RCBS Chargemaster Modifications

In Blog by Rich28 Comments

Hey guys, I have seen a lot of people asking about how to reprogram their RCBS Chargemaster 1500 to make it more accurate and faster. There isn’t a whole lot that needs to be written about reprogramming your RCBS Chargemaster so its more of a “Let me just show you” sort of scenario. The two key components are the straw and the software reprogramming if you want to improve your RCBS Chargemaster. Go to any McDonalds and grab a straw, its the perfect fit for the dispenser tube. Cut it leaving yourself a half inch to an inch or so of material sticking out the end of the dispenser tube. I’ve found that by cutting a saw tooth pattern into the end of the straw it helps as the RCBS Chargemaster is at trickle speed and it allows fewer grains to drop from the tube at a time.

Straw Modification for the RCBS Chargemaster

When you push the straw into the spout of the RCBS Chargemaster, push it all the way. You literally want to block the entire opening of the dispenser tube where the powder funnel is at the back of the RCBS Chargemaster. Mark the leading edge where it is exposed on the open half of the dispenser tube, and cut a small narrow opening in the tube for powder to drop into.

RCBS Straw Mod

Sawtooth Straw Mod

Reprogramming the RCBS Chargemaster

From there you just have to edit the software of the RCBS Chargemaster. To enter the programming settings press and hold the “EDIT MEM” and “ENTER” buttons at the same time. The first three settings are what you want to change. Program the first value to 7.0, the second value to 2.0, and the third value to 0.5. What you are telling the scale is at what point to shift speeds of the dispenser. These settings tell the scale to stay in high speed till within 7 grains of the desired charge, it will stay at medium speed until within 2 grains of the desired charge, and it will start to trickle at 0.5 grains under the specified powder charge. Special kudos to the guys at the Primal Rights forum for coming up with the magic size for the rear straw opening!

Dispenser Opening Mod

Dispenser Opening Mod

Electrical Line Noise

Another thing I’ve often read about is how noise, voltage fluctuations, and other electronic noise in the power lines can affect the RCBS Chargemaster and its accuracy. This typically manifests itself by the wandering scale zero. You would notice this after a charge is thrown, and you have dumped the pan. The scale should be reading exactly what the pan weighs in a negative number, because you zeroed the scale with the pan on it. If you notice that number changing by a few tenths of a grain higher or lower, that can be line noise. I looked into different ways of dealing with this and some can be very expensive and some much more affordable when trying to address Electro-Magnetic Interference (EMI) and Radio Frequency Interference (RFI) on the RCBS Chargemaster.


Ferrite Choke to reduce line noise!


One of the easier solutions I found was at Radio Shack. Electronics stores often have what are called ‘chokes’ on the shelves. Its a two halve plastic snap on with a ferrite core that helps reduce and block those kinds of interference we just discussed. I gave it a whirl and bought a two pack. I snapped one over the power line right where it plugs into the wall, and another right before it reaches the RCBS Chargemaster. I immediately noticed greater stability in the zero of my scale. The zero does not wander hardly at all at this point, and when it does it is by a mere 1/10th of a grain, which is the rated accuracy of the scale in the first place!

Wrapping up RCBS Chargemaster Modifications

These simple mods have reduced the throw times and increased the accuracy on my RCBS Chargemaster to almost 100% where before the mods I would get overthrows approximately 30-40% of the time. If I was to load 100 rounds of rifle ammunition it might take me 130-140 actual charges dispensed before I had 100 of them at the charge weight I wanted. I recently loaded 300 rounds of 6.5 Creedmoor for the 2014 Sniper’s Hide Cup using my RCBS Chargemaster and if I had three charges that I tossed and reweighed that was a lot these days. With these mods I get excellent accuracy from the RCBS Chargemaster scale and as a result my time sitting at the reloading bench is much more efficient. Less time at the bench equals more time on the range! Go give this a try and see what you think!

Update on 6/8/16

After trying some of the Chargemaster reducing inserts from David Moore, I have to recommend these over the straw mod moving forward. It’s a much more elegant solution to the same problem and it takes almost no fiddling to get it running. Just open the package, install the sleeve, double check your speed settings, and you’re done! They function the same way, by reducing the amount of powder that can progress down the tube at any given time. I recommend getting the option accuracy sleeve that further reduces the tube aperture even below what the brass insert achieves. For $18 shipped, you can’t go wrong. For ordering information on these, see the Chargemaster Reducing Inserts article!

Chargemaster Reducing Inserts Brass

Owner and Proprietor of AccuracyTech, LLC. Rich is a Firearms Enthusiast, Precision Rifle Competitor, and Writer. He is committed to bringing readers quality reviews and articles related to the Precision Shooting Sports. If you have any questions for him, please use the contact form on the site.


  1. I’m looking at this article for the first time. having an issue where trying to change the dispensing speed. Push the EDIT MEM and ENTER buttons but flashes AUTO PARA and METER but can’t really see how to stop it or change it. Thanks, oldmodel12

    1. Author

      It flashes continually? Mine flashes those for about two seconds then stops and displays a value, at that point hitting enter allows you to scroll through the different parameters. Try shutting it off and turning it back on and try again?

      1. Wow, thank you so much for the quick reply. I was not expecting any thing about it for a couple of days.
        I did as you suggested and will see how it works tomorrow as I changed only the first three numbers as your article suggested.
        Hopefully I didn’t mess it up with all my earlier attempts.
        Thanks again and will let you know if it worked.

          1. Rich, did a 110 rounds today at 30.5 grains. 40% was .1 grain high. Going to replace straw with new one smaller opening in dispensing tube. Still seems the trickle is too fast for the scale brain and doesn’t wait for the scale to stable and goes again leading to over fill. Thanks, Charlie.

          2. Author

            Charlie, I saw a big improvement in overthrow percentage by reducing the opening at the back of the dispensing tube. It’s almost closed off, with a small opening to allow powder from the hopper to enter.

            You can always tweak the parameters a bit. Set the trickle number a touch higher away from the goal and see if that helps.

          3. Big improvement. The small hole with smaller points on the straw made only about 15% overthrows. May make the hole even smaller. Haven’t used extruded powder but will try before I change. But the ball powder really comes out that small hole. Thanks again.

          4. Rich, used the Varget and for the most part was best this ChargeMaster ever did. However think making an even smaller hole about the size of a BB will make it better. Will let you know. You would think RCBS would fix this problem, eh?Thanks.

          5. Author

            They have to make it work well with everything so it works great with nothing, unfortunately. Don’t overlook the chokes, that helped a lot!

          6. Rich, made a new straw and the hole is only about 2-3mm…gets the Varget right about 47/50…been using for about 200 loads…also used CFE 223 and need a smaller hole than that but much better than it was…no unders only over-throws…have taken to “under” measuring by .1 grain and trickle out to the correct weight…a little slower but can get really close to exact weight.

          7. Author

            I’m thinking different straws for different powders might be beneficial since some are so different

  2. Rich I just bought a new chargemaster and before it arrives I wanna try your “choke” method and purchase two locally….seeing it’s not here yet do you have the diameter opening of the choke you used ? Noticed they come in multiple sized openings and I’m looking for a snug fit…if not then maybe the cable dimensions as long as they didn’t change from one year to another …..thanks John

    1. Author

      Hey John, I’ll try and mic it after work tonight, it’s was a fairly small size, bigger wouldn’t have been better. Let me see if the size is on them.

    2. Author

      I measured the chokes, they’re about 0.47″ thick and the opening for the cable is right about 0.2″ so pretty small, hope that helps!

  3. Rich just for future info the snap choke ferrite cores are sold at radio shack which you mentioned ….part number 273-0067 and packages as two for 3 bucks….I’m sure they can be grabbed online also but then shipping things even this small they nail you for…I measured rcbs chargemaster power cord and came up with 3mm and the above part number fits snugly around the cable and stays secured and in place….hope this helps anyone else inquiring about them

      1. I can only say if you don’t wait for the weight after the CT shows you will be off even more in your fps average. I now use another scale to re weigh and the RCBS is frightening some times on what it actually is throwing. After the CT message many, many times the weight is off even though it said was okay when it chirped and stopped dripping.
        I’ve used the straw and slowed down the speed, thanks to Rich, but I’m about to toss this and go to the balance beam.
        Check with a chronograph and another scale, especially with Varget, where one kernel is .02 grains.

        1. Author

          Good point, Charlie, I’ve seen the weight change between measured and what it shows after the count myself.

          Don’t give up on it, get the ferrite chokes and redo the straw if need be! I have to redo it on my new chargemaster because I made the opening in the hopper too big.

  4. Hi guys

    I tried what you said but i am pretty sure i messed it up.
    Does anyone know what the different parameters have to be and what the letters stand for?

    1. Author

      If you re enter the settings you will see what their current values are by just hitting enter to scroll through.

  5. Will these mods work on earlier model chargemaster? The one where the scale sits beside the powder thrower.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.