Pressure signs?? ELD-X

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Wondering if anyone can help me with a couple new load work ups. I am working with the new Hornady ELD-X 200gr .308s in 300 WM (rem 700 sps) and .308 win. (LR/SR clone). Since there is very little data available for these so far, I started today by attempting to determine charge limits. Hoping some of you can look at the pics I've included and let me know how I'm doing as far as pressure signs. All primers remained seated and the case walls showed no signs of stress such as cracks. All .308 loads above 37gr show ejector ring, and all above 38gr have a raised ring around the firing pin indentation.

For the 300 WM I had no available data using MAGPRO, so I determined my start load based on my own experience with Berger 210 VLDs. I loaded 12 rounds .020 off the lands starting at 70.5gr ending 76gr in .5gr steps.

For the .308 I used Hornady's Data for IMR 4064. I loaded 14 rnds COAL 2.800" starting at 36gr ending at 42.5gr in .5gr steps.

I shot these across a chrony and collected the following data, pics of the brass follow.

300 WM MagPro

01. 70.5gr 2676fps
02. 71.0gr 2820fps
03. 71.5gr 2825fps
04. 72.0gr 2821fps
05. 72.5gr 2816fps
06. 73.0gr 2831fps
07. 73.5gr 2867fps
08. 74.0gr 2986fps
09. 74.5gr 2902fps
10. 75.0gr 2931fps
11. 75.5gr 2867fps
12. 76.0gr 2909fps

.308 Win IMR 4064

01. 36.0gr 2240fps
02. 36.5gr 2246fps
03. 37.0gr 2264fps
04. 37.5gr 2271fps
05. 38.0gr 2288fps
06. 38.5gr 2307fps
07. 39.0gr 2350fps
08. 39.5gr 2415fps
09. 40.0gr 2430fps
10. 40.5gr 2388fps
11. 41.0gr 2436fps
12. 41.5gr 2472fps
13. 42.0gr 2499fps
14. 42.5gr 2545fps

 

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more

 

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Bear with me, too bad you can only upload 6 at a time

The ejector imprint seen on load 10 was not from this firing.

 

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continuing with the 308 brass

 

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more .308

 

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nearly there

 

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Just a little more info

The loads I am currently using are

300 WM 210gr berger HVLD over 71.5gr of MagPro COAL 3.525" avg velocity of 2648fps SD 9.5 yielding .25 MOA from my near bone stock rem 700 sps (forend Stiffened and free floated and action glass bedded)

308 win 190 SMK over 41.9gr IMR 4064 COAL 2.795" AVG VEL 2494fps SD 6.0 yielding sub 1/4 MOA form my built LR/SR clone (AEROPRECISION M5 upper and Lower Black Hole Weaponry 18" 1/8.5 twist 3 land polygonal barrel)

 

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more info

The brass used in this test was once fired military brass FC head stamps for the 300WM and LC for the .308.

Case prep included for the .308, small base full length resize, primer pocket crimp removal, flash hole uniformed, length trimmed, deburred, and chamfered. Headspace was checked using a case mic as well as a Dillon case gauge.

For the 300 it was collet resizing to remove the bulge, then neck and shoulder bumped back. Length sized, chamfered and deburred, and flash holes and primer pockets same as the 308s. Head space cross checked with case mic.

 

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I should also note that there was no increase in bolt lift tension on the 300WM loads, and the .308 functioned properly with the exception of a failure to fully chamber the final load cycling from 42gr to 42.5.

The final round did chamber fine manually and extract/eject properly.

Also inspection of some recently fired brass from my 190gr SMK load as well as some 178 gr GMM factory ammo, also show ejector marks and the raised ring around the firing pin.


Just checked the BCG on the .308, the ejector is extremely stiff, could this account for the ejector imprints vs extrusion from pressure?

 

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New Question

Since It appears I'm way off on my start load, How do I determine what is a safe bottom end for the .308?

I just checked a fired case and it holds 56gr of water which is 3.62874 grams or 3.62874 cc volume. What is considered the safe lower limit of case volume for a charge?

if I have this right, the formula cc = VMD * grains, VMD for IMR 4064 = 0.0745 so 3.62874 cc / .0745 = 48.707919 grains of 4064 to fill the case to the top of the neck.

The roughly .73" of seating depth equals around 12 gr+/- accounting for the boat tail,so by my calculations the usable internal volume without compressed load should be around 37.6gr.


In other words how low can I go? What is the safe minimum percent of case volume?

 

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Well between work schedule, high winds, and a broken firing pin, I finally managed to get back to the range. I decided to purchase some Lapua brass and start from scratch.
To start I neck sized the Lapua brass and primed it with Fed match large rifle primers.
projectile is the Hornady 200gr ELD-X
Powder is IMR 4064
COAL is 2.815"

I ended up doing an extended OCW in 2 sessions of 9 loads each from 36.4 to 39.9 grains. Results and pictures are below.

1. 36.4 gr AVG 2058 ES 16 SD 8
1. 2052
2. 2065
3. 2050
4. 2066
5. 2060
2. 36.6 gr AVG 2075 ES 16 SD 7
1. 2083
2. 2072
3. 2067
4. 2081
5. 2078
3. 36.8 gr AVG 2084 ES 26 SD 11
1. 2070
2. 2081
3. 2080
4. 2094
5. 2096
4. 37.1 gr AVG 2120 ES 27 SD 10
1. 2109
2. 2121
3. 2120
4. 2136
5. 2116
5. 37.3 gr AVG 2131 ES 36 SD 15
1. 2142
2. 2128
3. 2143
4. 2107
5. 2135
6. 37.5 gr AVG 2133 ES 34 SD 14
1. 2117
2. 2151
3. 2123
4. 2144
5. 2133
7. 37.7 gr AVG 2143 ES 47 SD 23
1. 2159
2. 2119
3. 2164
4. 2117
5. 2154
8. 37.9 gr AVG 2172 ES 47 SD 18
1. 2189
2. 2178
3. 2178
4. 2172
5. 2142
9. 38.1 gr AVG 2160 ES 35 SD 15
1. 2148
2. 2144
3. 2167
4. 2179
5. 2166
10. 38.3 gr AVG 2239 ES 45 SD 18
1. 2212
2. 2231
3. 2253
4. 2242
5. 2257
11. 38.5 gr AVG 2241 ES 33 SD 12
1. 2234
2. 2251
3. 2255
4. 2244
5. 2222
12. 38.7 gr AVG 2247 ES 30 SD 11
1. 2242
2. 2251
3. 2264
4. 2246
5. 2257
13. 38.9 gr AVG 2257 ES 23 SD 8
1. 2257
2. 2258
3. 2270
4. 2255
5. 2247
14. 39.1 gr AVG 2261 ES 32 SD 12
1. 2268
2. 2260
3. 2260
4. 2275
5. 2243
15. 39.3 gr AVG 2272 ES 29 SD 11
1. 2276
2. 2286
3. 2257
4. 2274
5. 2269
16. 39.5 gr AVG 2279 ES 25 SD 10
1. 2284
2. 2292
3. 2267
4. 2275
5. 2278
17. 39.7 gr AVG 2287 ES 38 SD 14
1. 2276
2. 2286
3. 2307
4. 2269
5. 2299
18. 39.9 gr AVG 2291 ES 30 SD 11
1. 2294
2. 2293
3. 2286
4. 2306
5. 2276