Saturday, August 25, 2007

7.62x54 Bulgarian light ball


Years ago I read an article. The subject was precision hand loading for accuracy. This article appeared in a magazine devoted to hunters who typically shoot at long distances. As might be guessed, the piece was all about the details of building very special ammunition. The key to exceptionally accurate ammo is keeping every factor, every component, as close to perfect as possible.

The title of this article was “The name of the game is the SAME”

In taking a ‘Look Inside’ the 7.52x54 Bulgarian light ball recently available, I was thinking that another phrase might be more fitting. “The name of the game is..... close enoughski”

Tearing down and examining various ammunitions I have come to expect most to have some component, or some factor, less than perfect. With few exceptions this has been true.

With this Bulgarian offering every single component and chosen measurement factor had accuracy issues. No attempt is made here to be mean, and it must be remembered that this is only 10 rounds, out of millions produced.

Let us take a look at the subject:

Photo Sharing and Video Hosting at Photobucket

Photo Sharing and Video Hosting at Photobucket

As usual, components were weighed with an RCBS 10-10 scale. Components were measured with Mitutoyu digital micrometers and a Central caliper. The bullets were pulled using an RCBS collet type puller mounted in an Ammomaster press.

The components found:

Photo Sharing and Video Hosting at Photobucket

The ammunition is brass cased, and berdan primed. Neither bullet nor primer is sealed in any way. The bullets pulled with very little effort, but erratically. This was due to the case mouths being crimped into bullet cannelures inconsistently. On most loading equipment the case mouth crimp depth is dependant on case length. The longer the case, the heavier the crimp, all other things being equal.

The components were measured in as consistent a manner as possible, but some measurements were made two or three times. It’s easy to move along quickly when each measurement is the same, but when they vary so much extra care must be taken to be accurate.

Photo Sharing and Video Hosting at Photobucket

While making neck diameter measurements, something special was noticed. It seems the cases were sized quite small, then the bullets were seated in a non-concentric way. In other words, they are not centered in the necks. On seating, the bullets stretch the case neck. In this example the necks were stretched all to one side, to the tune of .003” off center. This proved difficult to photograph, but here’s my best attempts:

Photo Sharing and Video Hosting at Photobucket

Photo Sharing and Video Hosting at Photobucket

The neck diameters were also out of round by over .001”, but this was mostly caused by the bullets varying at least that much in roundness.

Some data on case and cartridge dimension:

Over all length of loaded cartridges: From 3.000” to 3.020”, with a spread of .020”. The optimal specification is 3.010 according to the Handloaders guide to cartridge conversions.

Case lengths: 2.100” to 2.110” with a spread of .010”. Optimal is 2.050 based on the same source. This case length variation accounts for the inconsistency of case mouth to bullet crimp, in my opinion.

Cartridge base diameters stretched from .4821” to .4850”, with a spread of .0029”. Case neck diameters varied from .3330” to .3358”, doing my best to deal with the uneven neck stretch.

Once pulled down, the powder was checked and weighed. It’s a medium length extruded grain resembling IMR 3031, but clearly not exactly the same. Charge weights varied significantly, from 49.5 grains to 50.1 grains. The powder appeared in decent condition despite its 50 year life in an unsealed case.

Photo Sharing and Video Hosting at Photobucket

The bullets were interesting. They are a hollow base spitzer design. The indentation in the base measured a whopping .160” deep. Bullet weight variations were on the heavy side ranging from 150.5 grains to 151.9 grains, with a 1.4 grain spread.

The bullets have a lead core, with a copper plated mild steel jacket and a deep cannelure.

Photo Sharing and Video Hosting at Photobucket

Bullet diameters measured from .3092” to .3112” with a surprising range of .0020”. That’s quite large by any standard I have ever seen. While these bullets should be safe in any 7.62x54 rifle, accuracy of any kind would be amazing. Nominal bore diameter in this round is .311”, with many hand loaders looking for .312” or even slightly wider in the quest for accuracy. My own Mosin bores slug from .312” to .315”. A bullet that much undersized must simply bounce down the bore.

There is a chance the very large indent in the base acts exactly like the one in the Minne ball of civil war fame. Pressure pushes the bullet base walls outward against the bore, sealing it and forcing it into the rifling. If this is the case, then accuracy might not be horrendous after all.

Also noted was the depth of bullet seating in the case neck. With variations, it averaged a very short .217” deep. This is not even one bullet diameter. With rough treatment the bullet will shift in the neck, once again damaging accuracy. Treatment as ‘rough’ as chambering a round from the magazine might do this.

Photo Sharing and Video Hosting at Photobucket

Case weights were the widest ranging of any one lot I have ever seen. The lightest was 145.6 grains, the heaviest at 152.5 grains, with a spread of 6.9 grains. External measurements found no large difference, so I can only guess the weight variation is due to case wall thickness.

My conclusions are.... well..... just mine. To be honest I am no trained scientist nor do I play one on television. I don’t have a big sweaty brain. Heck, I’ve never owned a pocket protector in my life! I’m just an interested hobbyist attempting to understand my interests a bit better, and share my interest at the same time.

I see nothing in this ammunition that screams *unsafe* to me. In fact, I suspect it will be completely dependable. My only criticism is from an accuracy viewpoint. I fully expect this Bulgarian 7.62x54 to be as reliable as fifty year old military ammunition can be. It’s probably 100% sure fire, I’m guessing it will function perfectly. That said, I am as curious as a hound in a sausage factory to see how accurate this ammunition is. I also want to run it across my chronograph which I have found to be a good indicator of accuracy potential, or lack of.

I’ll report back after that range day....... this should be interesting. There’s always the chance my conclusions are completely wrong. This might be the most accurate ammo ever fired in a Mosin Nagant.

Stranger things have happened. There was the time I ate all those bean burrotos.............. I was wrong then too.


(Follow up note: Pay attention!!!)

I have shot this ammunition quite a bit since writing this article. Two things need to be mentioned.

1) It proved to be exceptionally accurate against all predictions. I stand amazed.

2) In my shooting I found it has a high incidence of leaking primers (about 10%) and shooting glasses must be worn without fail! Others report split cases. Be careful!


No comments: