you in the 'looks' area.

I knew nothing about machining. Still don't. But have learned a tone making buckets and buckets if chips. Both aluminum and brass.

I bought me a HF 8x14 bench lathe and ruined a set of jaws getting +/- 0.00001 run out. But I got zero runout. Good start.

Objective was to get bullets worthy of use in one of your 270 AMs.

First attempt was to stage 7MM Berger's to .277. Corbin made me a die. He said that it was too much swage but to know I'd have to try. I tried. It didn't work. Typical for me.

Running Dan Lilja's bc spread sheet said thar simply increasing length without increasing weight wouldn't get me a significant bc increase.

That's when I got the lathe and came up with a tip design to fit the 270 NAB and Ballistic tip. I chips quite a few feet if brass rod before converting the lathe to CNC to get some thru put. used LEGOs Mindstorms components for then CNC. Laugh if you wish. But it worked.

Tips were well within my very tight specs. However without an automatic feed, even w/CNC it was too slow to pencil out.

A commercial bit was $15,000.00 minimum order. Well out of reach to get a $0.15 Point.

Kevin Cram made up a very well working meplat trimmer which allowed a very straight face for the tip to butt against and a uniform length which was critical for proper seating of the tip.

Eaglet's computer calcs said the bc was increased from 0.497 to probably 0.658. Significant! Never got to confirm.

Bullet weight increased from 150 to nearly 160 grains. Length of the tipped 150 NBT/NAB was right there with Richard's 195 WC.

End result was thar re-tipped Noslers shot along with the originals which is very well in this rifle.

The down side was that less than 20% of the tips passed my quality control.

I've come up with several hundred of Richard's originals, 150Bergers shoot very well in this barrel and Berger announced imminent release of a 170 gr offering which pretty much quenched my motivation.

Reason for the low QC results was flexing of the 3/16" brass rod. The steady rest was almost 1" from the chuck jaws which, unless I had the cutter ground exactly correct and took very small cuts there was a very small flex in the rod. This flex was hard to detect but raised its ugly head at the 200 yard target.

I think I ran out of persistence with the 277 project.

I do have that 375 AM which sucks me back in this realm. I went with the 375 vs the 338 with the thought that one day there would be a bullet that would raise 375 AM performance to its proper position ABOVE its little brother. The 338 AM.
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Old 03-17-2013, 08:18 PM
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Re: Boosting BC of commerical bullets.....

Quote:
Originally Posted by screech View Post
Should be interesting. How are you attaching them
They are press fit and WILL NOT come out.
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Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
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