Here's something that's never been discussed on the forums, and I thought that it's a topic that warrants it's own thread (as opposed to being posted in the big Mk13 thread). Recently, a small group of 8 or 9 original prototype/sample Stiller Mk13 receivers popped up in the collector market and were sold. I have 2 of them in my possession, but only one of them is mine (serial number 3), the other receiver belongs to my brother (serial number 12). Collectors were limited to purchasing just 1 receiver, not multiples, in order to keep things fair.
When Crane put out a solicitation for the Mk13 receivers, Stiller made 25 of them according to Crane's specifications. The 8 or 9 receivers that recently hit the collectors market were from this original batch of 25 receivers. These Stiller Mk13 receivers are considered to be prototypes and/or sample pieces for Crane, and were never issued.
Stiller based these prototype Mk13 receivers off their Tac 300 receivers, but the 2 types of receivers have some differences. The biggest difference between a Mk13 receiver and Tac 300 receiver is the lack of the flat left side on the Mk13 receiver. This is because Crane specifically requested round receivers for their Mk13 program. Stiller assumed that the entire receiver should be round, even though Crane was only referring to the bottom of the receiver (such as a round bottom Remington 700 receiver compared to a flat bottom Winchester Model 70 receiver), so Stiller didn't cut the flat into the left side of the receiver like the Tac 300 has.
The armorers from Crane inspected these 25 prototype Stiller Mk13 receivers and liked what they saw, but they did request a few changes to the receivers. Here's a list of changes that Crane requested Stiller to make:
● Remove the "C" serial number suffix (the "C" suffix stood for "Crane")
● Remove the space between the "MKA" serial number prefix and the rest of the serial number
● Add one more digit to the number portion of the serial number (4 digits to 5 digits)
● Move the engraved serial number from the left side of the receiver to the right side of the receiver
● Remove the gas vent hole from the receiver
● Add an RFID tag to the left side of the receiver that has a 2D barcode, Stiller manufacturer cage code, Mk13 receiver part number, and Mk13 receiver serial number
There's also another for differences between the 25 Mk13 prototype receivers and the issued Mk13 receivers, but I highly doubt that these were changes that were requested by Crane. I think that these are just things that Stiller did on their own, for whatever reason. These are just some things I've noticed when comparing the prototype Stiler Mk13 receivers to the issued Stiller Mk13 receivers:
● The prototype receivers don't have commas in the FFL markings, the issued receivers do have the commas in the FFL markings
● The prototype receivers have a slightly thicker outline to the "MK13 300WM" markings than the issued receivers (bold text vs regular text)
● The prototype receivers have a slightly different letter font and size to the "MK13 300WM" markings than the issued receivers (this can really be seen when comparing the "W" and "M" letters on the receivers)
● The prototype receivers have a slightly different letter font and size to the "SPF LLC WYLIE TX" markings than the issued receivers (this can really be seen when comparing the "W" letters on the receivers)
● The prototype receivers have a shiny finish bolt shroud and bolt knob, the issued receivers have a matte finish bolt shroud and bolt knob
The 25 prototype Stiller Mk13 receivers were never built by Crane or issued to any military unit. The owner of Stiller might have kept some of these 25 prototype Mk13 receivers for his personal collection or for the company's records, and he might have sold and/or given away some of these prototype Mk13 receivers to employees and friends. I have no idea who had these 8 or 9 prototype Stiller Mk13 receivers that were just sold to collectors, or if there's any other prototype Mk13 receivers out there. I assume that none of the 25 original prototype Stiller Mk13 receivers were destroyed, so they have to be somewhere. However, myself and other big Mk13 collectors had absolutely no idea that these prototype receivers even existed before these receivers popped up for sale. I assume that these receivers are also unknown to just about everyone on this forum, so this thread should have some interesting information for the collector community.
Well, that's enough typing, here's a bunch of photos of the prototype Stiller Mk13 receivers for you all to enjoy. I also took a few photos of my other 2 Stiller Wylie Mk13 receivers (build into Mk13 Mod 5 and Mod 7 rifles) so that the differences between the prototype receivers and the issued receivers can easily be seen:
