Well, I built a 16 inch 350 Legend AR15 upper this spring using a CMMG barrel. I used it to take a doe this year using the 165 grain FTX, and the cartridge and bullet worked great. I can only relate my experiences as they relate to my 16 inch CMMG barrel.
I have reloaded for 25 years, and this cartridge provided some first time surprises and challenges, the first of which was a lack of information or advice regarding loading for it. I guess it is so new that there is not much out there. The best information I have found so far is a piece by Lane Pearce from Shooting Times "Reloading the .350 Legend" which you can find on line. Lots of great data and advice there, some of which mirrored my own experiences.
https://www.shootingtimes.com/editorial/reloading-350-legend/377056 I found that: 1.) the published Hodgdon load data for Lil Gun was HOT as in TOO HOT for my gun. The 25 grain start load drives a 170 grain bullet from my barrel at 2,250 FPS and is safe. That is what I load and I cannot go higher with Lil Gun: 26 gave erratic velocities and loose primers, 27 gave me 2450 fps!!!!!!! with a 170 grain bullet!!!!!!!!! and a blown primer, and a bulged case. That was a first for me. USE EXTRA CAUTION with this cartridge, work up your loads slowly in small increments and a chronograph is your friend. 2.) The COAL that Hodgdon published were too short in my gun ( I believe some of their published lengths are shorter than the factory rounds are loaded for the same bullet) and caused feeding issues in my barrel. My CMMG magazine allows COAL of 2.3, as does my chamber and throat. As long as your chamber and throat will allow, you may want to seat your bullet out some to facilitate better feeding. 3.) The CMMG 5 shot magazine (made by Duramag aka C-products) is a quality item, but there was simply a ridiculous amount of spring tension caused by the large amount of excess spring material used to reduce the cartridge capacity to 5 rounds. There was so much tension the bolt was having trouble stripping off the rounds from the magazine. I cut about half of these excess "un sprung coils" out and the whole problem was fixed. 4.) The Hornady Custom Grade 4 die set works great. The included taper crimp is the way to go to get a consistent neck tension and prevent bullet set back, all while not messing up the case mouth which the cartridge head spaces on. 5.) People complain about the .355 bullet diameter, however I have decided is a non issue. The factory .350 legend projectiles are made to work at 350 legend velocities. I buy them (when available) and use them. For practice and load developement I have used a $ 20 dollar LEE .356 sizing die to reduce some of the hundreds of 180 grain speer hot cor that I have on hand from .358 to .356. I would not trust them to expand like the Winchester 180 that is made for the Legend, but they allowed my to work up a load for the 180 grain weight without shooting up my very limited supply of Winchester 180 grain .355 legend bullets. 6.) The 350 legend, at least in my gun is not a super precision long range round, but rather a very practical 150 yard big game round. My good loads were consistent 2 to 1.5 moa and I was well satisfied with that. The recoil is mild and I think it is probably in a ballistic sweet spot as far as terminal effectiveness.
And another thing. Lil Gun works great in my barrel with the Hornady 165 FTX and 170 SP, but I could not get the 180 weight bullets to shoot worth a hoot with Lil Gun. IMR 4227 is my go to for the 180 bullets, and it seems a lot more forgiving and less prone to pressure spikes.
Thanks for listening and I hope some of this helps someone out. Be safe out there!
Rimfirerifle
