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Discussion Starter · #581 · (Edited)
I found a clue as to why Hornady's new 100 CX is not expanding as well at low speeds as the GMX it replaced. There is a crimp on the ballistic tip as seen in the image below.

Contrary to marketing hype, a ballistic tip does not promote bullet expansion - it impedes it. Monolithic bullets with BTs have to have a larger expansion cavity behind the tip to promote expansion. I've tested bullets with their BTs removed and they expand more and to larger diameters without the tip.

(31) 6.8 SPC Bullet Performance | Page 11 | 6.8 SPC Forums (68forums.com)

In this situation, I was trying to remove the CX's tip for the next test series, but it wouldn't pull out. Closer inspection found that the BT had a crimp around it. I have deformed monolithic bullets before trying to seat them on compressed loads. I ended up testing them just to see what happened and their expansion was impacted/deformed.

When a bullet impacts an animal, it has to transition into a denser medium. If the bullet doesn't immediately expand to a larger diameter and shorten in length, it becomes unstable and yaws. You can see from the recovered bullets below that they were slow to expand then yawed.

I will continue to test. But beware, the CX appears to have lost at least 500 fps of slow speed expansion capability and may behave as an FMJ at 200 yards and beyond.

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Discussion Starter · #582 · (Edited)
I went to a Scheels in Colorado to check-out new boxes of Hornady CX factory ammo to see if those bullets had a crimp on the ballistic tip. I was only able to find 6.8mm SPC 100 CX and 7mm-08 139 CX ammo on the shelf. I open the boxes and found there was no crimp on the ballistic tips. This is good news! However, it raises the question if the crimp was part of initial production and then removed. When I get back home, I will check the lot of the 100 CX components I have so others can check their supply. I will also contact Hornady to see if the crimp was part of an initial production and then removed. It will interesting to see if they reply as there has been no response to my message regarding the error in the 6.8mm SPC 100 CX’s posted BC.

100gr CX Component Lot # 2212103

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Discussion Starter · #583 ·
Several of us recently picked-up the 6.8mm 85-grain frangible flat-based lead-free RRLP bullets on close-out at MidwayUSA this past summer. RRLP stands for “Reduced Ricochet Limited Penetration.” RRLPs were originally designed for military and tactical applications in close quarters, urban combat environments. According to Barnes, their RRLP bullets can also be used for shooting steel targets, competition, plinking, hunting, and personal/home defense.

I was hoping this bullet might be usable for shooting varmints and hogs near buildings with reduce potential for ricochet. I conducted a low- and high-speed terminal performance test just to see how the bullet reacted and get an initial look at what it could do. Based on this limited testing, I would expect limited penetration on a hog and over penetration on raccoon. I am not sure how I will use this bullet. Here is a summary assessment.

  • The RRLP is an OTM not a hollow point. OTMs typically yaw then fragment by breaking in the middle of the projectile. The RRLP doesn’t appear to be any different in this aspect. I will measure the copper jacket thickness when I return home.
  • The core is a compressed metal powder with a silvery-exterior. You can see cracks in the compressed powder core as the bullet yawed and started to break-up during the 1900 fps terminal performance test. The bullet over penetrated through the phonebook and 6 magazines.
  • The high-speed test did not have much water jug reaction, leaving a finger-size hole through the phonebook, no indication of a significant temporary wound channel, and penetrated 3 magazines deep. The pieces recovered from the bullet trap are shown in the image below.
  • This bullet is designed for reduce ricochet in urban environments so breaks apart when hitting hard surfaces like sidewalks, road surfaces, and brick/rock walls. Hitting ground in the country may not reduce ricochets.

Please share any experiences you may have had with this bullet. It is unlikely that I will accomplish further testing.

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Discussion Starter · #584 ·
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spyglass, I did a preliminary test with the 150gr Federal Round Nose (RN) using the alternative bullet trap (wet soaked newspaper) a couple of weeks ago. I was doing a min-max velocity test with the two 100gr GMXs I had left. When testing the .223 55gr GMX, I found that the GMX bullets were always loosing their pedals going through the phonebook and had to switch to using the alternative bullet trap. This experience made me question whether this was the case with the 6.8mm 100gr GMX which had also lost pedals in prior testing. Testing the 100gr GMX in the alternative bullet trap did show near perfect weight retention at high energy levels (no pedal loss) and also verified successful expansion in the 1600 fps range. Measured expansion between both bullet trapping methods was within 0.015" which is essentially the same result.

I also wanted to see how the 100gr AB would do when driven at higher velocities using the alternative bullet trap. Weight retention was identical to prior tests using the water jug/phonebooks and expansion was within 0.010".

To answer your question, I had one 150 RN remaining after a CFE powder vs velocity ladders so launched it into the alternative bullet trap. When recovered, the 150 RN had mushroomed nicely and showed good weight retention. It's copper jacket was thin and peeled away like the 130gr Rem CoreLokt. I will accomplish a full test series on the 150 RN but it will be a couple of months before I get back to the range. This will have to do for now.

From 6.8 SPC II - 18" ARP 1:11 barrel (65F)
150gr Federal RN - 2260 fps (31.3gr CFE223) [BC 0.261]

Caution - these loads worked in my rifle but this is no guarantee that they will work safely in yours.
Go to the First Page for Quick Links to all the bullets tested


Have you thought about testing the new Sierra Game Changer bullets?
 

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Discussion Starter · #586 ·
Sierra's GameChanger bullets are their new Tipped GameKing bullets. For 0.277/6.8mm, they only have 140 and 175 grain versions which are not suitable for the 6.8mm SPC. I did test 130gr GameKings and found they were designed for 270 Win velocities.

 

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spyglass, I did a preliminary test with the 150gr Federal Round Nose (RN) using the alternative bullet trap (wet soaked newspaper) a couple of weeks ago. I was doing a min-max velocity test with the two 100gr GMXs I had left. When testing the .223 55gr GMX, I found that the GMX bullets were always loosing their pedals going through the phonebook and had to switch to using the alternative bullet trap. This experience made me question whether this was the case with the 6.8mm 100gr GMX which had also lost pedals in prior testing. Testing the 100gr GMX in the alternative bullet trap did show near perfect weight retention at high energy levels (no pedal loss) and also verified successful expansion in the 1600 fps range. Measured expansion between both bullet trapping methods was within 0.015" which is essentially the same result.

I also wanted to see how the 100gr AB would do when driven at higher velocities using the alternative bullet trap. Weight retention was identical to prior tests using the water jug/phonebooks and expansion was within 0.010".

To answer your question, I had one 150 RN remaining after a CFE powder vs velocity ladders so launched it into the alternative bullet trap. When recovered, the 150 RN had mushroomed nicely and showed good weight retention. It's copper jacket was thin and peeled away like the 130gr Rem CoreLokt. I will accomplish a full test series on the 150 RN but it will be a couple of months before I get back to the range. This will have to do for now.

From 6.8 SPC II - 18" ARP 1:11 barrel (65F)
150gr Federal RN - 2260 fps (31.3gr CFE223) [BC 0.261]

Caution - these loads worked in my rifle but this is no guarantee that they will work safely in yours.
Go to the First Page for Quick Links to all the bullets tested


:unsure:I just noticed the 100gr Accubond did not form a flat disc like before. I wonder if the 110gr AB would form a curl too in this media? The GMX 1670fps is not too bad. Too bad they stopped making them for the defective CX.
 

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Discussion Starter · #588 ·
WV, the 100 AccuBond is still a flat, hammer-like mushroom compared to the other two bullets in the test (100 GMX and 150 RN) in the picture. Also consider that the test you referenced was a max speed test the was 350 fps faster than the original 100 AB test done at 100 yards.
 

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I went to a Scheels in Colorado to check-out new boxes of Hornady CX factory ammo to see if those bullets had a crimp on the ballistic tip. I was only able to find 6.8mm SPC 100 CX and 7mm-08 139 CX ammo on the shelf. I open the boxes and found there was no crimp on the ballistic tips. This is good news!

100gr CX Component Lot # 2212103

View attachment 77672
I bought 4 boxes of Hornady 6.8 SPC CX yesterday in South Georgia lots 949179 and 4872223. No crips on the tips on any of the bullets as well.
 

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Discussion Starter · #591 · (Edited)
The 8.6 BO is an interesting beast. Faster barrel twist rates significantly benefit monolithic bullet expansion. Below is a graph of .224 55gr GMX expansion at different twist rates and Kinetic Energy (KE) that was posted earlier in this thread. I tested 62gr GD and 64gr BPB lead-core bullets, but they were unaffected by different twist rates and came out of the bullet trap looking like clones.

The 8.6 BO's 1:3 twist would create massive rotational forces and associated bullet expansion, especially with the Barnes TSX/TTSX bullets I saw in the Faxon load data. I only found one subsonic hunting bullet from a quick on-line search that was from Gorrila Ammo. The subsonic load data I saw was all for target bullets.

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The 8.6 BO is an interesting beast. Faster barrel twist rates significantly benefit monolithic bullet expansion. Below is a graph of .224 55gr GMX expansion at different twist rates and Kinetic Energy (KE) that was posted earlier in this thread. I tested 62gr GD and 64gr BPB lead-core bullets, but they were unaffected by different twist rates and came out of the bullet trap looking like clones.

The 8.6 BO's 1:3 twist would create massive rotational forces and associated bullet expansion, especially with the Barnes TSX/TTSX bullets I saw in the Faxon load data. I only found one subsonic hunting bullet from a quick on-line search that was from Gorrila Ammo. The subsonic load data I saw was all for target bullets.

View attachment 78150
The 1:3 twist causes problems with expanding projectiles.
They spin so fast it tends to expand the tip at exiting the barrel. Especially with a monolithic projectile.
 

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Discussion Starter · #594 ·
The fastest load listed with the longest barrel was 2400 fps equating to 576,000 RPM. I saw only 5 bullets listed for 8.6 BO supersonic operation. Note, some of my Valkyrie loads are running 377,000 RPM. The 8.6 BO subsonic's RPM is 240,000. That is well within most cartridges' supersonic rotation but, a bullet would have to be specifically designed for that environment because monolithic subsonic bullets are typically made with softer copper.

It would be best to open up a specific thread for further discussion regarding the 8.6 BO.
 

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It is important to note that the amount of centripetal force increases linearly with increase in diameter, but in a squared fashion with RPM's. In other words the combination of larger diameter increases the force trying to open the tip, but the increase in rotational speed much moreso.
 

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Discussion Starter · #596 · (Edited)
Hornady 100gr CX Update
Note, this is testing of bullets sold as a component. Performance of factory ammo has not been verified.

I have contacted Hornady regarding both the incorrect BC and lack of low-speed expansion of component bullets from Lot #2212103. Regarding the advertised BC of 0.262 vs 0.303 measured, Hornady said they have the "top of the line Doppler Radar" to determine BC. Read between the lines, Hornady doesn't make mistakes and todate made no effort to double check their data.

Regarding the lack of low-speed expansion of the component 100 CX bullets, Hornady said what I called a crimp was a finishing mark that had no effect on the bullet's expansion. I've had similar marks on copper bullets from seating stems caused by cases with too much neck tension or compressed loads disrupt expansion. Hornady did offer to give me a return authorization to send the bullets back for them to test. I have accepted but have yet to receive authorization.

To learn more about the CX's low-speed expansion potential, I removed the ballistic tip and shot it as a hollow point. The results are presented below. While the CX's (Lot #2212103) minimum velocity expansion has yet to be determined and is faster than 2200 fps; with the ballistic tips removed, the CX-minus-BT's minimum expansion velocity is less than 1600 fps ... a 600+ fps difference. Any manufacturer that claims the BT promotes bullet expansion is likely spewing just marketing hype. I have tested several other BT bullets that all expanded more with their tips removed but not this much. I found the CX's BT is a harder plastic than the GMX's it replaced. I also was unable to remove the entire BT and had to push the stem of the tip into the expansion chamber. It was held so tightly by the "finishing mark" it couldn't be removed as I've been able to do on other bullets.

I will keep you advised as the situation evolves. I need to buy a box of factory ammo and test it to verify if there is any difference in terminal performance. This is too big an issue to not ensure it is fully understood.

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Hornady 100gr CX Update
...
I will keep you advised as the situation evolves. I need to buy a box of factory ammo and test it to verify if there is any difference in terminal performance. This is too big an issue to not ensure it is fully understood.

View attachment 78234
Thanks for the update. According to the ballistic tables I've run on the factory CX the no expansion threshold is starting at or before 100 yards. That ain't good. That would explain, assuming the factory ammo bullets match the ones you have, the lack of stopping power I experienced. I'm particularly interested in the test results of the factory ammo so please do a test on it.


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Discussion Starter · #598 ·
I've been unable to find a box of CX locally. There are some on-line but shipping make the cost soar. Would anyone be willing to pull five (5) 100 gr CX bullets and contribute them for testing? If so, please send me an IM. Thanks for the consideration.
 

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Hornady 100gr CX Update
Note, this is testing of bullets sold as a component. Performance of factory ammo has not been verified.

I have contacted Hornady regarding both the incorrect BC and lack of low-speed expansion of component bullets from Lot #2212103. Regarding the advertised BC of 0.262 vs 0.303 measured, Hornady said they have the "top of the line Doppler Radar" to determine BC. Read between the lines, Hornady doesn't make mistakes and todate made no effort to double check their data.

Regarding the lack of low-speed expansion of the component 100 CX bullets, Hornady said what I called a crimp was a finishing mark that had no effect on the bullet's expansion. I've had similar marks on copper bullets from seating stems caused by cases with too much neck tension or compressed loads disrupt expansion. Hornady did offer to give me a return authorization to send the bullets back for them to test. I have accepted but have yet to receive authorization.

To learn more about the CX's low-speed expansion potential, I removed the ballistic tip and shot it as a hollow point. The results are presented below. While the CX's (Lot #2212103) minimum velocity expansion has yet to be determined and is faster than 2200 fps; with the ballistic tips removed, the CX-minus-BT's minimum expansion velocity is less than 1600 fps ... a 600+ fps difference. Any manufacturer that claims the BT promotes bullet expansion is likely spewing just marketing hype. I have tested several other BT bullets that all expanded more with their tips removed but not this much. I found the CX's BT is a harder plastic than the GMX's it replaced. I also was unable to remove the entire BT and had to push the shaft of the tip into the expansion chamber. It was held so tightly by the "finishing mark" it couldn't be removed as I've been able to do on other bullets.

I will keep you advised as the situation evolves. I need to buy a box of factory ammo and test it to verify if there is any difference in terminal performance. This is too big an issue to not ensure it is fully understood.

View attachment 78234
This is exactly why I do not use a tip in either of the CBB MKZ's for 6.8.
Tips in copper monolithic projectiles inhibit expansion.
Also why we do not use tipped projectiles in 6mm, 6.5, 300 BO or x39
 
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