Bringing this one back up to add some new info. Long story short this past Spring I decided to build a switch barrel rifle based off a Zermatt Arms Origin action. One barrel was to be an existing .223 Rem barrel from a
Savage 112BVS that I have used for PDogs the past several years. This was mainly so that I could upgrade from an internal 4-round magazine (which I invariably ended up single loading while shooting) to a detachable box magazine and also to put the rifle in a KRG Bravo chassis to match my other PDog rifle. Since the Origin action was going to have a 0.385in bolt face having a second barrel chambered in either 7.62x40 WT or .300 HAM'R for use the remainder of the year was a logical step.
Unfortunately, circumstances, resource availability, and budget made neither of those chamberings attainable at that time. Thus I ended up with a 1 in 8" twist 19" barrel chambered in .300BLK. Cliff Notes version it's a hammer with every bullet I've tested in the 100gr-135gr range using H110 and Starline brass.
I did make sure to grab some CE 100gr Raptors! This have proven quite accurate .300BLK bolt rifle clocking in around 2525fps from the 19" barrel. Recalling the previous discussion of how the Raptors just barely fit in the 7.62x40 WT and wondering if they might be a no go for the 300 HAM'R due to the longer case length I decided to investigate now that I finally had some Raptors in hand.
Starting with a brand new Starline 300 HAM'R case (1.5930in) quickly showed that indeed the top driving band would be below the case mouth, even seating the raptor at the maximum OAL of 2.260in. Trimming the case to slightly below max for 7.62x40 WT (1.565in) results in being able to seat the Raptor at less than maximum OAL. In the image below that case is listed as the "pseudo 7.62x40WT". For reference my .300BLK (aka 7.62x35) charge is 19.84gr of H110 and it fills the BLK case right to the neck-shoulder junction resulting in minimal compressed load. Looking at how far the Raptor protrudes past the neck-shoulder junction on the pseudo 7.62x40 WT; recalling
@Michael458 has already demonstrated that you can indeed compress 25.5gr of Lil'Gun into a 7.62x40 WT case and because the 300 HAM'R is nearly the identical case n theory one should be able to utilize the 100gr FB Raptor in the 300 HAM'R using slightly shorter than spec cases.
If I ever do procure a 300HAM'R barrel with a suitable twist rate for the Raptor I will likely test this theory. However, since my current AR-15 300 HAM'R barrels are 1 in 15" and 1 in 13" respectively it is not prudent to proceed at this time.
Side Note: Although I did not do a 100% exhaustive search very few companies that chamber small shank Savage barrels offer either the 7.62x40 WT or 300 HAMR as an option. I do have a part# for the reamer from PT&G and gauge as well as a suitable barrel blank, but I'm not willing to endure that potential cluster just yet.
Although not an option for testing the Raptor theory, Wilson has come out with a barrel conversion for the Ruger American Ranch rifle:
Wilson Combat's 300 HAM'R conversion kit for Ruger American rifle barrel. Caliber conversion kit for owners of the Ruger American rifle chambered in 300 BLK.
shopwilsoncombat.com
This is an interesting option since that rifle accepts STANAG and not AICS pattern mags (20 or 30 rounds versus max 10 rounds).
