I love that velocity in a hunting bullet. The accuracy... not so much. Hopefully, these bullets will be the perfect mate to the upcoming Howa bolt action.
Testing NEW 6.5mm Cerberus 90 Bullet
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We'll tweak that li'l sumbitch as necessary. Next run — due in just days — is gonna be the brass version, Cerberus 85CZ, so it'll be a whole 'nuther experience, yet again.
Ric, middle bands on C90 are each 0.020 wide, with the rearmost band abutting the boat tail being 0.075. Design is grooves cut into bearing surface like a Barnes, as opposed to a driving band "bore rider" design.:: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets
:: I Drank the Water :: Revelation 21:6 ::
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Bill
Maybe I missed a post in other thread but have you shot a series of groups with a known accurate load? I know you stay on top of these things just wondering if you had anything to compare it to.
ETA: I measured a Barnes 120 TSX and the relief grooves and remaining bands look to all be .069". I don't know if that's something to consider, just throwing it out there. They've done years of research and it may help John as well as everyone else reach their goal a bit quicker.
RichardLast edited by ricsmall; 02-28-2016, 04:02 AM.Member since 2011, data lost in last hack attack
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Guys, need some brainstorming to improve accuracy of these Cerberus bullets. I'm wracking my brain, asking myself, "What could possibly go wrong?" There are many possibilities.
1. Are copper bodies machined concentric?
2. Are aluminum tips machined concentric?
3. Is nose cavity drilled on center?
4. Is tip seated on center?
5. Is tip knocked off center as is rams up the feedramps and slams to a stop in the chamber?
6. Does bullet like chamber?
7. Does chamber like bullet?
8. Is there an optimal seating depth?
9. Is there an optimal — oh, what's the term — front-to-back weight distribution of the material in the bullet?
10. Are the bullets consistent with each other, that is, exact clones?
I ask myself, "Is it problematic that it's a two-piece bullet?" But, then again, other tipped bullets are two-piece, and if they have a lead core, a copper jacket, and a polymer tip, they're three-piece!
Need some theories here, no matter how wild, to help diagnose this. What can be done to improve accuracy?:: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets
:: I Drank the Water :: Revelation 21:6 ::
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Originally posted by BluntForceTrauma View PostWe'll tweak that li'l sumbitch as necessary. Next run — due in just days — is gonna be the brass version, Cerberus 85CZ, so it'll be a whole 'nuther experience, yet again.
Ric, middle bands on C90 are each 0.020 wide, with the rearmost band abutting the boat tail being 0.075. Design is grooves cut into bearing surface like a Barnes, as opposed to a driving band "bore rider" design."Those who sacrifice liberty for security, deserve neither." Benjamin Franklin
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Holding off on the second run of copper. Going forward with the first run of brass. Have mechanized tip-seating method for the brass version, so should be more consistent.
Don't know about the Center of Gravity. I'm lacking technical expertise. Looking at the market, I see CGs all over the place. Lapua's 6.5 100 Scenar, for example, is literally half lead, half empty nose cavity. I know the Cerberus design is more well-balanced than that, with a slight weight bias toward the rear like almost all target bullets.
If we can get the kinks worked out, it's quite possible from a 16-inch barrel we could have a 0.450 BC bullet in copper going 2900 fps and a 0.420 brass version going 2950 fps. I'd feel really good about that.
But we need less than 1 MOA, for sure, and if we got 0.5 to 0.75 MOA from standard reloading I'd be happy to call it done.:: 6.5 GRENDEL Deer and Targets :: 6mmARC Targets and Varmints and Deer :: 22 ARC Varmints and Targets
:: I Drank the Water :: Revelation 21:6 ::
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I think you would be lucky to get those bullets to shoot perfect on your first attempt.A little adjusting of the bands of width and or depth may be required too.How close are the weights of your test bullets?Keep it going,you are on the right track.By changeing from copper to brass construction you are throwing in another variable.
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Originally posted by BluntForceTrauma View PostGuys, need some brainstorming to improve accuracy of these Cerberus bullets. I'm wracking my brain, asking myself, "What could possibly go wrong?" There are many possibilities.
1. Are copper bodies machined concentric?
2. Are aluminum tips machined concentric?
3. Is nose cavity drilled on center?
4. Is tip seated on center?
5. Is tip knocked off center as is rams up the feedramps and slams to a stop in the chamber?
6. Does bullet like chamber?
7. Does chamber like bullet?
8. Is there an optimal seating depth?
9. Is there an optimal — oh, what's the term — front-to-back weight distribution of the material in the bullet?
10. Are the bullets consistent with each other, that is, exact clones?
Item 5: Is there any way to check this?
Items 6-7: Seems impossible to determine at this stage.
Item 8: Quite possibly.
Item 9: You mean, is there an optimal Center of Gravity? That seems possible, too. Might require testing many different variations to find out, though.
I ask myself, "Is it problematic that it's a two-piece bullet?" But, then again, other tipped bullets are two-piece, and if they have a lead core, a copper jacket, and a polymer tip, they're three-piece!
Need some theories here, no matter how wild, to help diagnose this. What can be done to improve accuracy?
2. If accuracy problems persist, alter bullet design. Produce new batch. Test. Repeat as necessary.
ETA: The Cerberus looks like it was made by being turned on a lathe. http://www.65grendel.com/forum/showt...l=1#post126924
Perhaps that manufacturing method can induce slight variations in weight, shape, concentricity?
In contrast, Barnes punches the TSX and TTSX into the desired shape from sized copper slugs.
- https://www.youtube.com/watch?v=aiw5EkqxnQQ
- https://www.youtube.com/watch?v=GCgr8JOde-ALast edited by stanc; 02-28-2016, 11:26 PM.
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Remove the tips and shoot the shank alone. Removes a whole set of variables.
If the shank shoots then the tip is moving the CofG axially in which case the bullet does not stabilize or you have good old fashioned eccentricity.
If the shank does not shoot then the engagement with the rifling or the base if the bullet is not behaving.
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Here is my input on the 90 g Cereberus
All my work was with my 18" Lilja. Max COAL for this chamber is 2.273 for 123 AMAX and 2.250 for 123 SST.
Loads were done with H335 because of my previous experience with down-loading for gels, and all the methods were the same as given in Chapter 6 of the 6.5 Grendel Reloading Handbook Vol 2.
I was a bit conservative on loads because 31 grains of H335 fills the Grendel case to the neck, and the C90s seat significantly into the case. All loads only had one shot due to supply of bullets. The usual disclaimers about load data apply. Start lower than these listed and work up, looking for signs of pressure on primers and case heads.
Hornady brass and REM 7.5 primers. Loaded to 1.667 ogive. It was 76 F today at the range.
28.5 g - 2673
29.0 g - 2759
29.5 g - 2777
30.0 g - 2793
30.5 g - 2855
There were no ejector marks or flattening of primers. Probably could go a bit higher as PA_Allen did.
Now for the gels. I loaded down to give approximately 2250-2300 fps which would be equivalent to what the bullet would be doing at about 300 yards.
First shot was the C90 without tip. It fragmented on impact and the core exited the top of the second gel. My apologies for the bubbles in the gel. The dispersion of fragments was about 3 inches. in diameter and penetrated about 3-4 inches.
Looking at the side of the gel. Bullet entered from right.
The second shot was the C90 with a tip. The tip delayed opening to about 7 inches of penetration. Dispersion was limited to about 1.5 inches. The core exited the top of the second gel.
Looking at the top of the gel. Bullet entered from the bottom.
Now Sneaky had drilled out the hollow core of the C90s to end up with what I will call S83s
Shot without tip dramatically opened at impact with a fragment dispersion of about 6" and frag penetration of about the same. The core travelled 34" and was recovered. Pic below.
Looking at the top of the gel. Bullet entered from the bottom
And finally, an S83 with tip reacted the same. Tip delayed opening to about 7". The tip can be seen in the photo below at about 8.75" facing backward. The core traveled 32" and was recovered. pic below.
There are more fragments created by these bullets than the Controlled Chaos, and they are opening up more at low velocities. see http://www.65grendel.com/forum/showt...l=1#post125242
Sneaky's modifications did help in opening up the C90.
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