by Tom Gaylord
Writing as B.B. Pelletier

Sig P365
Sig Sauer P365 BB pistol.

Part 1

This report covers:

  • The test
  • Realism
  • Fresh CO2
  • Oiled the pistol
  • Hornady Black Diamond
  • Sig BBs
  • ASG Blaster BBs
  • Daisy Match Grade Avanti Precision Ground Shot
  • Nature of CO2
  • Shot count and blowback
  • Trigger pull
  • Installing the CO2
  • Summary

Today we look at the velocity of the Sig P365 Air Pistol. If you’re new to airgunning you need to know that CO2 responds best to two things — high temperature and a long barrel. The temperature was fine when I tested the gun (74 degrees F) but we are dealing with a compact pistol whose barrel has to be short. That will affect the power of any CO2 pistol, regardless of the maker.

The test

I shot through the chronograph at 2 feet distance from the start screen. I waited a minimum of 10 seconds between shots in today’s test. Sometimes the wait was much longer but it was never less. Later in the report I will address why this is necessary.


I have told you how realistic this pistol is. I still have to check the gun every time I handle it because my 9 mm P365 that is always loaded is in my office all the time. It would not do to pick up the wrong pistol!


Fresh CO2

For this test I loaded a new CO2 cartridge. I always put a drop of Crosman Pellgunoil on the tip of each new cartridge before piercing it. When the cartridge is pierced the oil is blown into the valve and it gets on all the o-rings and seals inside. It keeps them fresh and doing their job. At the end of the report I have an important message about piercing this pistol, so don’t miss it.

Oiled the pistol

I talked to Ed Schultz of Sig regarding the P365 and he told me this BB pistol tends to run dry. Oiling some key points will help ensure smooth reliable operation. Just pull the slide as far back as you can and hold the pistol upside-down to access the oiling spots under the slide, as shown in the photo below that Ed sent me.

P365 oil
From Ed Schultz to you. These are the 4 places to oil the P365 slide periodically. Also oil each new CO2 cartridge.

Ed says Sig is looking into an oil they can sell for this purpose, but for now you can use a 20-weight non-detergent motor oil that has an o-ring conditioner in it. Crosman Pellgunoil is a good choice!

Hornady Black Diamond

First up was the Hornady Black Diamond BB. The P365 magazine holds 12 BBs, but I loaded just ten for this test. That way I can test the magazine hold-open function as well.

Ten Black Diamonds averaged 298 f.p.s. Since these were fired first there was a broader spread of velocities. The low was 287 and the high was 319 f.p.s. — shots one and two, respectively. That’s a spread of 62 f.p.s. The average was pretty close to where it should be, even though the extremes are far apart. It’s listed at a maximum of 295 f.p.s. and that’s what this one gets. And, the magazine hold-open works exactly as it should. I will tell you in a bit why the spread was so large.

Sig BBs

Sig doesn’t make BBs — yet. So they don’t have their own brand of BBs to sell, but they do include a small plastic packet of steel BBs with each gun. So I tried them. They averaged 299 f.p.s. with a spread that went from 293 to 305 f.p.s. That’s a difference of 12 f.p.s. Now that the CO2 gas in the cartridge is being used the gun is settling down. Often the first couple shots after piercing a cartridge have liquid CO2 in the valve that bollixes up the velocity, as you saw in the first string.

ASG Blaster BBs

Next I tried 10 ASG Blaster BBs. They averaged 299 f.p.s. with a low of 293 and a high of 304 f.p.s. The spread was 11 f.p.s. That’s close to the Sig BB performance. I’m not saying Sig rebrands those particular BBs — just that all steel BBs perform about the same in this pistol, once it settles down. So the Hornady BBs would also be like these is I hadn’t fired them first.

Daisy Match Grade Avanti Precision Ground Shot

The last BB I tested was the Daisy Match Grade Avanti Precision Ground Shot. For this one I am going to show you the entire string — shot-by-shot.

2…………did not register

It’s pretty obvious what happened in this string. These BBs started out just as fast as the first three, then around shot number three the liquid CO2 ran out and only gas was left in the cartridge. That’s when the velocity starts to drop. Let’s see why.

Nature of CO2

CO2 develops pressure when the liquid inside the cartridge flashes (evaporates rapidly) to gas. At 70 degrees F its pressure is around 850 psi when it is contained in a vessel with no escape. But, as it evaporates while the gun is shot, it cools the surfaces of the gun that it comes in contact with, which is all of the gas chambers and ports inside the gun. In turn this lowers the temperature and also the pressure of the CO2 gas, resulting in lower velocity. That’s why I wait at least 10 seconds between shots — to allow the gun to normalize and not cool down too much.

Shot count and blowback

I had heard somewhere that the P365 gets about 40 good shots per CO2 cartridge and this test bears that out. The slide is small so it’s also light, so the blowback isn’t as strong as with some larger pistols. Still the slide does move all the way back and you do feel it.

Trigger pull

The trigger has a light pull with some travel. It feels like a double action pull because of the travel. To begin shooting you have to cock the hammer by pulling back the slide unless the slide is already locked back and you just release it after loading a fresh magazine. The trigger pull is a surprisingly light 3 lbs. 13 oz. Several times the pistol surprised me by firing before I was ready. I’m glad that happened when the BB trap was only three feet away and not when I was shooting at a target! I’m making a note to myself to respect this light trigger.

Installing the CO2

I purposely waited until now to discuss this procedure so it doesn’t get overlooked. The P365 pierces the CO2 cartridge when the magazine cap is screwed down, like many gas pistols. But, there is a thick face seal (where the flat end of the cartridge bears against as it is pierced) in this magazine and the CO2 will leak out until the cap fully compresses it — so there is a special knack to piercing the CO2 cartridge in this pistol. The first couple cartridges I installed lost a lot of gas before I got them sealed.

The trick is to screw the magazine cap down until it’s tight against the cartridge. Then hold the magazine body in one hand and the Allen wrench in the other hand with the hands rotated so that relaxing them would give the end cap almost a full twist. When you do this, just let each hand go its way and finish screwing the end cap down. The CO2 will hiss for an instant if you do it right and you won’t lose much gas, if any.

P365 gas
To pierce the CO2 cartridge quickly, hold the magazine in one hand and the Allen wrench in the other in such a way that the hands move in opposite directions to screw the cap down rapidly.

Once I did this, the cartridge was pierced just as quickly as any air pistol could. When I did the velocity and shot count test the cartridge was pierced this way, so no gas was lost.


It’s been fun getting acquainted with this little BB pistol. Because I am so familiar with the firearm already, I felt I was shooting with an old friend.

Accuracy comes next, but that isn’t the final report. I then want to talk about using this airgun and others as a self-defense training tool. I will show you my carry holsters and discuss how I use the gun to train. Until then!