Sig Sauer P365 Part 5

Sig Sauer P365 Part 5

Velocity checks – A fast miss vs. a slow bullseye

By Dennis Adler 

What a good training gun should be, the Sig Sauer P365 gives you a proper hands-on experience comparable to the centerfire model. It is not perfect, but it delivers on feedback and accuracy, if not the velocity of larger blowback action CO2 models.

About 30 years ago, I used to keep a custom built S&W Model 25 with a 2-inch barrel close by when I was off in the desert testing four wheel drive vehicles. A Model 25 is a .45 ACP revolver. A 230 grain hard ball out of a 2-inch barrel wasn’t exactly setting any velocity records. You didn’t need Shoot-N-C targets at the range; you could shoot and see the bullet going downrange. (Not really but muzzle velocity was about 650 to 700 fps). One thing I can say though, is that I didn’t miss too often with that snub nose .45 S&W revolver. What it taught me was that velocity isn’t always as important as accuracy, and that may be the best takeaway from the Sig Sauer P365 CO2 model. It’s not going to surpass other larger blowback action CO2 pistols sending .177 caliber steel balls downrange, but it is probably going to outshoot most of them.

My only problem with the P365 was in turning down the seating cap, which is pretty shallow to contribute in scaling down the CO2 components to meet the centerfie gun’s Micro-Compact specs.

Fumble fingers

Shop Benjamin Rifles

I have been a little slow in turning down the seating screw cap because it is shallow and there’s very little room for the head of the wrench in the base. I was taking two motions with the wrench to get the job done and a little CO2 had been escaping each time. What I found works best, is after threading the cap onto the magazine, so that it is finger tight, put the wrench into the opening and rotate your hands so that you are twisting the magazine counterclockwise while turning the hex head tool clockwise to get the cap threaded down and pierce the CO2 in one continuous motion. With the shorter threads on the cap this worked effectively and I heard no CO2 escaping. The best part of this is that the cap turns into the magazine with very little fumbling to align it. There are some other threaded caps that make this simple job a contest of dexterity. Not so with the Sig’s CO2 magazine.

The threaded seating cap screws into the magazine easily, no fumbling to align the threads like you find on many other designs that have removable seating caps.
Turn the cap down finger tight. It has a couple of more turns left in this photo. It will end up almost flush. Then insert the wrench and position your hands so you are turning both the magazine and wrench to thread the cap all the way down and pierce the CO2. It needs to be one continuous motion. If you fall short, CO2 will begin to escape. Takes a little practice but isn’t hard to do.

Velocity recheck  

Since the first velocity tests were with what I’ll call, “leaked CO2” I am going to run the Umarex Precision steel BBs a second time before starting on comparisons with other brands. With the freshly inserted CO2 the P365 clocked a slightly higher average velocity of 281 fps for the first 12 rounds with a high of 292 fps. Accuracy, shooting through the chronograph again gave an impressive 12-shot spread of 1.0 inches with a best 5-shots into one hole, (actually more than five hits), with a spread of 0.4375 inches. Like I said, it might not be a world beater for velocity, but the little Sig can punch tight groups downrange and push that slide back into your hand with enough recoil to give a palpable sense of having fired a small caliber handgun. That’s worth 20 to 25 fps.

After using Umarex BBs for the initial velocity test, I added in four other brands of .177 caliber BBs for comparisons.

I decided to jump from one extreme to the other by shooting the second velocity test with Air Venturi Dust Devils. These lighter weight 4.35 gr. frangible composite BBs gave the old Umarex Walther PPK/S a new lease on life for velocity in the plus 300 fps range, and I expect they will do the same for the new Sig Sauer. The answer here is yes and no. Yes, velocity increased to Sig’s advertised 295 fps but accuracy took a hit as did consistency of feeding and trigger resistance. I won’t call it a feeding problem because the gun still works, but all the smoothness is gone. I wouldn’t recommend the Dust Devils for this pistol. The slight gain in downrange velocity is no trade for 1.75 inch groups from a blowback action pistol that was delivering 1-inch and under on steel BBs.

I re-shot the velocity test with the Umarex Precision steel BBs because I had lost some air tightening down the seating cap the first day. Velocity was up a little, but still under 300 fps, but when you can shoot groups like this with a 3.1 inch barrel from 21 feet firing offhand, velocity doesn’t seem quite as important. A slow bullseye is better than a fast miss.

What advantage is there to trying another brand of steel BBs in the P365? If that BB is Hornady Black Diamond, there is a chance the gun will pick up a few fps. As it turns out, the Hornady hit an average of 280 fps, just a hair lower than the Umarex, and accuracy was not quite as good. This is the outcome with Black Diamond about 50 percent of the time with blowback action pistols. Still, 12 rounds of Hornady covered 1.43 inches with fairly linear groups hitting a little below POA with a best 5-round spread of 0.74 inches. With the Sig I have found that POA at 21 feet should be right on top of the bullseye and not a traditional 6 o’clock hold. The gun hits a little low with the fixed sights.

My groups were not quite as close with Hornady Black Diamond, but very linear for the most part with straight lines of hits. No noteworthy improvement in velocity.


I decided to run the Crosman Copperhead next and change CO2. (I had already shot about 60 rounds through the gun between set up and velocity tests). The Copperhead clocked 279 fps, just under the Black Diamond by 1 fps average and with a fresh CO2. The Sig again hit below POA and put 12 shots into 1.5 inches with a string of 5-shots at 0.75 inches.

Everything is fairly consistent with velocity hovering around 280 fps (except for the Dust Devils, which were faster but didn’t function well in the Sig), and accuracy with 12 shots averaging 1.0 to 1.5 inch groups from 21 feet.

After a failed couple of runs with Dust Devils, which seemed to cause minor internal issues with feeding and the action, I decided they were not for the Sig and went to the Crosman Copperhead coated steel BBs. Velocity was still under 300 fps but the accuracy was pretty good. The gun shot low with everything except Umarex steel BBs. No good explanation, the gun knows what it likes.

The Remington came in within a fraction of the Copperhead for velocity and accuracy with a best 5-shot group at 0.76 inches. Overall, best accuracy was achieved with the Umarex Precision steel BBs. Is it just a coincidence perhaps? One more target then. At 21 feet,  2 rounds of Umarex punched into 1.5 inches, not quite as good as before but with a solid 5-shot group inside 0.75 inches. The Sig is nothing if not consistent and it is shooting groups comparable to 5-inch barrel 1911 CO2 models.

Back up the middle and around POA, the final test for the day was back to Umarex Precision which gave me another tight group, though not quite as good as the morning’s first test. Still, there’s nothing here not to like, when all 12 rounds are in the 10 and X rings.

We’ll wrap up Saturday (or Sunday weather permitting) with the job of a CO2 understudy, a 7-yard combat shooting test with the blowback action P365 against the actual 9mm Sig Sauer model.

A word about safety

Blowback action airguns provide the look, feel and operation of their cartridge-firing counterparts and this is one reason why they have become so popular. Airguns in general all look like guns, blowback action models more so, and it is important to remember that the vast majority of people can’t tell an airgun from a cartridge gun. Never brandish an airgun in public. Always, and I can never stress this enough, always treat an airgun as you would a cartridge gun. The same manual of operation and safety should always apply.

2 thoughts on “Sig Sauer P365 Part 5”

  1. Concerning the CO2 leakage and your comment about velocity. I thought that as long as any liquid CO2 remained in the cylinder that the pressure remained constant at about 1100 psi at room temp.

    • From all of my experience with CO2, as the volume of CO2 remaining decreases, velocity begins to decline. With the situation I described, I probably lost 2 seconds of CO2 fumbling with the seating screw, and that could have (and proved to) have resulted in a lower velocity with the first tests.

Leave a Comment