“The soundless death coming from the ‘nowhere’ always shattered the guerrilla morale. The initial shock and the ensuing panic usually prevented the enemy from executing necessary defensive measures. By the time their leaders decided what to do, it was too late for them to do anything but flee or perish. So whenever given a chance we killed in silence.”
I can trace my interest in shooting suppressed all the way back to those 4 sentences. It’s a quote from a WWII SS officer in Devil’s Guard, a book about the First Indochina War. I first came across the quote as a reference in another book, Silencers In the 1980’s—which I read when I was young and impressionable—it has stuck with me the 20-odd years since then.
Being a single-shot Thompson/Center (T/C) handgun hunter, I have been exposed to the blast of rifle calibers out of short, handgun-length barrels more times than I would like to count. That is the other reason I have long been fascinated with shooting suppressed — no need to scramble for a pair of headphones or fumble with ear plugs when a good shot presents itself in the field.
I have owned a .30 caliber suppressor for several years now, a ‘Thundertrap’ by AWC Systems Technology. I’ve had various T/C barrels threaded for it and have tested it on a number of different .30 caliber rounds: .32ACP, .32 S&W Long, .300 Whisper, 7.62×39 and .308 Winchester, but in the last few months I’ve settled on one of my favorite suppressed .30 calibers: the .32 H&R Magnum. Specifically, I settled on the .32 H&R Magnum in my 10″ T/C pistol.
All the T/C barrels made in this caliber are actually .308 bore, but the .312 bullets intended for this caliber shoot just fine through them. This provides the nice added benefit of having a wide variety of bullet options to choose from when perfecting your own custom load.
Suppressed shooting and handloading really go hand-in-hand. The loudest noise of a suppressed round is the “sonic crack” associated with a bullet breaking the sound barrier. However, it’s rare to find off-the-shelf ammunition that can eliminate this sound under a wide variety of conditions such as different barrel lengths, altitudes, and atmospheric conditions. Even rounds marked “subsonic” are not guaranteed to perform optimally under the conditions you know you will be shooting. In order to make a round that suits your suppressed needs for these demands, you will have to make it yourself.
My initial suppressed loads for this caliber were right out of the Hornady reloading manual: 85gr JHP traveling 800 and 900fps. Using Blue Dot, the loads for these velocities are 5.0gr and 5.7gr, respectively. Both loads are extremely quiet through a high quality suppressor like the Thundertrap. When I test fired these in the hills near Wells Creek, Oregon, the sound of the 85gr JHP hitting the metal target was much louder than the sound of the round firing. My uncle mistakenly left his hearing protection on at the beginning of the tests and was surprised to hear the bullet hit the target down range—he hadn’t heard the round being fired!
While I was happy with these results, and knew those loads would be good for small game, I wanted to see if I could improve upon them by pushing the little .32 H&R Magnum to its suppressed limits. As far as I could find, there is no published load data for the .32 H&R Magnum with heavy 150gr+ bullets. It was time for me to develop some.
A few factors influenced the project: the T/C is a 1:10″ twist barrel, which presents a few challenges in selecting a bullet that will travel with stability at subsonic speed. Generally speaking, you need to hold the bullet weight to less than 170gr in 1:10″ twist .30 caliber barrels if you are shooting subsonic. If you want to go heavier than that, you should use a 1:8″ twist barrel. Since the .32 H&R Magnum is designed as a small pistol caliber, case capacity becomes a limiting factor as well.
I chose the Hornady 160gr FTX MX for this development, a bullet intended for the .308 Marlin Express. It is slightly longer than the other .30 caliber FTX bullet, meant for the 30-30 Winchester; as a result, its weight distribution yields good flight stability at subsonic speed. It’s also a nice mid-weight rifle bullet that will seat into a .32 H&R Magnum case with enough room left for fast-burning powder.
Extrapolating from existing data on 85gr and 100gr JHP loads, dealing with the limited case capacity, and avoiding possible overpressure issues, I switched to Red Dot powder and used just 1.5 grains for my first round. Unfortunately, using such a small amount of powder left me with a bullet stuck 3/4 of the way down the barrel. Annoying, but not a total surprise; I figured that might happen when I readied to pull the trigger.
I called my dad to talk about the problem and he made a fine point, saying, “Better than blowing it up.” He went on, “At least now you know there aren’t any pressure issues to worry about. Give 2.3 grains a shot.” Taking his advice, I popped out the stuck round and proceeded with making a few rounds using 2.3 grains of Red Dot. This worked in that the bullet actually exited the barrel with this load, but penetration was limited and the oblong entrance hole indicated the bullet was not traveling with stability. Based on stability calculations, the 160gr FTX MX will begin losing stability below 700fps and I figured this one was moving around 600fps, though I did not put it over a chronograph. My standard poor man test for penetration is 10 inches of interlaced phone books wrapped together with duct tape. This load pushed the 160gr FTX MX about 1.5 inches into it.
I upped it to 2.8 grains of Red Dot and found I was getting closer. No sonic crack, good penetration (more than 2.5″ into the phone books), and a nice sharp entrance hole. I put this load over the chronograph and they were only averaging about 720fps. In my experience, there is a sweet spot for suppression in the 700fps to 800fps range. If you are shooting suppressed and you want your shots to be BB gun quiet, try to develop for this velocity range. You give up some terminal foot-pounds performance in doing so, but you’ll certainly catch your target by surprise.
Looking to find the sound barrier edge, I methodically upped the grain count until I was testing 3.5 and 3.6 grains of Red Dot. Even 3.6 grains only upped the average velocity to 824fps. I was starting to wonder how far up I would need to go in order to get close to 1000 fps. At 3.9 grains I found an average of 881fps. Bumped it again, this time to 4.4grains, and finally got to an average velocity of 961 fps. This is a perfect speed for shooting suppressed while still having power at the target. It’s a good thing, too, with a 4.4 grain powder load the 160gr FTX MX is just about sitting on top of the powder when seated properly.
A 160gr Hornady FTX MX traveling 961fps gives the little .32 H&R Magnum 328 foot-pounds of energy at the muzzle, and 301 foot-pounds at 100 yards. Take it out to 200 yards, and it still delivers 277 foot-pounds of energy.
If you zero your sights at 100 yards, this round arcs as high as 3.3 inches at 75 yards, but it quickly drops to -5.9 inches at 125 yards, and -14.4 inches at 150 yards. This is lobbing them in a bit, but that is the case with any .30 caliber bullet traveling at subsonic speeds. What’s important is that the bullets have bite when they get there, and your target won’t hear it coming.
Here are the load details: Note: load data is provided for reference only. Load at your own risk and always cross-reference with manufacturer’s data before loading
- Load Name: .32 H&R Thunderstruck
- Caliber: .32 H&R Magnum
- Bullet: Hornady 160gr FTX Marlin Express (.308)
- Powder (Amount): Red Dot (4.4gn)
- Primer: Federal 100, small pistol
- Velocity: 961fps
- Energy, Muzzle: 328 ft-lbs
- Energy, 100yards: 301 ft-lbs
The formula I have adopted for calculating bullet stability is included below, written in Microsoft Excel format for ease of use.
- WT = weight of bullet (grains)
- DIA = bullet diameter (inches)
- TWIST = rate of barrel twist (inches per turn)
- BL = overall length of bullet (inches)
- V = bullet velocity (fps)
The existing data suggests the Stability Factor for bullets traveling subsonic velocity should exceed 2.0 and in my personal experience, this advice holds true.
Attribution: Peter Cronhelm, “The Search for the Ultimate Subsonic Bullet.”
About the author:
I’ve spent 11 of the last 14 years at Microsoft, working in Hardware,Robotics and large format multi-touch displays. In the odd years, I launched the company Vioguard as a co-founder and director of product development & manufacturing. I also designed and now manufacture Hellbreaker, a unique receiver for the M4 carbine and AR-15 family of firearms. I grew up in southwest Oregon, went to Oregon State University and now live in Eugene with my wife and our two boys. – John Sharps