Here's how the part weights and Effective Spring Weight break down:
13.75 grams - OEM Plunger (Average of 3 as new) 0% change in effective spring rate
13.23 grams - OR3GUN Competition Plunger (anodized version) ~ 10% reduction in effective spring rate
15.06 grams - OR3GUN Multi-Use Plunger (anodized version) ~ 5% reduction in effective spring rate
When you look at the differences, they are minor in relation to the entire cycling part weight (bolt, slide, link) and the spring weight itself is the primary difference. A change in charging handle for the bolt makes a bigger change in cycling part weight than the different plungers. The Competition version is only about 1/2 gram lighter than the factory plunger.
The release of our Adjustable Spring Retainer (ASR) during SHOT Week, addressed the tuning ability of the Competition Spring Plunger to get that magic ~ 7-8% reduction in Effective Spring Weight. This part replaces the plastic, factory 'Return Spring Retainer' that holds the back of the spring in the gun with one that has 4 positions (1 lighter, 3 heavier) that allow additional tuning of the Effective Spring Rate. This will allow users to find the right combination for their given selection of loads and the tolerances of their gun. The Competition ASR has been designed first (as usual) for the realm of 3-Gun competition, where a 930 owner typically favors certain exact loads for clay stages, knock-over steel, poppers and spinners, then finds a low-recoil slug that sights in well with their gun. Once they get all of these standard competition loads dialed in, they typically buy them by the case load and that is all their gun will ever shoot. Set your 930 up to run them in all conditions and you'll never look back.
We're always taking customer feedback into account when designing new products and versions of products. As a company focused heavily on competition, other applications are sometimes a few months behind and require doing things with a different perspective in mind. This forum thread is an example of how a product for the same gun can evolve to the specifics of different markets for the same gun. The Multi-Use Plunger came into production as a result of the vast majority of 930/935 owners simply wanting to reliably shoot inexpensive bulk packs, but still have the gun survive the heavy stuff. Cowboy loads were certainly off the table, but a box of full power slugs once in a while was still on. Shorter barrels mean shorter dwell time, but that is the case on ALL loads, so the Multi-Use Plunger is extremely versatile.
The power factor (load weight x velocity) of common shotgun shells range from 375 (Winchester AA 980 FPS) to 1138 (Winchester 3.5" Turkey). From the factory, the 375 PF stuff simply won't run at all in a 935 and won't reliably cycle the 930. It is a contest in a 935 (when shooting 1138 PF loads) to see whether your face or gun gets beat up first. It simply isn't practical for any autoloading shotgun to operate both of these extremes reliably without changes to the hardware that favor one end or the other. As expected, most autoloaders run most reliably on the average load. Some of the more expensive inertial guns conveniently gloss over the fact that you will need upwards of 1250 FPS to reliably cycle them. We keep hearing how much more reliable they are, but the fine print reminds us that paying twice as much for your ammo can sometimes have that effect. The 930's dual gas system can run a wider range than most, but it helps to pick an end of the spectrum to tune for.
We have been in testing for a while on a 3rd captured-spring plunger version (@ 13.26 grams) in combination with a modified version of the ASR for possible inclusion in our upcoming Field Combo 2.0 that should be available around April. It would allow a fairly simple choice between ~ 10% reduction and 0% reduction in Effective Spring Rate, with the intent that the owner would be able to reliably run a bunch of bulk loads in practice and change the setting for full spring weight before they head out to hunt with full boat loads. Removing the recoil pad (2 screws), inserting a punch and rotating a 'dial' between two positions would be the complete changeover process to go between the extremes. That's not a very practical proposition for 3-Gun competition from stage to stage (though not too much more work than a choke change), nor does it make much sense for someone running loads that all fall into the average range. It DOES make sense for someone that does two remarkably different tasks with the same gun and has a few minutes between those tasks to set it up properly for each.
Again, we're always looking at ways to accommodate the various ways the 930/935 is used within the practical limitations of physics and how the platform deals with those limitations.
William
http://www.OR3GUN.com