The 3 1/2" barrels used in the 6906/3913 are only 1/2" shorter than those used in the 59XX series guns. Half an inch.
During armorer classes armorers have generally been told to use whatever ammunition is being issued by an agency. In the various armorer classes I've attended S&W armorer instructors haven't really gotten into much discussion regarding ammunition (nor have the instructors from other gun companies, for that matter), other than to recommend using good quality ammunition of the proper caliber. S&W realizes that many agencies who use 9mm guns also often use one of the +P or +P+ loads produced by the major American ammo makers who have earned ammo contracts from LE/Gov customers. Remember that one state agency essentially pioneered the development and refinement of the 115gr +P+ loads used in in S&W M39's (in Win & Fed versions), and later in other alloy framed S&W 9's. They used that load for something like 30 years.
Back when I asked about +P ammo in my first armorer class the instructor mentioned that +P & +P+ ammo would naturally subject the gun to more stresses and accelerated wear, so properly maintenance and inspection was important. Replacing recoil & mag springs and making sure the guns were properly lubricated were important.
Also, we were told that increased recoil forces could act on the gun in other ways that might be monitored. For example, we were told to periodically check the slide stop lever, because increased recoil forces (vibrations) might potentially cause it to acquire an inward or outward bend at some point. One way described to check for this was to look at the frame of the field stripped pistol, from below, and check to see if the space between the back of the slide stop lever and the frame was even, meaning the rear of the lever wasn't closer to, or farther from, the frame at the rear than at the front of the lever assembly.
Sometimes this space might become tighter at the rear of the lever and the lever might start to run against the frame (and the lever's tab might protrude farther into the mag body). Sometimes it might be too wide and the lever's plunger might start to shift outward to the point that it might slip off the sideplate. The space should be approx even along the length of the lever.
While the factory uses a tool called a "lollipop gauge" to check the space between the rear of the lever and the frame, this tool isn't provided to armorers in the armorer kit (we were told it's a production gauge).
Armorers used to be taught how to adjust the angle of the slide stop lever (meaning the 90 degree angle between the pin of the lever assembly, which enters the frame, and the lever body which runs parallel to the frame). This involved careful placement in a vise and the use of a lead Babbitt bar. We were also taught how to remove the small roll pin and replace the plunger & spring, if needed. In more recent years armorers have been told that if the lever becomes out-of-spec in any way that it should just be replaced. Period. It's easier and quicker. No guess work by a lesser experienced armorer involving a vise and banging on a part.
This makes sense when you consider that armorer classes are only so long (and have become shorter) and that armorers aren't being trained as gunsmiths, but just to the point that they can diagnose simple problems and make simple repairs and corrections "in the field" (meaning away from the factory). They aren't being trained to act as technicians or gunsmiths.
Now, not all +P and +P+ ammo is arguably the same, either. That's why I only use +P & +P+ loads made by one of the major makers who have acquired experience making it for LE/Gov agency customers over the years. Some +P loads are barely distinguishable from regular pressure loads by their felt recoil. Others may have some more noticeable 'snap' to them.
Just the other day I was shooting a mix of some 9mm loads through one of my small S&W 9's, made up of some standard pressure Win 147gr JHP's, some standard pressure Speer load (which escapes me at the moment), some Rem 124gr +P GS loads and some Win 127gr +P+ loads. While I could tell the difference between the loads if I were to stand still and focus on just feeling the recoil while shooting very slowly, when I was running through the various drills at speed, engaging different paper & metal targets of various size, using cover/barricades and having to identify threat vs. non-threat (no-shoot) targets, etc, I didn't notice any difference among the different rounds as they were mixed in the mag loads. My attention was otherwise occupied.
Now, other folks who are more sensitive to felt recoil might have done the same thing, using the same mixed ammunition, and related a different experience. Just depends.
Once upon a time our issued & training/qual loads were standard pressure 147gr JHP's. Then we went to the 127gr +P+ loads for duty and used standard pressure 147gr loads for the bulk of training/quals (due to the cost of the +P+ loads), but ended up using the recycled 127gr +P+ loads for training & quals when issuing new duty ammo, which was 124gr +P loads. Then the 124gr +P loads became both duty & training ammo (because of affordability of that load under contract pricing). It remains the issued load for anyone using an alloy S&W 9 at this time.
As far as the 3rd gen .45's and +P loads? Well, the 4513TSW/457 has a 3 3/4" barrel, which is only half an inch shorter than the 4566TSW's 4 1/4" barrel. Just half an inch. Even the M&P 45 models only have half an inch's worth of difference between them (4 1/2" & 4").
Half an inch difference in barrel length doesn't exactly keep me awake at night.
I have .45's with barrel lengths of 3 1/4", 3 1/2", 3 3/4", 4 1/4", 4 1/2" & 5". I use the same good quality modern JHP loads in all of them. I realize the older, more traditional JHP loads might not offer reliable and robust expansion from the shorter barrel lengths, but the ammo companies have been making some pretty decent improvements in their defensive bullet designs in recent years.
Here's a couple of older Ranger SXT/T-Series loads fired from my CS45 (3 1/4" barrel) in a 4-layer denim/gel block test. One is the standard pressure load and one is the +P load. The results were 802fps13"/.76" for the standard pressure load and 839fps12"/.77" for the +P. Can you tell which is which?
And, just to show that you can't really predict what's going to happen with any particular bullet on any given shot, here's the same loads fired from a Commander (4 1/4" barrel). 846fps/14"/.79 for the standard pressure round and 901fps/11.5"/.77 for the +P.
Now, I prefer to carry the standard pressure load, especially in the lighter alloy guns. Less felt recoil and better controllability.
In the last couple of years I've been carrying the Rem 230gr GS (non-bonded) load in the same guns, and I'd carry the Speer 230gr GDHP (standard pressure load) in them, as well.
I'm more concerned about good feeding & functioning of the different loads in my .45's, and using modern bullet designs, than the muzzle velocities.
Also, it seems the ammo makers have been paying attention to their LE/Gov & private gun owner customers when it comes to the popularity of the smaller, shorter barreled guns in recent years. They've been paying attention to how their defensive bullets can offer performance within wider velocity windows, it seems. (Look at Speer's production of a 230gr Short-Barrel load in .45, for example.)
This isn't the 1960's or 70's ... although we still have the older design ammunition available, as well.
+P or +P+ in Alloy Frames
Linear Mode
