30 BR subsonic loads
 

I just built a 30 BR with a 8 twist barrel on a Rem. 700. I shoots 168 SMK's @ 2500, and in just about one hole @ 100 yds. What I would like, is to come up with a subsonic load. Do you use a filler of some type with the reduced loads? I tried some 2400, 5744, and 2015 today,I could get it to 1150 fps but some times the vel. would be half of that. I weighed all charges. It seems that the 302 Whisper is about the same. I would be verry thankfull for any help.I would like to shoot 180- 220 gr. bullets subsonic. I am new to this forum. Thanks Glenn

I would say all of the powders you listed are a little fine grained for using in a "high power" case like that. You would desire the free space in the case to be at least 50% full of powder after the bullet is seated and 100% would be better just as long as you don't over pressure but that is usually not a problem when loading subsonic charges. Trail Boss is the most bulky at the moment and will help fill up the case. Clays, TiteWad, 700X, N320, Green Dot any fast powder that fills up the case with a small charge. Since you are using a bolt gun you can use the fastest powders which will give the lowest sound level and you don't need to worry about cycling. I suggest you go to the Hogdon powder site and get their powder speed burning chart. When you get to the fastest powders like N310 and Bullseye they are very unforgiving if you put too much in a case.

Whatever you do, dont call JD Jones looking for info.

I know all about that from 15 yrs. ago. Never called again.

Glenn , I just finished an XP-100 barrel in 30 BR using the "robinette" reamer last weekend. After throating it for 220's my plan is to start at around 11 grains of SR 4759 as soon as I get by Sportsmans Warehouse to pick some up. Trail Boss would also one of my choices .
The case has almost 70% of the volume of a 308 by my calculations.

Updates on how Trailboss worked out?

Grateful any updates on how Trail Boss works. Currently struggling with 3 - 6 inch groups at 100 using Lapua 200 grain subs ... but one hole 50 - 60 yard groups.

Would the 220 SMKs be a better bullet to try?

my round of choice is the 220 SMK sub 1" groups at 100 are very common.

Do you have a 220 grain SMK load for the 30BR/302 Whisper you would be willing to share?

My supersonic loads - 125 <==> 185 are great but I continue to struggle with a subsonic load.

Could you tell us what your barrel length is? Bore friction is a problem when shooting subsonic jacketed bullets in long barrels. Having excess case capacity doesn't help at all in acheiving velocity consistancy.
30 Luger 14.3 grain
30 Carbine 21 grain
300 Whisper 25 grain
7.62x39 Rus 35 grain
30 BR 41 grain
308 Win 56 grain.

Even the 300 whisper has considerably more case capacity than is needed to shoot a 240 Grain SMK's at 1000 fps from an optimum length barrel (10" to 12").
You may be tempted to reduce the case capacity by seating the bullets deep in the case, but having a large jump for the bullet to reach the lands (and seal the barrel) is counter productive to velocity consistancy. If you're only shooting at 100 yards you may be able to live with quite a bit of velocity spread, but don't expect one hole groups. Expect vertical slots. You can reduce case capacity by filling the case with epoxy, then drilling out the desired case capacity.
20 to 25 grains H20 is reasonable for 220 or 240 SMKs.