Cavity back bullets

[Huntchic]

Just got my hands on some 105 and 118 grain pills.
im excited to give these a try since my past experiences with different mono bullets in other calibers ( very limited) haven’t done well on critters. I’m hopeful these will change that and going to give them an honest try.
I have TAC , X Terminator and CFE 223 on hand.
I'm going to try CFE223 first. There is limited info on loading the 105 and 118 grain bullets so can someone who has used these or currently use these give me some idea on what velocity from an 18” barrel at different grain loads or some insight of what you have seen with these powders. Im trying to come up with a 105 bullet load for upcoming whitetail but only have a few of these to work up n hopefully try out terminal results on a deer or two. I have looked at other mono manufacturers data like Barnes but rather have something with the actual cavity backs like velocity at different loads and what you found as a max loading.

grateful on any insight with this.

[grayfox]

This will be my honest impressions (I don't know how to give any other), and is not intended to disrespect the CBB guys, who are doing or trying to do a good job (their loads come from Druid hill which has a pretty good rep on here).
I got a box of the 105's, the 118's, and a box of the 105 ammo/Grendel for some evaluation of my own.
First, the ammo, on the website (I will attach a screenshot) it is advertised as 2750 from an 18" barrel. I did not get that type of MV from either my 22" preferred barrel (I list these b/c they are really good barrels), which showed 2267-ish, nor from my 20" lilja barrel, which gave 2639 MV. The ammo showed nothing to write home about, as far as accuracy, although it was -- I would say -- average from my bench position, from guns that will do 0.75" (AR-20) and 0.5" (22", howa); best I showed was about 1.35"/100 yds (eyeballed on a grid, not measured b/c I had other loads doing much better). The SD's were also not spectacular, which is a key determinant for me, as it shows me how repeatable the ammo is, and how well it would continue to group downrange. But this is just the ammo, perhaps a handloader could and should do better... only I would be skeptical if you ever get 2750 for the 105 ammo in an 18" barrel. I didn't come close until I used my 22" and even then it was a bit short.
Handloading this ammo, sorry I don't have any data for the grendel, I actually was trying it out for my 16" "mini-creed" ranch in 6.5 Creedmoor. I didn't get either the 105 or the 118 to show anything I could count on, but my testing so far was sort of limited and my timeframe is short (deer season fast approaching)... maybe later on, who knows.

As to workups for you, since there isn't any mfr published load data (that I could find), you can take the approach of working up using something close and similar in lead-free, in this case I would suggest the 100 gr Barnes data, work up like I say. Expect MVs to be about 50 ft/sec less than a comparable load in the 100 gr Barnes (I use ttsx but their load data is all the same). As an example here from real life, in my 20" AR I typically get the 100 ttsx to go 2680-2700 while <52 ksi... so I would expect the 105, in my 20", to fetch about 2630-2650. Which is what the factory ammo did, so I take that as a sort-of confirmation that I am in the right ballpark.
What does this mean for an 18" barrel - well, expect an MV around 2610-2625 at best. From your powders listed I would suggest the Xterminator first, when I model the TAC and the CFE for 18" (I have shot the ttsx, 20" AR, with CFE and again, not the greatest) their powder burn rate is lower than desirable (CFE about 82% burn), (Tac a little better at 91%), both TAC and Xterm gave me an estimated 2610-2630 in 18" barrel. Xterm gave 100% burn, yes it is a fast powder but it suits the barrel and still gives an expected max MV in my range.

Ballistics. Hopefully the BC numbers given on the site are more accurate than the MV, they quote 0.480 for the 105... So with an MV of ~2625 you would be looking at an effective range of ~200 yds -- that's using criteria I would use, others may have different criteria. I will also attach a ballistic screenshot. If you wanted to go all the way down to 1000 fpe, you could take it out to 300 yds, but until I can get some independent verification of the BC, I'm a little hesitant to go that far. 200 yds, with an accurate (SD <10 and group <1.00"/100) in my gun, would be ok for me.

So that's pretty much my take at this point, a combo of actual and analyzed results... but that's IMO for what it's worth.

CBB-105Ammo.png
CBB-105Bullets.png
CBB-105-Ballistics.png

[Huntchic]

Gray fox that was exactly the info i was looking for. I looked at data on Barnes and couple others in the 100- 115 grain range to get an idea of the load ranges. Ive had good success using X- Term in 5.56 and 300 Blk so thought it would be a good candidate to try. I have looked for days for data and pretty much found very little. The accuracy is going to be most important to me. If they wont group 1/2 to maybe 3/4 MOA i wont be happy. lower Velocity doesn't surprise me because most mono's in that weight class seemed to run slower based on load data but i thought perhaps the "cavity" might somehow give it more speed. Ill give them an honest try and see what they do for speed and accuracy. As you know ive got an excellent 129 ABLR load and a very accurate 125 Partition load also. Just thought i would try the 105's but was using 2725- 2750 fps ballistic calculator. ultimately if i cant get the accuracy then nothing else will matter to continue testing.
Thanks for your replying to me, I was starting to think maybe nobody had anything to participate with. I appreciate honesty above all else and happy you give it.

[LRRPF52]

We have a Custom Search Engine for the site that has 50+ hits (I stopped counting.) for Cavity Back Bullets, including independent performance in gel, performance on game in the real world, load data, muzzle velocities, expansion characteristics, etc.

The 105gr MKZ is a harder bullet than the 118gr, so it likes more impact velocity for expansion.

The 118gr will expand at lower impact speeds.

You might hit pressure pretty fast with XTerminator and not get the most mv you might be looking for, though the 105 MKZ has a generous pressure relief band on the shank.

Best speeds will come from common ball powders, namely AA2520, BL-C(2), CFE223, and LVR.

[grayfox]

Having a cavity back is a neat idea, and could help in some ways. OTOH, mass is mass, and they have 5 gr more than a barnes... supposing that 5 grs is all pushed out front, above the case rim, the 105 still has some copper taking up space inside the case... and I'm not knocking the space, if there is extra room (for powder) it will be incremental, so the only thing you need then is a powder that suffers from "not enough room" before hitting a 52 ksi max. So it's not like anyone is offering a free lunch so to speak. Still there could be some advantage, I'd like the 100 ttsx better if I could get more speed/ or heavier at that same speed. For barnes the better pill is probably the 115 Tac-tx (which I have and shoot), so maybe the CBB 118 might be workable like the 115 tac/tx... I just didn't get there. CFE did work for the 115, so it could be a go-to for that 118 bullet. just start low and work up. For the 118 I'd say maybe 2430 tops in an 18" barrel, extrapolating from my 115 gr/ 20" loads.

[Huntchic]

Thanks LRRPF52, From what i was told the 105's are now made "softer" Like the 118 grain has been. Claim is both are supposed to expand down to 1500 fps. I was thinking if the 105 could run at about 2600 in the 18" and about 2400 in a 12" it might have terminal results like the 129 ABLR. Gray fox helped with input on some 120 pro hunter work ups and i got very nice accuracy with them but the bc is lower than say the 123 SST however the pro hunter may have better terminal performance at closer range under 150- 200 yards. I was going to try the cavity backs especially the 105"s to see if i can get good accuracy and decent velocity to where they might do as good or better terminally than the 129 from a 12" barrel. I'm going to try both the X-Terminator and CFE223 powders to see which does better.

[CavityBackBullets]

The loaded ammo uses AA2460 for the 105gr and AA2520 for the 118gr.
Velocity numbers are from David at Druid Hill.
I prefer 8208 for the Grendel myself.

You must start with a clean barrel. Because of how soft the copper is compared to any others any copper from other bullets can effect accuracy adversely.
Some barrels dont care, some do. We use C100 copper, most all others use C110 to C145 copper.

The cavity isnt as much about more room for powder as is it is for pressure handling.
It does a bunch of things I have been laxed at doing a write up about.

Like LR said there is quite a bit of data on this site.

One thing I always hear is they are so long.
We have found you can take 90% of the depth of the cavity and subtract it from the projectile OAL when figuring needed twist rate.
Also quickload and comparable programs do not compute properly with loads for CBB's.
This confirmed in a conversation with Litz and real world results.

Isn't it funny how some use 1200 lb-ft of energy as a low point one game. While others use 750 lb-ft of energy.
As well in different comparisons from the same people.

Now after 8 years there is information all over the place as to CBB's effectiveness and accuracy.

Do you have any 8202 to use?
Xterm and AA2520 are the same powder.
223 is a good powder but it will hit pressure faster than others.

[CavityBackBullets]

This will be my honest impressions (I don't know how to give any other), and is not intended to disrespect the CBB guys, who are doing or trying to do a good job (their loads come from Druid hill which has a pretty good rep on here).
I got a box of the 105's, the 118's, and a box of the 105 ammo/Grendel for some evaluation of my own.
First, the ammo, on the website (I will attach a screenshot) it is advertised as 2750 from an 18" barrel. I did not get that type of MV from either my 22" preferred barrel (I list these b/c they are really good barrels), which showed 2267-ish, nor from my 20" lilja barrel, which gave 2639 MV. The ammo showed nothing to write home about, as far as accuracy, although it was -- I would say -- average from my bench position, from guns that will do 0.75" (AR-20) and 0.5" (22", howa); best I showed was about 1.35"/100 yds (eyeballed on a grid, not measured b/c I had other loads doing much better). The SD's were also not spectacular, which is a key determinant for me, as it shows me how repeatable the ammo is, and how well it would continue to group downrange. But this is just the ammo, perhaps a handloader could and should do better... only I would be skeptical if you ever get 2750 for the 105 ammo in an 18" barrel. I didn't come close until I used my 22" and even then it was a bit short.
Handloading this ammo, sorry I don't have any data for the grendel, I actually was trying it out for my 16" "mini-creed" ranch in 6.5 Creedmoor. I didn't get either the 105 or the 118 to show anything I could count on, but my testing so far was sort of limited and my timeframe is short (deer season fast approaching)... maybe later on, who knows.

As to workups for you, since there isn't any mfr published load data (that I could find), you can take the approach of working up using something close and similar in lead-free, in this case I would suggest the 100 gr Barnes data, work up like I say. Expect MVs to be about 50 ft/sec less than a comparable load in the 100 gr Barnes (I use ttsx but their load data is all the same). As an example here from real life, in my 20" AR I typically get the 100 ttsx to go 2680-2700 while <52 ksi... so I would expect the 105, in my 20", to fetch about 2630-2650. Which is what the factory ammo did, so I take that as a sort-of confirmation that I am in the right ballpark.
What does this mean for an 18" barrel - well, expect an MV around 2610-2625 at best. From your powders listed I would suggest the Xterminator first, when I model the TAC and the CFE for 18" (I have shot the ttsx, 20" AR, with CFE and again, not the greatest) their powder burn rate is lower than desirable (CFE about 82% burn), (Tac a little better at 91%), both TAC and Xterm gave me an estimated 2610-2630 in 18" barrel. Xterm gave 100% burn, yes it is a fast powder but it suits the barrel and still gives an expected max MV in my range.

Ballistics. Hopefully the BC numbers given on the site are more accurate than the MV, they quote 0.480 for the 105... So with an MV of ~2625 you would be looking at an effective range of ~200 yds -- that's using criteria I would use, others may have different criteria. I will also attach a ballistic screenshot. If you wanted to go all the way down to 1000 fpe, you could take it out to 300 yds, but until I can get some independent verification of the BC, I'm a little hesitant to go that far. 200 yds, with an accurate (SD <10 and group <1.00"/100) in my gun, would be ok for me.

So that's pretty much my take at this point, a combo of actual and analyzed results... but that's IMO for what it's worth.

CBB-105Ammo.png
CBB-105Bullets.png
CBB-105-Ballistics.png

2267 from your 22in barrel? am I reading that right?

[grayfox]

CBB, my bad... I meant 2667, good catch! From my 22" Howa.

While I might come back to them after hunting season, right now as stated the timeframe is kinda short, so what I could do, was this much.
I had worked, a few years ago, with the controlled chaos bullets, didn't really get what I was looking for there, either, tossed them out.
Nor with the 110 trex, which also have a good rep on here. The tips kept falling out but randomly. (Whether the tip is necessary or not for a mono, I don't know, but I like consistency). I have some of them left, again might revisit later... or maybe not in their case. I'm pretty much 50/50 on them.

And certainly, for the MKZ's this is just one guy's results, one time. Others will doubtless vary. I will update if/when I can return to them.

[Huntchic]

I don’t have any 8202 powder.
Have over 10 lbs of x Term and 7-8 lbs of TAC
plenty of CFE too.
I Think I’ll work first with X-Term per y’all advice and I’ve had good success with X-Term.
I’ve used the search here and over internet very limited info with XTerm , TAC some with CFE and good bit with XBR.
it would be helpful if you had load Data sheet with different powders, minimum and maximum loads showing Velocity at certain barrel length like a 20”.
I actually forgot that XTerm and AA 2520 were same. That might help finding more information. What OAL is the factory loaded 118 and 105? I will check my rifles but being this is first time loading these it would give me a number to check my lengths against to see if I’m in the ball park. Saw many use 45 off the lands but I’ll play with length after doing Ladders.

[grayfox]

The websites discussions and powder load data I have seen say that Accurate 2230 and Xterm are basically twins. Of lately they report that 2230 has a bit more temp control but still basically the same. But do your own research to confirm or adjust this. 2520, the "Camp Perry powder," is a bit more like Varget class (from the burn rates) but does not have the temp stability of Varget. Hodgdon's list:

Xterm1.png

[Huntchic]

Yes i am aware of that information. One of the reasons I use TAC pretty often. They burn closer than X-Terminator does.
I leaning towards using Barns load data for reference. They have reasonable respected data. Im Just not sure about the difference the Cavity makes because i see references to Cavity "Handling" pressure better. Take that as meaning perhaps at the same charge weight the Barnes would have a higher pressure than the Cavity Back at same weight. Also closest Barnes to the 105 CBB is 100 grain TTSX. The 118 gr CBB is between the Barnes 115 and 120 grain. If i plug in the Velocity numbers given by Barnes into Ballistic calculator My current loads for 129 ABLR show more energy at say 100 yards and overall more range distance down to 1000 foot pounds of energy. If the velocity actually matches the Barnes. Actual Chrono data will verify The CBB vs Barnes. Ultimately If the CBB energy runs equal to the 129 ABLR it will come down to accuracy, repeatability (SD) and terminal performance on actual deer. I'm planning on first two deer this year shooting 1 with 129 ABLR and #2 with the CBB. There are 2 of us using 18" Grendels this year so that would give us out the Gate 2 deer with each Bullet to compare. We will be shooting through the shoulder shots on all deer. Depending on the Results I will compare the 12" Grendel with both bullets on a deer also.

[Huntchic]

When i Started on this quest my dream was a aprx. 100 grain bullet expands down to 1500 fps that could get around 1300 lb energy at 100 yds. and hold 1000 lbs energy to 250 from 12" barrel . That would require about 2550 fps out of a 12" barrel. Now that was the dream but I would be realistically good with something close to 1350 at 100 and 1000lbs to 200 yards. I dont plan to shoot the 12" to 250 at a deer size critter but would like to see those kind of numbers and expansion down to 1500fps. I can get all that with a 123 gr SST except i need the bullet to stay together and pernitrate with terminal performance not just pencil like an FMJ.

[VASCAR2]

It seems counter intuitive but in the 12” 6.5 Grendel I think I would lean towards the 129 grain Nosler ABLR (Accu Bond Long Range). The ABLR supposedly expands down to 1300 FPS and has enough mass to get good penetration. From reading on this forum the ABLR has been used effectively from several barrel lengths. I know the muzzle velocity will be lower than other hunting projectiles but it has a good BC and the lower expansion threshold. I haven’t personally tested the ABLR but I can’t hunt medium size game in my state with the 6.5 Grendel.


I checked and the ABLR has a .530 BC. Here is a link to the bullet description.

https://www.grafs.com/retail/catalog/product/productId/25912

[VASCAR2]

Here is a link to the google custom search of the 6.5 Grendel forum. I frequently use this search.

https://cse.google.com/cse?cx=016368947416500061353:paqd_0xcu1o&hl=en