Armory Sponsor
Posted: 8/8/2010 7:44:45 PM EDT
|
I noticed that the standard AP black tip round is 696gr, but the API gray tips that I have been using are only 639gr.
I know that the incendiary compound is going to cause the volume it occupies to be of lower density, but do these two bullet types have different penetrators within them? Or do all variations share the same steel penetrator? If the penetrator in the black tips weighs a good amount more than in the gray tips, I would like to buy some. We have been shooting at a 1-9/16" thickness steel drain cap at 300 yards, and the 639 grainers leaving at 3050FPS just about make it through the plate. They are making bumps on the rear of the plate. I think if it had a heavier core, they would be punching through. I'd like to see that. 
|
| I've cut a couple of each apart and the penetrators are aout the same weight in the 690 AP black tip and the API silvertip. The AP cores weighed average 390.5 grains while the cores in the API were a little heavier at 392.2 grains. In the ones I cut apart the AP core was 0.427.5" in diameter while the API was 0.428" diameter. They both were 1.858" long and shaped the same. I'm sure different lots may vary a little. Don't know why but the AP's do penetrate better than the API. Could be the incendiary going off on impact or the difference in weight of the entire bullet? Careful shooting steel plates that the jackets don't richochet back at you. Don't know the recommended distance to set the steel plates downrange but I've read to not shoot them closer than 200 yards???? |
| The original M8 API design was based on the M2 AP, but replacing the lead point filler of the AP with an incendiary mixture. The AP has a penetration spec on Armor Plate as 1" at 100 yards, while the M8 API is approx 7/8" at the same distance. The difference was due primarily in the different bullet weights of the M2 vs the M8, which affects the Ballistic Coefficient and penetration. I've seen it speculated, but no statistics, that the incendiary ignition does degrade the penetration slightly. |
|
Quoted:
I've cut a couple of each apart and the penetrators are aout the same weight in the 690 AP black tip and the API silvertip. The AP cores weighed average 390.5 grains while the cores in the API were a little heavier at 392.2 grains. In the ones I cut apart the AP core was 0.427.5" in diameter while the API was 0.428" diameter. They both were 1.858" long and shaped the same. I'm sure different lots may vary a little. Don't know why but the AP's do penetrate better than the API. Could be the incendiary going off on impact or the difference in weight of the entire bullet? Careful shooting steel plates that the jackets don't richochet back at you. Don't know the recommended distance to set the steel plates downrange but I've read to not shoot them closer than 200 yards???? Pics? |
|
Quoted:...I've read to not shoot them closer than 200 yards????
At 200 yards I've had small twigs/leaves cut out of the trees around me by jacket splat. If everything is just right it can happen. Not sure if it would seriously wound you -but I think it would at least sting! 
|
|
Quoted:
I've cut a couple of each apart and the penetrators are aout the same weight in the 690 AP black tip and the API silvertip. The AP cores weighed average 390.5 grains while the cores in the API were a little heavier at 392.2 grains. In the ones I cut apart the AP core was 0.427.5" in diameter while the API was 0.428" diameter. They both were 1.858" long and shaped the same. I'm sure different lots may vary a little. Don't know why but the AP's do penetrate better than the API. Could be the incendiary going off on impact or the difference in weight of the entire bullet? Careful shooting steel plates that the jackets don't richochet back at you. Don't know the recommended distance to set the steel plates downrange but I've read to not shoot them closer than 200 yards???? You cut API rounds apart? That doesn't sound safe. |
|
Quoted:
Pictures of API and AP cores. AP on top, API on bottom. Used a copper tubing cutter to cut the jackets apart in the middle. Careful as the cores will chip and dull your tubing cutter. http://i233.photobucket.com/albums/ee84/rgpic/P8160077.jpg Cool, thanks! |
|
Quoted:
If they're only making bumps on the back side I doubt a marginally heavier penetrator will make much difference. Actually, they are right on the verge of making it through the plate. I have fired a handful of shots at the plate so far. The 639gr APIs at near 3000FPS leave a small bump on the plate rear at 300 yards. Increased to 3050FPS, they are very close to fully penetrating, and one actually poked its nose through the back side. I just walked down and measured the plate, and it is actually 1-5/8" thickness exactly. I'm not sure what hardness of steel the plate is...it appears to be some sort of large pipe cap. I have it hanging from a 2x4 with chains, and it is tilted down a few degrees so hopefully ricochets aren't aimed back at me. But at 300 yards I am fairly confident in my safety and always wear shooting glasses. I am going to order the APs right now and see how they do against it. 
I just took photos so you can see what is happening now. http://img716.imageshack.us/img716/5194/bmgpenetration.jpg http://img830.imageshack.us/img830/8621/bmgpenetration2.jpg |
|
So are the fmj rounds with a steel core being called AP? I have recovered several steel cores from my backstop and am wondering what the diff. is. Are AP cores harder or different than steel like tungstun?
@matt304: have you shot at that plate closer. I have some of those blind flanges and wonder if there is way more energy at 100 yards than the 300 you have posted |
|
Quoted:
So are the fmj rounds with a steel core being called AP? I have recovered several steel cores from my backstop and am wondering what the diff. is. Are AP cores harder or different than steel like tungstun? FMJ rounds without the black tip have a regular soft steel center. The black tip AP rounds have a hardened steel core. Cut both kinds open last week using a milling machine. The regular soft steel cored insert was easy to cut. Just as soon as I tried to do a black tip AP round, the machine I was using started to shake & the flycutter I was using to cross section the round, dulled really quick. That steel insert in an AP round is REALLY hard!! 
Oh, one other thing, tungsten & steel are two totally different materials. Look them up on Wikipedia for the details.
|
|
Quoted:
Quoted:
So are the fmj rounds with a steel core being called AP? I have recovered several steel cores from my backstop and am wondering what the diff. is. Are AP cores harder or different than steel like tungstun? FMJ rounds without the black tip have a regular soft steel center. The black tip AP rounds have a hardened steel core. Cut both kinds open last week using a milling machine. The regular soft steel cored insert was easy to cut. Just as soon as I tried to do a black tip AP round, the machine I was using started to shake & the flycutter I was using to cross section the round, dulled really quick. That steel insert in an AP round is REALLY hard!!
Oh, one other thing, tungsten & steel are two totally different materials. Look them up on Wikipedia for the details. Yep, one of the guys on biggerhammer had a spectrograph analysis machine used for typing alloys. Could detect to like .5% of alloy for trace metals. He hit one of the steel cores with it and found no tungsten. They are just REALLY hard steel. I have shot a 1 1/4 inch MILD steel plate with 40+ of the M2 AP. Only 4 have gone completely through but the plate wasn't rigidly mounted so some energy was likely lost on impact. I have also seen AP cores fracture and break upon impact, probably due to over hardening and becoming slightly brittle. I also have an AP core at work that survived an impact with a giant boulder at 150ish yards. It knocked a head sized chunk out of the rock and got deflected into the ground. The stupid AP core is STILL SHARP and only a little scratched up, looks almost identical to a non-fired and pulled AP round that I sectioned out of a pulled bullet. That AP core hitting rock was the most impressive thing I've seen with the 50BMG to date. |
|
Quoted:
So whats the penetration on mild plate steel with regular fmj... 1"? unlikely, the mild steel cores deform on impact. Have seen some seriously funny looking ball cores after impacting things like sewer man hole covers. I personally wouldn't rate the M2 AP as 1 inch of actual "armor" steel. Maybe 3/8-5/8 of actual hardened abrasion resistant steel. But from what I've seen against my mild steel 1 1/4 inch plate, I don't think it would fare well against actual hardened 1 inch armor. |
Armory Sponsor