The AR-15 is an extremely popular weapon, for a variety of reasons. Due to the number of internal parts and external accessories available, it is a very common weapon for people to build.
Many people like to build their own AR-15s because it allows them to fine-tune exactly what the weapon can do for them. It also gives you a better appreciate for the weapon as a whole, while allowing you to customize nearly every aspect of it.
No matter what the part is, there’s bound to be hundreds of different manufacturers making one. With this wide assortment for each individual part, it’s easy to see how customizable the AR-15 platform can be.
But, before looking into building your own AR-15, one very important decision must be made. What caliber do you want the weapon to shoot?
Now, this is a simple question with a plethora of answers. For brevity’s sake, I will keep this list to some of the most common builds. I will also focus on calibers that can be built on the traditional AR-15 lower.
Background Info
The biggest limiting factor in the caliber is the size of the magazines and magazine well. As you will see, there are some extremely large caliber bullets that have been fit into short casings. These rounds were designed specifically for AR-15s.
However, some of the classic larger caliber cartridges, such as .308 Winchester and .338 Lapua, are longer cartridges that won’t fit into the magazine well of a standard AR-15 lower.
Common Calibers
If you do a little research, there are a few common calibers that you can build an AR-15 in. Some of these are: .223/5.56x45mm, .300 Blackout, 6.5 Grendel, .458 SOCOM, .50 Beowulf, 6.8 Remington, and .22LR. While there are countless more options, these are just some of the most common. We will briefly go over each one, and make a few recommendations.
.223/5.56x45mm NATO
2235.56x45mm NATO
This is the classic. A “normal” AR-15 fires .223. It is a fun to shoot round that is easy to find. There are many different ammunition options available to you.
We recommend this caliber for general shooting, varmint hunting, and potentially competitive shooting. With the proper gun, this could be decent at longer ranges.
Due to the cheap prices available, it is also a good round for plinking.
.300 Blackout
This is one of the most popular options out there. It is a .308 bullet in a necked down case. As you can imagine, this provides excellent terminal performance, but will die off at distances greater than 300 yards.
We recommend this one for home defense and medium game hunting. This would definitely be suitable for deer hunting.
6.5 Grendel
6.5 Grendel is somewhat of a jack of all trades. It was designed to be an improvement over the traditional 5.56x45mm cartridge, in terms of ballistics and effective range.
The bullets are larger and heavier than 5.56x45mm NATO, but they are fired slightly slower. Due to the added size and weight, these rounds will perform better in a target. 6.5 Grendel also offers a greater effective range than 5.56x45mm NATO, and can be shot out to around 1000 yards.
We recommend this caliber for long range shooting, competition shooting, and potentially some hunting. While there are better options for deer hunting, this caliber would be acceptable in the eyes of most.
.458 SOCOM/.50 Beowulf
These two calibers are lumped together because they are so similar. They are both extremely large bullets that are in a specialized cartridge that will fit a standard AR-15 lower.
The .458 SOCOM came first, after demands from the special ops community for a round that had more stopping power than the traditional 5.56x45mm. The projectiles of both of these cartridges are absolutely massive.
For home defense, these rounds can’t be beat. However, keep in mind that the range of these calibers is severely limited due to the weight of the bullets. Similarly, they are popular rounds for big game hunting at close range. Simply put, whatever you hit with one of these rounds will go down.
6.8 Remington
6.8 Remington is similar to 6.5 Grendel in that it was designed to be an improvement over 5.56x45mm NATO. The projectiles are larger, but are fired slightly slower than the 6.5 Grendel projectiles.
The projectile is actually from a .270 Winchester cartridge. Most hunters know that this round is extremely popular in the deer hunting community. For this reason, this round is another option for deer hunting. We prefer .300 Blackout, but 6.8 Remington will also work. The range of this round is slightly greater than that of .300 Blackout.
7.62x39mm
As backwards as it seems, you can build an AR-15 in an AK-47 caliber. However, there are a few reasons that we recommend not doing this.
First, 7.62x39mm is generally considered inaccurate. Part of this comes with being shot from an AK-47, but it also comes from the round being less accurate than some of its competition.
Second, due to low gas pressure, a traditional AR-15 may have trouble chambering a 7.62x39mm round repeatedly. We would avoid that.
The size of the bullet is great for terminal performance, but it is also very similar to .300 Blackout. While 7.62x39mm is a viable option, .300 Blackout can outperform it in almost every aspect.
The one plus side that 7.62x39mm does have is that the ammunition is cheap.
.22LR
Many people know that .223, or the classic AR-15, is actually very similar in size to a .22LR projectile. There are plenty of conversion kits out there that will allow you to shoot .22LR from an otherwise stock AR-15.
Due to how cheap this rimfire ammunition is, this is a great round for plinking and for teaching firearms safety. best ar 15 scope for .22lr is good option for ar15 owner.
Pistol Cartridges
Similarly, there are conversion kits out there to allow your AR-15 to shoot pistol cartridges. These are nifty, but in our opinion, they lack much of a purpose. For general rifle shooting, there are far better options out there.
Conclusion
As you can see, there are quite a few options out there. Keep in mind that this is just the beginning, and there are even more calibers available to you!
While it can seem like a difficult decision to make, keeping in mind what the weapon is for will help to make the decision.
To end the mass killings that we are having I think this would be the answer, convert all AR15s to 22LR and all new AR15s be built in only 22LR ,anyone reading this and understanding firearms knows that the death toll would drop by 99% if this happened And the people owning AR15s could still enjoy shooting them .
Criminals don’t follow laws, and do not buy guns legally. Shootings happen more in gun free zones bc criminals knows there won’t be anyone there to defend themselves. They just don’t follow laws. If not guns it would be something else. Cain killed Abel with a Rock. We have become a nation that has forgotten God. We pass evil laws, and praise it. We took God out of everything. You reap what you sow. Planned parenthood has killed more people each year than guns. But they don’t care. Their just not going after ARs, but their going after semis as well. This would not stop mass shootings. Criminals would just be smileing and laughing. They would still be able to get the calibers they want. But hurts law abiding citizens. No new gun law is going to stop it. We need to turn to God. And get back to God.
Amen brother. Very well said….
Awesome reply!
But they could not possibly understand after such a comment!
Don’t give pearls to swine!
You tell em!!! But its not like they will listen to the truth. Im just glad to see there are at least some decent people out there still.
This blog is about AR-15 caliber options. Please post your comments somewhere else.
That is not the answer at all, How are you going to enforce this? your not. People need to be taught about firearms while they are growing up, they need to know that a gun is not a toy. As there are way to many people that are not educated on what guns can do. But to say that they are like a knife, as they can take a life. I believe that with this generation they grew up playing violent video games that were never even a thought 40 years ago, and they think it is ok to kill when they get mad like in the games. Think about it, Kids now days were not disciplined like we were 35-40 years ago, we know right from wrong unlike the idiots now days
Bill Purdy: You obviously are not very familiar with 22lr muchless firearms. The 22 LR is almost the same bullet as the .223 / 5.56. The major difference is the .223/5.56 has a lot more powder (volocity). A 22lr is a very deadly round and you can get back on target faster than a .223/5.56. To say a 22lr would reduce mass shootings by 99% is simply moronic at best. It really is irritating when people want to force laws and stupidity on others without any real knowledge.
There are people that deer hunt with a 22lr. So please tell me how is a 22lr less lethal? Keep in mind mass shootings have all been at very short ranges so the 22lr is just as deadly. The bullet will pass through the target NOT dissipating all of its energy. So at that point more powder / velocity / energy etc, is a moot point at best.
So please after this enlightening info please inform me, how is a 22lr going to “reduce mass shootings by 99%”?
Really one of the most stupid things I have read in a long time. Congrats….. 🙁
Well mainly, you cant hunt deer with a .22 in most states,my AR15 shoots a 68 grain bullet at 2850 fps.i have hits at a thousand yards with it.your piddly. 22 shoots a 30 grain bullet at best 1000 fps. Anyone that tries to compare the two cartridges is totally and unfortunately terribly misinformed.
You are a fucking retard
lets do this
end double stack magazines
as a rule people do not reload they will pull the trigger until the gun is empty.
so we have single stack magazines, you can have as many bullets as you want you just cannot have a double stack. much more than 10 rounds and the gun will jam. States can make there own ruled about what becomes of old magazines
So it is not the AR or the AK that do all the killing it is the hand gun.
so lets get ride of high capacity magazines, instead of 15 in a 9mm we have 8 that is the way GOD meant it to be.
and oh by the way, it is not the ARs or the AK it is the high capacity 9mm hand guns.
junfan40@icloud.com
Where do you get your numbers from.
Because that is totally wrong FBI stats. Shows that less than 400 firearm deaths are caused by all long guns. Not just AR15’s
hey bill more murders have been done with the lowly .22lr than all most all the calibers combined its the mobs favorite round nice and quiet and cheap considering that they are going to ditch the gun asap…..so no the death toll would not drop by 99%……………
Now lets place blame on the size of the cartridges i.e. calibers not the persons pulling the trigger lets ignore the Constitution and the freedoms that it is ment to protect
If your willing to give up freedom for security you don’t deserve to have either any just to inform you seeing that you have this idea of a 22lr round being less deadly do some research you find that 22lr have killed more than a few just ask any Mobster hitman they like the 22lr one behind the ear is all it takes and less likely to match the bullet to the firearm due to the damage on bullet from hitting bone so your above statement is WRONG
Thanks for coming out
This would be a good idea except that when you buy or build a long range firearm you intend to shooting a distance. I know my 22 wont shoot a half a mile but my 303 will my 22 wont drop a beer my 303 will some times the size of the round your shooting needs to be big enough to save your life and not piss of the 3 little bears. Lol
So in other words, just let cops and crooks have the “Killer” AR15. I suppose you are one of those that think AR stands for assault rifle. Do you know why theirs no shootings,armed robberies, car jacking,or anything like it.do you think maybe its because we have open carry,and everybody’s “packin”
What?!
What are you doing on this site?
Your sound exactly like a communist wanting to take away liberty’s!
Pansy!
Your a moron.
Did you know motor oil is good for your lawn? Don’t listen to all the haters. Get about 20 quarts and pour it all over it and you will never have to water again.
you do realize the 22 LR is capable of terminal results on all large game animals found in North America right? Its all shot placement. That said, people kill people. that is it it in a nutshell. the gun is just a tool. wake up people
Bill, I have a hand built AR 15 chambered for the 6.5 Grendel. I also have a Ruger 10/22 with a 22 inch barrel, an aftermarket trigger assembly with a 2.7 lb trigger release and a 4×12 scope. Now that I’ve figured out what ammo the Ruger loves, I’m printing 3/4 inch groups at 100 yards. It’s fun! But at 200 hundred yards and beyond? It’s neither accurate nor much fun.
But my AR 15? At 100 hundred yards? .6 inch grouping. 200 hundred yards? One inch grouping. 300 hundred yards? 2 inch grouping on a good day. Less than 3 inch on a bad day. 500 hundred yards? 6 inch grouping or less is my norm and the Grendel still has the punch to take down deer with one shot. You just need to know the bullet drop with the cartridge you are shooting to be accurate. I love long distance shooting. It tests your talent, hard earned skills, math and patience.
The death toll dropping by 99%? All long guns are less than 500 out of the over 15,000 murders by firearms each year. That includes shotguns, bolt action rifles and 22lr rifles. Do your research and it will back up what I just told you. Personally I’m keeping my 6.5 Grendel and then someday giving it to my nephew.
I don’t know if Bill is just having a troll moment, goofing around, or is dead serious.
Hopefully, he’s either goofing, or trolling, but being serious wouldn’t surprise me in the least.
I just bought a .450 Bushmaster upper, and can’t wait for it to arrive in the mail.
I notice it’s absent from the list above, but since it’s close enough to the .458 SOCOM and the .50 Beowulf, I’ll let it slide.
I also really enjoy the 9mm pistol conversion I built on a dedicated pistol lower. So much fun with the 32 round SMG mags. Liberals hate it!
With the limited capacity of the .450 BM, though, it should be much more leftist friendly, lol.
Why do you writers, TV personality, spokesperson stop calling firearms weapons. Your not helping the fight to keep the 2nd Amendment. Please think before you speak. We out here in the world really enjoy your platform but not the name calling. Thank you for your time
Bill purdy is full of shit on the conversion of the AR -15 being better off as a 22LR criminals will always have guns and bigger than any darn 22LReven georgia said it was nessary that we keep equal arms and ammunition for all free men to maintain a free state even aginst a corrupt goverment! And mine is a 5.56 Nato and i and others shall never surender these firearms, we have that right to keep and bear arma given to us by God himself and the constitution backs that up under 5he 2nd admendment, & if our government ever triess to change that is a decleration of war aginst we the people
@bill purdy 22lr is the most deadly round at the cheapest price
It has the power to penetrate and commonly in regards to crimes, not enough to exit, which causes it to bounce around until it lodges somewhere inside. This results in a “magic bullet” a body with an entry in a non-lethal place no exit but death nonetheless.
As both military and a forensic science major graduate…you are hilariously misinformed and need to conduct further research from credible sources vice spouting liberal rhetoric that is baseless and thats putting it mildly.
But its purdy you think it would stop criminals from committing crimes
Are there any builds that come close to a 30-06 with an AR15 platform rifle? Sorry if my question is otherworldly, just very curious.
Thanks.
If you build a .458 socom make sure you use a re-enforced upper the basic upper has a tendency not to withstand the pressure I had a incident using 220 grain the bcg slammed the chamber so hard it bent my upper receiver which I had to bang out w a hammer,. Just an FYI