This report covers:

  • Foster fitting
  • Electricity
  • Fill probes
  • De-facto standards
  • Standards that work
  • PCP hookup
  • Ammo
  • Summary

Today I write about a subject that plagues us all — standards. There are so many that it seems as if there are none.

Foster fitting

At the beginning of this month I lamented that the Foster fitting on the first Seneca Eagle Claw rifle I tested was super-hard to attach to. I had no idea that Foster fittings came in many different sizes. Read this Airgun Wire article by Tom McHale to learn more.

I always wondered why some Fosters were hard to attach to — now I know. But the knowing may not help that much!

Foster male
The male Foster fitting that BB thought was universal comes in many incompatible flavors.


You learn real quick when you travel that electricity is different wherever you go. Not just the shape of the plugs that go into the wall, either. In much of Europe, the AC electricity is 50 cycles per second/Hz, while here in the US it’s 60. Does that matter?  Well, your US alarm clock may lose time if the cycles are fewer AND if your clock is running directly on the power grid electricity. One way around this is to put a converter in the clock and convert the power to direct current that the clock then runs on.

It’s not just clocks. Microwaves, coffeemakers, clothes washers and scads of other appliances that use time in their operation also have to be considered. And the problem goes beyond just time. An electric motor that’s built to run on 60 Hz alternating current will run slower on 50 Hz — even if the voltage has been rectified to correct parameters. That’s not good for the motor.

Fill probes

I once had an airgun maker tell me their airguns were made to accept a “standard 8 mm fill probe”. Great! Except for one or two things. First, how long is the probe for their guns? Will someone else’s short probe even put the air release holes far enough into your fill port to get air into the gun?

Also, where are the air release holes located on the probe? Are they somewhere that the air they release has a chance to enter the air intake port on the gun being filled? Or are they out so far that they are on the outside of the gun’s fill port?

I criticize Air Arms for their odd-looking fill adaptor, but given that Foster fittings aren’t all the same I guess it doesn’t make any difference.

Air Arms adaptor
The Air Arms fill adaptor is goofy-looking, but it works.

If you look at the fillers and adaptors for precharged airgun on the Pyramyd Air website you will find 50 different items.

De-facto standards

There are some things that have become standards just because they were first and people have used them, mostly without complaint. The 1/8″ BSPP (British Standard Parallel Pipe) thread is one example. But there are still problems with even this. The Koreans, for example, don’t make their thread sizes in this nearly-universal size, or at least they haven’t in the past. So there are a lot of fill probes that won’t attach to air hoses without going through another fitting adaptor ritual. As Jefferson Airplane taught us, “One pill makes you larger. One pill makes you small. And the ones that mother gives you, don’t do anything at all…”

Find a Hawke Scope

Standards that work

Okay, what about standards that do work? Still talking about high pressure air, scuba tanks have a couple standards that are fairly universal. In my limited experience, DIN 200 bar and DIN 300 bar fittings are the same, except for their lengths and the pressures they are designed for. DIN stands for Deutsches Institut für Normung (German Institute for Standardization).The hole in the 300 bar fitting is deeper than the hole in the 200 bar fitting, but the diameter and threads are the same.

300 bar DIN
The 300 bar DIN has a deeper hole than the 200 bar, but the threads and diameter are the same.

Oddly enough, rotary airgun magazines have some commonality across brands. A Marauder mag, for instance, fits several different PCPs. And, when that is the case, usually a single-shot tray will also interchange between platforms.

Marauder mag
Many airgun companies use the same magazine as the Benjamin Marauder.

PCP hookup

Years ago Pyramyd Air discovered that connectors were a major obstacle to new buyers of precharged airguns. So they created a “PCP Hookup” tab on each PCP main page that shows the buyer what will fill the gun. It’s down by the description. Each of the items in that dropdown page can be clicked on and it takes you to a sub-page of fill devices that attach to the Air Arms Adaptors.

One of these days I will have to write a blog that’s devoted to filling precharged guns, because there are several things to be considered. It’s not just the fill device, but also the input connector and the hose that connects it to the fill device.


No problem with airgun ammunition — right?

Wrong! Just try to load the oversized Marksman BB (diameter of 0.1765-inches) into any normal BB gun!

DON’T TRY IT! I already did and I still have a BB jammed in my 1976 Pioneer BB gun shot tube!!! Steel BBs are 0.171 to 0.173-inches in diameter, and don’t try telling me that a couple thousandths of an inch make no difference. They really do! I have had woodworkers tell me that thousandths of an inch aren’t important, and for projects like building houses they aren’t. But when it comes to ammunition, they really matter. 

Even big bore air rifles come into play on this one. My AirForce Texan loves bullets sized 0.4575- to 0.459-inches in diameter and will not tolerate them smaller than 0.456-inches. That’s why I went to Mr. Hollowpoint for my Texan bullets and I found some that the rifle really likes. 

But there are at least three different sizes of .45 bullets and they either will or will not work in a gun, depending on its barrel. There are 0.451-0.452-inch pistol  bullets that are for the lower-powered airguns. Then there are 0.454-inch bullets that are for Hatsan guns. Finally there are 0.457-0.459 bullets that are for the more powerful air rifles.

I have tried on this blog to help those new to big bore airguns understand the ammo issues. The barrels of the Korean big bores that I have tested, for example, were sized to fit lighter weight pistol bullets. They liked bullets sized 0.452-inches in diameter.

I see that Pyramyd now offers a 166-grain lead bullet that’s 0.457-inches in diameter and that might be good for a test with my Texan at some point. It sure would go fast!

Pellets are a different matter. They tend to fit all airguns of their caliber, though we all do know that some pellets shoot better in certain airguns than others. Years ago there was a small issue with some oversized .22-caliber Eley Wasps that were made large to fit specific vintage pellet guns, but as long as you knew that, everything worked out well.


Standards are in place to make things more compatible, but when they are either disregarded or mismanaged they can make the situation worse instead of better. What are your concerns about airgun standards?