MK262 and M855 queston.
- Thread starter LeeAdama
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bullseye308
Member
I think something real close to this was covered recently. First of all the powder is not available to us reloaders, so the charge weight won't really matter. It probably isn't the same powder in both rounds anyway. They are loaded for a set of standards predetermined for that round out of the weapon it is intended to be fired from.
As for the difference in flash or noise, it would most likely be very close.
Now a ? for you, why are you asking this? What is it that you want to know?
As for the difference in flash or noise, it would most likely be very close.
Now a ? for you, why are you asking this? What is it that you want to know?
I'm researching reloading on many types of 5.56mm rounds.
Roccobro
Member
AR15.com had a 20 page thread on this topic a few years back. Google and you'll get many good forums with mounds of information on this particular items. Snipershide.com had a good thread too.
Justin
Justin
A few years is a long time.
Roccobro
Member
And the info is still true for your "research". 
Justin
Justin
counterclockwise
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About 1.5 grains less for the 77 gr SMK. BUT, it probably was not the same powder.
One reason this question is fallow, is that reloaders have known that hot rod .223 NATO loads tend to beat up the brass, such that only a few cycles are obtained before the primer pocket gets too loose to use. So, there is not too much interest in these kinds of loads.
One reason this question is fallow, is that reloaders have known that hot rod .223 NATO loads tend to beat up the brass, such that only a few cycles are obtained before the primer pocket gets too loose to use. So, there is not too much interest in these kinds of loads.
Why would they use less for a heavier bullet?
LeeAdama, military goods are put out to bid. Many vendors respond. Often they issue purchase orders to more than one vendor. Each vendor is allowed to produce the product as necessary to meet the specification in the solicitation. Components may vary from time to time and vendor to vendor, as long as the performance and prescriptive specifications are met.
This means ammunition doesn't get exactly the same powder all the time. It changes. Thus, unfortunately, your questions cannot be answered simply. Sorry, but that's the complete truth. Ask anyone who buys surplus ammo and tears it down. Weigh the powder. Weigh the brass. You never know what you're going to get.
I really urge you to find books and other resources, and read. Read. Read. It is clear that you have much to learn. The members of this forum want to help. Do them a favor and do as much background search as possible first. Go look up the past and current solicitation spec for ammo and see what the vendor had to meet.
This means ammunition doesn't get exactly the same powder all the time. It changes. Thus, unfortunately, your questions cannot be answered simply. Sorry, but that's the complete truth. Ask anyone who buys surplus ammo and tears it down. Weigh the powder. Weigh the brass. You never know what you're going to get.
I really urge you to find books and other resources, and read. Read. Read. It is clear that you have much to learn. The members of this forum want to help. Do them a favor and do as much background search as possible first. Go look up the past and current solicitation spec for ammo and see what the vendor had to meet.
This has been true since they put nitro powder in a metallic cartridge case a hundred and thirty years ago.
Go find a book with reloading data and see for yourself. All else being equal (and that qualifier is very, very important) heavier bullets get less powder, lighter bullets get more powder.
By the way, this is only true in modern metallic reloading. Shotshells and black powder may differ.
Thanks for the advice ants.
Not disagreeing but that seams weird, you would think they would use more slow burning powder to get the heavier bullet up to speed.
Look at it this way, LeeAdama.
A lighter bullet gets out of the chamber and moves down the barrel faster. As it moves down the barrel, it leaves more 'chamber volume' behind it for the hot expanding gases. To keep up the pressure, you need more powder.
A heavier bullet does the opposite. Since it accelerates slower, too much powder will surely go over max pressure before the bullet gets down the barrel. So you use less powder. That is one of the reasons heavier bullets often get less velocity. Less powder, less acceleration, but the heavier mass still has kinetic energy.
Faster versus slower powders have nothing to do with this. Most powder burns before the bullet has moved a few inches. Fast versus slow is a matter of the curve you can map with pressure vs. time. Different curves have different affects on the bullet, barrel, recoil, gas production (if a semi-auto needs gas), harmonic vibration, etc. This can make a big difference in point of impact on the target versus point of aim through the sights. One can carefully tailor ammunition for different effect by trying different powders for a given bullet.
Go to the Hornady web site and look for a button on ballistics resources. I believe they have a multi-part tutorial on the subject. Very interesting stuff.
A lighter bullet gets out of the chamber and moves down the barrel faster. As it moves down the barrel, it leaves more 'chamber volume' behind it for the hot expanding gases. To keep up the pressure, you need more powder.
A heavier bullet does the opposite. Since it accelerates slower, too much powder will surely go over max pressure before the bullet gets down the barrel. So you use less powder. That is one of the reasons heavier bullets often get less velocity. Less powder, less acceleration, but the heavier mass still has kinetic energy.
Faster versus slower powders have nothing to do with this. Most powder burns before the bullet has moved a few inches. Fast versus slow is a matter of the curve you can map with pressure vs. time. Different curves have different affects on the bullet, barrel, recoil, gas production (if a semi-auto needs gas), harmonic vibration, etc. This can make a big difference in point of impact on the target versus point of aim through the sights. One can carefully tailor ammunition for different effect by trying different powders for a given bullet.
Go to the Hornady web site and look for a button on ballistics resources. I believe they have a multi-part tutorial on the subject. Very interesting stuff.
Thanks.
Cool. Once you get the basics, you will see that fast and slow powders do have much to do with bullet selection. It also has a lot to do with the particular cartridge. Large magnums generally have more case volume for slow powders, because with enough slow powders you can build a lot of velocity. Smaller case capacity is where you might want to use fast powders, which are rather velocity challenged anyway.
Either way, the fundamentals always apply. Best of luck, friend.
Either way, the fundamentals always apply. Best of luck, friend.
Why powder burn rates do the 5.56 MK318/M855 and 7.62x39 use?
Unknown. Refer to post #10. They do not necessarily use the same powder all the time. Given the performance of NATO and U.S. milspec 5.56 it is probably a fairly dense slow powder that fills the case completely (milspec actually runs higher pressure than commercial ammunition).
Go look up surplus military powders. You will find that they use designations like WC820 and 846 and 860, or DP2230-C, or other names you can't find commercially. On the other hand IMR4895 and BL(C)-2 were former military powders that are now commercial powders. Mil and commercial are sometimes the same, sometimes different.
Since hundreds of different manufacturers around the world have produced 7.62x39 (probably half of them following no specification whatsoever) over the last 60 years, there is absolutely no telling whatsoever the powders they used.
This is like asking what compound of rubber is in a certain size car tire made by hundreds of manufacturers over 60 years. Answer: Lots of different compounds.
Go look up surplus military powders. You will find that they use designations like WC820 and 846 and 860, or DP2230-C, or other names you can't find commercially. On the other hand IMR4895 and BL(C)-2 were former military powders that are now commercial powders. Mil and commercial are sometimes the same, sometimes different.
Since hundreds of different manufacturers around the world have produced 7.62x39 (probably half of them following no specification whatsoever) over the last 60 years, there is absolutely no telling whatsoever the powders they used.
This is like asking what compound of rubber is in a certain size car tire made by hundreds of manufacturers over 60 years. Answer: Lots of different compounds.
Maybe the M855 and MK 318 have a full case capacity though they use a different powder?
The MK318 powder is more efficient and burns all of its powder before exiting unlike older powders which blow a lot of unburnt powder at the end of the muzzle. Maybe the MK 318 uses a powder like Hornady's superformance?
rcmodel
Member in memoriam
Older powders do not blow a lot of unburned powder out the end of the barrel.
Muzzle flash is superheated gas coming in contact with oxygen in the atmosphere.
All powders do it to some extent.
rc
Muzzle flash is superheated gas coming in contact with oxygen in the atmosphere.
All powders do it to some extent.
rc
You clearly know more about this than I do.
Roccobro
Member
This is true for *most* users here. RC has a humbling effect.
Justin
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