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Boosting BC of commerical bullets.....

 
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  #15  
Old 03-18-2013, 09:28 AM
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Re: Boosting BC of commerical bullets.....

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Originally Posted by HARPERC View Post
Roy nailed it, main difference being I didn't have my looks to fall back on, when my skill level proved insufficient to the task. Very cool to see it done.
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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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  #16  
Old 03-18-2013, 09:46 AM
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Re: Boosting BC of commerical bullets.....

Fifty....


how about turning that boat tail on the 375 cal Accubond to reduce the bearing surface and increase the BC ? along with your tip of course !

put me down for 100 pcs..... pre-ordering now just in case you decide to sell a batch
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How is it y'all still don't know the difference between CALIBER and CARTRIDGE ??

"In guns, particularly firearms, caliber or calibre is the approximate internal diameter of the barrel, or the diameter of the projectile it fires."
WIKIPEDIA


"Fear of weapons is a sign of retarded sexual and emotional maturity"
Sigmund Freud
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  #17  
Old 03-18-2013, 09:48 AM
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Re: Boosting BC of commerical bullets.....

Kirby

What type of time do you have invested in one bullet, ie. how long does this process take.
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  #18  
Old 03-18-2013, 10:01 AM
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Re: Boosting BC of commerical bullets.....

Quote:
Originally Posted by Swamplord View Post
Fifty....


how about turning that boat tail on the 375 cal Accubond to reduce the bearing surface and increase the BC ? along with your tip of course !

put me down for 100 pcs..... pre-ordering now just in case you decide to sell a batch

The baring surface on the 375 cal, 300 gr Accubond is not a problem, its actually pretty good and does not limit velocity potential at all. Its the new 338 cal version that has a very long baring surface length and that is because they basically only increased the length of the body on the 250 gr version to get the 300 without changing ogive design or boattail design.

In all honesty, I do not think you could do alot with the boat tail to increase BC. Most of the BC is made with ogive design and meplat shape. You would only be looking at an increase in the thousandths range modifying the boattail. You may also weaken the solid base and if the Accubond looses its support cup, penetration will suffer dramatically.

Another issue is consistancy, I have no desire to mess with any part of the rear of the bullet because that is critical as far as accuracy is concerned. In reality, you can get away with more run out on the tip of a bullet then you can if you have run out on the base of a bullet where it contact the crown of the muzzle when fired.

I have tested some prototype 265 gr Aluminum Tipped 338 cal bullets from the old Wildcat bullet company that had very poor aluminum tip run out. At 1000 yards, I tested these in my 338 AM loaded to +3500 fps. One test lot of ammo was loaded with bullets that had tip run outs of less then 0.001". The other test lot of ammo had tip run outs that were all between 0.005 and 0.008". You could see the tips wobble as you rolled them across the loading bench surface.

I shot three, 3 shot groups at 1000 yards on paper and measured group size. The match quality run out bullets averaged 8.890" for three, 3 shot groups at that range. The bullets with poor tip run out averaged 9.783" for three, 3 shot groups at 1000 yards.

So while the poor tips did not shoot as well, at 1000 yards, they shot within an inch group size of the perfect tips...... I was amazed to see this. In my opinion, with a bullet of this mass, a very light aluminum tip will have very little influence if run out is less then 3 thou or so because the mass of the tip is not enough to influence the bullets center of gravity. Remember about the only amount of the bullet that is really out of alignment to any measurable degree is the very tip which weighs virturally nothing compared to the mass of these larger bullets.

Certainly we want everything to be as perfect as possible but having an absolutely perfect tip alignment is less critical then many would ever think. It suprised me!!! The difference is far less then most people would be able to tell down range as enviormental conditions can effect group size much more then a tip slightly off axis.

Now, as far as a boattail a bit off, that would cause serious accuracy issues because one side of the bullet could be released by the crown before the other and the escaping gasses would raise hell with the beginning flight path of the bullet and it would REALLY show up down range with poor consistancy and accuracy.
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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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  #19  
Old 03-18-2013, 10:02 AM
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Re: Boosting BC of commerical bullets.....

What if you were to reduce the diameter of the bullet slightly just in front of the ogive or at the boat tail ? just enough to shorten the bearing surface to an acceptable length
__________________
How is it y'all still don't know the difference between CALIBER and CARTRIDGE ??

"In guns, particularly firearms, caliber or calibre is the approximate internal diameter of the barrel, or the diameter of the projectile it fires."
WIKIPEDIA


"Fear of weapons is a sign of retarded sexual and emotional maturity"
Sigmund Freud
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  #20  
Old 03-18-2013, 10:09 AM
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Join Date: May 2004
Location: Alaska
Posts: 455
Re: Boosting BC of commerical bullets.....

oops, ya answered my question just as I typed and posted it, disregard the last Q
__________________
How is it y'all still don't know the difference between CALIBER and CARTRIDGE ??

"In guns, particularly firearms, caliber or calibre is the approximate internal diameter of the barrel, or the diameter of the projectile it fires."
WIKIPEDIA


"Fear of weapons is a sign of retarded sexual and emotional maturity"
Sigmund Freud
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  #21  
Old 03-18-2013, 10:15 AM
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Re: Boosting BC of commerical bullets.....

Quote:
Originally Posted by ICANHITHIMMAN View Post
Kirby

What type of time do you have invested in one bullet, ie. how long does this process take.

Once I had the collet system made, it took me around 15 minutes to figure out the correct amount to take off the ogive to match up to the tip diameter. That number is a given that can be repeated quickly from set up to set up so that is not something that needs to be done every time I set up.

Once I got a few ran and figured out the process, I timed myself to see how long it would take just or my information from a labor stand point just in case I ever decided to offer these bullets for sale(still undecided on that).

On the conventional cup jackted bullets, After a bit of time I could pump out between 2 and 3 a minute. So your looking at around 120 to 180 per hour. I am sure it would get quicker with more time and I can see possibly pushing this up to around 4 per minute pretty easily with so time and practice.

The simple version of the process goes like this:

1. Release the 6 jaw chuck pressure, insert a bullet into the collet, tighten down the chuck.

2. Use my part off tool which is set up in the correct position to take the correct amount of the ogive off the bullet. Part off the nose of the bullet at 430 rpms

3. Take some 0000 steel wool and remove the small burr left on the bullet by the part off cutter while the lathe is spinning at same rpm.

4. Use a small center drill to make a starter hole in the face of the larger bullet meplat. Not deep, only around 25 thou is plenty. Same 430 rpm

5. Replace center drill with #40 carbide drill (not needed for lead) and drill 0.098" diameter hole 0.400" deep into the nose of the bullet. Same 430 rpm

6. Run part off tool across face of bullet again to remove any left over lead scraps from drilling process.

7. Turn off lathe, insert 22 cal bullet seater stem into chuck in tail rest. Insert aluminum tip onto hole in bullet and use the tail stock to press in the tip into the nose cavity of the bullet. Done and repeat for next bullet.

the Barnes bullets are harder to do and I need to order in some different tooling to make it easier to do them. The solid copper bullets really like to gaul up so if you push the drill to hard then stick pretty tight so you have to go slower with these by a little bit. The tips have a 0.101" diameter shank post and in the lead bullets, the 0.004" press fit is perfect, on the solid copper bullets, its to heavy so I need to order in a drill with a 0.100" diameter which should be perfect for the Barnes bullets. Other then that, its the same process.

Again, not hard at all, anyone with a lathe and a bit of time can do this easily. I am going to sit down and sometime and try to figure out a system that could be used for a drill press as there are more guys that have a drill press then have a metal lathe. I think it could be easily done, just have to figure out the clamping system on the bullet, other then that it would be easy.

In fact, it may be better on a drill press as far as pressing tips in as well.
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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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