What happens when we hang a weight at the end of a rifle barrel? More to the point,
attaching a suppressor that is 9.3 inches long, has a diameter of 1.75 inches and
weighs 1.1 pounds – such a can has got to mess with barrel harmonics. What about
balance of the rifle, accuracy, any shift in point of impact and especially
shootability under field conditions?
Well, I got the means of exploring some of those issues. Because after more than
eight months, ATF finally sent its approval, and I wasted no time to pick up my SIG
SAUER SRD762 TI silencer, as they refer to it. From here on I’ll call it the SIG
Can, or simply Can. That is basically all it is. Except, behind this Can is a well
thought out design. SIG SAUER received awards for it. Their Can has no outer tube,
is made from Titanium parts welded together. This maximizes internal volume and
surface area while minimizing weight.
Suppressors ‘work’ by robbing the hot and high pressure gases exiting a barrel of
much of their energy. This takes place by a more gradual pressure reduction and by
cooling those gases. Instead of instantly discharging those high pressure gases to
ambient, a pressure differential of thousands of pounds per square inch (psi), which
is basically a controlled explosion, a suppressor like a muffler channels those gases
through several compartments. The result is a more gradual pressure reduction.
Simultaneously, there is significant cooling going on. That Can gets too hot to
handle in just a few shots from calibers in .308 Win class, for example. Heating of
the Can appears proportional to the powder quantity in the ammunition. The Can barely
warmed when used with subsonic loads of a 300 Whisper, where less than ten grains of
powder do the accelerating.
To say it up front, whatever else this SIG Can may do, it does make shooting very
quiet. That is especially the case with subsonic ammunition. There are no decibel
measurements. To say it scientifically, I know guys who can fart louder. While
waiting for the ATF approval I had done some planning, and my friend Ron some
machining. Add to that rifles from Steve. The first step for each rifle was a fit
check. That is, attaching the Can via its 5/8-24 threads and then looking down the
bore to confirm that it was indeed in (near) perfect alignment, meaning that a fired
projectile would not touch any of the 20 compartments inside the Can.
Next step: go out and shoot (through) the darn thing. I did this an hour before our
annual Turkey Shoot. First up, of course, was a 300 Whisper (the cartridge design
stolen by some big company and re-named as 300 AAC or Blackout). The 300 Whisper was
created to operate quietly with subsonic loads. And this SIG Can make it so. Next
up was Tikka T3 in .243 Win. No Can will eliminate the supersonic crack when the
fired projectile departs faster than the speed of sound. Shooting without ear
protection I could hear with how much violence 80 grains of Sierra smack a steel
plate some hundred and twenty paces away. Cool! And while the supersonic crack is
loud and annoying, the noise level is no longer damaging to our ears.
Nice! Too bad such healthy and environmentally friendly technology requires a $200
tax stamp and 8 month waiting period. May Trump trump that.
So much for the acoustics. All cans also have a positive effect on recoil. The
Sig Can is not as efficient as a dedicated muzzle brake. Still, adding that 1.1
pounds and streaming the gases out slower changes recoil from a punch-like impact
to a friendlier and lesser shove.
The first day of more serious testing, meaning shooting from the bench, happened
to be accompanied with strong and cold wind. That alone resulted in one data
point: the wind was strong enough that with Can installed, the rifles on the sand
bags wiggled slightly more than without. The crosshairs, at 10X or more power,
noticeably moved around more. Similarly, trying to aim offhand in windy
conditions was more difficult with the Can added to a barrel.
Then I opted for a structural test, simply because the opportunity was there.
Steve had a new 24” barrel for his TC Encore. He had ordered it with 5/8-24
threads. The Can also aligned just fine with this .338 WinMag barrel. And
since the holes in the SIG Can appeared to be right at 10mm, meaning a .40 S&W
bullet would fit, I told Steve to touch one off if he wanted to. He did. And
a fat smile came over his face. Because for the first time his .338 WinMag did
not punish him. The next couple of shots actually grouped OK. He ordered a
muzzle brake after that. And the SIG Can showed no signs of distress.
Getting into details, here are my observations:
.300 Whisper / aka AAC or Blackout
The Ruger American came with 16” barrel, threaded muzzle, and a trigger that
sucks. Allow a quick side note. Apparently many Ruger owners realized that the
triggers in the American are just too heavy. Timney to the rescue! Mine went
on backorder, since the demand was huge. But then it arrived, and all is better
now.
So far I spent most of my suppressor time with the Whisper. As is, this rifle
is too short to be a good offhand gun. Adding the SIG Can gave a more capable
balance. Some may not agree, since it appears heavier than a production varmint
rifle. Yet, because of the shorter barrel it also remained agile with the Can
out front. I’d say that if the typical bolt action rifle is to be carried via
typical sling during typical hunting, then this Sig Can should be married to a
barrel no longer than about 16”. Anything more, and field duty may become
burdensome.
It cannot be overstated that with subsonic loads the rig is a ton of fun to
shoot. I love the music of ricochets. By now I have dialed this rig in. It
will be rare that I’ll shoot it without that suppressor; I’d say the rifle was
made to go with a can. When zeroed at 50 steps with 180 grain lead bullets
going about 1000 fps (9.5 grains of IMR 4227), a supersonic, but by no means
maximum load firing a 125 grain Sierra softpoint (17 grains of IMR4227) is
approximately “on” all the way past 150 paces. That will be my hunting
combination – lead bullet in the chamber, soft points in the mag should another
shot be needed.
Another complaint: this Ruger only feeds pointed bullets reliably from its
6-shot mag. Even with supersonic loads this rifle/Can combo is not unpleasant.
That holds for a maximum load firing 110 grain Vmax’s. Three of those grouped
into .6” at a hundred yards. But zeroed for those 180s at 50, the Vmax’s print
some 8 inches high at 150. So they won’t get that backup job.
There is another concern. At subsonic speeds all .30 cal bullets seem to
perform like FMJs. I invested sixteen bucks into a little gadget that makes
hollow points into lead bullets. Did that to some 180s, and shot two into wet
newspapers. Well, 8 inches of paper and at least 12 inches of water (bottles)
did not stop them, and the holes did not suggest obvious expansion. We may need
to go supersonic for acceptable hunting performance on critters larger than
squirrels and rabbits.
.243 Winchester
Buddy Ron threaded the muzzle of my Tikka T3 during those long 8+ months.
Attaching the Can to that 22.6” barrel clearly made the rifle ‘heavy’ out front.
From the bench, accuracy improved with every load tested that day.
The Can also allowed me to shoot this rifle more accurately offhand. But it
clearly takes more muscle to get the crosshairs on target. Once there, though,
they don’t move off as easily as with the naked barrel. The Can did cause a
shift of impact. Here’s an example.
Note that the aiming point for each of the six shots was the upper circle. The
Can grouped those 70 grain TNTs several inches lower. Meaning I will have to
decide if I want to zero this rifle for suppressor use.
6XC
Just because I could, I also tested the Can on a Rem 700 with a 26” heavy varmint
barrel and chambered in 6XC. Same change in recoil as for the .260 Rem (see below),
but no change in accuracy. That 6XC is already more accurate than I can aim it.
Adding the Can made this into a ridiculous rig, both in weight and length. But I
have the option. Interesting was the shift of impact. With 65 grain Bergers it was
about an inch in elevation and half that in windage. Heavier bullets minimized
those effects. 90 grain Bergers almost shot to the same point of impact.
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.260 Remington
The Tikka CTR came from the factory with its 20” barrel threaded. Already a heavier
gun due to its medium-thick barrel, adding the Can fattened it to about as much as
one would want to handle offhand. Then it behaved in similar fashion to the .243.
That is, groups tightened (or is it that I simply could shoot tighter groups more
easily?). There was also a shift of impact, unfortunately not just in elevation,
but also to the right. Here it became obvious that the weight and effects of the
Can left more recoil than a dedicated muzzle brake. But it was noticeably different,
namely a pleasant shove.
Weeks later I had an opportunity to shoot at about 1000 yards. At least with 123
Amax bullets, the change in the point of impact seemed not as great as the 140s had
shown on paper at 100 steps. Out in the desert I wasn’t about to climb to that 1000
yds spot to set up and later retrieve some big enough paper target to measure the
actual difference.
.308 Winchester
Ron had also threaded the muzzle on the Mossberg MVP. With its 18.5” medium weight
barrel it as well seems to invite a can. Similar to the Tikka CTR, weight and balance
appear at a useful limit. For me the offhand accuracy improved, at least for a few
shots. It may become too much to handle near the end of a 40-shot silhouette match,
for example. Off the bench, accuracy also peaked. Never before had I been able to
get a sub-inch group. With this Can it happened. MVP and Sig Sauer have made friends.
Plans are in place to attach the Sig Sauer to a .223 Rem. Maybe even a .22LR, even
though nobody recommends much rimfire use with a can that could not be disassembled
for cleaning. Those .22s are dirty little beasts. Then again, silence is addicting.
And .308-class ammo may just burn off whatever .22s leave behind.
