BSA Ultra MMC, Scorpion & Hornet

What is a regulator?

A regulator is a device that regulates the pressure between the air cylinder/bottle and the firing valve. It allows air to to flow through to the action until it reaches a pre-set pressure and then it shuts off the air until a shot is fired, creating a constant pressure at the firing valve, when the gun is fired this pressure drops then the regulator opens to allow the air to flow through to the firing valve again until it reaches the pre-set pressure. By fitting a regulator you eliminate the power curve and the hunt for the sweet spot, that is common with most unregulated rifles. 


Where does the 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 long does it take to get fitted?

The actual regulator does not take long to fit but doing an X-Tune takes around 5-7 hours to complete if there are no other problems with the rifle. I normally only book in one rifle a week and the work is carried out over the course of the week. Have a look at the calendar page to see my availability. Bookings can be made via the eShop. 


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 regulator stops working at around 90 bar (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 gun to a higher pressure, which will further improve the shot count compared to the 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 to fit a longer air cylinder. 


What do you do when fitting a regulator?

  • the action is stripped, cleaned and examined,
  • any loose or ill fitting parts are tightened and/or refinished correctly,

  • burrs, crud, tool marks etc are removed or repaired,

  • any worn or damaged O rings are replaced and properly lubricated,

  • the regulator is set up for the calibre and length of barrel,

  • the firing valve is adjusted to reduce the difference in power between light and heavy pellets,

  • the standard metal spring guide is replaced with a lightweight spring guide,

  • a low friction "slip disk" is fitted to the hammer assembly,

  • replace the standard hammer weight with a lightweight short stroke hammer,

  • a suitable hammer spring is chosen and fitted to the rifle,

  • the trigger sears are polished and lubricated to make it smoother,

  • the ends of the hammer spring and firing valve spring are de-burred and polished,

  • the transfer port is modified to improve air flow,

  • check the barrel is aligned correctly and make sure the barrel is secure,

  • modify the port in the barrel to improve airflow,

  • check the barrel crown and repair/re-crown if necessary,

  • make sure the gun is in good working order,

  • reduce side play in the trigger blade and adjust the trigger,

  • set the power to make sure it is running below 12flbs, unless it is an FAC model,

  • I supply a work sheet with a list of the work carried out and an XTX Air sticker,

  • this list is not exhaustive and is subject to change as new ideas and modifications evolve...


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. 

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. 

Picture of an Ultra SE with different length cylinders laid out to give you an idea of the overall proportions >>here<<

BSA have been making some single shot Ultras (2013) with the air cylinder from the current SE model, they are only 175mm long, compared to the older Ultras that had 230 or 250mm long cylinders. If you have one of these then your expected shot count will be less than the older models. A longer air cylinder can be fitted if you want/need more shots per fill. 


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

Ultra 250bar

Scorpion 232bar

Hornet 232bar


HuMa BSA vs Tench (discontinued) regulators 

The HuMa regulator is designed specifically for the BSA Ultra MMC and Scorpion T-10 and single shot rifles, 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 also designed to fit the Ultra/Scorpion/Hornet. To make a Tench regulator fit a number of parts need to be machined and modified. This is why they cost more to be fitted than the HuMa and they are not a DIY fit regulator. Both regulators regulate very well and will flatten the power curve.


How do I send the rifle to you and what do I send?

I only need the action when fitting the regulator, please do not send the scope, stock, air cylinder or silencer, it may add to the return postage cost. 

Please make sure the trigger is well protected when packing because it is a weak spot.

The action should be wrapped in bubble wrap and put in a sturdy cardboard box. For some carriers the box will need to be under 610mm long.

Please note you are not allowed to post pressure vessels with most couriers, Royal Mail and Parcel Force have started destroying any bottles/cylinders they find in parcels. It is best to remove the air cylinder from your rifle before sending it to me, I will use my own cylinder for testing and setting up your rifle. I have added a how-to video to my YouTube channel that shows how to remove/refit the air cylinder from your rifle.

YouTube clip showing how to pack your action for posting

YouTube clip showing how to remove and refit your air cylinder

You can use:

  • Royal Mail Special Delivery, which is insured and next day delivery, which is £12.50 if it is under 2 kg and £28 between 2 and 10 kg. Royal Mail Price Finder

  • Parcelforce Express 48 - they only offer a max of £100 compensation for airguns.

  • You can use other couriers but please be aware that some will not offer any compensation for air rifles.

  • Delivery in person.

Ultras usually weigh under 2kgs if you do not go too mad with the packaging. Scorpions are very difficult to pack safely under 2kg, so best to package it properly and pay for the extra weight.

I will return rifles fitted with air cylinders with the fill port removed, to limit the risk of your rifle being destroyed by Royal Mail. I do so at your risk so it is best not to send it to me. 


Can I drop off and collect my gun rather than posting it?

Yes this is an option, if you want to drop it off and collect it the same day then please give me advanced warning so I can make sure I am available. 


Can I fit the regulator myself?

There is a HuMa regulator that can be DIY fitted. For more info have a look on the HuMa regulators page, they are available in the eShop.


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 and I will repair these for free for the person who originally had the regulator fitted as long as the rifle has not been tampered with.

If the fault is not related to the fitting of the regulator, I will inform you and quote to repair the problem before carrying out the work.

Please note that the warranty is a return to base (RTB) warranty, which does not include postage costs.

There are also loads of useful videos on my YouTube channel that show you how to carry out most of the general/common issues you are likely to encounter. 


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 sending it in for a regulator. This will give you a chance to spot any issues with the gun, which can be dealt with by BSA under warranty.


How much does it cost to have a regulator fitted?

Please have a look in the eShop or the price list page for more details and current prices.


How do I pay?

  •  You can pay by selecting the relevant options from the eShop,
  • You can either send the cash or cheque with the action (make sure it is insured because I will not be held responsible if your rifle and/or cash do not arrive),
  • If you are paying by cheque I will return your rifle once it clears. Please allow for the additional time while the cheque clears, typically 2 weeks,
  • You can also pay by bank transfer, via the eShop,
  • Cash on collection.

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, like reflex silencers. The original SAS type silencer that the older Ultras 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 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 reg is fitted, some do some don't but all will accept 28mm silencers. You can of course fit a Huub shroud and do away with a silencer altogether. 

I can machine a chamfer on some silencers to make them fit but it depends on the model of silencer.

Silencers tested on a multi-shot Ultra* after a regulator has been fitted that did not cause any problems:

Whisper, HW, BSA VC, Sirocco, Parker Hale...


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

I set the gun to around 11.5flbs using a heavy pellet in .177 and a similar power using a mid weight pellet in the .22.

I will not set your airgun to over 12ftlbs, so please do not ask.

If you want an airgun that shoots over 12ftlbs then apply for a FAC.


Do you only fit regulators?

No, I can swap or thread barrels, add custom parts, carry out repairs and service your rifle.

I can also make modifications to the stock, such as adjustable cheek pieces and hamsters etc.

I offer pressure gauges which are fitted to the end of the air cylinder, which will let you know how much air you have left in the cylinder so you don't get caught short when out shooting. Pictures and prices are in the eShop.

I can make custom probe knobs for Ultras and bolt handles for Scorpions and R-10s, have a look in the eShop.

If you can think of something that you want done then there is a good chance I can make it happen or I can put you in touch with somebody who can.

Prices vary depending on what you want do, so please feel free to get in touch for a quote.


Do you stock/sell spare parts?

I don't generally carry a large stock of spare parts apart form the parts used for servicing the rifles and fitting the regulators.

There is a selection of accessories and commonly used O rings available from the eShop.

If you need spare parts, I can source them from John Knibbs International, who are dealing with all the spare parts for BSA. You can have a look at their website for prices You are also welcome to source your own parts for me to fit.

Please note that if I need spare parts, repairs may take a bit longer, as they need to be ordered and delivered.


Will my gun need maintenance after fitting a regulator?

Like any mechanical device, a rifle needs regular maintenance. Parts wear and lubrication can dry out etc. The action should be wiped down regularly with gun oil that contains corrosion inhibitor (like Napier Gun Oil), moving parts should be lubricated and O rings should be lubricated with a suitable product, like Abbey SM50.

It is a good idea to clean your barrel with a pull-through after it has been worked on, when swapping pellet brands or if you notice the groupings opening up.

It is advisable to chronograph your rifle regularly, to ensure it stays below the 12flbs legal limit with any commercially available pellet. 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 a great way to keep an eye on the consistency of your rifle.


What lubricant/oil do you recommend for the airgun?

I use Abbey SM50 on the O rings and seals.

Any quality gun oil that contains a corrosion inhibitor is recommended for wiping down the action (like Napier Gun Oil), especially after using the airgun outdoors.

Spray the oil onto a cloth and then wipe down the action, do not spray the oil directly onto the action because if oil gets onto the hammer your rifle will become inconsistent and is not covered by the warranty.

The stock can be maintained using stock oil or conditioners, available from your local RFD/gun shop.

Please do not use 3 in 1 oil or motor/engine oil to lubricate your action, it will do 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 and 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 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 below the legal limit.


Did you design or develop the Tench or HuMa regulator?

- the Tench regulator was designed and developed by Tench, who has now sold his BSA regulator design to the RAT Works, I purchase the regulators directly from the RAT Works.

- the HuMa regulator was designed and developed by HuMa Air in the Netherlands. I am the UK distributor for HuMa Air products.


My airgun has been blueprinted or tuned, can I have a regulator fitted?

Yes, this is not a problem.


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.

You can also find out more on the BSA website

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

If you are sending me your rifle/action, please print out the form below, fill it in and include it in your parcel so that I know who you are and what you would like done to your rifle. Don't forget to make a booking before sending in your action. 

Worksheet XTX - xls

Worksheet XTX - pdf