BSA Scorpion/Ultra MMC/Hornet Info

Where does the HuMa regulator get fitted?

It is fitted in between the air reservoir/cylinder and the firing valve, adding 36-37mm to the length of your reservoir/cylinder, which means you may need to change your silencer/moderator or use a barrel extension.

How easy is a HuMa regulator to fit and can I do it myself?

The actual regulator does not take long to fit but you will also need to strip the rifle to replace/modify the transfer port and you will need to adjust the power as well. While the action is apart you can also service and tune some of the other parts of the rifle, following the guides on my website.  Have a look at the fitting instructions page for an idea of what is involved and what tools you may need. If you are not comfortable fitting a regulator yourself you can get it fitted by a professional, there is a list of some tuners on the Guides & Links page on the website.

What are the benefits to having a regulator fitted?

Unregulated rifles tend to have a “power curve” with a “sweet spot”. The first few shots after a fill may be under powered then the power increases until you get to the sweet spot, where they are more consistent, then the power drops off as the rifle runs out of air. Once your rifle is regulated you are in the “sweet spot” for the whole string of shots, until the cylinder pressure reaches the regulator set pressure (pressure setting varies depending on calibre and barrel length). The regulator makes the rifle more consistent and more air efficient, which improves the shot count and can improve accuracy. It also allows you to fill the rifle to a higher pressure, which will further improve the shot count compared to an unregulated rifle. Regulators are primarily for improving consistency and getting rid of the power curve, the fact that the shot count improves is a bonus. If you only want a higher shot count then it would be cheaper and quicker to fit a longer air cylinder.    

What can be done to your rifle? 

  • the action can be stripped, cleaned and examined,
  • any loose or ill fitting parts can be tightened and/or refinished correctly,
  • burrs, crud, tool marks etc can be removed or repaired,
  • any worn or damaged O rings should be replaced and properly lubricated,
  • the firing valve can be adjusted to reduce the difference in power between different pellets,
  • the standard metal spring guide (if fitted) can replaced with a lightweight spring guide,
  • a low friction "slip disk" can be fitted to the hammer assembly to reduce friction,
  • the trigger sears can polished and lubricated to make it smoother and more predictable,
  • the trigger can be modified to reduce side play and then set to your liking,
  • the ends of the hammer spring and firing valve spring can be de-burred and polished,
  • the transfer port can be modified to improve air flow,
  • the pellet inlet (magazine bridging part) can modified to make it easier to load magazines,
  • a short stroke hammer can be fitted to decrease the lock time,
  • you can modify the port in the barrel to improve airflow,
  • you can check the barrel crown and repair/re-crown if necessary,
  • make sure the gun is in good working order,
  • set the power to make sure it is running below 12flbs, unless it is an FAC model,
  • if you use the new style magazines you can remove the indexing,
  • you can fit an aftermarket regulator like the HuMa regulator,
  • this list is not exhaustive but gives you an idea of things that can be done to tune your rifle. 

How many shots can I expect from my airgun after the regulator is fitted?

  • .177 Ultra should give 55-65 regulated shots (from the standard 230mm air cylinder)
  • .22 Ultra should give 65-80 regulated shots (from the standard 230mm air cylinder)
  • .177 Scorpion should give 75-85 regulated shots (from the standard 325mm air cylinder)
  • .22 Scorpion should give 90-110 regulated shots (from the standard 325mm air cylinder)
  • .177 Hornet should give 80-85 regulated shots (from the standard 325mm air cylinder)
  • .22 Hornet should give 90-110 regulated shots (from the standard 325mm air cylinder)

If you fit a longer cylinder then the shot count will be higher than the quoted figures above.

The above figures are based on using an efficient pellet for setting the power, other pellets will vary:

  • in a .177 JSB Heavy 10.3g or Bisley Magnums,
  • in a .22 JSB Exact 15.9g/Air Arms Field 16g.

 Please note these figures are averages, some rifles may be higher or lower and it also depends on the pressure the reservoir has been filled to, the type of pellet being used, the power the rifle is set at etc. The higher the power the exponentially lower the shot count will be. 

There are a number of BSA air cylinders available and they are all interchangeable:

  • 175mm long  - fitted to Ultra SE rifles,
  • 230mm long - fitted to the old MMC Ultras,
  • 250mm long - fitted to Scorpion SE models,
  • 325mm long - fitted to the old Scorpion T10 and Hornet etc,
  • 425mm long - fitted to FAC/Export rifles. 

What pressure should I fill my airgun to after a regulator is fitted?

  • Ultra MMC 250bar
  • Scorpion 232bar
  • Hornet 232bar

The above assumes the air cylinder and associated parts are in good condition, using the standard length air cylinders.

HuMa vs Tench regulators 

The HuMa regulator is designed specifically for the BSA models, it does not involve any machining of the air cylinder and the rifle can be put back to standard if need be. The Tench regulator was designed to fit the Ultra/Scorpion/Hornet but it needs other parts to be fitted to get them to work properly, making them less DIY friendly. Both regulators regulate very well and will flatten the power curve.  

Will it affect my BSA warranty?

If you have any BSA warranty remaining on your rifle, then it will be lost. The BSA warranty is not transferable when the rifle is second hand, even if bought from a RFD. Generally very little goes wrong with PCPs, the usual faults are leaks which you can fix yourself following the guides on my YouTube/Vimeo channels.  

When is the best time to get a regulator fitted?

If the gun is brand new then it is probably best to run a tin of pellets through it before fitting a regulator. This will give you a chance to spot any issues with the gun, which can be dealt with by BSA under warranty.

Will my old silencer/moderator fit my rifle after it has be regulated?

Generally the Ultra* will be fine with any silencers/moderators that do not sleeve over the barrel. The original SAS type silencer that the older Ultra MMCs came with will not allow you to remove the filling cap without removing the silencer first.

*The later (2012) Ultras have a slightly longer air cylinder than the older ones, which means there is more chance of needing a barrel extension if you are using a silencer with an outside diameter of over 28mm. 

The Scorpion will be fine with silencers or shrouds with a maximum diameter of 28mm (like the Parker Hale) which will allow it to clear the air reservoir. I sell a small barrel extension in the eShop that allows you to fit standard silencers to the rifle. It is very close as to whether the HW silencer (30mm dia) will fit back onto the barrel after a regulator is fitted, some do some don't but all will accept 28mm silencers or shrouds.

What power do you set the gun to after fitting a regulator?

I would set the gun to around 11.5flbs using a heavy pellet, this gives you a bit of leeway for temperature changes, wear and tear and differences in pellets:

  • in a .177 I would use JSB Heavy 10.3g or Bisley Magnums,
  • in a .22 I would use something like the JSB Exact 15.9g/Air Arms Field 16g.

Please do not set the power of your rifle over the legal limit for your country/state, you could end up getting your rifle confiscated, you could end up in prison and you ruin the sport for everybody else. If you want an airgun that shoots over 12ftlbs then apply for a FAC.

Do you carry spare parts?

I carry the parts you see listed in my eShop, which are being added to all the time. If you need spare parts that are not listed in my eShop you can try some of the suppliers listed on my Guides & Links page.

 Will my rifle need maintenance?

Like any mechanical device, a rifle needs regular maintenance. Parts wear and lubrication can dry out etc. The action and stock should be wiped down with a corrosion inhibitor, moving parts should be lubricated and O rings should be lubricated with a suitable product, like Abbey SM50.

Please don't use 3 in 1 oil or engine oil to lubricate your gun, use proper gun oil.

It is a good idea to clean your barrel with a pull-through when changing brands of pellets or when you notice your groups opening up. 

It is advisable to chronograph your rifle regularly, to ensure it stays below the 12flbs legal limit with ANY commercially available pellets. Chronographs can be bought for as little as £40 and are a worthwhile investment if you want to keep yourself and your airgun on the right side of the law. It is also good to keep an eye on the consistency.

There are videos covering barrel cleaning, rifle maintenance and chronoing in my YouTube channel


What lubricant/oil do you recommend for the airgun?

I use Abbey SM50 or Bisley Gun Lubricant on the O rings and seals.

Any quality gun oil with a corrosion inhibitor like Napier Power Airgun Oil is recommended to wipe down the action, especially after using the airgun outdoors.

Do not spray oil directly into/onto the action because if oil gets onto the hammer it will effect the consistency and is not covered by the warranty.

The stock can be maintained using stock oil or conditioner, available from your local RFD.

Please do not use 3 in 1 oil or engine/motor oil on your action, it does more harm than good.


What are the best pellets for my airgun?

Generally BSA barrels tend to like larger sized pellets 4.52-3 in .177 and 5.52 in .22.

The actual choice of pellet is personal to your barrel/gun combination, there is no one pellet that is perfect for all barrels. The best way to find your barrels' favourite pellet is to try a number of different brands of pellets to see which gives you the best grouping, remembering to clean your barrel when swapping pellet types. Sample packs of pellets are available on the internet. I not recommend the use of pointed or plastic pellets if you plan on shooting accurately past 20yards.

When using a chronograph to check your airgun is legal, make sure you use a pellet that gives the highest power/efficiency.

In a .177 I would try Bisley Magnums, JSB Exact Heavy, JSB Exact 4.53mm, Daystate Sovereign, Air Arms Field.

In a .22 I would try Air Arms Field, Falcon Accuracy Plus, JSB Exact, JSB Exact Express, Daystate Sovereign...

It is your responsibility to ensure your airgun is set below the legal limit.

Where can I find out more information about my airgun?

One of the best resources for BSA airgun information is the BSA Owners Group forum www.bsaog.co.uk

You can also find out more on the BSA website www.bsaguns.co.uk

Ultra exploded parts diagram click me.
Scorpion exploded parts diagram click me.

How to strip a BSA Ultra MMC