Tag Archives: BNM

Sluggish Marauder Mag Fix: Try #3 – Change the Internal Spring Position – This is the best fix!

Please note that there are three posts in this series.  The method in the third post would fix just about any magazine while the other two helped some of the magazines:

  1. Sluggish Marauder Mag Fix:  Try #1 – Loosen the Center Screw
  2. Sluggish Marauder Mag Fix:  Try #2 – Dry Film Lubricants – Not a Good Fix – But Avoid 3-In-1 Dry Lube Because It Isn’t Dry!
  3. Sluggish Marauder Mag Fix:  Try #3 – Change the Internal Spring Position – This is the best fix!

Now on to the post:


Ok, in the first couple of tries, I had some success loosening the center screw on a couple of the sluggish mags.  Marginal improvement with dry lube but that didn’t fix two.  What resurrected the two worst magazines was to disassemble the magazines and move the spring’s anchor leg to the center hole.   What this did was to increase the tension of the spring and boy, did that fix the problem in spades.  In the future, I would try loosening the center screw and if that didn’t work, I’d go right to this spring adjustment:

Here are the steps:

  1. Note where the spring is at currently my looking in the holes in the back of the magazine.  If you see metal, that is the leg of the spring.  All of my mags have had the spring’s leg in the same place from the factory thus far:
  2. Remove the center screw and disassemble the magazine with a 1/16″ hex key.  Pay attention to how it fits together and also look for any debris or burs that might be causing drag:   

    In this next photo, look at the spring.  The downward leg is the bottom and the sideways leg is the top and the center of the drum has a slot that the top part of that spring nestles into:


  3. Move the drum’s spring to the center hole in the track where the pellets are carried.  . See the oily crap … I mean “film” in the mag?  That is courtesy of the 3-in-1 supposed dry lubricant that I will never use again and got cleaned out right after I took this photo:
    If you aren’t sure what hole I mean, look at this next photo.  Magazines PA2 and PA4 have the spring located to the new hole half way around the magazine track.  PA1 and PA3 still have the springs in the original hole and seem to work ok.  This is also a good example of how labeling your mags helps you keep track of what is going on.  PA1 was the worst by far.
  4. Align the drum with the top of the spring and then carefully rotate the assembly clockwise slightly angling the long part of the drum so it will clear the part of the magazine that forms the start/end of the magazine area that holds the actual pellets.

  5. Install the top so the brass pin that is embedded in the clear magazine cover rides in the groove of the drum.  I slide the cover on upwards from the bottom while keeping the center secure otherwise it will fly out.
  6. Re-install the screw.  Tighten it down until the cover can’t lift up and adjust the screw in/out until you feel the right amount of tension on the cover and it can move.
  7. Test by turning the top – you should feel way more spring tension now.

So in my testing, this worked great.  If just loosening the cover a bit works for you, then great.  If not, take it apart and move the spring.  Note – I did try spraying the good Dupont Teflon dry lube in one of the magazines and I can’t say that there is a noticeable difference.  You can if you want to experiment, but I’m not going to bother going forward.

I hope this helps you out!


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What to do if your Marauder Rifle Magazine is too tight in the BNM breech

My magazine was a bear to pull out from my CP1002 BNM breech.  I talked to Sergei at BNM about the tight fit and told me that they keep they keep their tolerances tight on purpose.  He would rather things be tight vs. loose and that makes sense to me.  So if your Marauder magazine is a bear to push in and out of the breach, a tiny bit of fitting is needed.  The bottom of the Marauder magazine can be lightly sanded to allow magazine to be inserted easier.  It probably is not the front to back dimension that you need to worry about so try the following first.

All you need to do is get some 320 grit sand paper, rub the bottom lightly, evenly and test.  You just need to do the part that slides into the receiver.  320 was all I needed it took off enough to do the job gut also left a fine enough finish.  Another benefit for those of you that may be nervous is that it can only take off a small amount of material.  It will fill fast so with each pass, use another exposed surface of sandpaper.  That is why you see two ends used on the second photo.

For mine to fit way better, it was just a tiny amount I had to take off.  So don’t go crazy and take off a too much too fast.  Literally, do 4-6 rubs, blow it off and test.  Do this until it fits.  I think I did all three of my mags with just a couple of rounds of sanding and testing each.

I could have sanded it with 400 grit and even gone up to a polish but just doing 320 seemed to work great so I stopped there.


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BNM Custom Airguns CP1002 Pistol – First Trigger Experiment and Match Grips

I bought a cool CP1002 pistol from BNM Custom Airguns.  Now they focus on making exceptional breaches and that Tippmann stock adapter is very cool also.  In talking with Sergio, because there is such a strong aftermarket with businesses that specialize on certain aspects, he has not bothered with the trigger.  Now that makes sense – triggers are really something that an individual has to decide on – do they want one stage or two?  Long pull or short pull?  Light pull or heavy pull? and so forth.

After doing some reading, I decided to install a roller trigger, thicker sear and adjustable sear spring.  They were all available from Alchemy Airwerks on eBay so I bought them and a few other items to try in the future.  Now there are a ton of options and I’ll try some others as well but this was a first try and it did help.

Years ago, I bought a digital Lyman trigger gauge that I am very fond of.  You basically install a 9 volt battery, hold down READY to zero it and then press Ready again to take the measurement.  You do this by putting the black fitting on the feeler on the trigger in the same spot as you slowly pull the trigger with the gauge.  My readings were all over the place from 4lbs 2.8oz up to 5lbs 5 oz.  In other words, it was heavy and inconsistent.  Couple this with how thin the stock trigger is and it really makes for a poor trigger.

Before you do anything, make sure the pistol is empty and that there isn’t any Co2 in it plus make sure the pistol safety is set to fire or you risk losing the spring and detent.  Notice that last part.  It’s a heck of a good warning to bear in mind – have it set to fire and protect it from being bumped.  That doesn’t always work out so well hence this post.

Second HUGE recommendation – Be sure to have one of the fuzzy work mats.  I’m not telling you this to be cool – they serve a real purpose.  The fuzzy surface cushions soft parts so they don’t fly away.  There is an unwritten shop law, the smaller the part, the further than darn thing will bounce never to be found or not without some monumental search with magnets, flashlights and a clairvoyant.

So here are the steps bearing in mind we really want to talk about the safety spring and detent:

  1. When you go to work on the trigger. you remove the right side grip plate and you are looking at a plate held in by 2-3 screws.  On my six month old 2240, it is three small 1/16″ allen screws.  Notice how I have the pistol up on wood blocks to ensure the safety is not pressed.  You absolutely want that to stay on the fire setting.
  2. When you do pull that plate off, be very careful to press the safety pin down.  It is made from cheap plastic and may pull out.  That is exactly what happened to me and the tiny detent ball and spring flew out.  Luckily the fuzzy matte caught both parts.  Click here if you need to learn how to reinstall the detent ball and spring – a new tab will open with a blog post I did about just that.
  3. Back to this story, with the plate off, you can see the trigger internals.  The big spring on the left is the sear spring, the plate at the top is the sear and then you have the trigger to the right.  I would recommend you take a quick photo with a digital camera or your phone so you can see how everything is oriented.  Out of habit, I always take photos now when I am working on complex stuff – guns, cars, etc.  This has saved my bacon many, many times.
  4. So my goal for this experiment was to replace the fixed sear spring with an adjustable one to lighted the pull, the thin sear with a thicker polished sear to improve consistency and the trigger with a trigger from Alchemy that both had a wider face to distribute load on the finger and a roller to ride the sear.
  5. Remove the existing parts.  I have big fingers so I use needlenose pliers on everything.  Depending on the angle, either long precision needlenose pliers or right angle pliers.  Do not lose your parts.  Put them in a cup or baggie for the future.  You will need to use the sear pin so keep it out.
  6. The new thick stainless sear was a tight fit on the sear pin.  I used a benchblock and hammer to gently tap the pin into the sear.  The pin should be sticking out equally on both sides.
  7. My next step was to use my Dremel with a rubberized polishing bur to make the trigger contact surface smooth and shiny on the sear before I installed it.
  8. I installed the trigger first by slotting it into the safety and putting it in the pin hole.  There was a spring washer on the original that I did not both installing.  I then installed the sear and the adjustable sear spring.  In terms of the adjustable spring, I overcompressed the spring to soften it and dialed the adjustment wheel down as far as it would go to lighten the load.  The first photo shows the original parts that were removed and the next two shows the new set up.
  9. Next, I used a pin point CLP applicator to lubricate the sear pin and hammer pin on both sides. This photo was taken when I had the grip frame off the gun.  You do NOT need to do that.  The main thing is the application of the CLP, or whatever oil/lubricant you want to use.
  10. I then put the plate back on the trigger group and function tested it making sure the safety worked, that the weapon fired and that bumping the gun didn’t cause an accidental discharge.
  11. Next, I bought custom target grips made on a 3D printer to fit my hand by PrecisionTargetGrips.com.  They are pretty interesting and really fill my hand.  I did need to use a chainsaw file on the right side to get the hole in the grip to match up with the hole in the grip frame.  I also needed to grind the screw down about 1/16″ so it would tighten all the way on that side.  The left  was just fine.  I liked the result but it is very different from what I am used to.
  12. Okay, the trigger felt better but what did the Lyman gauge show?  The average was 3 pounds 7.3oz and the highest I saw was 4 pounds 4.1oz. 
  13. So the next step was to test it at 25 feet.  I like Splatterburst targets – they are cheap and self-adhesive so I stuck an 8″ target up.  I went for the center first and had to get used to the new set up.  It was shot a 5 round group at about and inch.  The next 5 round set was at the bottom and it was around 3/4″ and then I shot the top and it was between 1/2-3/4″.  All were with the 15.89 JSB Diablos.

So, the experiment did yield a lighter and more consistent trigger.  The wider trigger face also made it more comfortable.  I used a MTM stand to hold the airgun while testing to have a steady platform by the way.  It reduced my tremor a lot and I am sure the weapon could have fired tighter groups if I had an even steadier stand.  For me, a heavy weapon is better as it absorbs my tremor more.  With a lighter gun, I really need a rock solid stand and bench to fire for accuracy.

All in all, I am very happy with the results.  I could lighten the pull up more but will stick with what I have for a while and see how it goes with pests.  I definitely recommend the BNM repeater.  Boy is it slick.

Next up in a few weeks will be installing a BNM system on my Crosman Custom Shop 2400KT.  I have the BNM parts on order, the 2400KT and am still deciding on the stock and scope.

2/25/20 Update:  I’m sad to say the website somehow lost the second post after this.  I tinkered with the airgun for a while and then sold it like so many of my projects.  


If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at info@roninsgrips.com. Please note that for links to other websites, I may be paid via an affiliate program such as Avantlink, Impact, Amazon and eBay.