107 SMK w/ 8208

[Gringoloco]

[Oryx]

I don't think that cleaning your primer pockets are going to have a dramatic affect on your MV SD. Uniforming the pocket depth and flash holes may help some. Careful charge weighing may help some as well

Low MV SD isn't always an indicator of accuracy/precision, but when reaching out into the mid and longer distances it can help with the vertical dispersion of shots. Lots of great groups have been shot with some pretty high SD's, however. Using only 3 rounds for a standard deviation isn't likely the best statistical measurement either .... it's a better indicator with larger sample sizes.

Ilove the 107 in the grendel! If you're getting .34" CTC groups your doing pretty good and all shots are likely touching Get some good 5-10 shot groups to see if it holds. ... Sounds like a great combo.

[StoneHendge]

SD's over 20 are not uncommon - I've gotten plenty of them with factory ammo and in testing. I wouldn't worry about them - all you care about is the charge that give you a low SD and accuracy. If that's at 27.9 grains, then I wouldn't worry what 27.5, 28.5, etc. does. I have plenty of single digits SD loads that gave me 20+ somewhere in my ladders.

The 205 and 205Ms should give you similar results with the Ms being more consistent. They are allegedly exactly the same, with the Ms made by more experienced employees.

[lazyengineer]

This is my all-time preferred bullet for Grendel - it really is a great little bullet, that I'm planning on shooting 1000 yard AR-Tactical class with this weekend in fact, in a formal Long Range NRA match. We'll see how it does, it's going to be running about 1118 fps according to my calculator on target. Which is right at the speed of sound, and definately well below the 1250 fps transition zone, so I have some concern to be honest. But that said, the 129 gr load I have doesn't even make it to 900 yards before going subsonic. Even 123 gr Hornady black, which I clock going subsonic right at 970 yards (ouch).

The SMK 107 is a fantastic bullet for Grendel, though I do run mine pretty hot.

[Oryx]

Bullets don't always become unstable after passing through the transonic zone, but chances certainly increase. Good luck in the competition and let us know how it goes! Who knows ... maybe the conditions will be in your favor and lower that transonic zone.

It will be interesting to see the calibers in the AR class and if there will be a mix of standard platform size and 308 size actions

[Harpoon1]

Which is right at the speed of sound, and definately well below the 1250 fps transition zone, so I have some concern to be honest......

https://youtu.be/YY3saHvMQPU

[lazyengineer]

No joy.

I shot 4 rounds at 1000 yards at sea level elevation. They glassed my traced, and I was on-target, but the round was so slow it didnt have enough speed to activate the sonic crack trace triangulation system.

So I wasn't able to see the impacts on the digital display.

Bummer. 6.5 Creedmoor did quite well at 1000, but perhaps 1000 is a bit too far for Grendel as a precision round.

[Gringoloco]

Lazy how far out have you shot them successfully before?

[lazyengineer]

Lazy how far out have you shot them successfully before?

I've connected on gongs at a thousand. But there is a big difference between hitting a gong, and shooting for score into the rings on a bullseye target. Alas, these targets dont have pullers, but instead run shotmarker, which requires a sonic crack. And I guess technically, one above the transition zone at that.