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Posted: 10/19/2010 8:59:00 PM EDT
I recently picked up some boxes of both 75gr and 68gr Hornady OTM bullets and found that they are almost identical in dimentions.  I was expecting the 75gr bullet to be longer and intended to use the 68gr bullet in my 1:9 twist barrels and the 75gr in my 1:8 or faster barrels.

I know Dr Roberts recommends the 75gr bullet but in the defensive ammo write up in this forum he suggests (among others) the 68gr bullet if you can't stabilize the heavier bullets.  So what I want to know is, how does Hornady make the 68gr bullet lighter?  Is the jacket thicker which would hinder fragmentation?  If that is the case, how has the 68gr bullet faired in gel testing?  Does anyone have a link to gel testing with the 68gr bullet?  I have found lots of info on the 75gr but have only seen the reference to the 68gr, not any actual pictures or results from testing.

I tried asking Hornady and got very little information in return.  Basically they told me that the 68gr bullet was a match bullet and hadn't been tested for expansion.  So is the 75gr bullet but it has been tested.  I assume the 68gr has been as well if it is a recommended bullet from Dr Roberts.
Link Posted: 10/21/2010 1:23:15 PM EDT
[Last Edit: 10/21/2010 2:07:40 PM EDT by Forgetfull]

Originally Posted By Altair:


I recently picked up some boxes of both 75gr and 68gr Hornady OTM bullets and found that they are almost identical in dimentions.  I was expecting the 75gr bullet to be longer and intended to use the 68gr bullet in my 1:9 twist barrels and the 75gr in my 1:8 or faster barrels.





I know Dr Roberts recommends the 75gr bullet but in the defensive ammo write up in this forum he suggests (among others) the 68gr bullet if you can't stabilize the heavier bullets.  So what I want to know is, how does Hornady make the 68gr bullet lighter?  Is the jacket thicker which would hinder fragmentation?  If that is the case, how has the 68gr bullet faired in gel testing?  Does anyone have a link to gel testing with the 68gr bullet?  I have found lots of info on the 75gr but have only seen the reference to the 68gr, not any actual pictures or results from testing.





I tried asking Hornady and got very little information in return.  Basically they told me that the 68gr bullet was a match bullet and hadn't been tested for expansion.  So is the 75gr bullet but it has been tested.  I assume the 68gr has been as well if it is a recommended bullet from Dr Roberts.






The 68gr is shorter than the 75. The 75 is just set deeper in the case. The 223 cartage for magazine fed guns must have a certain OAL in order to fit in the magazine.

Maybe not

Link Posted: 10/21/2010 4:47:32 PM EDT
Im not exactly sure why they are the same length but not all 1:9 twists will stabilize the 68gr.

I thin the conical part on the top of the projectile on the 68gr doesnt have as much lead in it as the 75gr do, so that part is mainly hollow while its mostly filled on the 75gr.
Link Posted: 10/21/2010 9:17:38 PM EDT
I checked with a caliper and it turns out they aren't exactly the same length.  The 68gr averaged .979" and the 75gr averaged .986".  That said, I can't imagine .007" being enough to make the 75gr bullet 10.3% heavier.  It either has to be a thicker jacket, a larger hollow tip, or a combination of the two to account for the lighter 68gr bullet.  

Maybe I'll try to cut both in half to compare but I've not been able to get the nice clean cuts I've seen pictures of here.  All I have is a dremel tool with a cutoff wheel and they end up looking like hack jobs (because they are).
Link Posted: 10/28/2010 6:47:17 AM EDT
Originally Posted By Altair:
 Maybe I'll try to cut both in half to compare but I've not been able to get the nice clean cuts I've seen pictures of here.  All I have is a dremel tool with a cutoff wheel and they end up looking like hack jobs (because they are).


Take a very small paper cup. Fill with epoxy. Carefully place bullet into expoxy. When epoxy dries cut bullet in half.  You can use a fine grit wet sand paper to clean up the edges
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