How close was these loads to Kaboom???

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Blue68f100

Blue68f100

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Earlier this week I had neighbors over shooting at my range. All was going well till my neighbor chamber some 223R, 68-69gr BTHP Match loads. I had my crony setup but was not sending data to my phone app. Any way the first shot registered 3740 fps out of a 16" NATO chamber 1:9 twist. :eek: I told him to stop and lets see whats up. He fired again still in the 3700 fps range. I told him we need to break those down to confirm the load. He wanted to keep shooting so my neighbor and I backed way off. He shot a total of 5, that were off the charts. The other 5 shot loaded at the same time landed in the 2650 fps which is normal.

He came over this morning and I quizzed him on his loads. What I found out was he substituted Hornady 68gr in place of Sierra. He did not think 0.1 gr lighter would make any difference. He was using 24.5 or 25.4 gr (not sure which one) of CFE-223, 2.250" OAL, CCI 41 primer. The brass was A-USA or PPU. Once I found that out I showed him the 2 bullets side by side. For those who are not familiar with these, the Hornady 68 gr bullet is 0.090" longer than the Sierra 69gr HPBT. Hornady recommends a AOL of 2.250" while Sierra recommends 2.260". My data books does not show CFE-223 powder, but Hodgdon's show it for the Sierra 69gr, 23.5-25.8gr. I normally use Varget with these bullets and the max is 1.2gr higher with Sierra's 69gr max at 26.1gr.

So it appears he just swapped bullets, Hornady for Sierra.

This is a good example why you MUST compare bullet profiles before substituting data.

Can some one please plug these number into Quickload to see how close it was to blowing his gun up.:eek:

Be Safe.
 
I believe you but that seems like an awfully high velocity. I guess I'm no help with an answer, but I will be following this thread cuz it looks like I may learn something.
 
I'm very intrigued as to how you can possibly gain 1000fps from a 223/556. I don't have any neat software but my gut is telling me the chronograph is to blame.

How did the brass and bolt head look?
 
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I would say the chrono readings were off. If he got 3700 FPS with a 68 Gr bullet I can't see how there wouldn't have been some serious pressure signs on the brass.

Can some one please plug these number into Quickload
Click to expand...
I'd love to see the numbers.
 
I question whether a scant .01" difference in OAL would do anything measureable to any caliber? I suspect that factory ammo varies by more than that quite often?
 
Hodgdon Load Data shows for 223 with CFE-223 powder and a 69 grain bullet:

starting load : 23.5 grains - 2788 fps

maximum load : 25.8 grains - 3029 fps

3700 to 3740 fps ??? Something is not right , either the amount of powder , type of powder or chrono numbers ! Hard to tell from here. Start over and double check loads and numbers. .01 difference in OAL should not make a difference.
25.4 grains of CFE-223 should be a safe load but not a 3700 fps load ?
Gary
 
224 bullet bearing surface

The 68 gr Hornady does have a long bearing surface that will raise pressure with the same powder charge, maybe? But adding 1000 fps, i think the chronograph is to blame.
th_BearingSurface_zpsbac6nfsu.jpg
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I don't think you could cram enough of that power in a .223 case to achieve those velocities. I've been loading for a shooting a 220 Swift for 30+ years and can tell you in all certainty that even IT isn't capable of 3700 fps with a 68 or 69 gr. bullet.

Now, apologize to your neighbor and check your chronograph. ;)

35W
 
I agree with those blaming the chrono. I get weird readings sometimes. Not sure if it's the angle of the sun or some other factor, but when I get a 168g .308 load clocking at 4,800 fps and the others are in the 2,600 range, and I'm still in one piece, I blame the chrono
 
The crony was 12' from the muzzle, never had a problem with it being off. Missing readings due to sun angle yes. There was pressure signs on the brass, aka ejector marks. You could definitely tell these were hot. With this Hornady bullet taking up 0.1" of case volume is a major bullet setback.

Like I said earlier my load books show 1.2gr less using the Hornady 68gr vs Sierra 69gr using Varget. But I have no idea what these number are for CFE-223.

I need to ask him again what his load was 25.4 or 24.5

Unfortunately I may never know since he shot the 5 out of 10 that were that way. I offered to break one down to see whats going on but he continued shooting.
 
25.4 grains is 103% fill. Pmax is 57,327. Velocity is 2770. To get that type of velocity you would be around 32 grains(130% fill) at a Pmax of 173,252. The pressure/velocity chart is quite amusing.
 
There is no possible way you got that much velocity out of a 16" barrel, with that weight bullet without blowing the gun up.

Crono error of some kind.

rc
 
It was likely a chrono error as others have suggested. Likely the screens where picking up flash, smoke or powder passing over ahead of the bullet. Did you give the cases and primers a good look. If the primer isn't showing any high pressure signs the extra high velocity probably isn't a correct reading.

Moving the gun back a few yards should correct the reading.
 
Had to be the chrono. It certainly wouldn't have been from a bullet/manufacture change without drastically altering the OAL somehow.
 
Definitely the chrono. I've shot a load that was seated with an overall length 0.020" shorter than standard (accidentally, no other factors changed) and in my 6.5x47 Lapua I gained a measly 75fps velocity increase. I've even substituted different brand bullets with all others factors remaining constant and at most there's a 100fps difference with the same bullet weights.

Heck, I shoot 69gr SMK near enough max load out of a 24" barrel and get around 2,800fps with it. No way you could get more than that with a 16" barrel.

In summary, I don't think the change of 1gr bullet weight and 0.010" seating depth would cause a 1,000fps gain. Definitely an issue with the chronograph.
 
These bullets are 0.090" longer so there is a setback of approx .1" not 0.010". I know that 0.010 or 0.020" will not make that much difference. But it was way more that that. 0.030" setback in a 9mm can double the pressure with some powders.

If it wasn't for the bolt marking the brass, primers flattened besides the noticeable sound difference I would have marked it as a bad crony reading. I had just shot my AR and recorded some velocity in the 3350 so I know the crony was working right. My gun has a 24" Bull barrel with a tight chamber. It has consistently been equal to and faster than a lot of published data. There is a flash hider on his gun where I have nothing on mine but that should have helped dispersed the blast. But these were light 55gr bullets, which I was expecting to be fast. Not 68/69gr bullets which are normally pushed in the 2500-2600.

I would still like to see what the QL numbers would be using this combo. For the extra long length makes a compressed load.

It may have been a crony error but I have a problem accepting it due to all the indicators of a very very hot load caused by a 0.090"-0.100" setback.
 
If you could get a free 700 fps just by changing to a different brand of bullet seated a little deeper, it would be regular practice by long range shooters who use strong actions and don't care about brass life.
 
I ran the numbers through QL and this is what it spit out. I got slightly different results than dragon813gt, but in the same ballpark. Take it for what it’s worth.

Cartridge = .223 Rem
COL = 2.250”
Barrel Length = 16.0”
Case = Standard SAAMI .223 Rem
————————————————————————————————————

Bullet = .224, 69, Sierra HPBT MatchK 1380
24.5 gr CFE223
46,411 psi
2590 fps
Seating Depth = 0.407”
Filling/L.R. = 95.3%

Note: The Filling/L.R. number is % of available volume under the bullet that the powder occupies when the bullet is seated to the specified COL.
————————————————————————————————————

Substituting Hornady bullet for the Sierra:

Bullet = .224, 68, Hornady BTHP M 2278
24.5 gr CFE223
48,907 psi
2641 fps
Seating Depth = 0.494”
Filling/L.R. = 98.1%


To get 3740 fps for the Hornady bullet would require:
32.9 gr CFE223
192,086 psi
Filling/L.R. = 131.7 %

In other words, there isn’t enough room under the bullet for that much powder. In fact, there isn’t enough case volume even without the bullet to hold that much powder. A standard SAAMI .223 Rem case will overflow with 30 gr of CFE223.
 
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