Thread: 8208, 168 eldm 16.5” barrel 8 twist questions re max charge etc

Hi all, I’m reloading 308 using 8208 and 168 eldm I was at range today and ran up a load on my new rifle starting at 40 and ended up at 43 gns 42 and 42.5 were best groups then it opened up but at 43 started to close again so I want to go to 43.3 but wanted to ask if anyone can run it through quick load re pressure, rifle is a 16.5” 8 twist. Average speed at 42 was 2565 average at 43 was 2620, ran some super performance 165 sst as well and got 2700 average. Any info would be appreciated.

I used to use 43gns 8208 with 168gn Makers, was a getting warm. Never tried std projectiles.
Now using different powder as 8208 got too hard to get for a while

16 inch Tikka T3x, 2650fps on the Garmin.

Hodgdon says 43.3 is max for a 168 Sierra hpbt.

As requested. 42gr:



43gr:

Originally Posted by Pommy

As requested. 42gr:

Attachment 273297

43gr:

Attachment 273298

Thats quite interesting considering the loads are both max in ADI and not quite max in the Hornady manuals.
ADI

Hornady 10th

I guess we can average it and say all 3 indicate max loads

Greetings,
The GRT predictions seem to be out of line with the Hodgdons data. The very early BM8208 appears to be somewhat faster than later production based on my chronographing in the .223. Chronographing data with the .308 and BM8208 showed a good match so this appears to be the slower stuff. Your velocities seem to be in line with the Hodgdons data or perhaps a little faster. I would tend to take the Hodgdons data for the .308 as more reliable in this case.
GPM.

If your barrel were extended out to 24" to match the one in the data, the software's predicting that the 42gr load would be producing 2785. Or 2840 at 43gr. I.e. you'd be getting more velocity than either Hornady or Hodgdon/ADI got with an ELD/SMK.

Trusting the "velocity is the best predictor of pressure" approach, that would make me cautious of the 43gr load.

Originally Posted by Pommy

If your barrel were extended out to 24" to match the one in the data, the software's predicting that the 42gr load would be producing 2785. Or 2840 at 43gr. I.e. you'd be getting more velocity than either Hornady or Hodgdon/ADI got with an ELD/SMK.

Trusting the "velocity is the best predictor of pressure" approach, that would make me cautious of the 43gr load.

Where or can you still download Gordons Reloading tool thingy? Seems like a good extra "thing" you can use along with comparing multiple published reloading manuals.
I would have expected ADI to be on the warm side but the with Hornady being based in the "land of the litigious" I would have expected theirs to be quite conservative but in this case perhaps the outer way.

Below are the results of my testing on day 1, Ive loaded 42. 42.7 43 and 43.3 ill try 5 shot strings tomorrow and see how it goes, 43.3 is hot however I did see one max load was 43.9 ….. not sure I trust that. The bottom two strings were with factory ammo and the results of super performance 165 ssts were good, I think 2600 is a good number for me out to 500yds so that is where I would like to be, 42 and 42.7 seemed to be a sweet spot . thanks for the info I very much appreciate it.

Greetings @Nga,
That is now three sources all on the same page. The outlier is GRT so can be discounted. Comparing the velocity data from Hodgdon for 43.3 grains of 8208 in 24" and 15" barrels give a velocity loss of 20 fps velocity loss per inch. My son chronographed 43 grains of 8208 in an 18 inch barrel with the 165 grain BT at 2,700 fps so your results are in line with this.
Regards GPM.

With respect GPM I think your last reply needs a bit more context. Reloading manuals are always based on the "work up" principle, meaning that the max load shown is to be approahed with caution, not just thought of as a target etc. There are many variables a reloading manual can't account for, brass capacity/chamber size being quite significant. The OP didnt say what signs he was getting at 43.0 to say the load was warm, but anything that tells ya things are getting warm shouldnt be discounted.

Quickload and GRT are both excellent predictors of pressure, far, far more accurate than anything else available to a reloader short of proper pressure measurement equipment.

That's an interesting interpretation GPM.

All three sources are saying that the top speed with that powder and that weight bullet should be no more than about 2700-2750 in a 24" barrel.

When adjusted for barrel length, Nga is matching/slightly exceeding those top speeds already with 42gr. 42gr is obviously short of any of the published max charges. So do you:

A) conclude that since Nga is apparently getting a bit more pressure/velocity per grain, 42gr is maybe a sensible place to stop?
B) Say no, 42 is a smaller number than 43. The books say you should be able to use 43... so you should use 43! And just consider the extra 100fps a happy bonus?

Greetings @Tentman, @Pommy and @Nga,
The point of my posts was to point out the variable data for BM8208 which is important if you want to navigate your way through it. Somewhere between the manufacture of the early test batches and the early powder arriving in NZ the speed of the powder was slowed. I tested the powder in my .308 in 2,000 as IMR8208. It was tested against AR2206 and AR2206H. The chronograph showed 8208 was slightly faster than AR2206 and a bit faster again than AR2206H. This matched the Hodgdon data quite well. Fast forward a few years I tested BM8208 in both the .222 and .223. Velocity was considerably lower than predicted, even in the 26 inch barrel. Both Hornady and Handloader showed significantly higher charges to achieve the same velocity. So there are some bugs in the data and the GRT data is so out of step with real world chronographed and pressure tested data that I believe, for this cartridge powder combination, it should be discounted. BM8208 seems to lose rather less velocity than some other powders due to reduced barrel length. Based on the Hodgdon data the loss is 20 fps per inch between 24 a d 15 inches. Between 24" and 16.5" the velocity loss will be less per inch. I would expect the 16.5" max velocity to be a little less than 2,600 fps. For me I would go no further than 43.0 grains. Nga will decide how far to go.
GPM.

I cant understand the obsession of people to get to (and exceed) max loads just for a few fps more.