Problem with 8MM Cast Bullets

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tkcomer

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I have an old K-98 8MM Mauser. The barrel slugs out at .317/.323. The barrel is shiny with nice grooves in it and a nice crown. I bought some 170gr non-checked, flat based bullets from Hunter's Supply sized at .324. I'm shooting low power loads with Unique. With the bullets seated just above the first lube groove, the OAL length is 2.746. Max length for this round is 3.250. Now then, the bullets are shotgunning out of this barrel. Can't even begin to stay on an 11x8” sheet of paper at 25 yards. I've tried two loads so far. 14grs and 13grs of powder. Max is 17grs. There is zero leading in the gun. In fact, it's amazingly clean after the 20 round sessions. It acts like the bullets are too small and are scooting down the barrel, but I would expect to see leading if that were happening. To the cast shooters out there, any idea of whats going on?
 
They don't advertise the hardness, but I can't scratch them with my fingernail. My 30 caliber Laser Cast bullets are too hard for my Win 94 and low power loads. I get leading in the first few inches of the barrel, but they still shoot great. That's what's puzzling me about this gun. No leading at all. None. My next step is to load them at 10grs and hope they get a grip on the rifling.
 
Well, I tried the 10gr loads at 33 yards. Better, but still wildly inaccurate. You can see the results here: http://www.pixagogo.com/5724124248 The last two went under the box. STILL no leading whatsoever. But now I see powder flakes in the barrel. I was able to keep most on the paper this time. Should I go to 9grs of powder? Or should I bump them up to max and see what they do?
 
Don't know, I'm at work without access to books. Seems like your max for Unique is a bit much, but who knows. I normally shoot between 8 and 9 grains of Uniquie out of my 303 Savage for a 165gr cast bullet. I have no idea what your case size is or anything else, and it's dangerous to guess. The real way to do this is start low and work your way up. So far you've started at 14, moved to 13, now to 10. I dunno. I would think 12 is about max, but like I said, I don't have access to any guides right now. You really need to look at the pressure of those loads. Where are you getting them from?
 
The Lyman Cast Bullet Book says a minimum of 13grs and a maximum of 17grs for a 181grn gas checked bullet. Since mine is a non-check design, I “figure” I shouldn't run them that hard. The fact they got better at 10grs seems to indicate I may need to back down more. But still, shouldn't these bullets lead if I'm pushing them too hard?
 
Wrong pressure and bad fit will cause leading. Determining wrong pressure means comparing the BHN to the pressure of the load.
 
If velocity is 1600fpf and up with no gas check, I would suscpect the problem to lie therein.

I have good accuracy in my MN and GC 50/50 WW/lead with 12.5 grains of Trail Boss. Try som TB and check it out.
 
Sounds like your bullets are the right size and hardness. Perhaps your velocities are just to slow to stabilize. You’re not seeing ANY leading, so this would support the right size/low velocity theory. Try something a little hotter: 15, 16, & 17 grain of Unique. Stock military Mausers have long barrels, that creates a lot of drag on tight fitting slugs, and with light loads there's limited powder volume to propel them.
 
Ok, I'm home now and have some books to work with. So...

Neither the regular Lyman nor the Cast Bullet Lyman books show any pressure ratings at all for the 8mm Mauser. So that's a dead end. The 8mm Mauser case capacity is 3.69cc and the 308 Winchester is 3.43cc and that's close enough to use.

The Lyman Cast book shows 178gr bullet and 10gr of Unique for the 308 produces 23,400 CUP of pressure. 27,000 CUP is about as high as you want to go with a bullet of 18 BHN. We don't know what BHN your bullets are, but lets say they are around 18. You said 10 worked better, and for the best accuracy, you want to go as close to, but not over, the max of 27,000.

With that information, I'd say try 10.5, 11, 11.5, and finally 12gr of Unique. If we're right with the BHN, each set will be a bit more accurate than the last until we go over. When we go over, accuracy goes to the dogs. We know that 13 is too high, 10 is OK, and unless you've got really soft cast bullets, the prize will be somewhere between 10 and 13.

Good luck!
 
Sounds like your bullets are the right size and hardness. Perhaps your velocities are just to slow to stabilize. You’re not seeing ANY leading, so this would support the right size/low velocity theory.
Click to expand...

That doesn't explain why 10 grains did better than 13 and 14, though, does it? Anyway, more pistol powder will create more pressure, not much more speed. More SLOW powder would create more speed and not so much pressure. If he did need speed, and I'm not sure he does, he'd need something other than Unique.
 
So, do I need to slow these down or speed them up? The 10grs of Unique didn't do THAT much better. I was just able to keep more of them on paper.
 
I would be cautious about using under 10gr of Unique due to the volume of the 8MM case. I'm guessing that you're getting around 1400 +fps with 10gr and 170gr cast bullet. Inconsistent ignition using under 10gr of Unique, could stick a bullet.

It's hard to say why your not getting more accuracy from that rifle with that bullet, it could be the bullet to barrel fit, maybe inconsistent ignition, I don't know.

As Palehorsman mentioned, Trail Boss's higher volume may help with consistency between shots.

I do know that Unique has been used for decades to shoot reduced cast bullet loads accurately, out of all kinds of rifles.

I have the Lee Karabiner mold that drops a 225gr gas check bullet of .327 diameter that I have done some tentative testing, using IMR4227 and IMR4198 powders. I do need to get back to that sometime.



NCsmitty
 
I do have IMR 4227, but haven’t seen load data with it for this caliber. My only other choice at this time would be with Ramshot's Tac, which would be way to hot for this bullet using .308 data. I did notice at 10grs some loads fired “weak”. Do people think this is a bad powder choice? Do I need more pressure? Just trying to find out what direction to go.
 
I gave you my thoughts already. I also agree with NCSmitty. There's no need to drop less than 10. Your sweet spot is going to be somewhere around 11.5 or so, best as I can figure. But the way to find it is by 1/2 grain increments. Jumping around willy nilly is a bad idea and not productive most of the time.

Really no kidding go take a look at that link I gave you. They know a lot about shooting cast bullets. Read up on it and then decide for yourself which way to go. That's the very BEST advice I can give you.
 
Low Density Makes Me Nervous...

I've had good luck with 2400 in my 30-06s & the Lyman 170 gr gc. 03-A3 will drop them into 3" easily at 100 yds with absent recoil, or dang near it. I use 2400 in 303s, too, but haven't yet loaded 8x57s with it. Ought to do well, nonetheless. Unique is a little too bulk-less in those big cases and I haven't used it for them in years, though that's not to say it can't be - it just makes me nervous... :scrutiny:
 
Your charge is TOO low. You are not pushing hard enough to stabilize the bullet. Don't worry about leading at first, work UP until you either get excessive leading or your accuracy is best.
Just because you don't have a gas check does not mean you must go slower. With proper sizing, lube, and alloy, you can do without a gas check. The right lube is important. I know I've seen a White Label lube that the yadvertise 2700 fps with no leading, but they don't say if it is gas checked or not.

"The Load" iirc is 13 grains of Red Dot and a 30-caliber cast bullet.
 
Let me ask this. Is it possible for bullet/gun combo that's shooting this badly to ever have acceptable accuracy? Would the right powder/speed every bring this combo together? I'm going to try half grain increments starting at 10.5grs, but I'm highly doubtful this combo will ever shoot straight. I've seen this once before in a 44 mag levergun. But I was using .429 plated bullets, so there was no leading there either. They also threw a shotgun pattern, but nowhere near this bad. The bullets were too small for the gun. A swap to .431 Laser Cast bullets solved the problem. That's what makes me think my bullets are too small. But the lack of leading is throwing me off.
 
Buy a Lyman "M" die. Get a larger bullet diameter, at least .002" over groove diameter. Your bore may look fine to you, but the 8mms i owned had the throat completely shoot out of them. With no support of the round at the nose , accuracy was bad. Try seating your bullets to a longer COL, hit the rifling if possible, may not still fit you magazine. Just neck sizing your brass may work also. I dont think Unique is the problem with that bad an accuracy.
 
That was another thought. Too long a bullet jump. With a bullet barely in the case, it measures 3.012". Not much I can do about that. No way that I can seat to the lands with this bullet.
 
It's official. These cast bullets aren't going to do good through this gun. You can see the results here:http://www.pixagogo.com/5724124248 It's the last three at the bottom. Click on a pic to make it bigger, then click on original at the top to blow that up. I tried bumping up the load to 15grs Unique. Wildly inaccurate. Then I tried my new powder I ordered, 12grs of Trail Boss. Still inaccurate. But I kinda like this stuff. Fills the case up and it seems the kick was less sharp than Unique. Then I tried 12grs of Trail Boss with 198 Privi FMJs. I was kinda disgusted by this time so I didn't really try that hard, but eureka, the gun printed a group. The only bad thing is, the front sight on the gun is already drifted way left. Not sure I can correct this. I'd be afraid to drift it further. Just thought I'd let the gang in on my results.
 
. The only bad thing is, the front sight on the gun is already drifted way left
Click to expand...
The group i see(last photo) is hitting to the right of the point of aim. Move your front sight to the right. Your group will then move left.
 
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