Reduced load subsonics and cold temps

[mgunderson]

Been shooting a 30br reduced loads (1300 fps) at 300m. The colder temps in Minnesota have been brutal for combustion stability. Shooting from a heated building, but only limited help with the open window.

Surprised by by how poor the combustion quality was with the reduced loads. Not the typical speed reduction we see in the winter. Need to rethink my approach. Looking for any practical experience with subsonics and longer distances.

 

[Walt Krafft]

Primer size? Try a hotter primer.

 

[GLO123]

Try magnum primers and Varget.

 

[Ray123]

I have a bunch of subsonic loaded for the 8.6 blackout rd tested them in warmer weather but it's too cold to go out and shoot them now....for personal comfort. It would be interesting to see what the velocity and S/D would be...They were running in the 990 to 1050 fps range, depending on bullet weight. So I'm reloading different cartridges, for when it gets a little nicer weather, access is limited in the higher elevations.

 

[Culater]

Trailboss powder will do the trick

 

[Ray123]

Yes, Trailboss powder (if you can find it ) is good for any low velocity load ...I use it in 300 blkout but it wouldn't cycle with light bullets to the 50BMG...
it brings up the load density to where ya won't have a problem with case capacity.. especially in the 30 br with slow twist and light bullets...how slow is your twist? 1-18 twist won't be helpful for subsonic...cold weather makes it worse...but high elevation is a plus for bullet stability.
If you had and 8 twist go for heavey bullets seated deep in the case to take up space...similar to a 300 Blackout, with similar fast burning powders...chronograph and work down to the subsonic, don't want one stuck in the barrel. The formula for trailboss is on line...it works with any cartridge...it's something like, (memory?)...look at your fired case and see where your COAL would be with a seated bullet...fill the case with power, slowly with your fingers drop in the bullet ...is that your COAL that you are going to shoot?.. if not pour out or add powder until your close to exact COAL. Take out tbe bullet weigh the powder...70% will be your starting load..never crush the little doughnut shaped powder when seating a bullet, according to the manufacturer...powder compression is a no-no here...probably changes the burning characteristics...when your powder is no longer fluffy little doughnuts.

 

[Hoot]

As far as I'm concerned, there's 3 more months before comfortable (for me) weather returns up here in MN.
It's supposed to be enjoyable.

PM me where you shoot in MN. We may be neighbors and never know it. I'm the Rifle Range Coordinator for Minnetonka Sportsmen.

Hoot

 

[mgunderson]

Been shooting small rifle magnum primers. Switched to magnum primers early on trying to get trailboss yo be more stable. Many of the things mentioned work at 200 yards, but longer is where it gets exciting.

I am running a 7 twist at 17 inches in a bolt gun. Trailboss is about 3 moa at 300m, but will get another look at the low temperatures. Neck tension is important and the groups improve each time the neck tension goes up. This is a 30 br so it is a little lacking in the neck tension department as a result of necking up brass.

 

[Walt Krafft]

Try a hard jam in the rifling.