I have a dealer sample HK 53. I bought a four position burst pack for it. Mainly because I could. The pack came off a MP-5 so I figured the hammer spring was wrong. Thing is on HK Parts they list the same spring for 9mm, 40?S&W, and 5.56. Did the springs change at some point or do I have other problems.
I was running berdan primed wolf if that maters. I'm sure it's primers are pretty hard. Same ammo runs good with the SEF pack.