Help with converting .300 BLK to 5.56

[Brandon3434]

I recently bought a 300 blackout AR. The 300 ammo is very expensive. I've googled on how to make my 300 able to shoot 223 and or 556. All I can find is how to make 223/556 into 300 and most people say all you need is the barrel. Is this true for 300 to 223/556? If not then what else would I need?

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[Joe13]

I recently bought a 300 blackout AR. The 300 ammo is very expensive. I've googled on how to make my 300 able to shoot 223 and or 556. All I can find is how to make 223/556 into 300 and most people say all you need is the barrel. Is this true for 300 to 223/556? If not then what else would I need?

You should get a second opinion but it's my understanding that you only need to replace the barrel and probably a new gasblock and tube unless your inks ones fit.


Mags and bolt are the same.

 

[Stomper]

IMO, get another complete upper.... and make SURE you don't mix them with the wrong ammo!

 

[nwslopoke]

I am in the process of collecting parts for a 7.62x39 pistol build but 5.56 uppers are so inexpensive it's killing me. I'm thinking just continue to collect 7.62x39 parts and buy the 5.56 pistol upper now. I can use the same lower.

 

[The Heretic]

Just get a 556 upper and then you can switch back and forth without having to mess with the barrel/etc. The uppers are inexpensive.

As Stomper says, don't mix the ammo up - google what happens when you do.

 

[BlindedByScience]

Another vote for a complete upper. Five second caliber swap, can't lose having a couple calibers to shoot.

 

[Kruel J]

Swap barrels and you're done. No need for a complete upper.

 

[Stomper]

Options..... Capt. Beef Jeeky n' Cheddar.... OPTIONS!!

 

[ConcernedCitizen]

The first question is whether you have the tools needed to rebarrel an upper, and if you are comfortable doing so.

If you have to buy an armorer's wrench or pay someone to swap barrels for you, you're probably better off buying a complete upper and selling yours to recoup some of the cost. Odds are your net cost will come out close to the price of a new barrel either way.

 

[Brandon3434]

The first question is whether you have the tools needed to rebarrel an upper, and if you are comfortable doing so.

If you have to buy an armorer's wrench or pay someone to swap barrels for you, you're probably better off buying a complete upper and selling yours to recoup some of the cost. Odds are your net cost will come out close to the price of a new barrel either way.

I do not have the tools so I would either be buying them and watching a lot of YouTube videos or taking it to someone. The reason I want to be able to shoot the 556 is because the ammo is cheap. I still want the option of the 300 to deer hunt. So I am not too concerned about the cost of the parts needed to convert it.

 

[Sawdust]

I do not have the tools so I would either be buying them and watching a lot of YouTube videos or taking it to someone. The reason I want to be able to shoot the 556 is because the ammo is cheap. I still want the option of the 300 to deer hunt. So I am not too concerned about the cost of the parts needed to convert it.

If the cost to convert (parts and tools) is not too much of a concern then I would suggest a second complete upper assembly. You would be able to set up zero'd sights on each and be able to swap calibers/uppers as needed. Two rifles in one!

 

[Brandon3434]

If the cost to convert (parts and tools) is not too much of a concern then I would suggest a second complete upper assembly. You would be able to set up zero'd sights on each and be able to swap calibers/uppers as needed. Two rifles in one!

Do you have an estimate on how much this could cost me?

 

[etrain16]

Do you have an estimate on how much this could cost me?

Complete uppers can be had, with decent quality, for under $300.

Check out Palmetto State Armory as a start. They often run great sales on complete uppers, often with free shipping. And uppers don't require an FFL, they ship straight ot your home address.

 

[Tony617]

You can find fully assembled uppers from Primary Arms or Palmetto State Armory:

AR-15 & AK-47 Parts & Accessories | Primary Arms

Ammunition, AR15 Parts, Magazines, Bulk Ammo - Palmetto State Armory

You may want to consider putting colored tape to differentiate your magazines if you still have some magazines loaded with 300 BLK. There are pictures of AR15 kabooms with a 5.56mm barrel firing a 300 BLK round.

 

[Lazyfaire]

Just get a 556 upper and then you can switch back and forth without having to mess with the barrel/etc. The uppers are inexpensive.

As Stomper says, don't mix the ammo up - google what happens when you do.

I also agree with the 'get another full upper in 5.56'. I have both calibers in separate rifles and have had to color code guns, ammo, mags and bulk ammo cans so that I do not mix them up, which I have done before. I really don't recommend doing that! Love my 300 BO tho.

 

[Camelfilter]

There may be 5.56 complete uppers which interest you for sale here. No idea.

Alternatively, as mentioned, PSA pricing/quality really currently can't be beat. Get in there email list for daily deals, find your deal, then don't read it again until your looking for something specific.

 

[bbbass]

I bought a PSA complete upper for my daughter for a little over $100. But I much prefer Hardened Arms uppers. Hardened Arms

Edit: I also bought a really nice upper in .223Wylde from ARparts.com at Gunbroker.com, shoots both .223 and 5.56

 

[etrain16]

Oh, forgot about Hardened Arms too - they sometimes run good prices on complete uppers.

 

[osprey]

Switching barrels is going to be a pita if you want to retain both caliber options. Buy a complete 5.56 upper. Many deals out there for around $200 minus bolt carrier group and charge handle. You can use the bcg and ch from your 300blk. I especially like some of PSA's CHF double chrome lined machine gun FN barrels on some of their uppers although they will command a bit more $.

 

[Caveman Jim]

You can find fully assembled uppers from Primary Arms or Palmetto State Armory:

AR-15 & AK-47 Parts & Accessories | Primary Arms

Ammunition, AR15 Parts, Magazines, Bulk Ammo - Palmetto State Armory

You may want to consider putting colored tape to differentiate your magazines if you still have some magazines loaded with 300 BLK.

And it's a good idea to place the same colored tape on the upper to match the magazines.

I use only 20 round Pmags in my 300BLK pistol to differentiate from my 223/556 AR's of which I only use 30 round USGI magazines. Pretty easy for me not to brain fart on this.