Entry level (i.e. economical) AR Complete Upper

[Dolomite_supafly]

Considering the ammo you plan on shooting I would choose a 1/9 over a 1/7. Also with the shorter barrel you are not going to get the velocity needed to reach the heavier ammo's full potential. With a 9 twist barrel the bullets are not going to be as overstabilized as with a 7 twist. Overstabilization is what prevents bullets from tumbling and fragmenting upon impact like they were designed to do. You either need the bullet to tumble upon impact so it fragments or you need enough velocity for the bullet to come apart upon impact. Now this can be mitigated with modern ammunition designs but I would be willing to bet 95% of those who have ammo set aside are saving FMJ rounds that are 62 grains or 55 grains. And these are going to work better with a 9 twist than a 7 twist barrel.

Most of this has to do with down range performance rather than CQB distances. At longer engagement distances, like we are seeing overseas, the faster twist barrels are overstabilizing the bullets so that when they hit a "soft" target at the lower velocities they do not tumble and fragment. And because the velocities are lower at this point the bullet will not come apart upon impact either. This leads to a 22 lr type wound as the bullet is too overstabilized to tumble and too slow to disrupt the bullet's integrity.

The only time I would recommend a 7 twist barrel is when the barrel is long and the person is planning on using heavy bullet pretty much exclusively. The reason is those heavy bullets need the added velocity to work well at any distance beyond probably 100 yards. A short barrel with a 7 twist shooting heavy bullets has got the sorst of all worlds. The barrel is too short to getthe velocity up and the twist is too fast for the bullet to tumble. Another thing ot consider is with a longer barrel in a 7 twist gun you can be limited on how light you can go depending on bullet design. I do know with a 7 twist 53 grain SMK's will come apart from centrifugal force at 3300 fps and 40 grain VMax bullets at about 3400-3500 fps.

When looking at stabilizing heavy bullets I will say this. I shoot 69 grain SMK's out of a 16" 9 twist barrel and they are very accurate. So a 9 twist barrel should stabilize anything up to that.

None of this really matters unless you realize this rifle may someday be used for something other than the range. I know we are not at war now but you never know when the rifle you build might have to be used in that role.

As far as cycling goes a rifle should cycle pretty much anything US made if it is setup correctly and broken in. If a gun is shortstroking using Remington UMC then it has issues other than the ammo. Could be the gas port hole is drilled too small or off a little allowing the gas block to partially block it.

Dolomite

[Murgatroy]

I just want to offer this advice. I went the cheap route and regretted it. Save up a little bit longer and get better parts. A BCM upper is not much more than what you are looking at and the quality is so much better as is their BCG. As far as a LPK look at the G and R LPK at WWW.GandRtactical.com

If you want a cheap stock I recommend the barebones BCM one as it is A) Cheap Excellent quality and C) Lighter than the Magpul Moe.

You may spend 150 more but the quality and customer service you will receive makes up for it.

Scrape the Magpul MBUS front sight as it is not made to go on a gas block and it is the incorrect height. It will melt. Ask me how I know.

I understand that BCM is one of the better makers, but PSA is gaining a good reputation as well, do you have anything other than opinion to back this statement up? I am not trying to be confrontational, I am just trying to get all my ducks in a row as the OP and I are in the same boat and following each other's posts.

[Dolomite_supafly]

I just read a lot of the PSA website. They are as good as BCM or alt least say they are. I would not have a problem with PSA stuff based on what I have read. I will say BCM stuff is also very high quality stuff and their customer service is second to none.

Dolomite

[Murgatroy]

I just read a lot of the PSA website. They are as good as BCM or alt least say they are. I would not have a problem with PSA stuff based on what I have read. I will say BCM stuff is also very high quality stuff and their customer service is second to none.

Dolomite

That was the basic opinion that I was gathering from my searches. Granted, I don't have the hands on experience, but I have spent over 40 hours just researching these builds to ensure that I am not throwing money away. From everything I have gathered, PSA is twice the product at half the price, just as BCM was a few years ago.

[TMF]

Most of this has to do with down range performance rather than CQB distances. At longer engagement distances, like we are seeing overseas, the faster twist barrels are overstabilizing the bullets so that when they hit a "soft" target at the lower velocities they do not tumble and fragment. And because the velocities are lower at this point the bullet will not come apart upon impact either. This leads to a 22 lr type wound as the bullet is too overstabilized to tumble and too slow to disrupt the bullet's integrity.

The only time I would recommend a 7 twist barrel is when the barrel is long and the person is planning on using heavy bullet pretty much exclusively. The reason is those heavy bullets need the added velocity to work well at any distance beyond probably 100 yards. A short barrel with a 7 twist shooting heavy bullets has got the sorst of all worlds. The barrel is too short to getthe velocity up and the twist is too fast for the bullet to tumble. Another thing ot consider is with a longer barrel in a 7 twist gun you can be limited on how light you can go depending on bullet design. I do know with a 7 twist 53 grain SMK's will come apart from centrifugal force at 3300 fps and 40 grain VMax bullets at about 3400-3500 fps.

Dolomite

Any insight as to why standard military M4 rifles are all 1:7 then? I've seen wounds sustained at 150-250ish with green tip that left pretty knarly exit wounds; it didn't seem like there was any issue burning through at that range. A few years back everyone started using 77 grain BH and now that seems to be the cool flavor, but I never really looked into performance. I just figured heavier round = better put down power at close range. Either way, no one is walking away from a couple rounds of 5.56 to the torso area no matter what the weight or twist, but I'm curious to hear if there is a good reason other than general contract purposes for why the military has stuck w/ 1:7 for so long if the wounding capabilities aren't as good as 1:9.

[Guest Xring04]

I've used two of the PSA kits and I am very pleased with the outcome.

[Guest Xring04]

my 20 inch FN upper.

[mikegideon]

Any insight as to why standard military M4 rifles are all 1:7 then? I've seen wounds sustained at 150-250ish with green tip that left pretty knarly exit wounds; it didn't seem like there was any issue burning through at that range. A few years back everyone started using 77 grain BH and now that seems to be the cool flavor, but I never really looked into performance. I just figured heavier round = better put down power at close range. Either way, no one is walking away from a couple rounds of 5.56 to the torso area no matter what the weight or twist, but I'm curious to hear if there is a good reason other than general contract purposes for why the military has stuck w/ 1:7 for so long if the wounding capabilities aren't as good as 1:9.

From what I've read, the military uses 1:7 to stabilize the L-110 tracer round. There are very few loads, like the 77 gr SMK, that won't be stable in a 1:9 twist and still can be loaded to mag length. Twist rate is about bullet length, not weight.

[TMF]

From what I've read, the military uses 1:7 to stabilize the L-110 tracer round.

Hmmm, that seems like a big waste. Kinda like forcing yourself to buy a Porche because you already have Porche seat covers. I guess I wouldn't put it past the government procurement system though. So would a regular BH 77gr perform well out to distance in a 1:9?

[Capbyrd]

Palmetto State is gaining quite the reputation as a quality company. However, it is worth noting that they have recently had several problems with their complete uppers. An example was a midlength upper that shipped with a carbine length gas tube. Basically, a single shot rifle. Their customer service has been getting things taken care of and they are changing their QC processes because of these problems but be sure to look over complete uppers from them if you buy one.

I personally have a PSA LPK in one of my rifles and have no problems with it. It functions just fine. And I'd like to pick up the 20 inch FN upper at some point as well.

[Murgatroy]

Palmetto State is gaining quite the reputation as a quality company. However, it is worth noting that they have recently had several problems with their complete uppers. An example was a midlength upper that shipped with a carbine length gas tube. Basically, a single shot rifle. Their customer service has been getting things taken care of and they are changing their QC processes because of these problems but be sure to look over complete uppers from them if you buy one.

I personally have a PSA LPK in one of my rifles and have no problems with it. It functions just fine. And I'd like to pick up the 20 inch FN upper at some point as well.

That is the only complaint that I have been able to find, and I have read from them that they now test fire each upper before shipping to ensure that doesn't happen again.

[mikegideon]

Hmmm, that seems like a big waste. Kinda like forcing yourself to buy a Porche because you already have Porche seat covers. I guess I wouldn't put it past the government procurement system though. So would a regular BH 77gr perform well out to distance in a 1:9?

You mean BTHP, like a Matchking? Sierra sez no. Requires a minimum of 1:8. They fly real well in my 1:8. Haven tried them in one of my 1:9 carbines, but really don't see the point with Eotech and Aimpoint sights.

[mikegideon]

Palmetto State is gaining quite the reputation as a quality company. However, it is worth noting that they have recently had several problems with their complete uppers. An example was a midlength upper that shipped with a carbine length gas tube. Basically, a single shot rifle. Their customer service has been getting things taken care of and they are changing their QC processes because of these problems but be sure to look over complete uppers from them if you buy one.

I personally have a PSA LPK in one of my rifles and have no problems with it. It functions just fine. And I'd like to pick up the 20 inch FN upper at some point as well.

Geez, how could they make that mistake?

[Dolomite_supafly]

Hmmm, that seems like a big waste. Kinda like forcing yourself to buy a Porche because you already have Porche seat covers. I guess I wouldn't put it past the government procurement system though. So would a regular BH 77gr perform well out to distance in a 1:9?

Not sure about the 77 grain out of a 9 twist but according to the miller formula it can. I have alsor read reports of people shooting them effectively out of a 9 twist. And actually a 9 twist would be a better alternative for short barreled guns intended to shoot the 77 grain bullets. The reason is they are barely stabile but still stabile enough for flight but will tumble readily in soft targets. And this would be great considering the low velocities the 77 grain round starts with. You need every advantage you can with a slow starting velocity and the SMK's that tumble readily do have an advantage over FMJ rounds of any weight.

Out of a 16" carbine the velocity of the BH 77 grain load is roughly 2700 fps and at 300 yards it is only 2000 fps. Out of a 14.5" gun the same load is only 2,400 fps at the muzzle and 1,750 at 300 yards. At the extended ranges with a 7 twist barrel the bullet is likely to just pass through because of the reduced velocity and overstabilization. With a 9 twist it will tumble and hopefuly come apart but at a minimum it will at least tumble.

If someone wants to test this set some water jugs aup at 100, 200, 300 and 400 yards and fire the 77 grain loads out of a 7 twist gun. I bet at the 300 and 400 yard ranges you are going to see a very small exit hole. Now the same load out of a 9 twist gun will likely tumble at the extended ranges causing more damage.

Also, what makes SMK's better than FMJ's is the thin jackets used on SMK's. The thin jackets work as well and often better than SP's. Definitely better than any FMj at an extended range regardless whether the FMJ's tumble or not.

Any insight as to why standard military M4 rifles are all 1:7 then? I've seen wounds sustained at 150-250ish with green tip that left pretty knarly exit wounds; it didn't seem like there was any issue burning through at that range. A few years back everyone started using 77 grain BH and now that seems to be the cool flavor, but I never really looked into performance. I just figured heavier round = better put down power at close range. Either way, no one is walking away from a couple rounds of 5.56 to the torso area no matter what the weight or twist, but I'm curious to hear if there is a good reason other than general contract purposes for why the military has stuck w/ 1:7 for so long if the wounding capabilities aren't as good as 1:9.

What rifle were these wounds made with? 14.5" M4, 16" carbine or the 20" carbine?

I think their decision to go with a faster twist was in a quest to turn a short-medium range cartridge into a long range cartridge by using heavier bullets. Some say it was for the NATO tracers but we already had effective tracers in our supply system. Personally I do belive it was an attempt to extend the range of our AR platform beyond the original 300 yards capability.

The original incarnation of the AR with its 55 grain bullet and 12 twist barrel was devastating for a couple of factors. First the velocity was very high because of the longer barrels and faster twists. And with the 12 twist barrel the bullet readily tumbled and then fragmented because it was stabile in flight but not in soft tissue. But the original incarnation was a short range cartridge that was designed for engagements under 300 yards. The 55 grain loading left a 20" barrel at roughly 3,200-3,300 fps and fragmented and tumbled upon impact. It was a very devastating round indeed inside of its limitations.

People do regularly get hit and survive being hit with a 5.56. When that happens it is because the bullet did not tumble or fragment because the distance was at extended ranges. Most people are going to survive a clean 22 caliber hole so long as it doesn't hit vital blood supplies or CNS. When the bullets fragment or tumble that is where the damage comes from. And when a bullet is overstabilized it will not tumble and if velocity is below the bullet's fragmenting threshold it will just pass through just like a 22lr. Just as you I have seen it first hand. Had a guy we brought in that had been hit in the upper left thigh. He was walking and talking with very little blood.

Here is a very good study on the performance of various loads for the 5.56.

http://www.texassmallarmsresearch.com/TechInfo/556Performance/556Performance.pdf

Note page 4 that M855 bullets do not reliably fragment at velocities below 2,500 fps in a7 twist barrel. And considering out of a M4 (14.5" barrel) the M855 is at 2,900 fps but at 200 yards it is only going 2,400 fps, well below the fragmenting threshold for that round. This means at roughly 150 yards the m855 fired out of a M4 will no longer reliably fragment. Or out of a 16" carbine that range is extended to roughly 200 yards but not much more. All of this is because of the twist rates. The tumbling is what starts the fragmenting process.

This is the reason why the Marines are having less issues than the Army. They use 20" rifles that extend that range some because of the extra velocities.

Ideally what the military needs to do is go back to the old ay of thinking. Have a 0-300 yard cartridge and a 300+ yard cartridge rather than trying to make the current 0-300 perform duties as a 300+ yard cartridge. There are plenty of calibers out there that would fit the 300+ yard category without much additionl weight that needs to be carried. Look at all the 6mm and 6.5mm calibers that are being used in 1,000 yard competitions. Any one of those would be better than ANY 5.56 loading beyond 300 yards.

Again we are talking performance beyond the original 300 yard capability of the 5.56.

Dolomite

[Capbyrd]

Geez, how could they make that mistake?

Great question. But they did. More than once. Likely a **** employee. Regardless, they took care of the problem and have taken steps to ensure it never happens again.

[Guest Xring04]

Geez, how could they make that mistake?

I talked with them direct about the problem. They had 3 guns go out with wrong sized gas tubes. They were assembling carbines, and switched to mid length uppers. Through a complete failure in their QC (their words) they let the 3 slip by. Now they test fire every upper.

They owned up to their mistake and made it right for all involved. They also took steps to be sure it never happened again. They did enough to keep getting my business.

[mikegideon]

I talked with them direct about the problem. They had 3 guns go out with wrong sized gas tubes. They were assembling carbines, and switched to mid length uppers. Through a complete failure in their QC (their words) they let the 3 slip by. Now they test fire every upper.

They owned up to their mistake and made it right for all involved. They also took steps to be sure it never happened again. They did enough to keep getting my business.

I just can't imagine them not catching that when it happened. The gas tube was barely sticking into the barrel nut. I don't know if tightening the QC will fix that kind of stupid.

[Guest]

What do you guys think about this? Surplus Ammo & Arms Complete AR-15 M4 16" Upper Receiver 5.56 1:9 - Surplus Ammo

Chrome Moly (means chrome lined, right?)

.750 M4 profile

A2 flash hider

1:9 twst

Comes with Magpul fore-end so I could attach my light to it.

Looks like I could have both flip-up sights and optics attached

Actual 5.56 chamber

Please let me know if there are any issues with this brand, and otherwise I'll get one ordered. Thanks!

[mikegideon]

Chrome Moly (means chrome lined, right?)

No

[TMF]

What rifle were these wounds made with? 14.5" M4, 16" carbine or the 20" carbine?

I think their decision to go with a faster twist was in a quest to turn a short-medium range cartridge into a long range cartridge by using heavier bullets. Some say it was for the NATO tracers but we already had effective tracers in our supply system. Personally I do belive it was an attempt to extend the range of our AR platform beyond the original 300 yards capability.

The original incarnation of the AR with its 55 grain bullet and 12 twist barrel was devastating for a couple of factors. First the velocity was very high because of the longer barrels and faster twists. And with the 12 twist barrel the bullet readily tumbled and then fragmented because it was stabile in flight but not in soft tissue. But the original incarnation was a short range cartridge that was designed for engagements under 300 yards. The 55 grain loading left a 20" barrel at roughly 3,200-3,300 fps and fragmented and tumbled upon impact. It was a very devastating round indeed inside of its limitations.

People do regularly get hit and survive being hit with a 5.56. When that happens it is because the bullet did not tumble or fragment because the distance was at extended ranges. Most people are going to survive a clean 22 caliber hole so long as it doesn't hit vital blood supplies or CNS. When the bullets fragment or tumble that is where the damage comes from. And when a bullet is overstabilized it will not tumble and if velocity is below the bullet's fragmenting threshold it will just pass through just like a 22lr. Just as you I have seen it first hand. Had a guy we brought in that had been hit in the upper left thigh. He was walking and talking with very little blood.

Dolomite

Wow, incredibly infomative. This is neat stuff to know and I'm a little embarassed that I don't. I'm simply familiar with the varying speeds at distance and barrel length, but don't know much in regards to twist. It was green tip (M855) out of a 14.5 barrel. The exit wounds themselves were not symmetrical like a pass through from a 7.62 x 39, but this could also be due to the position of the individual during the engagement and how the trajectory was affected by bone.

I've seen a lot more 7.62 x 39 wounds than 5.56, and generally speaking, 5.56 was incredibly devastation in comparison. This could also be due to the fact of the close engagement range and the user, but nonetheless, most 7.62 rounds passed through in a very linear fashion while the 5.56 generally didn't.

Another interesting thing to point out in regards to M855 is when fired through a 1:12 it begins tumbling within 25m. I had heard this before but saw it for myself on a range where some of the rounds were impacting the paper sideways.

I do feel like I became smarter in regards to my ammo though.

[Guest]

Ok guys,

Would I be kicking myself later for any reason if I get this upper from PSA. Palmetto State Armory 16'' CMV Chrome-lined, MP inspected, M4 Complete upper

There aren't a lot of details given, but is the gas-tube mid-length? It looks to be shorter. I have read that mid-length prevents operational problems over carbine length.

I probably will only shoot M193 and 855 or equivalent 55/62gr for the forseeable future, so 1:7 will be just fine right? Any concerns with this upper?

I would then add the Magpul handguard Magpul MOE? Hand Guard for M16/AR15 rifles

-- Is there a best recommended mount for the Magpul handguard to get to a lightmount

and I am thinking their standard mil-spec stock kit. Palmetto State Armory Classic Stock Kit

[Guest]

Ok in response to my last post, I think these 2 are the 16" mid-length offerings:

Palmetto State Armory 16'' Hammer-Forged, Mid-length, upper

Palmetto State Armory 16'' 4150 CMV, Chrome-lined, Mid-length Upper

The 2nd one is a little cheaper, though I'm trying to figure out why. And are both of these nearly $100 more expensive than in my post a few minutes ago just because they are mid-length? Is mid-length that important? Sorry for new newbie questions..... there is so much to learn when you're an AR-newbie.

Thanks

[mikegideon]

You won't go wrong getting a carbine length gas system.

[Dolomite_supafly]

You won't go wrong getting a carbine length gas system.

+1

They are the most reliable but they can be harder on parts than a rifle length gas system. The carbine length are also less sensitive to budget ammo than rifle lengths.

Dolomite

[Guest]

Thanks guys. I got a DPMS parts kit, so it should stand up to as much abuse as I'll likely put through it (i.e. round count). Perhaps I'll build a heavier-duty one down the road.

I'll go with the first Upper linked (carbine length) and a carbine length MOE grip, and stock AR mill spec stock/buffer kit. Thanks for all the help guys.

Ok just one more question;

With the stock front sight on the upper, can I pick any standard rear flip-up sight? These will serve as full-time iron sights for now, and when the budget allows, I'll add an optic of some sort. Won't the permanent front-sight get in the way? However, almost all PSA uppers have the permanent front sight.