Sport BCG Specs
Long time lurker first time poster.
As the title says what are the specs on the Sport model bolt and carrier?
I've searched the forums and even my google-fu hasn't turned up anything on what materials, finishes, or inspection process S&W is using.
The only thing I've found so far is the carrier is a Semi-Auto version.
Thanks in advance!
Usually if a bolt is HP/MP tested it will be marked as such. The gas key and carrier are chrome lined but I don't know what material is used to make the bolts. One issue I have seen on a couple of Smiths is the keys had very light staking and the screws holding the keys weren't real tight. This was on guns that had hundreds of rounds through them. Eventually I think a problem would have developed but we torqued the screws and re-staked them.
Hello and welcome aboard!
Mine is from the original run of 15-Sports that had the A2 rear sight. This was back when the MSRP was $650, and they could be had for $550.
The only thing I know for certain is that the 15-Sport BCG is properly staked semi-auto carrier and has a chrome lined gas key and bolt carrier. It does have the "O" ring upgrade on the extractor to increase extractor tension. I've seen no outward indications or signs that it is magnetic particle tested, high pressure tested, or shot peened.
I've wondered about the BCG spec. I theorize it could go both ways...
Scenario 1: The BCG is carpenter steel but S&W forewent the MPI, HPT, shot peening and other mil-spec testing acronyms to cut production costs. In this case, S&W statisticians surmise that the failure rate of the BCG and subsequent costs of warranty repair/replacement are lower than equipping the entire production run of 15-Sports with a full mil-spec BCG.
Scenario 2: In addition to the omission of features that dropped materials and production costs, S&W saves money via the economy of scale. A combat trigger is a combat trigger. A standard safety is a standard safety. So for the entire production run of M&P 15 rifles, no matter the model variant, they order up the same exact mil-spec BCG. They publish the specs of the BCG on the higher priced rifles in the line. They omit publishing the specs of the BCG on the 15-Sport listing to imply a functional difference between their entry level rifle and the higher price points.
After a while, I stopped wondering. All that matters to me is that through all of the rounds I've put downrange, the stock M&P 15-Sport BCG did not fail.
I believe mine used to be market MP. Hard to tell now from use but when researching, many found that the M&P bolts were HP tested and MP batch tested.
You won't see a full auto carrier in any S&W product-unless they do up a special order run for a LE agency.
As someone else noted, for ecomony of scale, all the carriers/BCGs are probably the same. You might save money on not machining the forward assist notches on the carrier, but then you'd have to inventory a different part. Probably a wash in terms of cost.
The vast majority of carriers today are 8620 steel. Out of curiosity, I looked up the specs on Carpenter 154 & 158 steel but it's been 40+ years since Strength of Materials, no way I can make an intelligent comparison of the various steels.
Obsessing about the intricate details of the military specification is pointless. The AR specs were originally set in the mid 1960's using 1950's materials and methods. There have been a lot of improvements since then. CNC machining centers remove a lot of potential for human error. Outside of specific contract requirements, inspection frequency generally relates to the tolerance range and criticality of the part. If inspection failures hit a trigger point, the frequency of inspection goes up and can result in scrapping that part lot.
Back when the making of iron & steel was a black art, proof testing each critical part/assembly made sense (also was a revenue stream for the crown/government). However, proof testing didn't detect the incorrect heat treatment of the first 1.2 million 1903 Springfield rifle receivers (low number Springfields). The defects surfaced in actual use. S&W warrants the product against material and craft worker defect for life, that should reassure you as to expected quality.
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