PTS EPM1 magazines not working in your gun. This is why.

Ox AirtechJan 31, 2026, 6:02 a.m. PST

I get this question a lot, so figured a post would be fitting.

Q: "These x type magazines won't feed in my gun, the first few rounds dribble out. What's wrong?"
Short Answer: You're tappet spring is too weak.

Detailed Answer: First you need to understand how a gearbox works.
This is great little animation showing the internals.
https://youtu.be/qlW11m5d4Uk?si=56BYNkPP9lZLPazc

The parts labeled are the ones we need to know for this issue. Tappet Plate, Tappet Spring, Air Nozzle, Cylinder Head

Some magazines require an extremely strong spring to feed bb's properly, this is especially true with the PTS EPM1 magazines as they are designed to hold 240 bb's. When fully loaded the spring is applying so much feed pressure that when the air nozzle closes to push the next bb into the barrel, the upward force from the bb's is causing the air nozzle to not align and seal properly, therefore you get an improper feed and shot.

The solution is an upgraded or after market tappet spring that has more force to pull the tappet plate and air nozzle forward with greater strength, this reduces the upward push effect of the bb's and allows the air nozzle to close into the barrel properly.

Another more rare condition, is the air nozzle isn't fitting tight to the cylinder head, and has too much slop. This will get amplified by a strong feeding magazine as well. The solution here is to replace the cylinder head and air nozzle with a tighter fitting combination.

Both solutions require a complete removal and disassembly/re-assembly of the gearbox.

Gearbox.png

2 comments

@dbeezyFeb 1, 2026, 6:24 p.m. PST
Would you say the EMP1 Shorties or the Regular EMP1s are more consistent? I bought a couple of the shorty ones and I haven't ran into any issues, is there any things you would recommend I look out for and know in terms of maintenance for them, or is it pretty much the exact same as a regular EPM1 in a smaller form factor?
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@oxairtechFeb 2, 2026, 5:53 a.m. PST
I haven't had too much personal experience with either the EPM1 shorties or the regular EPMs, but from the players on the field I see fewer problems with both compared to the 240rounders. Really just depends on the gun and the factory parts. Airsoft guns and parts have lots of tolerance inconsistencies, just the nature of the beast, and after all they are just toys, so the same stock combination, may not produce the same results. One of our local player bought a schwack of regular EPMs and could only half load them. Fully loaded and they just squirted out the barrel, yet in a different stock gun, same make and model, no issue. As for maintenance on the mags themselves. Yes they should be taken apart and cleaned, especially if your a "mag dropper", I've cleaned sand, sticks, leaves, all sorts of debris out of the feed path that will impact feeding. They can be pain to disassemble and re-assemble, especially getting the spring back in, but when you get it apart I use Qtips and silcione oile to make sure everything is wiped down and clean and then dry Qtips and Blue Shop Towel to make sure it's nice and dry before re-assembly. DO NOT LUBE THEM!!! Oiled BB's don't hop very well. You can find replacement springs for some models of mags, but very rarely should you have to do that. I have some 20 year old G&P midcaps still working.
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