Time for some 5.45x39 speculation

[USSA-1]

If one were to manufacture a 5.45x39 to American standards for bullet design and jacket wall thickness, would there be in increase in performance over comparable 5.56mm loads?

Considering this bullet is slightly smaller in diameter (.221 compared to .224), this necessitates a slightly longer, but thinner bullet for the same given bullet weight. The longer bullet, at the point of 90 degree yaw, immediately prior to fragmentation should give a larger permanent wound cavity and provide an increased density of fragmentation due to it's longer body.

If I'm correct in my few assumptions, then this should be a mroe effective anti-personnel round when compared to a similar weight bullet in 5.56mm.

Time for some speculation....any thoughts on it's performance?

USSA-1

[Ned Christiansen]

I have searched and searched for somebody making brass-cased ammo for this, something with bullets that are a cut above the stick it in an AK level of quality that's currently available. I had hoped maybe the Finns were loading it, but as far as I can tell, there is no 5.45 that is the next level up in accuracy. It would be interesting if there was....... maybe in one of those bolt guns in this chambering that were being offered back before you could get the ammo.

Not to say that what's available ain't worth having, I've been mighty pleased with the Bulgarian and especially the Russian surplus. It's stay under 3" all day long in a Smith & Wesson M&P15R (using Zeiss Varipoint on 4X), and I have the idea that with a free floating barrel and maybe a bigger scope, and trying a little harder, it might stay under 2, 2 1/2". That's more than good enough for the purpose at hand.

But yeah, 5.45X39 coming out, say, the Lapua factory with a bullet made for accuracy and not volume, I'm thinking the cartridge design has a huge accuracy potential, but that there are very few guns that could bring it out.

[Robb Jensen]

I predict that when comparing similar bullets say 70gr 5.45x39 to 75-77gr 5.56mm there won't be too much difference in terminal ballistics.

[Marcus L.]

You also need to take into account that with a longer bullet, it's harder to maintain a weight distribution that allows for early yaw unless you use lighter metal in the nose or a hollow nose. For early yaw, you must have the weight distribution shifted to the rear so that when the bullet upsets its spin when entering tissue, the rear flips over and leads. All projectiles will flip to have their heavier rear lead in flight unless they are spinning which constantly corrects this and keeps the light end leading. Also, the longer the projectile, the more disruption force is needed to flip the bullet and make the heavier rear lead. Longer is not always better if you want a bullet to yaw, tumble, and fragment. Another load that "seems" like it would be superior to the 5.56 is the Chinese 5.8x42mm which you see in the middle:

5.56 NATO, 5.8x42mm, 5.45x39mm

The 5.8mm is actually loaded no hotter than the 5.56. The Chinese use a weak steel case, a cheaper powder, and the bullet construction is designed similar to a M855 penetrator with pretty much no fragmentation ability and a slow yaw. Not all that impressive really compared to a .223 Federal Tactical Bonded 62gr load. It could really be improved on if quality components were used, but then you could also just go with a 6.8 SPC and have truly measurable improvements over the 5.56, 5.8, and 5.45.

[Steve]

i would like to see a scout rifle in this round....NED

[Bill Alexander]

RWS manufactured a sniper grade (HPBT)5.45x39 for some time for the East German bolt action in this caliber. Unique in this was that the round was almost oversized to take up play in the essentially AK chamber. Typical projectiles with a layout per the M74 will exhibit BC values approaching 0.400, with the 60 grain Barnhaul round having a BC of 0.406. Shank lengths are extremely short with the ogive nearly meeting the boat tail which dicatates that the rifling needs to be faily deep grooved.

Brass cases are rare but do exist. One particular military (not US) group contracted for over 10,000 units. Examples are not headstamped for either caliber or manufacturer.

The onset of yaw in the caliber in military grade steel core ammunition does not rely on the mass distribution so much as the movement of the core within the jacket during rapid decelleration. The thick gilded steel jacket precludes fragmentation in most cases but bullets are frequently recovered with bent noses and body flattening. The mechanism is quite interesting as it is substantially less velocity dependent than fragmentation, giving greater margin to short barrels and longer ranges.

The 5.8x42 seems to place more emphasis on the AP ability than any other design consideration. In the ball form the core is alloyed and work hardened. Before underestimating the cartridge the driving design constraints need to examined.

Bill Alexander

[Zhukov]

The onset of yaw in the caliber in military grade steel core ammunition does not rely on the mass distribution so much as the movement of the core within the jacket during rapid decelleration. The thick gilded steel jacket precludes fragmentation in most cases but bullets are frequently recovered with bent noses and body flattening. The mechanism is quite interesting as it is substantially less velocity dependent than fragmentation, giving greater margin to short barrels and longer ranges.

It's interesting you mention that. I saw an article online written by Dr. Fackler about the weird yaw cycle of 5.45x39. Unfortunately, I did not have the presence of mind to save it. In it, he had examined another caliber - plain FMJ bullet construction - which yawed just like 5.45x39. He concluded that the air tip in 7N6 was therefore not the culprit as he had originally surmised.

I'd love to find that article again.

[DocGKR]

Fackler ML and Malinowski JA: "Internal Deformation of the AK-74; A Possible Cause for its Erratic Path in Tissue". The Journal of Trauma. 28(No.1 Suppl):S72-S75; January 1988.

[Marcus L.]

That's an interesting concept, Mr. Alexander. However, the rear portion of the core shifting to the front doesn't seem to entirely explain how a bullet will tumble. If the rear weight of the bullet shifts prior to a yaw, then there is no longer an unstable weight distribution and thus no driving force to cause a flip. If the hollow nose deforms on impact resulting in the nose jacket shifting away from the axis, then that can initiate a tumble. Either way......the greater the total weight percentage of the bullet there is towards the rear, the more rapidly the flip cycle. This seems to be the most reliable method of initiating a tumble from my understanding.

To the original poster.....since the wounding mechanics of permanent crush cavity and temporary stretch cavity are limited by the overall size, velocity, and wounding mechanism of the projectile......then any advantage you might gain in tweeking out the 5.45 will probably not gain you any measurable advantage over the 5.56. By increasing the caliber size, maintaining good velocity, and tweeking the wounding mechanics of a bullet you will have measured improvements. 6mm SAW, 6.8 SPC, 6.5 Grendel are good places to start.

[Jack-O]

Barnaul loads a 55gr JHP in this caliber. While I have not shot it into gel, the other barnaul HP's i have dissected looked as if they might actually expand or fragment similar to the Sapan/Wolf mil classic x39 stuff. the bullet and jacket design was remarkably similar to the ulyanovsk loaded 8M3.

has anyone tested either the 55gr SP or HPBT in 545 from Barnaul?