Yes and no. Short answer no. You had to have CO permission to take a pistol, and it had to be a NATO round (they said .45 would be okay, it ended up being 9mm only). Not many people did it either because of the guys wanting to take .44's, they ruined it. Infantrymen are all different types, from highly skilled and intelligent, to dumber than a rock. I wasn't SF either, but I worked close to them, mostly their gunsmith. I was an SDM instructor at the Stryker Brigade Advanced (Infantry) Skills Center. You can look up info on it here:
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA512136 but it doesn't really say much. Scroll down to section 09, the sbct. "Developing Agile Adaptive Soldiers". You can get the idea that we were trying out new ideas and you may find the article informing. The article is by my former bosses, Col. Brown, CSM Dedrich, the only guys this school answered to.
This is where I saw an E7 (the chief) cuss out an O3 too. He did half of it standing at attention. He got promoted two months later to E8, and I bet you don't see much of this in the real Army either and it is most certainly against regs. SHE came to an infantry school and told us we had to teach her POG unit how to use M4's. She wanted us to cancel a scheduled course to do this. The chief handled it wrong, but he didn't take crap from nobody and working at that school didn't exactly make you a "by the book soldier". Quite the opposite. I felt like "The Dirty Dozen" the whole time I was there. We had our own uniform and, well, got away with murder. I told you it was the perfect job. Anyway, that article refers to the school as "SBASC" and is in context to a larger picture of the Bde. and shooting was only part of what we did. In addition to this, we "hosted" a sniper course (the real deal, how many of those are done at Ft. Lewis? War creates special situations I guess) Barrett sent one of their guys to give a class on the XM107 (where we smoked an armor plate with Raufoss ammo) and I gave demos to the US War College. I still have the coin.
As for rifles, you weren't SUPPOSED to mod them, but they didn't say anything either. It kind of all started when we got a new 1SG that was a ranger hero. They let him get away with murder because he was supposed to turn the unit into a killing machine. He was pretty bad@ss, short as a smurf, but hardcore. I was 6'2" 220 and I wouldn't mess with his 4'10" (maybe with boots) 130lb (wet?) frame. Anyway, we got him because of this and when he got to that unit, he took shooting very seriously. On day one, he did an informal QA with the company. Some answers were: worked on Lynch mission, Army, SF, SEAL?, Marine and foreign sniper schools, 40 something confirmed kills. I'll never forget that answer, this unit had never deployed and CIB's were rare in the Army then.
Also, in the beginning like I said, SDM's did not get SDM rifles, they got a bipod, an ACOG, and an old cotton Garand sling. So concessions were made for this in particular. At the school, we (the instructors, not the students, although once or twice a student brought a toy in) regularly brought our own gear. Some was for formal and informal testing, some just for fun.
I have all of the SDM course on a disc, it has pictures of us playing with some of this I think, but I can't put it on here, sorry. Wife is home, time for dinner, take care!