post your results with 4198.... please:smile:

Ricky,
Thanks for posting the data...

250 SMK's I'm jealous... a have a couple thousand 240 grainers but no 250's...

Now things are getting wacky with the 200 grain Laps and 4198...

More loads and a pattern developing:

Grains Av Vel (fps)
11 895
11.5 944
12 975
12.5 1064
13 Didn't try
13.5 1120

Tried 14 grains behind a 220 RN - weird velocity spikes.

BUT!

With the 250 SMKs (How much I hate using them at all!!!) and crying tears between each shot.

16 grains - 4198

a. 1080
b. 1077
c. 1108

Av: 1088fps and SD of 17fps

Now we are getting somewhere - the 250 fills the volume of the case well and the 16 grains sits deep enough for some consistent ignition.

Next steps:

a. Try 15.5 and 15.8 grains of 4198.
b. Get some 240SMKs!
c. Ignore the 200 grain Lapuas...

Wish me luck.

Just ordered some 240 grain SMKs to try. I'm thinking 15.5 grains should give me the starting point for the load.

Now what is the better muzzle velocity to head for? 1040 or 1050fps as average?

I can recommend the 240 smk's in the 300 whisper... glad i bought a couple boxes a while back on the cheap as they are getting pricey.... paid 100.00/500 shipped

Received some 240s to try this weekend. They are about the same length as the 250s (1.65 for the 250 vs 1.58 for the 240) so I am quietly confident. Bearing surface seems to be the same ratio.

What these seem to be doing, and what is different from the 200 grain Lapuas, is restricting the volume of the BR case to a capacity where the 15 - 16 grains of powder can ignite consistently.

Results hopefully on the weekend.

Using 240SMKs ==> 15.5 grains of 4198 = 1020 fps average (good) but Standard Deviation of 48fps (bad).

Trying 16 grains of 4198 and 17 grains 3031.

Then trying for accuracy at 100.

Latest results with 240 SMK

Using 16 grains of 4198:

a. 1054
b. 1122
c. 1055

Av. 1077 SD: 38. Take out the b shot and you've got some good results noting the small statistical model.

Using 17 grains of 3031:

a. 987
b. 1083
c. 1160
d. 1114

Average of 1086 but SD of 73.

Now to accuracy testing at 100.

Notwithstanding the high SD; the 17 grain load group 3 in a 2 inch group at 100 and one flier (first shot?).

The 16 grain 4198 load shot a 2.5 inch group.

So comparing this result to the 200 grain Lapua at the start of the thread. We have:

a. improved accuracy

b. improved velocity

c. improved on shot to shot variation

Where to from here....

While generally happy with the load I think I shall try 15.9 grains for a ten shot group and concentrate on forming a consistent group with that load.

Great info.

Let me know how accuracy testing goes.

OK, this is where things have gone from the frustrating to the obsessive and back again.

Range testing the 15.9 grain load revealed a good group for three of the five shots of about an inch - two touching one out. The other two were six inches vertically low. So this is the same grouping as from the start and indicates the extreme velocity spread (ES) is much too wide.

So what? This is where it gets technical and goes straight to the heart of why Whispers/subsonic loads are so frustrating. Let's see if I can get the description right. The pressure curve in the case is not uniform because the powder is not burning at the same rate from shot to shot. Because the powder is not burning at the same rate from shot to shot, the gas pressure is different from shot to shot and the velocity ranges high and low - which is what you'll see in the velocity spikes in the records detailed above.

It is blindingly obvious in hindsight but the sort of thing you need external advice on. It was also the conclusion that I was coming to after having standardized the load, the seating depth, the velocity etc etc.

The answer is that if you are seeing perfectly vertical groups go to a faster burning powder. With the BR case size you need to look at something in the burn range of IMR4227, H4227 or AA1680 ie a powder that suits both rifle and pistol, very fast so that it can used in a 22 Hornet and also a magnum pistol case.

Back tot the drawing board/reloading bench. My ideal load will have the following characteristics when using a 240 grain SMK.

Velocity: 1045fps
SD: 11 fps
Group at 100: about an inch and hopefully less.