Bobcat,
Thanks for your reply. Can you load the 80gr bullets to magazine length or do you had feed each one?
I like the heavier bullets after reading about some the the tests that were done at ar15.com, but you need significant velocity for reliable fragmentation. That's why I like what I read in the Sierra reloading manual about AA2520, but with the AR, you have to be careful to stay away frompowders that are dirty. Unless I hear otherwise from someone who knows, I'm going to give AA2520 a try.
-SS
reloading for an AR15
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ShootingStar
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BobCat
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ShootingStar,
Sorry for the late reply.
They are well over magazine length, and are loaded one at a time during the match. I really ought to have made that clear since seating an 80-grain bullet deep enough to wind up with a magazine-length round can lead to high pressures.
There is a tool called a Stoney Point gauge that is used to measure where the rifling starts in relation to the cartridge head. I made a "work-alike" from a resized case, with the primer flash hole drilled out and primer pocket threaded (as I recall) 10x32. Put a bullet in the case neck, very long, and a threaded rod through the primer pocket. Seat the cartridge, allowing the rifling to push the bullet into the case. Press firmly on the case to be sure it is seated against the shoulder. Screw the rod in until it contacts the bullet base, and run a nut down (to the casehead) to lock the rod from turning.
When you pull the cartridge (case, anyway) out, the bullet may be stuck in the rifling. If it is, tap it out with a wooden dowel (or cleaning rod if you are careful of the muzzle crown). Put it in the case until it stops against the threaded rod.
If you measure - either from the tip (not best, too much variation) or from a datum point on the ogive, to the case head, you get a length. If you load all your rounds some fixed amount - say 0.010" - shorter than that length, they will have a 0.010" (or whatever you set) jump to the rifling.
To get to the same datum point, drill a hole smaller than the caliber but larger than the tip (i.e. someplace on the ogive) in a piece of stock you can fix on one arm of your caliper. Stoney Point sells this tool too - I'm just a cheapskate.
People tell me to measure the throat erosion periodically with the gauge described above, and re-adjust seating depth based on how much the rifling has eroded away. I might get around to it, but if not then the worst is - still safe, just have more jump to the rifling than might be optimum.
These leave at about 2700 ft/sec. I don't know about fragmentation - all I want is a nice round hole in the paper (in the *center* of the paper!).
I hope this helps. If my explanation of measuring to figure seating depth is too funky, rest assured there are clearer explanations of this on the web - you'll find them.
Regards,
Andrew
Sorry for the late reply.
They are well over magazine length, and are loaded one at a time during the match. I really ought to have made that clear since seating an 80-grain bullet deep enough to wind up with a magazine-length round can lead to high pressures.
There is a tool called a Stoney Point gauge that is used to measure where the rifling starts in relation to the cartridge head. I made a "work-alike" from a resized case, with the primer flash hole drilled out and primer pocket threaded (as I recall) 10x32. Put a bullet in the case neck, very long, and a threaded rod through the primer pocket. Seat the cartridge, allowing the rifling to push the bullet into the case. Press firmly on the case to be sure it is seated against the shoulder. Screw the rod in until it contacts the bullet base, and run a nut down (to the casehead) to lock the rod from turning.
When you pull the cartridge (case, anyway) out, the bullet may be stuck in the rifling. If it is, tap it out with a wooden dowel (or cleaning rod if you are careful of the muzzle crown). Put it in the case until it stops against the threaded rod.
If you measure - either from the tip (not best, too much variation) or from a datum point on the ogive, to the case head, you get a length. If you load all your rounds some fixed amount - say 0.010" - shorter than that length, they will have a 0.010" (or whatever you set) jump to the rifling.
To get to the same datum point, drill a hole smaller than the caliber but larger than the tip (i.e. someplace on the ogive) in a piece of stock you can fix on one arm of your caliper. Stoney Point sells this tool too - I'm just a cheapskate.
People tell me to measure the throat erosion periodically with the gauge described above, and re-adjust seating depth based on how much the rifling has eroded away. I might get around to it, but if not then the worst is - still safe, just have more jump to the rifling than might be optimum.
These leave at about 2700 ft/sec. I don't know about fragmentation - all I want is a nice round hole in the paper (in the *center* of the paper!).
I hope this helps. If my explanation of measuring to figure seating depth is too funky, rest assured there are clearer explanations of this on the web - you'll find them.
Regards,
Andrew
Retractable claws; the *original* concealed carry
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ShootingStar
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BobCat,
Thanks, good info. Most of my ammo won't require that degree of perfection, but I do want to load some match rounds to see what the rifle is capable of. I will print that out and put it in my reloading manual for future reference.
What do you think of the 75 gr Hornady OTM compared to the Sierra 77gr OTM. From what I have seen the Hornady are cheaper, but are they as accurate?
-SS
Thanks, good info. Most of my ammo won't require that degree of perfection, but I do want to load some match rounds to see what the rifle is capable of. I will print that out and put it in my reloading manual for future reference.
What do you think of the 75 gr Hornady OTM compared to the Sierra 77gr OTM. From what I have seen the Hornady are cheaper, but are they as accurate?
-SS
A democracy is a sheep and two wolves deciding on what to have for lunch. A Republic is a well armed sheep contesting the results of the decision. - Benjamin Franklin
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BobCat
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ShootingStar,
1) I giggled like a little child when I read, "I do want to load some match rounds to see what the rifle is capable of." These rifles are amazing. I think you will be pleased, amused, and amazed when you actually do see what the rifle is capable of.
2) I don't know between the Hornady and Sierra. My experience is limited to Sierra 69 g Match King, and Nosler 80 grain - whatever their match bullet is called. And all sorts of cheap IMI / Winchester 55 and 62 grain bullets for "practice" rounds.
Several people have told me they really like the Berger 75 grain match bullet They say they can load it to higher velocities than other bullets around the same weight, so it gets there sooner and spins faster while it is on the way. Still, all I know about is paper-punchers. Terminal ballistics on anything but paper is another story.
Regards,
Andrew
1) I giggled like a little child when I read, "I do want to load some match rounds to see what the rifle is capable of." These rifles are amazing. I think you will be pleased, amused, and amazed when you actually do see what the rifle is capable of.
2) I don't know between the Hornady and Sierra. My experience is limited to Sierra 69 g Match King, and Nosler 80 grain - whatever their match bullet is called. And all sorts of cheap IMI / Winchester 55 and 62 grain bullets for "practice" rounds.
Several people have told me they really like the Berger 75 grain match bullet They say they can load it to higher velocities than other bullets around the same weight, so it gets there sooner and spins faster while it is on the way. Still, all I know about is paper-punchers. Terminal ballistics on anything but paper is another story.
Regards,
Andrew
Retractable claws; the *original* concealed carry