First of all, a qualifying remark: Water testing is NOT a very scientific method for testing the performance of various rounds, in that it can accurately predict likelihood and extent of expansion or fragmentation, but cannot accurately predict penetration of main projectiles or fragments. Given that, it is a more accurate method than shooting phone books, newspapers, clay, or broken water heaters. DocGKR, quoted by Old_Painless on the wonderful Box O Truth, stated "Be aware that water generally reveals the maximum upset which can occur to a projectile in soft tissue -your actual result in living tissue may be somewhat less. You can also use the water testing to get a rough estimate of bullet penetration depth in soft tissue--bullets penetrate approximately 1.6 to 2 times as much in water as in soft tissue." Ratios of 1:2 to 1:1.6 (5:8 for the OCD) constitute a large variance, so take the following data with a grain of salt. It is, however, likely that water penetration between 19.2 and 24 inches can be considered inconclusive: within the above ratios it is impossible to determine whether such rounds will underpenetrate. Given the nature of this procedure, it is a source of hypothesis generation only, with such theses able to be tested more adequately with ballistic gelatin.

Now on to the meat of the post.

There has been much discussion of late on the Prvi Partisan 75 gr BTHP bullet, loaded in the Match loading and the Wolf "Multi Purpose Tactical" loading (I believe this to be the case). Questions were made concerning its low muzzle velocities - with numbers ranging from the 2200s to the 2400s - out of common length carbine barrels. I wanted to see for certain if this round would have desirable terminal effects or if the jacket would be thick enough to inhibit deformation at these low velocities. Given that the jacket on the Prvi 62 gr SP was not thick enough to inhibit expansion and fragmentation when shot into water out of a 16 inch barrel, BUT the jacket on the 62 gr BTHP prevented such, I did not have any predictions as to any findings.

Materials and methods:

One 36"x16" plastic container.
Duct tape
Water

Bushmaster XM15, 16 inch barrel, 1/9 twist, chrome lined.
Prvi Partisan Match 75 gr BTHP, 3 rounds*



I cut a 4" x 3" hole in the container and layered the hole with duct tape, on both sides, so as to ensure water-tightness. I chose this method, as opposed to water jugs, for three reasons:

A, It should be easier to recover projectiles and fragments.

B, Due to the jug's odd shape, it should be easier to judge penetration. The width of the jugs is not the same from top to bottom.

C, I have always been concerned that the plastic material on the jugs altered the ballistic properties of the rounds. When testing with jugs myself, and viewing the results of others, I always see dents left by fragments and fragments themselves stuck in the jugs.



The box was shot at about 15 feet.

I have no chronograph, altimeter, or barometer. But it was damn hot.

*I was hoping that hydrostatic shock would not bust the container - allowing me to test several rounds - but alas I was wrong. Thus only one round was tested.

An image of the most visible fragment (far right), and of the damage to the box.




An image of the projectile at rest. It penetrated deep into the water (no surprise): 29 inches, approximately, equating to - according to the ratios above - 14.5 to 18.125 inches in ballistic gelatin. While water is not as valid as ballistic gelatin, I think we can safely assume that this round will meet penetration requirements.



Images of the recovered projectile:











Recovered diameter: .59 inches/1.4 cm.

If I was to look at the recovered projectile, I would stipulate that it was an expanded soft point. It appears to have mushroomed much less than fragmented (I recovered only three fragments). The pushed back petals resemble recovered A-max and long range V-max rounds I have recovered, as well as those on the 62 gr Prvi SP. As the jacket delaminated from the core in transit, the lead-less jacket appears very similar to those of both the Prvi 62 and 55 gr SP.

I would venture to guess that either this round acted like a bona fide hollowpoint, or that it broke at the cannelure and traveled "point forward", exposing the lead core to resistance. In the former case, I would be wary as to what range the round would continue this behavior. As to the latter, I would have expected to recover a greater portion of the bullet - namely, the top half.

I also noticed that my extractor beat up this brass much less severely than the Prvi brass cased soft points or 55 gr fmj. Perhaps this is a phenomenon that was merely not present in the one round fired.

I feel more comfortable in this round's capacity as a self defense cartridge, but would have to see ballistic gelatin data to be sure. At any rate, it will not replace the Black Hills BB or HSM loaded Hornady 75 gr OTM for me any time soon, as these rounds are only a tad more expensive (24 dollars for a box of 50 from HSM), are more accurate, have a flatter trajectory, and are - from what I saw today - still better terminal performers. I will attempt to construct a more durable water-container, so that I may "calibrate" my findings with rounds known to act a certain way, such as the Hornady 75 gr.

Very nice little write up!  I for one appreciate it because I'm fond of this Prvi load.

-X

Thanks for posting this.

Great Post

Thanks

Quoted: Very nice little write up!  I for one appreciate it because I'm fond of this Prvi load. -X

+1 here

accurate, cheap, and brass cased to boot.

I have a mild steel plate I put out at 50 yards for plinking fun. Without a doubt the privi 75 grain puts the deepest craters in the steel. Better than RG 62 grain, any 55 grain and any .308 ball I have tried.  

how would it be for hunting deer or wild hog at close range?

Quoted: how would it be for hunting deer or wild hog at close range?

At close range, if and only if the above results are repeatable and accurate, it would probably fair very closely to the heavier .223 soft points. 14.5 - 18 inches of penetration and .5 through .6 inches expansion with moderate fragmentation is around what we expect of the 64 gr Power Point at most common velocities, or the Federal 64 gr SP (with around 14 inch penetration) at lower (14 - 16 inch barrel) velocities.

Contrast this with the 60 gr Nosler Partition, which experiences moderate fragmentation, .4 inch expansion and 16 - 19 inches penetration out of carbine barrels, or the TBBC which hovers around .45 inch expansion and 17 inch penetration with almost perfect weight retention out of 14.5 and 16 inch barrels.

With appropriate shot placement, the round should be effective against deer or hog at close range ASSUMING the above results are repeatable. Until further, more reliable data is available I would still use one of the SP listed if I was concerned with meat destruction, and one of the heavy OTM if I was not.