Ak47/74 which is better 7.62x39 vs 5.45x39?

[Guest Cory2]

I will state it in fewer words. There is no end all be all caliber, just like there is no end all be all pistol or rifle. However, since bullets rotate as they travel through space (the atmosphere in this case) they contain more energy, the larger the diameter of the bullet the faster the outside parts are moving, the more energy they then have. Therefore a large bullet spinning at the same velocity as a small bullet will have more energy stored in it, just as a small bullet (half the mass) of a large bullet traveling at twice the speed of the large bullet will have 2 times as much energy as the large bullet, if they are not rotating. However if they are both rotating at the same speed the equation to determine their total energy becomes more complicated. If you really want to see all of the equations for these they are available on the net.

That being said, I am not going to type out a thesis on kinetic energy on a gun forum lol.

[glockster157]

Y'all are making this way too complicated....I have a 45-70 and it is fun to shoot, I have a Polish Tantal and it is fun to shoot. If I didn't reload and cast bullets I would be able to enjoy the 5.45 Tantal but probably not the 45-70, factory ammo costing what it does for that caliber. Same with my 375 Win, 375 H&H and 458 Win, etc. So if you want to pay 300 per K get a 7.62x39 and if you want to pay 139 per K get a 5.45x39...or just get one of each and shoot them with both.

[Jonnin]

Right. And the momentum that I mentioned is also over simplified, I never meant to say it was a realistic way to model the thing. All I was saying is that both variables matter and velocity is often over-rated. A tiny slug @ 3k FPS does certain things well. A brick dropped from an airplane does other stuff really well. Somewhere between the 2, we make our choices depending on what we like/dislike or want/need.

[TN Outlaw]

i think im going with the 5.45 but i will have to wait till next week to get one, had to dish out a couple hundred to fix my truck ): but i will still be at the gun show this weekend sometime to look at some thanks for all the info guys i appreciate it

[Guest Cory2]

i think im going with the 5.45 but i will have to wait till next week to get one, had to dish out a couple hundred to fix my truck ): but i will still be at the gun show this weekend sometime to look at some thanks for all the info guys i appreciate it

Buy what you like, it is your purchase and your decision. In reality the need for them in a combat situation is extremely low, and even if you do find your self in that situation, both rounds are more than capable of killing a person.

We are arguing over stuff that doesn't really matter, because in the end you can only be so dead.

[peejman]

I will state it in fewer words. There is no end all be all caliber, just like there is no end all be all pistol or rifle. However, since bullets rotate as they travel through space (the atmosphere in this case) they contain more energy, the larger the diameter of the bullet the faster the outside parts are moving, the more energy they then have. Therefore a large bullet spinning at the same velocity as a small bullet will have more energy stored in it, just as a small bullet (half the mass) of a large bullet traveling at twice the speed of the large bullet will have 2 times as much energy as the large bullet, if they are not rotating. However if they are both rotating at the same speed the equation to determine their total energy becomes more complicated. If you really want to see all of the equations for these they are available on the net.

That being said, I am not going to type out a thesis on kinetic energy on a gun forum lol.

Since you brought it up... the rotational energy of a bullet is much less than it's translational energy, hence it's typically neglected.

For a 7.62mm, 123gr bullet traveling 2400 ft/s while spinning at 250,000rpm:

Translational KE = 0.5*m*V^2 = 1571 ft-lbs.

Rotational KE = 0.5*I*w^2

I = mass moment of inertia, approximating a bullet as a cylinder = 0.5*m*r^2

Combining, Rotational KE = 0.25*m*r^2*w^2 = 15 ft-lbs.

Thus the translational KE is 99% of the total.

[Guest Cory2]

I came up with 28.81 kg/m, or ~208 ft/lbs. But I did the equations seperately and did not combine them as you did. One of us did something wrong, and it is quite possibly me lol.

Though, just going on feeling, I don't think 15 ft/lbs would stop a 7.62x39 bullet spinning at 250k revolutions per second.

Edit#2: I accidentally put typos in the title instead of in reason for editing like I meant to.

Edited August 19, 2011 by Cory2
correcting my failur

[Guest Cory2]

But this is all besides the point completely. For all intents and purposes the 7.62 has more energy (in every way) than the 5.45. But the 5.45 is much cheaper, the op already made up his/her mind to go with 5.45 so the discussion is pretty much over

[K191145]

I have the Romanian ak47 and wouldn't trade it for anything.

Aww man, I was going to offer you a Wilson Combat 1911, Colt Python, and a Holland & Holland British double for it but since you wont trade it I guess i'll have to pass on it.

[Moped]

If your going to a gunshow and expecting to find a cheap AK, you're going to be sadly disappointed. I rarely find good deals at shows anymore. If I go, I'm paying more attention to what people are carrying around, than what is on the tables. For me, I'd go with a Siaga and convert it as BKHelm said. They are probably the easiest, best quality to be had in either caliber. The conversion process is easy and you will really get to know the rifle. It's easy enough that I was able to do it!!!

[frontier737]

Deleted

Edited August 21, 2011 by frontier737
Not right place to ask this question

[TN Outlaw]

But the 5.45 is much cheaper, the op already made up his/her mind to go with 5.45 so the discussion is pretty much over

Actually after i posted that im still trying to figure out which one i want i cant decide

[TNRat]

im interested in getting an ak47 and would like to know the pros and cons to 7.62x39 vs 5.45x39 all info is appreciated

The question is not "What is best?" The question is "What is best for me and my needs."

Both have their positive attributes so you can't go wrong with either.

[Guest Cory2]

It essentially comes down to this.

7.62x39= more powerful and less cheap, but still pretty cheap.

5.45x39= Cheaper and more accurate.

[Guest bkelm18]

Suffice it to say, either rifle will perform better than you (not many people can actually push the limits of their weapons) and will exceed any intended use you have for it. Both will function fine on the range or in a SHTF scenario.

[Urse]

Here are a couple of videos that offer comparisons of the two calibers. Jim Fuller is considered by many the finest AKsmith in the country.

http://www.youtube.com/watch?v=5VFkgZij5eg&feature=related

http://www.youtube.com/watch?v=iwKf-yoEhnM&feature=related

If I could have only one AK I would choose the 7.62. The 5.45 is tempting but the 7.62x39 is available in the AK, SKS, CZ 527(bolt gun) and the RAA BARS-4-1(also a bolt gun) platforms. There are plenty of readily available reloading supplies for the 7.62x39. The actual diameter of most 7.62x39 ammo is between .310 & .311 but the .308 bullet can also be used. The vast majority of AK parts and pieces imported into this country have been 7.62x39. For me this all adds up to more flexibility with the 7.62 round than the 5.45. While it is true that the 5.45 can be had for $139/k I have been collecting AKs for several years and have owned eleven 7.62 variants as opposed to one 5.45. I have gone through thousands of 7.62 rounds and have a healthy supply of ammo on hand. If you are planning on actually training with your AK and will be shooting thousands of rounds then it may make sense to go with the 5.45. People that load their guns up once or twice a month during the summer and go to the range to blow through a couple hundred rounds are gonna see less long term economic gain in the 5.45 because they may never go through 2k rounds. As has been stated already either will serve you well. I have always subscribed to the "hole will not get smaller" philosophy but that said I would not want to be shot by a .22 much less either of these rounds. When the zombies attack if I am inside it will be a 12 gauge in my hands and if I am outside it will be a .308. This of course is all just one opinion Your Carnage May Vary and good luck with you choice!

[TN Outlaw]

i will be shooting it very often and i was wanting it for a SHTF weapon and home defense weapon.... can you get a 5.45x39 with a chrome lined barrel?

[Mike]

Yes, Bulgarians and Russians both come with cold hammer forged chrome lined barrels.

Mike

[poak]

Jim Fuller is considered by many the finest AKsmith in the country.

Fuller is the man.

Talk about a guy who CAN polish a turd, take a look at a few of the Century builds he's un-f#$%ed.

[Jonnin]

The actual diameter of most 7.62x39 ammo is between .310 & .311 but the .308 bullet can also be used. The vast majority of AK parts and pieces imported into this country have been 7.62x39. For me this all adds up to more flexibility with the 7.62 round than the 5.45.

FWIW the 303 brit is .311 diameter and I have been using that in my 765. It may or may not be a great choice for the 762 -- I have not tried that, but the 303 is still available in most reloading stores. They are usually sorta large, so it may be a bit of a thumper at 180 grains in an AK.

[packingvol]

i will be shooting it very often and i was wanting it for a SHTF weapon and home defense weapon.... can you get a 5.45x39 with a chrome lined barrel?

Most 74s will have a chrome lined barrel, as long as you stay away from century. I also think the Romanian imports had non chrome barrels. The good "deal" on 74s right now are the Waffen works and interarms. Both are built from matching Bulgarian kits with chrome lined barrels. The Waffen guns are assembled in Knoxville. You will get a Knoxville tn manufacture stamp on the receiver. How cool is that!?

[Guest bkelm18]

Outlaw, I blame you for resurrecting my urge to get another AK. I've been eyeballing an Arsenal SGL21. It wants me. I want it.

[TN Outlaw]

Widener's Reloading and Shooting Supply INC .... how good is the ak in that link?? it doesnt have a chrome lined barrel so does that mean i will just have to clean it more often? how well built are those if anyone knows?

[Mike]

I'd stay away from it. Not only does it not have a chrome lined barrel, it has a nato length stock, and more importantly, they don't list who built it.

Spend a few more dollars on a known quantity rifle from a reputable builder.

Mike

[TN Outlaw]

who builds good ak74s in 5.45x39 that are reasonable in price?