Where to go from here? 308 Win with Berger 168 gr Hybrid

[SGK]

Minimum load for Varget and Berger 168 gr bullets is 38 grains. Maximum load listed for this combo is 42.5 grains.

I loaded a single round at each of the following charges (CBTO of 2.228”) and looked for pressure signs

o 40.50 95.3% of listed max 2283 fps

o 40.70 95.8% 2374

o 40.90 96.2% 2357

o 41.10 96.7% 2359

o 41.30 97.2% 2375

o 41.50 97.6% 2381

o 41.70 98.1% 2387

o 41.90 98.6% 2445

o 42.10 99.1% 2469

o 42.30 99.5% 2458

o 42.50 100.0% 2479

o 42.70 100.5% 2548

o 42.90 100.9% 2523

I used a CBTO of 2.228" which I estimated as a 50 thou jump - I later revised this estimate to 48 thou jump. Fired April 15, 2019. No obvious pressure signs. (Velocities light but may simply be the placement of the Two Box Chrono – if the two boxes aren’t at the same height it can lead to substantial absolute errors in recorded velocity. I primarily use the Two Box for measuring velocity variance when shooting groups.)

Having covered the lower loads with safe pressure I focused on 42.50 and above in 3 shot groups stepping 0.2gr at a time, again looking for pressure signs. Loaded 3 rounds at each of the following powder charges. I probably could have skipped the first couple. I used a CBTO of 2.218” CBTO this time (an estimated 58 thou jump).

o 42.50 Varget

o 42.70 100.5% of listed max

o 42.90 100.9

o 43.10 101.4

o 43.30 101.9

o 43.50 102.4

o 43.70 102.8

o 43.90 103.3 (still plenty of room in case)

(A CBTO of 2.218” equates to a COAL of 2.917 – 2.923”. Still too long for magazine feed. Berger manual used a COAL of 2.81” which would be another 110 thou of jump!! To clear the magazine CBTO would have to be less than about 2.130” – approx. 148 thou jump and a COAL of 2.830”. Don't mind single-feeding target ammo.)

Fired above series April 28, 2019

o 42.50: 2632, 2595, 2600. ES 37 SD 20.07 Avg 2609

o 42.70: 2619, 2646, 2635. ES 27 SD 13.58 Avg 2633

o 42.90: 2632, 2661, 2663. ES 31 SD 17.35 Avg 2652

o 43.10: 2661, 2647, 2654. ES 14 SD 7.00 Avg 2654

o 43.30: 2672, 2678, 2690. ES 18 SD 9.17 Avg 2680

o 43.50: 2684, 2703, 2707. ES 27 SD 12.29 Avg 2698

o 43.70: 2715, 2710, 2688. ES 27 SD 14.36 Avg 2704

o 43.90: 2716, 2711, 2710. ES 6 SD 3.21 Avg 2712

(note how absolute fps figures for same powder charge differ markedly from the first single round test due to Two Box placement over two different days - so compare only within tests done on same day with same position of Two Box vs rifle and target)

Primers still look good. First pic attached focuses in on last 3 loads. Second pic shows "groups". Where I have written SD at target it is the velocity SD measured by the Shotmarker which won't be as good as the Two Box. As a quick comparison, I also very casually fired 6 rounds of ammo I have previously used with this rifle just as a comparison: Avg 2757 fps, SD 20.95, ES 56. (Ammo produced from my brass and 168gr Sierra Match King, 44.5 gr of N540, by HPS Target Rifles in the UK. Not optimised in any way for my individual rifle.) Tighter group than any of the above. See last pic.

My loads are still producing lower average velocity than the HPS ammo. HPS ammo has a CBTO of 2.214" versus my rounds with CBTO 2.218 albeit with entirely different bullet and hence large difference in COAL.

I'm a bit unsure of where to go next. I don't believe I have hit excess pressure signs but I tested up to 103.3% of listed max at which point (albeit a sample of just 3 shots) velocity SD/ES collapsed to very respectable figures. At a CBTO much greater than 2.216" (estimated 50 thou jump) I wouldn't feel like I had a lot of bearing surface in the case neck. Should I test seating depth here with jumps of, say, 90, 70, 60, 50 (the first two would obviously reduce case capacity and I think increase pressure versus prior tests) or keep pushing forward with increased powder charge?



(Brass for these tests was 2x loaded so still expanding in capacity)

 

[Bc'z]

Looking at poi, 43.5 says more powder.
43.7 leveled off and has basicly same vertical dispersion as 43.9.
I personally would load 43.8 and start a seating depth test moving in .003 increments.

 

[Richard Coody]

I use 44gr varget with 168 hybrid hunters with great results. I wanted a mag length load since this is a hunting rifle. Seating depth test wound up 0.080 off jam.

Now with the vld 168 hunters i use the same 44gr load but using the berger seating depth method and a little fine tuning i wound up 0.113 off a jam.

 

[SGK]

I think I am going to check seating depth in 10 thou increments from an estimated 50 thou jump to 80 thou jump with the 43.90 gr charge. Hybrids are meant to be depth tolerant but a lot of case capacity is consumed when moving from 50 jump to 80. With 50 thou jump I can hear the powder moving when I shake a cartridge. Not so by 70 jump.

 

[abersfelderami]

"keep pushing forward with increased powder charge"

 

[ebb]

6.5 Creedmoor they shoot out of the box.

 

[Bc'z]

I think I am going to check seating depth in 10 thou increments from an estimated 50 thou jump to 80 thou jump with the 43.90 gr charge. Hybrids are meant to be depth tolerant but a lot of case capacity is consumed when moving from 50 jump to 80. With 50 thou jump I can hear the powder moving when I shake a cartridge. Not so by 70 jump.

50 thou are big moves.
Personally I like .003 its amazing how it comes together rather quickly.

 

[SGK]

10 thou moves.

 

[David101]

I would suggest AR2206H which is Hogdon H4895 and upto 45.6 but that is hard on cases backing it off to 45.1, This has proved to be a very good load in my rifle.

 

[Ned Ludd]

I am running the 168 Hybrids out of a rifle with a 30" barrel, chambered with .085" freebore. At a COAL of 2.915" in Lapua Palma (small rifle primer brass), the 168s are seated ~.015" off the lands. 43.8 gr of H4895 is giving me approximately 2900-2910 fps. Although I'm not using Varget with the 168s, I have extensive experience loading for .308 Win with both Varget and H4895. A charge weight of Varget somewhere around 0.4 to 0.8 gr more than my H4895 load (i.e. ~44.2 to 44.6 gr Varget) would tune in nicely at approximately 20-30 fps slower than 43.8 gr H4895. If you can give us the specs of your rifle (barrel length, twist rate, etc.), and your case volume (or brand of brass you're using), it would allow us to provide you with better feedback.

My guess is that your groups can be improved markedly when you optimize seating depth. I would suggest stating with the longest COAL/CBTO you feel you can get away with (even if it's ~.050" short of touching the lands), treat that as your "zero" or "reference" point. I would do a coarse seating depth test initially, ultimately seating the bullets as much as .030" to .035" from your reference point in .005" increments. I suspect you might find something worth pursuing in that region, but if not, you can always move them farther off the lands. Obviously, you can't go in the other direction if there won't be any bullet shank left in the neck (FWIW - a conservative estimate of the minimum bearing surface you want in the neck is about 1/2 of the bullet diameter). If you have to go farther off than that, be sure the velocity doesn't start to go up too much as you will be reducing the effective case volume as you seat the bullets deeper. Nonetheless, you can continue to seat them shorter until you find a region that groups well. If necessary, you can then fine tune in that region using .003" increments. Again, it may be necessary to reduce the charge weight slightly to keep the velocity where it was if you have to seat the bullets markedly deeper.

I wouldn't be too concerned about the difference in velocity as compared to your HSP load. For starters, it uses a different powder (N540), which is a double base, high energy powder. Varget is a single based moderate energy powder, so I wouldn't expect it to generate comparable velocities. The major benefits of Varget are that it has a very good burn rate for .308 Win with bullets in the 168 to 200 gr range, it is generally relatively easy to tune, and it has good resistance to temperature-induced velocity changes. Unless you're giving up 100-150 fps (or more), I wouldn't be too concerned about the velocity as long as you can get the precision tuned in nice and tight.

FWIW - the charge weights listed in reloading manuals are for mag length loads (i.e. COAL = 2.810"). Further the velocity estimates they provide for a given charge weight are for a 24" test barrel. Longer barrels will generally give greater velocity when loaded to equal pressure. You are certainly doing the right things - starting low and increasing charge weight in moderate increments, looking for pressure signs as you go. However, pressures signs such as flattened or cratered primers, hard bolt lifts, etc., are not very sensitive and can sometimes be misleading. This is a perfect example of where a copy of the reloading program "QuickLoad" can be very useful, expediting the reloading process, as well as possibly providing some peace of mind that you're not doing anything that might be a safety issue. It is more than worth cost and can be run on either PC (Windows) or Mac platforms (Mac requires some form of PC emulation software such as "CrossOver"). I would suggest looking into getting a copy:

https://www.neconos.com/details3.htm

 

[SGK]

Thanks all. I will try to respond to all the above.

I was a little concerned about pushing forward with increasing powder charge when perhaps the rifle might prefer a bigger jump. I understand seating jumped bullets deeper will, all else being equal, increase pressure. (Yes I noted the shorter 2.810” COAL assumption in the loading manuals.)

@ebb perhaps that bodes well for my custom build 6mm Creedmoor by Dana English but I still want to get this one right.

The rifle is a Blaser R8 Professional Success (sporter) with standard weight barrel (17mm) 580mm in length. So 23”. 1:11 twist. I don’t expect it to be a “tack driver” per se but I haven’t reached with my own hand loading the best this thing can do based on prior shooting with HPS ammo. Brass is Lapua standard 308 Win - I made a mistake not buying the Palma variety.

As noted above, a CBTO of 2:218 (an estimated 58 thou jump) yields a COAL of 2.917-2.923 depending on the individual bullet. So an average COAL of 2.915” would have me seating for a much bigger jump than Ned’s rifle. Maybe my freebore is eroded or maybe it is just long to begin with.

I will try to take a pic of a seated round with bullet next to it to judge the amount of bearing surface in the neck. It sounds like I have room to test in both directions. (Power was out at the house for almost two days following a thunderstorm on Sunday night. And we live in suburban south Miami...)

Unfortunately the straight pull Blaser action doesn’t provide as sensitive a platform for feeling “heavy bolt lift.” It is designed for fast cycling for driven boar hunting, for example.

I need to look at Quickload again. As a Mac user I was deterred but if it can run on something like Crossover as opposed to having to buy a full emulation software and Windows license that would be good.

Edit: I trim my cases to 2.005”

 

[ebb]

OK just thought I would mention it.

 

[Ned Ludd]

Thanks all. I will try to respond to all the above.

I was a little concerned about pushing forward with increasing powder charge when perhaps the rifle might prefer a bigger jump. I understand seating jumped bullets deeper will, all else being equal, increase pressure. (Yes I noted the shorter 2.810” COAL assumption in the loading manuals.)

@ebb perhaps that bodes well for my custom build 6mm Creedmoor by Dana English but I still want to get this one right.

The rifle is a Blaser R8 Professional Success (sporter) with standard weight barrel (17mm) 580mm in length. So 23”. 1:11 twist. I don’t expect it to be a “tack driver” per se but I haven’t reached with my own hand loading the best this thing can do based on prior shooting with HPS ammo. Brass is Lapua standard 308 Win - I made a mistake not buying the Palma variety.

As noted above, a CBTO of 2:218 (an estimated 58 thou jump) yields a COAL of 2.917-2.923 depending on the individual bullet. So an average COAL of 2.915” would have me seating for a much bigger jump than Ned’s rifle. Maybe my freebore is eroded or maybe it is just long to begin with.

I will try to take a pic of a seated round with bullet next to it to judge the amount of bearing surface in the neck. It sounds like I have room to test in both directions. (Power was out at the house for almost two days following a thunderstorm on Sunday night. And we live in suburban south Miami...)

Unfortunately the straight pull Blaser action doesn’t provide as sensitive a platform for feeling “heavy bolt lift.” It is designed for fast cycling for driven boar hunting, for example.

I need to look at Quickload again. As a Mac user I was deterred but if it can run on something like Crossover as opposed to having to buy a full emulation software and Windows license that would be good.

Edit: I trim my cases to 2.005”

I am running QuickLoad with Crossover. It works just fine.

FWIW - it is likely that your rifle simply has a longer throat than mine. Mine was cut with a reamer I had specifically designed to give .085" freebore. Not a bog deal, you an still seat them approximately where you want and then work within a seating depth range around that point to identify the optimal seating depth window. Having used the 168s Hybrids for several years, I have been pretty happy with their loading/precision characteristics. Nonethless, if your rifle has a much longer throat, you might also consider 185 Hybrids or even the 200.20X bullet.

 

[SGK]

Thx

I had a friend run Quickload for me. It seems I'm still in the safe zone. It's not until 46.40 gr that I get the Dangerous Load warning. I still feel like I should narrow down seating depth before pushing higher. (I've not attempted to measure case capacity. I did this once before with some other brass but basically I think the H2O process is highly susceptible to user measurement error.)

Cartridge : .308 Win. (SAAMI)
Bullet : .308, 168, Berger Hybr G7 #30425
Useable Case Capaci: 49.604 grain H2O = 3.221 cm³
Cartridge O.A.L. L6: 2.918 inch = 74.12 mm
Barrel Length : 23.6 inch = 600.0 mm
Powder : Hodgdon VARGET *T

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.227% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-02.3 97 43.00 2579 2481 48757 7337 97.3 1.232
-02.0 97 43.10 2584 2491 49087 7352 97.4 1.228
-01.8 98 43.20 2590 2502 49420 7367 97.4 1.225
-01.6 98 43.30 2596 2513 49754 7382 97.5 1.221
-01.4 98 43.40 2601 2524 50092 7397 97.6 1.217
-01.1 98 43.50 2607 2535 50431 7412 97.6 1.214
-00.9 99 43.60 2612 2545 50773 7426 97.7 1.210
-00.7 99 43.70 2618 2556 51117 7441 97.7 1.206
-00.5 99 43.80 2623 2567 51464 7455 97.8 1.203
-00.2 99 43.90 2629 2578 51813 7470 97.9 1.199
+00.0 99 44.00 2634 2589 52165 7484 97.9 1.196
+00.2 100 44.10 2640 2600 52519 7498 98.0 1.192
+00.5 100 44.20 2645 2611 52875 7512 98.0 1.189 ! Near Maximum !
+00.7 100 44.30 2651 2622 53235 7526 98.1 1.185 ! Near Maximum !
+00.9 100 44.40 2657 2633 53596 7540 98.2 1.181 ! Near Maximum !
+01.1 101 44.50 2662 2644 53960 7554 98.2 1.178 ! Near Maximum !

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 99 44.00 2746 2812 61263 7377 100.0 1.119 ! Near Maximum !
Data for burning rate decreased by 10% relative to nominal value:
-Ba 99 44.00 2486 2306 43261 7258 92.3 1.296

 

[Ned Ludd]

For the most useful output, you need to measure your case volume with water...QuickLoad's preset case volume values are way off if you're using Lapua brass. Here is a fairly simple and reproducible method for doing that: http://forum.accurateshooter.com/threads/case-volume-determination-pic-heavy.3896148/

Having used quite a bit of Lapua standard brass with 168 Hybrids, I can tell you that loads with QL-predicted pressures up to ~59-60K psi gave pretty good brass life. If the predicted pressure was a little hgher, in the 60K to 61K range, the primer pockets would open up in 4-5 firings (or less). Not to worry, you can switch to Palma brass the next time you need to buy some.

Optimizing seating depth at this point is not going to hurt you, even if it requires a little more tweaking later. You should be able to find something that shoots well in the region away from the lands to which your load is constrained.

I made a file in QuickLoad using your actual data as best as I could translate it, along with my measured Lapua Standard case volume. I used the COAL value you listed above, and adjusted the burn rate (Ba) until the velocity matched your measured velocity of 2712 fps for 43.9 gr Varget). The output was close to what I would expect for your setup (i.e. MAX pressure of 62K psi is exceeded at 45.0 gr Varget - see below). However, the caveat is that I had to adjust/increase the burn rate value for Varget by a LOT to generate 2712 fps as the velocity output. That often means some other input is not correct, or you have a Lot of Varget with a burn rate substantially higher than the default value in QuickLoad. Anyhow, you're doing the right things. Keep going and I'm sure you'll get it tuned in just fine.

 

[SGK]

Thanks. I wouldn't trust the absolute velocity figures I provided. The one problem with the Two Box Chrono is that its absolute velocity figures are affected by placement of the boxes - particularly their relative height. Its power comes in very accurate measurement of variance. Note the difference in velocity measured for the same charge one range trip to the next was over 100fps. The average velocity recorded by the Shotmarker (adjusted for the 100 yard distance to muzzle) is going to be a more accurate estimate of muzzle velocity. I need to pull that data from my Shotmarker.

 

[Nature Boy]

Looking at poi, 43.5 says more powder.
43.7 leveled off and has basicly same vertical dispersion as 43.9.
I personally would load 43.8 and start a seating depth test moving in .003 increments.

I see the same

 

[Ned Ludd]

Thanks. I wouldn't trust the absolute velocity figures I provided. The one problem with the Two Box Chrono is that its absolute velocity figures are affected by placement of the boxes - particularly their relative height. Its power comes in very accurate measurement of variance. Note the difference in velocity measured for the same charge one range trip to the next was over 100fps. The average velocity recorded by the Shotmarker (adjusted for the 100 yard distance to muzzle) is going to be a more accurate estimate of muzzle velocity. I need to pull that data from my Shotmarker.

If you obtain a better velocity data set, PM me with the charge weight, COAL, temp, etc. (any pertinent inputs you have) and I'll be happy to run the numbers again in QL.

 

[SGK]

I quickly grabbed the data off my Shotmarker before leaving the house this morning.

43.9 gr 2464 fps SD 6.8
43.7 gr 2448 fps SD 9.9
43.5 gr 2440 fps SD 11.7
43.3 gr 2416 fps SD 15.5
43.1 gr 2402 fps SD 8.3
42.9 gr 2393 fps SD 12.4
42.7 gr 2376 fps SD 11.5
42.5 gr 2355 fps SD 15.9

Plugging 2464 fps @ 300 ft for this projectile into my ballistic calculator yields a muzzle velocity of 2554 fps. Temp would have been circa 78F.

 

[JFrank]

I’m a bit of a 308 guy, no expert of course but those speeds seem a little low.
My 168 gr class of Bullets run around 2700 FPS with 43.6 gr Varget and shoot well, RL-15 gets a bit more speed