? 6.5 Grendel subsonic w IMR 4198, anyone tried this yet?

[SDguy]

Just wondering if anyone has tried IMR 4198 for sub sonic 6.5 Grendel loads?

[VASCAR2]

I don’t remember anyone testing IMR4198 which is a fast powder with a burn rate similar to Accurate LT30. Sierra has data for super sonic loads. Curious what weight bullet your wanting for sub sonic loads?

There is a google custom search for this forum. You might research other sub sonic 6.5 Grendel loads.


https://cse.google.com/cse?cx=0163689474...cu1o&hl=en

[Klem]

Guy,

I might comment here.

H4198 is used by Blackout shooters to keep the bullet below supersonic, but still allowing semi-autos to cycle. Typical loads are around 11.8gns of 4198 with heaviest 30cal bullets: 200-220gns. With the case being only 25gn H[SUB]2[/SUB]O fills are up around the 90% which is fine for safety. For this to be reliable it also helps to have pistol length gas and a short barrel to keep the velocities down.

With Grendel it gets difficult with its case being larger (36gn H[SUB]2[/SUB]O), and the heaviest bullets lighter, around 160gns. 11.8/4198 in a Grendel will only be about 45-50% full. Below 60-80% full and it gets dangerous with either flashover, or failure of the neck to expand and seal (gas comes back into the chamber). It can also smoulder and delay fire. That's why bulky powders like Titegroup and Trail Boss are sold, to fill the void in large cases to safe levels. Another way around it is to push the powder against the flash hole with a synthetic filler like Dacron (sleeping bag fill). It burns reasonably cleanly. We're not talking about needing to flush the burnt cordite bags out of naval artillery with water and compressed air for the next shot, so you should be OK.

The deal is, you can probably load Grendel safely to high subsonic - up to 1010fps, but getting it to cycle in a semi-auto is going to be a mission.

[mtnlvr]

Here's a link to my subsonic solution. It has worked well for the limited number of rounds I've fired.

http://www.65grendel.com/forum/showthrea...post300916