The 8x60 S

Since I parked up my .256Newton loading due to the rifle having a cracked stock, I haven’t had an obscure caliber to play with until I picked up a Brno Model 21 in 8x60S. The great thing about 8x60
Is that it doesn’t require difficult to obtain brass, dies or bullets.

I was gifted 30 pieces of gold, I mean Norma brass, from forum member aimless, and with a borrowed set of 8x57 dies and the worlds crappiest brass trimmer, I knocked out 10 test cases.

Load data for the 8x60 is a bit thin, limited to only a couple of older powders and mostly heavier projectiles, I erred on the side of light and used an 8x57 starting load of 45gr of Win760, and a handful of pulled old 150gr Interlocks I found.

Attachment 200537

Off to the range I went to today. After setting the dual triggers I attempted to fire the first round, and got nothing more than an audible click... aghast, I thought I had a firing pin fault, with no struck primer. After some head scratching I realised that the safety was on! The Brno model 21 allows you to set and fire the triggers, but seems to internally block the firing pin from moving far enough to hit the primer, rather than block the movement of the trigger itself. Anyway, firsts rounds round and I was pleasant lit surprised by the light recoil. I was quite please and thought to myself either I’m getting tougher or these big 8mm’s aren’t that bad after all. But my pleasure was short lived when the crony told me why the recoil was so light... only just over 2000fps! I had definitely erred on the light sight. I guess when they are nudged closer to something more like 2500 that it’s going to get a bit stouter on the shoulder.

I was pretty happy though with the first group, only at 50m, but without really trying too hard. There is a lot of potential here for a nice accurate shooting stick. I just don’t know what box of bullets to go for. I could play it safe and just get more Interlocks but I’m also tempted by 150gr Sierras or 170gr Hot Cor. Roll of the dice I suppose.
Attachment 200538

I used to have a Sako 8x60 (on a FN mauser action, before Sako made their own). mine loved 196 gn.
look at American 8mm-06 loading data and compare it to European 8x57 data to get in the ballpark on powders and projectile weights.

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Originally Posted by Basenjiboy

I used to have a Sako 8x60 (on a FN mauser action, before Sako made their own). mine loved 196 gn.
look at American 8mm-06 loading data and compare it to European 8x57 data to get in the ballpark on powders and projectile weights.

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I had a look at Hornadys 8mm-06 data; starting load is 51.6gr of Win760 giving 2500fps with a 150gr interlock. I figured that would probably be about my max load. Actually max load will likely be decided by how much recoil I can be bothered with! If I get to around 2500fps that will be fine.

Recoil would be light. My light 98 8x57 was getting a bit snappy with the 180gr geco loads. Meant to be up over 2500fps with 24" barrel (packet info)
No recoil pad at the time.
Put a about a dozen down range and was starting to feel it
Saw it on the other post. Nice rifle

Gidday - if you weight a case that has been fired in the rifle, then fill it to the case mouth with water (make sure its exactly flush) that'll give you the case volume in grains of water. Send me that and youf barrel length and I'll run load data for you in Quickload and or GRT.

Oh - Hornady 170s are great, I can spare you a few to test if you like.

@Tentman read before that you rate those SSTs in the 8mm
Not as explodey as most SST's then?
Whilst the geco 184gr roundnose certainly did the job the other day, it isn't the most aerodynamic of projectiles.

Ive only shot two deer and maybe a couple of Tahr, but everything dropped like it should, maybe a bit of size makes SSTs ok.

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Originally Posted by Tentman

Gidday - if you weight a case that has been fired in the rifle, then fill it to the case mouth with water (make sure its exactly flush) that'll give you the case volume in grains of water. Send me that and youf barrel length and I'll run load data for you in Quickload and or GRT.

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Cheers mate I'd love to take you up on that offer but I don't have any suitable scales to weigh a case filled with water. Tried it on the pams kitchen scales but they only weigh to the nearest gram, no decimal point, and they are probably not accurate anyway. Next time I go visit someone with reloading scales I will find out.

Use your loading scales eh?

I haven't yet devised a method of balancing a water filled case on the scales without it falling over. I will consume some more beer tonight and see what I can finagle.

Edit : Ok I just needed more beer to steady my hand. I got it to balance eventually.

Case weight : 176.5gr
Case with water : 243.7gr
Water : 67.2

Attachment 200609

That approach has always worked pretty good for me . . . . But thinking about it, since I hardly ever have a beer these days maybe thats why nothing much gets achieved!

I have a 8 x 60 that I have not shot yet , need to slug the bore though as i think it’s a .318 bore which really sucks

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Originally Posted by Lucky

I have a 8 x 60 that I have not shot yet , need to slug the bore though as i think it’s a .318 bore which really sucks

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What type of rifle? I did some 'research' (beer and internet) before I fired mine, as the calibre marking is hidden underneath the base for the claw mount. The side of the barrel is stamped '7.9' but research suggest that all Brno's were made with .323 bores and both the 8x57 and 8x60 Brno's were all stamped with '7.9'.
I did read somewhere that german law prohibited the manufacture of new firearms with a .318 bore instead of .323 after a certain date (sometime before ww2) but now I cannot find the page I read it on.
If its a Brno I'm confident its a .323, but if its pre-WW1, then anyone's guess.

Oberndorf Mauser , post WW1 , I think late twenties , yes supposedly after WW1 they went to .323 but they must of had some smaller barrels still that slipped through , I have only used a micrometer on end of barrel and it’s definitely smaller than .323

Not all you read about the 8x57 is based on fact - aAmerican gun writers have a lot to answer for. I have a 1920s (probably) Kettner 8x57 barrel fitted to a Brno action, it slugs at .320 and shoots just fine with .323 projectiles (and factory ammo). An 8x51 has a .319 bore and shoots 323s as well, althoughits much more accurate with .320/321s . And I have a std 323 one.

My understanding is that the change in proof laws meant that rifles chambered in 8x57 after WWI had to have a throat that would safely allow them to shoot all projectiles. This the concept that is beyond the understanding of many american writers. Next time I stumble accross an authoritative affirmation of this concept I must properly reference it!

However Quickload (developed and owned by a German) says there are two versions of the 8x60, one at 318 and an "S" bore one at 323.

The move to .323 happened in 1905, but gunsmiths carried on using .318 bores for decades after. Apparently Sako and FN did it right into the 50's, but that's internet forum information, I haven't read anything more definitive on that.

Fingers crossed its .323 though. I had Commission 1888 rifle about 8 years ago and managed to get some .318 200gr bullets direct from Woodleigh, but they said it was a once off and they don't usually ship directly to customers. I didn't end up using any of them and eventually sold them on trademe after 6 months of listing them!

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Originally Posted by -BW-

I haven't yet devised a method of balancing a water filled case on the scales without it falling over. I will consume some more beer tonight and see what I can finagle.

Edit : Ok I just needed more beer to steady my hand. I got it to balance eventually.

Case weight : 176.5gr
Case with water : 243.7gr
Water : 67.2

Attachment 200609

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I don't know if you saw my edit Tentman but I persevered and figured out the magic of balancing. I guess it just required more effort!

Here is some Q/L data for 760:

Cartridge : 8 x 60 S
Bullet : .323, 150, Hornady SP 3232
Useable Case Capaci: 66.315 grain H2O = 4.306 cm³
Cartridge O.A.L. L6: 3.291 inch = 83.59 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Winchester 760

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 74 48.00 2229 1655 22000 6440 75.4 1.565
-18.0 76 49.20 2286 1741 23356 6699 76.9 1.527
-16.0 78 50.40 2343 1829 24798 6958 78.4 1.490
-14.0 80 51.60 2401 1921 26333 7216 79.9 1.454
-12.0 82 52.80 2460 2015 27967 7472 81.4 1.419
-10.0 84 54.00 2519 2113 29709 7725 82.8 1.384
-08.0 85 55.20 2578 2214 31564 7976 84.2 1.351
-06.0 87 56.40 2638 2318 33542 8222 85.5 1.317
-04.0 89 57.60 2698 2425 35654 8463 86.8 1.285
-02.0 91 58.80 2759 2535 37908 8698 88.1 1.252
+00.0 93 60.00 2819 2648 40317 8926 89.3 1.216
+02.0 95 61.20 2881 2764 42891 9148 90.5 1.182
+04.0 97 62.40 2942 2883 45649 9361 91.6 1.148
+06.0 98 63.60 3004 3005 48602 9565 92.6 1.116
+08.0 100 64.80 3065 3130 51769 9759 93.6 1.085 ! Near Maximum !
+10.0 102 66.00 3127 3257 55169 9942 94.5 1.054 ! Near Maximum !

And here is the prediction for your 45 gn of 760 load:

Cartridge : 8 x 60 S
Bullet : .323, 150, Hornady SP 3232
Useable Case Capaci: 66.315 grain H2O = 4.306 cm³
Cartridge O.A.L. L6: 3.291 inch = 83.59 mm
Barrel Length : 24.0 inch = 609.6 mm
Powder : Winchester 760

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms


+00.0 70 45.00 2091 1456 18956 5795 71.5 1.662

The load/velocity "match goes some way to validating the rest of the table above. I'd be very careful about working up but the 8x60S is no pussycat! And 760 suits it well.

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Originally Posted by Lucky

I have a 8 x 60 that I have not shot yet , need to slug the bore though as i think it’s a .318 bore which really sucks

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If it is .318 I have quite a few 318 projectiles which I can spare....

Awesome data thanks man. I didn't think I would have to go up to 55gr to get 2500, but I will plan out my working up loads accordingly.
I can't imagine how much of a shoulder thumper it will be with 60gr!

Im running my 8x57 Model 21 with the very slim Kettner barrel (so its a very light rifle) with 170s at 2680 and its very nice to shoot. Its one of the few rifles I have that like (in terms of accuracy) to be run "hot" - not that this is a hot load, it was just as far as I was comfortable to take a very slim barrel of unknown provenance.

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Originally Posted by Allgood

If it is .318 I have quite a few 318 projectiles which I can spare....

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Definitely keen on those , need to get the bore measured properly first though which I admit is above my pay grade , i believe you can swage down a .323 bullet as well as another option , sorry getting off the original thread topic here

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Originally Posted by Lucky

Definitely keen on those , need to get the bore measured properly first though which I admit is above my pay grade , i believe you can swage down a .323 bullet as well as another option , sorry getting off the original thread topic here

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When I measured my m1888, I just pushed a cast lead .323 bullet down the bore with a cleaning rod. Just be sure to drill a small hole in the back of the projectile to centre the cleaning rod so it doesn't scratch the bore, and cover the end of it with some cloth so lead doesn't get stuck in the thread. Then you can use a micrometer on the bullet.

my Sako 8x60 (note not labelled as 8x60S) was definitely .318 bore

Second round of testing showed somewhat disappointing but predictable results.
I tried batches of 3 rounds at 1gr increments from 47gr to 52gr.
The chrony was being temperamental AF so I only got a few readings, but enough to tell me that 52gr was only nudging just under 2400fps. Accuracy was in the range of 2.5" at 100 so close enough for government work, although I was hoping for better based upon the nice group I shot at 50m with the 150gr interlocks.
Recoil was still pretty mild at that load.
Looks like I have a few more steps to go, perhaps 55gr and beyond.
Time to brew up another batch from 53-58gr. I feel like I should be reaching 2800 at least, since the 8x57 can achieve that with 150gr
Accuray

your recoil with a 150grn projectile shouldnt be huge.....even a .270win pushing out a 150grn pill at high 2000s mark isnt overly nasty,and your rifle will do so with a hell of a lot less effort as barrel id wider so pressure will be less,bearing surface will be much less,equal and opposite reaction and all that jazz....
a hot 150grn load in a 30/06 is less pushy than in a .270w so yours should be less still.

about the bore size thing......look at the wee 7.62x39mm with its .308 or .310 or .312 options.....so 4 thou difference and it still safely handles them all,at worst you would have 5 thou difference and your bore being loads older is possibly worn????

True, felt recoil won't be any worse than the 8x57 until I push the 8x60 to its limits, which I probably won't do. I'll be happy with x57 equivalent. I did think that those loads may be a few hundred fps higher than that though. I underestimated what all that extra case capacity would do to lower the velocity when its not being used.

Today’s testing results were mixed. A bit of scope coming loose and a bit of erratic chrony numbers.
I have settled on using 57gr of 760, giving around 2600fps with 150gr Sierra SP.
Recoil is definitely getting snappy.. I think this load will be plenty enough to knock something over.
I may experiment with some different bullets though, I think accuracy could be better.