My AR is chambered for 5.56, which I understand allows me to shoot either 5.56 or .223. My understanding had been that 5.56 cases were heavier duty allowing for a hotter load than .223. Here is where my confusion starts. I had been using LC 5.56 brass when I picked up a box of Lapua brass. While it is sold as .223, the walls are significantly thicker than the LC brass. So much so that the charge I worked up for my MK262 clone (26.3 gr. VARGET) will not even fit in a Lapua case. What gives?
- Thread starter rsplante
- Start date
Re: 5.56 vs. .223 confusion
This is just what Lapua brass is about.
You will have to work your load up again to get that same FPS.
An auto loader will beat up brass more than a bolt, so using Lapua might not be worth the price as there won't be the life span pay off.
LC brass is typiclly rather heavy relative to other makers.
IMO run the LC in the AR and Lapua in the bolt for maximum life on the $$$ brass.
This is just what Lapua brass is about.
You will have to work your load up again to get that same FPS.
An auto loader will beat up brass more than a bolt, so using Lapua might not be worth the price as there won't be the life span pay off.
LC brass is typiclly rather heavy relative to other makers.
IMO run the LC in the AR and Lapua in the bolt for maximum life on the $$$ brass.
Re: 5.56 vs. .223 confusion
Search google for 5.56 vs. .223 and you'll find the specifics.
In short though, 5.56 is allowed more pressure, and more headspace than .223; thus .223 is safe to run in a 5.56 chamber. For the same reason, it is "not necessarily" safe to run 5.56 in a .223 chamber, though it is generally just fine to do so.
The maximum allowable pressure is only partly connected to case thickness. However, *just because* a cartridge is allowed (according to spec) to have more pressure, doesn't mean it'll have a thicker case.
The lapua brass has thicker walls because Lapua has provided quality, heavy duty brass that will last a long time for you. Enjoy.
Another factoid: The relationship between 7.62 NATO and .308 are almost exactly opposite that of the 5.56 and .223... .308 allows for higher pressure than 7.62, though 7.62 still allows for more headspace than .308, just like 5.56 allows for more HS than .223.
Hope this helps.
Search google for 5.56 vs. .223 and you'll find the specifics.
In short though, 5.56 is allowed more pressure, and more headspace than .223; thus .223 is safe to run in a 5.56 chamber. For the same reason, it is "not necessarily" safe to run 5.56 in a .223 chamber, though it is generally just fine to do so.
The maximum allowable pressure is only partly connected to case thickness. However, *just because* a cartridge is allowed (according to spec) to have more pressure, doesn't mean it'll have a thicker case.
The lapua brass has thicker walls because Lapua has provided quality, heavy duty brass that will last a long time for you. Enjoy.
Another factoid: The relationship between 7.62 NATO and .308 are almost exactly opposite that of the 5.56 and .223... .308 allows for higher pressure than 7.62, though 7.62 still allows for more headspace than .308, just like 5.56 allows for more HS than .223.
Hope this helps.
Re: 5.56 vs. .223 confusion
sorry to bear the bad news but 26.3g of Varget behind a 77smk is unsafe in any brass. You might want to let the people shooting next to you know that your loads are far out of spec so they can scatter.
MK 262 is a highly specialized powder and that allows it to run the speeds it does within pressure specs, the Navy could have just slammed 26.3g of Varget into a case but they didn't for a reason. You should worry about the important stuff, like being safe. Run safe velocities using commercial powder and just put another click on the sight to shoot the same p.o.i.
sorry to bear the bad news but 26.3g of Varget behind a 77smk is unsafe in any brass. You might want to let the people shooting next to you know that your loads are far out of spec so they can scatter.
MK 262 is a highly specialized powder and that allows it to run the speeds it does within pressure specs, the Navy could have just slammed 26.3g of Varget into a case but they didn't for a reason. You should worry about the important stuff, like being safe. Run safe velocities using commercial powder and just put another click on the sight to shoot the same p.o.i.
Re: 5.56 vs. .223 confusion
The Lapua brass is thicker. Try 24.5 gr Varget. I have gotten great results with 77gr, 75gr and 69gr bullets. My primers are CCI 5.56 nato spec small primers.
The Lapua brass is thicker. Try 24.5 gr Varget. I have gotten great results with 77gr, 75gr and 69gr bullets. My primers are CCI 5.56 nato spec small primers.
Re: 5.56 vs. .223 confusion
The .223 is SAAMI registered for 55,000 psi, but I have found that the brass is good to QL 80,000 psi.
That big safety margin can be exploited in some guns, but the AR15 does not have adjustable gas.
The AR15 is up to the pressure, just too much energy goes into pushing the bolt back too fast.
This piece of brass in an AR15 did 4200 fps 33 gr Vmax and is destroyed. That is way passed the QL 80,000 psi that makes for long brass life with .223 case heads.
The best way I have found to find the threshold of long brass life in a handload work up is not to wait for primers to fall out [very inconsistent like hanging chads] or to feel the effort to insert the next primer [very inconvenient at the range]. The best is to measure the extractor groove diameter all the way around before and after firing.
What does it all mean?
Differences in pressure between 223 and 5.56 are moot.
The .223 is SAAMI registered for 55,000 psi, but I have found that the brass is good to QL 80,000 psi.
That big safety margin can be exploited in some guns, but the AR15 does not have adjustable gas.
The AR15 is up to the pressure, just too much energy goes into pushing the bolt back too fast.
This piece of brass in an AR15 did 4200 fps 33 gr Vmax and is destroyed. That is way passed the QL 80,000 psi that makes for long brass life with .223 case heads.
The best way I have found to find the threshold of long brass life in a handload work up is not to wait for primers to fall out [very inconsistent like hanging chads] or to feel the effort to insert the next primer [very inconvenient at the range]. The best is to measure the extractor groove diameter all the way around before and after firing.
What does it all mean?
Differences in pressure between 223 and 5.56 are moot.
Re: 5.56 vs. .223 confusion
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">The .223 is SAAMI registered for 55,000 psi, but I have found that the brass is good to QL 80,000 psi.
That big safety margin can be exploited in some guns, but the AR15 does not have adjustable gas.
The AR15 is up to the pressure, just too much energy goes into pushing the bolt back too fast.
This piece of brass in an AR15 did 4200 fps 33 gr Vmax and is destroyed. That is way passed the QL 80,000 psi that makes for long brass life with .223 case heads.
</div></div>
Now THAT is an ejector kick mark! Wow!
Did the extractor survive?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">The .223 is SAAMI registered for 55,000 psi, but I have found that the brass is good to QL 80,000 psi.
That big safety margin can be exploited in some guns, but the AR15 does not have adjustable gas.
The AR15 is up to the pressure, just too much energy goes into pushing the bolt back too fast.
This piece of brass in an AR15 did 4200 fps 33 gr Vmax and is destroyed. That is way passed the QL 80,000 psi that makes for long brass life with .223 case heads.
</div></div>
Now THAT is an ejector kick mark! Wow!
Did the extractor survive?
Re: 5.56 vs. .223 confusion
Try 23.6 instead of 26.3. Don't think 36.2, 32.6, or 62.3 will fit in the case either.
I know someone that used to run 27.2 grains of a certain powder behind a certain 75 grain bullet in the old thinner Lapua brass. When the brass started shipping as thick brass, he adjusted his load accordingly, or so he thought.
He blew up 2 rifles in 9 days, the first time landing in the hospital. The second just locked up the rifle and ruined the bolt.
Try 23.6 instead of 26.3. Don't think 36.2, 32.6, or 62.3 will fit in the case either.
I know someone that used to run 27.2 grains of a certain powder behind a certain 75 grain bullet in the old thinner Lapua brass. When the brass started shipping as thick brass, he adjusted his load accordingly, or so he thought.
He blew up 2 rifles in 9 days, the first time landing in the hospital. The second just locked up the rifle and ruined the bolt.
Re: 5.56 vs. .223 confusion
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">Did the extractor survive? </div></div>
Yes.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: turbo54</div><div class="ubbcode-body">Did the extractor survive? </div></div>
Yes.
Re: 5.56 vs. .223 confusion
25.0 Of Varget 77smk FTW.
25.0 Of Varget 77smk FTW.
Re: 5.56 vs. .223 confusion
That's actually what I have been shooting recently. 25.0 gr VARGET 77gr SMK, and am thinking of changing to the CCI primers after I use up the 1500 205M's that I have left.
By the way, I examined the LC brass carefully after shooting 10 at 26.3 and had no signs of overpressure. I didn't feel comfortable playing on the edge though, so I have backed off to 25 gr.
That's actually what I have been shooting recently. 25.0 gr VARGET 77gr SMK, and am thinking of changing to the CCI primers after I use up the 1500 205M's that I have left.
By the way, I examined the LC brass carefully after shooting 10 at 26.3 and had no signs of overpressure. I didn't feel comfortable playing on the edge though, so I have backed off to 25 gr.
Re: 5.56 vs. .223 confusion
The 5.56 just has a more generous throat. The higher pressure loads CAN flow the
case neck into the .223 throat and pinch the bullet, driving pressures to unsafe
levels. That's all there is to it.
The 5.56 just has a more generous throat. The higher pressure loads CAN flow the
case neck into the .223 throat and pinch the bullet, driving pressures to unsafe
levels. That's all there is to it.
Re: 5.56 vs. .223 confusion
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fully Involved</div><div class="ubbcode-body">I had been using LC 5.56 brass when I picked up a box of Lapua brass. While it is sold as .223, the walls are significantly thicker than the LC brass. So much so that the charge I worked up for my MK262 clone (26.3 gr. VARGET) will not even fit in a Lapua case. What gives? </div></div>
Change ANY component and you need to go back to low powder charge weights and work you way back up. Changing cases counts as changing one of anything in the load recipie.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fully Involved</div><div class="ubbcode-body">I had been using LC 5.56 brass when I picked up a box of Lapua brass. While it is sold as .223, the walls are significantly thicker than the LC brass. So much so that the charge I worked up for my MK262 clone (26.3 gr. VARGET) will not even fit in a Lapua case. What gives? </div></div>
Change ANY component and you need to go back to low powder charge weights and work you way back up. Changing cases counts as changing one of anything in the load recipie.
Re: 5.56 vs. .223 confusion
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fully Involved</div><div class="ubbcode-body">That's actually what I have been shooting recently. 25.0 gr VARGET 77gr SMK, and am thinking of changing to the CCI primers after I use up the 1500 205M's that I have left.
By the way, I examined the LC brass carefully after shooting 10 at 26.3 and had no signs of overpressure. I didn't feel comfortable playing on the edge though, so I have backed off to 25 gr. </div></div>
I'm glad to see reason prevailed. People need to remember precision shooting is not about having 100fps over the next guy. It's just not worth pushing loads that far over the manuals, even if they work once that does not predict future performance or accidents. leave a margin of safety, if not for you then for the guy next to you at the range or competition.
A big problem is that competitive shooters are not kicked off the line more often for shooting loads that show signs of overpressure. They would stop pushing the envelope if they started forfeiting entry/range fees. any blown primers or excessive bolt lift should be grounds to end the shooters day.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fully Involved</div><div class="ubbcode-body">That's actually what I have been shooting recently. 25.0 gr VARGET 77gr SMK, and am thinking of changing to the CCI primers after I use up the 1500 205M's that I have left.
By the way, I examined the LC brass carefully after shooting 10 at 26.3 and had no signs of overpressure. I didn't feel comfortable playing on the edge though, so I have backed off to 25 gr. </div></div>
I'm glad to see reason prevailed. People need to remember precision shooting is not about having 100fps over the next guy. It's just not worth pushing loads that far over the manuals, even if they work once that does not predict future performance or accidents. leave a margin of safety, if not for you then for the guy next to you at the range or competition.
A big problem is that competitive shooters are not kicked off the line more often for shooting loads that show signs of overpressure. They would stop pushing the envelope if they started forfeiting entry/range fees. any blown primers or excessive bolt lift should be grounds to end the shooters day.
Re: 5.56 vs. .223 confusion
.223 case capacity varies, sometimes dramatically across brands, throw in foreign surplus and it gets worse. I use commercial US made and LC all the time with no issues within manual load specs for .223 or 5.56, I used some guatamalen surplus brass once and wasn't even at a max load and blew out primers and got the smallest belted magnum cases ever out of my 5.56 chambered AR, it was a lesson I'm glad didn't get learned the hard way and it could've because I wasn't checking each ejected case immediately since they are thrown four feet in front of the firing line, I do now with new loads.
.223 case capacity varies, sometimes dramatically across brands, throw in foreign surplus and it gets worse. I use commercial US made and LC all the time with no issues within manual load specs for .223 or 5.56, I used some guatamalen surplus brass once and wasn't even at a max load and blew out primers and got the smallest belted magnum cases ever out of my 5.56 chambered AR, it was a lesson I'm glad didn't get learned the hard way and it could've because I wasn't checking each ejected case immediately since they are thrown four feet in front of the firing line, I do now with new loads.
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