Subsonic vs regular
- Thread starter Talonstylz
- Start date
So what would be the benefit to having a subsonic load besides the “volume” it seems like.
And can it be achieved with a 124gr bullit?
NedwardFlanders
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- Location
- Saskatoon, SK
A supersonic bullet will lose stability for a brief instant when going subsonic. Going through the transonic zone causes loss of accuracy. Therefore if your exit velocity isn't enough to carry your bullet to the target while maintaining supersonic travel you can gain accuracy by loading subsonic instead.
This. All competition .22lr is subsonic for this reason. The drop through transonic kills accuracy as the bullet *shudders* in various ways depending on spin and other factors of design and mass. Think about what range you'll be shooting, whether your shooting habits are going to actually require the higher velocity of a supersonic bullet or you can live with lower velocity and a steeper trajectory, then make your choice.
Of course for Americans and those in some other countries suppressors also enter into this equation, but precision delivery on target is much more relevant even there. Hence the popularity in the USA of subsonic .300blk and a few other rifle rounds for hog control and other pest management. Lower noise when suppressed is certainly important, but a very heavy bullet hitting accurately does the job a lot better than a hotter round missing the target or just catching the edge of it.
Wow guys, a lot of amazing info.
How would one load for subsonic? Would I just keep dropping the powder charge until the velocity is under 1000 and still cycles?
Or is there a different way? All this covid boredom has me wanting to try new things.
Thanks.
How would one load for subsonic? Would I just keep dropping the powder charge until the velocity is under 1000 and still cycles?
Or is there a different way? All this covid boredom has me wanting to try new things.
Thanks.
Yes reduced loads, a note of caution some powders do strange things when reduced significantly below published loads, also be aware of squib loads sticking a bullet in the barrel is not good. Trailboss powder was developed for low velocity loads it is a bulky powder and fills case nicely but it doesn’t like to be compressed, there are probably published loads for this powder in 9mm.
That 'still cycles' part is the magic. I'm not a reloader so can't offer anything on that point, but one recent innovation in .22lr provides an interesting point of reference. CCI's new 'Quiet Semi-Auto' round is truly impressive for its compromise between a slightly boosted velocity over their old Quiet cartridge which was rated at 710fps from a typical rifle and wouldn't cycle most actions. The new Semi-Auto version is 5gr heavier at 45gr and rated at 835fps from a rifle, and it cycles most semi-auto actions on rifles and pistols just fine. No idea what magic they did with the powder but it's impressively quiet from a rifle and just about in that sweet spot for accurate shooting at shorter ranges where airgun tuners often go for the ideal compromise. Actually a little slow still compared to pellet optimum - for a good pellet like a JSB Exact Heavy 18gr that's closer to 900fps, maybe as high as 950fps in some barrels. But for keeping it quieter and given the superior inherent stability of a 45gr .22lr bullet with its much higher BCC compared to a diabolo pellet, seems 835fps is just fine.
Something to consider for shooting subsonic 9mm from a rifle/carbine is spring type. With my TNW Aero, there was the odd feeding issue using the stock spring with some types of 147gr subsonics. Very occasionally the bolt wouldn't quite go back far enough to feed the next round, resulting in a cartridge lodged at a slight angle with a dent in the copper jacket. JHP was slightly more likely to do this, the hollow nose catching on the upper edge of the chamber. It was only occasional but I don't like anything less than 100% reliability, so I looked into modifications. I ended up boring out the buffer weight (a separate steel weight behind the heavy bolt in this blowback design) and inserting a much heavier tungsten rod, and replacing the stock spring (which was getting too hard to compress at the back end of its cycle) with a flat wire spring almost double the stock spring length. Now it cycles flawlessly with anything subsonic I've tried, from 900fps up to 1120fps in 147gr from various manufacturers. The tungsten rod was an eBay find, heavier than gold for a given size, and the spring a standard AR thing bought from Reliable, from Strike Industries. They don't seem to stock it any longer but they're available elsewhere. Out of a 9mm pistol there may also be various spring types to choose from though I'm not sure how effective that change alone might be for cycling, given that you can't really change slide weight, and some 9mm carbines use non-AR type springs so likewise could be more challenging to tune.
That's pretty much it. The heavier your bullet, the easier it'll be to achieve that.
Not that for anything other than a semi (bolt action, single shot, lever-action or a revolver), cycling isn't a problem.
As for the sounds it makes, you won't notice that much of a difference unless you have a silencer.
