Mausers and COL

[meaty-btz]

This is half reloading, half C&R.

I was looking at molds for lead rounds for my VZ-24 and stumbled on a thread where they argued about the Lee Karibiner Mold (235gr).

So in pondering I will at some point slug the throat, but it got me thinking about COL on 8x57. So I checked with my Sierra Pro Hunter what maximum COL was and came out with a scary number. I had always loaded to data rather than check MAX COL and it worked well for accuracy.

My loads were always 3.1 COL per my data

Checked the max (engage the rifling with the sierra 170g5) and came up with 3.246

That is quite a bullet jump, but I was hoping it might also mean I have a generous enough throat to use the super heavy Karibiner, which I think would be more fun than a lighter lead bullet.

In your experiences with surplus and ultra-heavy bullets, anyone find feed issues with the long, heavy, bullets (200gr+)?

Just mulling options, the next step down is 170gr lead mold. hmm.

[Josh Smith]

Hello,

The original load, the 7.92x57j (actually "i" for infantry) was a bullet of about 227 grains at around 2100fps, propelled by Poudre B.

I made some of these up for my Gewehr 88 and they proved pretty danged accurate!

The subsequent load was 154 grains at about 2900fps.

Regards,

Josh

[meaty-btz]

where did you get your 227gr bullets?

Poudre B, where did you get a hold of that?

This would be lead and the loads would be 1700ish FPS estimating from others data.

I have Published Data on a 220GR Hornady SP running at 2420 FPS, that has gotta pack a wallop.

[Wernher von Browning]

COL on 8x57 is semi-meaningless because the design has a HUGELY long throat. I don't know why; maybe because it grew out of the older roundnose bullet application, maybe because they wanted to make it mud, dirt, and soldierproof.

One reason for published COLs may be magazine feeding.

The only way to be sure with a new bullet is to just toss the published COLs out the window and actually MEASURE -- many times, carefully, and average -- the COL for your rifle and bullets using a Hornady (or similar, competitive) gauge, measuring to where the bullet juuuuuuust

http://www.midwayusa.com/product/570611/hornady-lock-n-load-overall-length-gage-bolt-action

This uses a dummy case whose base has been threaded to fit the red-anodized gauge:

http://www.midwayusa.com/product/113560/hornady-lock-n-load-overall-length-gage-modified-case-8x57mm-mauser-8mm-mauser

I prefer to use one of my own fired cases, fireformed to my own chamber, to make such a case by drilling and threading the head, but I don't have the fine-pitch tap for that and most people won't have a lathe to cut single-point threads in a case like I do.

They show a caliper being used to measure COL, but a better way is to measure to some point on the ogive (doesn't have to be where the ogive actually engages the rifling, just so long as it's consistent).

Hornady sells another gauge for that, but I made my own. They don't have one specifically for 8x57, you might get away with a .308 gauge.

http://www.midwayusa.com/product/231904/hornady-lock-n-load-bullet-comparator-basic-set-with-6-inserts

Just to see how long the throat of an 7.92 x 57 (8mm) Mauser really is, have a look at the "official" SAAMI drawing (the European CIP drawing is similar but I can't find it as quickly -- the old mirror site in Finland no longer carries it):

http://www.saami.org/specifications_and_information/publications/download/206.pdf

Compare the chamber drawing for the 8x57 Mauser, on p. 32, with, say, the .30-'06 Springfield, on p. 56. Note the difference in lead to the rifling.

For those who reload the Swiss 7.5x55, the situation is a lot worse, but in the other direction. The reloading manuals seem to be unaware that there are two different chambers used for the same cartridge -- the 1911 rifles and the K31. The K31 has a WAY shorter throat, but the print manuals I've seen all give impossibly long COLs, because they seem to be based on the earlier M1911 rifles.

You have to check these things every step of the way on your own, don't trust any printed data from "experts" much less on the Internet, and work up your loads gently from the published minimums, watching for pressure signs.

I bought a Swiss K31 with some handloaded ammo once. The seller told me the load, it was at the published minimum -- yet gave a surprisingly high velocity (compared to the reloading manual claim). Once I got my Hornady gauges, I checked his bullet seating depth -- and found he was stuffing the bullet about 0.020" into the lands. I don't know if it would have wedged in hard enough to pull the bullet if I had un-chambered a live round or not, but the cork effect would explain the high velocities.