I was looking at getting into a 300blk bolt gun for subs, but with the cost of everything, I was wondering if there’s any difference really in the round vs a 308 subsonic? I’m already set up to load 308.
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300blk vs 308 subsonic
- Thread starter Jmccracken1214
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Let see, both shooting the same heavy bullet at subsonic velocity. Nope. The difference is the size of the action required.
The BO was designed for subsonic so the case capacity is optimized for that function. The 308 case capacity is really too large but can be "made to work" so to speak. Ultimately it depends on your intended use. I would choose the BO if I expected to shout this gun often and wanted accuracy.
You have about 150 more choices of powders with a Blackout. The case capacity of the 308 would make it possible, but a lot more difficult to have consistent subsonic rounds.
No matter how you slice it powder shift is definitely a thing. If you are not familiar with what that is it means the space left over in the case will allow the powder to shift around inside the case. One round will be 1300fps and the other will be 900fps. This is solely due to the powder being in a different orientation inside of each case.
No matter how you slice it powder shift is definitely a thing. If you are not familiar with what that is it means the space left over in the case will allow the powder to shift around inside the case. One round will be 1300fps and the other will be 900fps. This is solely due to the powder being in a different orientation inside of each case.
Yep, that’s why high volume powders like Trailboss are the go to for .308WIN subsonic.
300blk or .223 is fine for 300yard paper punching. .308 is overkill in that application IMO. If it's just a toy then I would go .223. Super cheap ammo! However 300blk will be a lot quieter with subs. You need to see the video of Travis Hailey shooting a 9' ar15 suppressed 300blk at 750yards with a stupid aimpoint! Personally I think he's a witch.
Same bullet, traveling the same velocity, with the same BC, makes zero difference what size cartridge shoots it. Same results.
Except with .300 BLK, you don't have to use special powders, and with .308 Win subsonics, it's a big pain in the ass, and you have to use Trail Boss powder, drill-out your flash holes to 9/64", and use magnum primers. I've made lots of .308 Win subsonics over the years, and I built a .300 BLK AR15 years ago. I want to buy a .300 BLK bolt-action next, and I'll stick to supersonics in my .308 Win.
Thank you. Thats the kind of info I was wondering about.
This thread sparked me to do some more (deeper) hands-on research with my .308 Win subs... Checkout the subsonics thread in the reloading section if you're interested... I will definitely be playing with this much more in the future. Plus, I was getting bored because all my load development has been completed with my commonly-used range guns and hunting rifles, and this gives me something new to fuck with. 
Titegroup solves the case capacity issue. I've been loading 45-70 with Titegroup and getting single-digit SD's.
I use CFE BLK in .300BLK with good results as well.
It seems that fast-burning powders are where it's at for subs.
This has not been my experience with Titegroup. In a 45-70 case, I get 4.8FPS SD's and 18FPS Extreme Spread with a 405gr LFP. I'd imagine the 45-70 case is one of the most extreme examples of a large case with minimal powder fill, especially with Titegroup.
Have had some good results for 308 subs
They are a pain compared to 300blk though. Much easier in the smaller cartridge and tons of powder and bullet options that will get good results.
They are a pain compared to 300blk though. Much easier in the smaller cartridge and tons of powder and bullet options that will get good results.
I have found 300blk subs to be far more accurate that 308. Just personal experience with multiple rifles
One of the biggest differences I could think of besides case capacity issues is 308W barrels don't come in subsonic twist rates and you probably don't already own a 9" 308W barrel in 1:7" on an SBR'd action. Once you start investing money in a 308W barrel that is properly suited for subs you should've just had it chambered in Blackout.
i've also had some good loads with titegroup and 308 subs. i've been using reduced loads of imr 4895 with 190gr to 220gr bullets in 308 with good results , it's also pretty position insensitive like titegroup
I was looking into what is the preferred twist rate for 308win subs, surprisingly most people seemed to recommend just sticking with a 10 or 11 twist. Which may be because that’s just what they already own, but it does appear these slower twists handle subs without too many issue.
I’d have thought 1:8 twists would’ve become more common in 308, seeing that it’s pretty much the go to twist for most cartridges these days, even with 300Norma 1:8 appears to be the most popular twist rate.
What will the 300bo do the 308 won't, nothing.
What will the 308win do the bo won't, that list is very long.
If you really get into subs, in general you will find about 80% of the info on the net about them is total B/S, and when it comes to 308 (& larger)that number increases about 15 %. ie When it comes to loading them, their ability's on a paper/steel target, as well as on meat targets at distances most would not believe unless they were there,...
I am well aware, there's a reason 300 blks are always a 1:8 or tighter.
But for one reason or another 308win has still stuck with slow twist barrels while more modern cartridges have standardized on tighter twist (almost always 1:8 it would seem).
However most people using subs in 308 don't tend to run the super heavy high BC bullets, so is probably the reason they can get away with the slower twists.
Because those barrels weren't designed, purchased, or chambered for subsonic ammo
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