I am now confident I have found the load that I can now replicate (probably) and hopefully really start honing in my shooting skills. it is 308 win with 41.5gr of Varget, Lapua brass after fire forming, cci 200 primers and 178 eld match seated about 0.020" (I think) off the lands. My loads end up being short compared to other factory ammo. So that's the short version. Long version has details/questions about load selection, the Magnetospeed and ballistics.
I'm still not 100% sure on exact powder charge between 41.5 and 41.8. the following are Hi, Lo, SD and ES from my magnetospeed (got comments on that thing) 41.5gr (first 5 shot) 2648 - 2628 - 7 - 20 41.5gr (10 shot total) 2649 - 2610 - 11 - 39
I've shot probably 60ish rounds of each in various positions and conditions. For example, there was a bright clear day a few weeks ago with almost no wind and had some great groups at 300 with 41.8gr. The single best group in all the testing I've done so far was with this load. Monday was very windy and shifty, the day I had alot more 41.5gr loaded up. Even though I couldn't put a great group together at 300, I felt like the ammo was performing well and the wind was mess with me. And at 100, it was no contest for both loads to give me about 0.60moa, with rangebuddy saying 41.5 was slightly smaller. Also, I only had 10 shot data for 41.2gr of Varget and the sd and es were closer to 41.8gr. I guess I should just go with 41.5gr and not worry about it, yes or no? Is there some sort of "low hanging fruit" trick I can go to lower my group size from 0.6moa to something under 0.5moa, for example?
Now the MAGNETOSPEED... I've mentioned often I'm an engineer and got started shooting later in life. I always try to use my "engineering hat" when shooting so the idea of precision shooting and barrel harmonics/dynamics/resonance/etc. always made complete sense to me. Enter the Magnetospeed with its "innovative" bayonet design. Coupling the idea of barrel harmonics with a thing that mount to a barrel, to the end no less, always seemed a little goofy to me. The wisdom of the internet claimed that there would not be any perceivable difference with or without it. HOGWASH. I had the three aforementioned loads (41.2, 41.5 and 41.8) and I basically shot three - 5shot groups. First 2 with the Magentospeed and the last with my suppressor. the 41.2 and 41.5 clearly had a much better group with the suppressor than the Magnetospeed. Roughly going from two groups of an inch or a little over, at 100 yards, to touching group size of about 0.6-0.8". The last load didn't have as stark of a difference, but the suppressor group did better than both chronograph-ed groups. I'm actually gonna call it shooter error because I was rushing it. Now all the sudden this thing feels a bit more useless to me. I'm 100% convinced it affect accuracy and I don't know if I see real value in even knowing the precise data. The only thing left, I'm currently attempting to an OCW procedure strictly using chronograph data to short cut load development for my 30-06. If this procedure truly works, meaning it can get a true sub-moa within loading about 25-30 rounds, then this thing will be worth it. Otherwise for what i'm trying to do with my 308 currently, the Magnetospeed is virtually useless.
So this leads to Ballistics and DOPE... Right now I'm just using the free app Strelok but definitely something between the velocities I'm getting and the app's calculations, I'm getting different numbers. First question, what is the app (paid or not) that most people like to use? Or is Strelok pretty good and I'm just using it wrong? The following are Yards - Strelok (in mils) - actual dialed (in mils) 100 - 0 - 0 300 - 1.31 - 1.5 400 - 2.22 - 2.7 600 - 4.36 - 4.7 Velocity used was 2640fps for the app. The corrections above I used for both 41.5gr and 41.8gr. The 1.5mil @ 300 I've confirmed on paper. The 2.7mil @ 400 was able to put me on an 8" steel plate 5 out of 5. The 4.7mil @ 600 is still a bit unknown to me. I don't know how big the plate is, my guess is 12", and I could only hit on average 3 out of 5. There was man sized silhouette that I could get 5 out of 5 though.
Rifle: 26" Shilen 308 barrel on a Savage model 12 with HS stock and heavy recoil lug (i'm so proud for installing that one myself). The rifle has a single port Silencerco ASR brake and I now try to shoot with my Omega 300 mostly because it's just awesome. Scope is swfa 5-20 with a badger unimount.
My first forever load was the first one I ever loaded. Its nothing special and nothing high performance, just the first beginning load up stuck together with a near min charge of H4350 and a 150 grain NP in a 270 Winchester. The first 3 shots were a nearly ragged whole clover leaf. 20 years later if that load doesn't shoot I need to clean the gun.
As to the optimal charge weight and using the chronograph to find a good load. There are different trains of thought, some believe in it others do not. I used the chronograph to develop my most recent loads and was able to pick some very consistent loads in about 15 rounds. The load for my 7mm08 was found strictly with the chronograph and has shot well but I haven't had enough time to put it on paper or at much distance. I did hunt with it with great results all season to 180 yards so nothing long. My load had an ES of 6 and a standard deviation of 2.8.
Used same process for my brothers 30-06 and found a good load for it as well with minimal shots, but I do not have the stats on his.
To me using the chronograph is a great way to take the human error out of shooting a ladder etc. Some are proficient enough at it, but with the time I have to devote to it as of now Im not that confident in my ability.
I have shot mine with and without the magnetospeed and there has been no bservable difference to this point. I do have a somewhat truck axle barrel, it is heavier than my rem sendero by a little bit.
A couple things. The chrono is a vital tool for shooting. So it will always come in handy. I would be lost without one.
Shooting suppressed vs. unsupressed can change up your load and your POI. Adding a suppressor adds about 3K-5K psi to the load. With your lighter charge of 41+ grains and longer barrel, it won't be as drastic. You should pick up some velocity with the can on, but not always. If you added the suppressor after sighting in and zero'ing at 100, you can often times lower your POI with the can on. The weight of the can pulls the barrel down some, and changes your POI a little lower. I would verify this. My bet is this is what caused the large difference in your drop. .2 mils difference at 200 yards tells me the zero is off and needs to be reconfirmed. .3 mils at 600 is a fairly large difference in calculated vs. actual drop. Plus, the suppressor generally damps barrel harmonics, and allows the barrel to shoot tighter groups. I see this often also.
If you are shooting 1/2 ish, I'd call it good and start shooting the rifle more. I'm not going to worry about which load shoots better with a .3 difference between loads. You are there and found the node.
Also, I would highly recommend a suppressor cover. When the suppressor heats up you begin to see mirage off the can. This will blur up the target and refract and bend the light. This will make the target appear where it's actually not and change your POI. Mirage does funny things.
Chad, as usual thanks for the info. Any recommendations on a suppressor cover? I didn't know that until this last time around.
Let me clarify about the chronograph, I just don't specifically like this Magnetospeed because it mounts to the business end of the barrel. Now that I've used it for a bit, the velocity data seems very useful but for someone like me, I don't think I will be using it often so I over thought the convenience of the Magnetospeed when I should have just gotten a model that doesn't mount to the barrel.
As for the can, I had no idea it had that much impact. I will look into this. I have no issue with the POI shift, it's the group size. The shift was roughly an inch towards the 5 o'clock direction. The magnetospeed vs nothing did not seem to have a shift, the groups just opened up.
Id do a little more looking. The magneto speed doesn't bother mine at all.
I have seen other build a mounting bracket/system that mounts the magnetospeed to the stock instead of the barrel. I know Jason had mentioned a similar idea but I don't know if he had ever done it or plans too. There are several on youtube that have homejobed one and I even think you can buy one.
My can moved my POI about 4 inches low and 1 inch right, but didn’t really change group size. I believe that anything, especially multiple things (can plus magnetospeed) can significantly change both POI and sometimes accuracy because of changing barrel harmonics.
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