Do an internet search of the first five words of this post’s title. You will get enough distinct hits for days of reading, as a hundred or more (in the first thousand or so) appear to contain substantive material worthy of consideration. In short, longstanding advice — from homicide investigators, prosecutors, defense lawyers, gun writers, bloggers, the self-defense firearms community, and those who actually consult and testify as experts in criminal and civil trials — urges (prudently) leaving a defensive handgun factory box stock, to avoid adverse consequences in a legal proceeding. Critics of such advice note (correctly) a near dearth of anecdotal trial reports and published appellate decisions suggesting there are adverse legal ramifications on account of modification to or installation of a non-factory standard replacement part (NFSRP) into a defensive handgun. So, are there legal ramifications or not? Yes, there can be. Are they adverse? Perhaps. Should one then automatically forgo a useful, desirable, and common handgun modification or NFSRP? Probably not.
Some discussion parameters. Any modification or NFSRP which is colored/finished other than with justifiable utilitarian purpose, rightfully argued as making a handgun unsafe, sold as or carries a name, logo, or other identifier exploiting a perceived legal loophole, lack of political correctness, or touts sex, drugs, rock, or killing (e.g., Rambo, Grim Reaper, Zombies), whether ostensibly righteous or not, or urges vigilante-like (e.g., “Punisher”) behavior, should be dismissed as off limits for a defensive handgun. Accordingly, they are excluded from the discussion here, as are modifications and NFSRPs installed by a manufacturer or agency armorer based on agency or department specifications. Also excluded are aftermarket grip panels and sleeves, “iron” and “night” sights, white lights, and lasers, as I believe their use is so pervasive that their existence and purpose are nearly universally acknowledged and accepted. I note some will disagree with my take on lasers, and others will have no issue whatsoever with fiber-optic sights, for which I harbor a small residual concern (which is rapidly disappearing as more defensive handguns come with those installed by a factory or custom shop).
What about a lightened or more crisp trigger pull, modifications which seem to generate the most debate? Unless the shooting in question was or is alleged to be the result of an unintended discharge, trigger characteristics ought not to matter. But I would nevertheless advise (absent a very good reason to do otherwise) against going any lighter than a bit just north of what expert gunsmiths and trainers familiar with the particular handgun platform believe is appropriate. That implicitly means going with parts which are sold for “defensive carry” or “duty,” and straying away from gunsmith modifications and trigger group parts identified as used for “competition.”
I acknowledge (and accept for myself) that a mild level of uncertainty will always persist as to whether a modification or installation of a NFSRP might (undeservedly) contribute to an adverse result in an otherwise “good” officer-involved or self defense shooting. Stated another way, is a prosecutor or civil plaintiff handed a “better” case, even when (as will almost always be the case) the modification/NFSRP is clearly irrelevant to what precipitated the shooting or its outcome, and therefore, its legality. The answer is they might, if the evidence gatekeeper, the judge, foolishly allows such into evidence and then compounds the error by allowing an erroneous, completely subjective opening statement or closing argument about it, which gunnies easily recognize as nonsense, but which a trial jury or an appellate court in review might not.
In the case of a criminal prosecution, the entire dynamic of a trial may be changed. Here’s why. LE shooting investigators, prosecutors, firearm examiners, judges, and juries are rarely gun modification or replacement part savvy. They may, on a lawyer’s urgings, erroneously think a modification or NFSRP is relevant to a disputed fact. Or, they may feel such reflects an unseemly (i.e., guilty) mindset of the shooter/defendant. In order to defend against such “evidence,” a countering explanation of the modification or NFSRP’s purpose/function must be tendered. How is this done? Likely the first attempt will be before trial, by motion to exclude such evidence. What and who your lawyer offers to do that depends on why and how and by whom the modification was made or the NFSRP installed. (It could matter whether the modification or installation of the NFSRP was made at the time of manufacture (e.g., at your request from a list of customer options), is part of a special edition model, or is something done after the purchase by someone other than the original manufacturer, including the gun’s owner).
If you gunsmithed the alteration or installed the NFSRP, you may need (as the best and/or only witness allowed) to testify and be the witness who introduces what material you relied on to choose the modification or NFSRP and why it was done. That can compel a completely different strategy in a criminal case where you as defendant cannot be called as a witness by the prosecution. In a criminal case, once you testify, you are fair game for just about any cross-examination. A jury might be inclined to believe you acted lawfully, but if they disbelieve any portion of your testimony, even something which isn’t dispositive, you might suffer an adverse result.
If someone else did the gunsmithing, you need to ask will that gunsmith or the part’s promotional material (or its inventor) be available/admissible to explain and will it/they make a positive impression on a judge/jury? Another point, maybe applicable in all cases — are there independent experts or a manufacturer’s engineer available and willing to testify as to the righteous utility and general acceptance of the modification or NFSRP? (Note, your attorney may not be able to compel an unwilling witness’s attendance across state lines without special proceedings).
I believe there are many modifications and replacement parts which, if you are inclined to depart from factory stock, should give you little pause. Examples include those which: Facilitate left-handed or ambidextrous use; are replacement parts very commonly installed on a given platform for operational ease or improved service life or reliability (e.g., Wilson Bullet Proof® or 10-8 Performance 1911 parts); address design issues (e.g., grip plugs for Glocks); modify trigger reach for small or large hands; improve magazine base pads (but do not add capacity); correct a documented factory function shortcoming (e.g., redesigned extractor, metal magazine release to replace factory polymer); customize grip and trigger guard for better fit/grip or recoil reduction (e.g., contours, texture, and reduction). How about a modification or a NFSRP which is perceived to have the sole or dominant purpose to increase shooting or reloading speed (e.g., lightening slide cuts, magazine release buttons, magwells) or accuracy (e.g., match barrel/bushing)? A bit more pause for the former, none for the latter. For sure, my observations are personal and subjective, since I am a frequent user of those (except slide cuts).
Executive takeaway: Consider the possible arguments — pro and con. Proceed cautiously, but don’t feel pressured not to modify/install what has utilitarian purpose and will be meaningfully helpful to the success of your likely mission, that is, the feared events which compelled you to own/carry the handgun in the first place. Never forget success in a gunfight is almost always more dependent on mind, mindset, and skill, than on equipment. Pay particular attention to what an NFSRP is named/nicknamed, how it is advertised, the nature of its users (is it primarily LEOs, gamers, competitors, genuinely self-defense minded owners, respected trainers), the handgun manufacturer’s recommendations and expectations regarding modifications, and what gunny brethren say about it (both the true and the false) in internet forums. Then decide whether you wish to engage the risk, however certain or debatable. Next, decide whether you or a professional should do the gunsmithing or part replacement. But bear in mind regardless of who does the modification or installs an NFSRP, and whether or not the modification or part is truly sensible and defensible, there is nevertheless a chance someone (preferably one knowledgeable and presentable, but usually not you) will need to explain/justify the what, how, and why here:
A final point. I have been asked from time to time about the LEO allowed to carry a personally owned “off-duty” handgun without restrictions, who carries the same make/model as his/her issued duty handgun, but makes modifications or installs an NFSRP not allowed by the agency for duty weapons. I have quickly advised against that, because it might result in the agency determining the LEO should not be provided paid defense counsel, and of course, the deviation from agency policy could be seen as an invitation to civil suit by a lawyer who has unbilled time on his/her hands. I would like to hear from MSW followers (who are LEOs) on this.