Background: I am always looking for ways to better control my firearms, doubly so with any polymer framed guns where the weight advantage is not on my side. While good form and strong grip are paramount, recoil and muzzle flip are disturbances in my sight picture that must be mitigated, and any advantage is an advantage.
Enter the DPM recoil reduction system; simply, it's a triple-spring guide rod replacement that is meant to counter the inertia of the firearm's slide moving rearward after ignition by spreading out the resistance over three progressively stiffer springs. Other similar systems have existed for some time (sprinco, et al), but DPM is popular and supports a massive variety of platforms, which is why I chose to test it. There are plenty of youtube and forum reviews offering subjective opinions on 'feel' and 'change in impulse,' but little in the way of measurement of factors I am interested in, specifically recovery time and muzzle flip angle. As I come into this from a competition frame of mind, I want to know what objective, measurable difference,* if any,* the system provides.
The setup: a modified P10-F (see my other post) firing 147g LAX ammo at ~135pf and measured with a MantisX 10.
One string of 10 rounds with each of the following:
- Stock guide rod, stock spring
- DPM guide rod, short (lightest) spring
- DPM guide rod, medium spring
- DPM guide rod, long (heaviest) spring
Results:
Analysis: As you can see, the difference between stock and the lightest spring setup is evident but minimal, with significant movement in both. Notably, the lightest DPM spring did average out to a reduced recovery time. One primary functional difference between them is that even the lightest DPM spring is significantly harder to rack than stock. Even though the DPM feels much stiffer, I did not see significantly increased nose-diving.
The major differences came with the medium and long DPM springs. The average recovery time for both was 0.3 seconds, a marked improvement from stock! Also, the muzzle movement plot for both is significantly tamed from the erratic movement of the lighter springs. This was obvious while shooting, as the dot was very constrained and easy to track throughout the slide's movement. Barring an outlier shot, the heavy spring resulted in muzzle movement of a small concentric circle around the target before settling, and readjustment between shots was extremely minimal. The recoil angle and muzzle rise were also categorically reduced from stock and lighter springs, and resulted in a very tight, repeatable pattern.
In the end, for my purposes, I decided on the use of the medium spring, even though the heavy spring objectively resulted in the greatest reduction of muzzle flip and recovery time. Why? Because by the graphs above, you can see the medium spring resulted in the majority of muzzle travel above the level X line, whereas the heavy spring produced much of its movement below; this is obvious nose-diving caused by the heavy spring weight, and not a type of sight picture disturbance I am as practiced with countering. I much preferred recovering from the majority-upward motion of the medium spring, as it was closer to the way my conventional spring setups behave.
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