450Bushmaster.net

I pulled this still shot from a video I shot last month, that's my 20" Bashmonster shooting a near-maximum charge of Lil Gun (35.0) with a 250-grain Hornady FTX. According to my best guesstimation, this load should be giving me around 2250 fps, and the accuracy is good enough when I do things properly, it's been awhile since I shot a big-bore semiauto off a bench, and I get jumpy and twitchy pretty quickly.

I don't know if this is a common occurrence with the 450, or any other AR-based rifle shooting somewhat stout loads. I'm not too worried about it, but it does seem like the bolt is opening a little faster than normal. I'm still working on my crimping, not quite satisfied with the consistency there, even though I'm not using a chronograph, they feel a little different from shot to shot.

Your thoughts?

As long as your AR is in good operation, there is no way for it to really "open early" as the gas system cannot move the bolt until the bullet passes the port.

The flame/flash is simply from your choice of powder. These powders and you can include 296/#9 and H100 plus a couple more, will be harder to ignite and usually producing quite a fire ball upon firing. (ESP with max loadings.) Firm crimps help a lil, but really no way around it completely in the AR platform.

I know I'm on the outside with this opinion, but I am no fan of the LIL GUN powder.

CW

That's the first time I've ever seen that happen when the AR hadn't broke apart! I've seen traces of smoke but never fire. Don't know what to make of that. I can't see the end of the barrel. Were you running a suppressor? I've read that they can breath backwards a little.

Hoot

BTW, 35 grains of Lil Gun may not seal the case to the chamber ahead of a 250 FTX. Usually take around 37 grains to get them running right. Were your cases coming out sooty?

If I had to guess, it’s from the carbine length gas system on the 20” barrel or case not sealing properly (as Hoot mentioned), or both. As long as your not seeing signs from unlocking early, I wouldn’t worry about it. As far as cases sealing properly, if you have a bunch of soot on the outside of the case, you might want to up the charge a little. I prefer to run loads that properly seal, but again, you don’t have to worry about it a whole lot, because most factory ammo I have shot (I don’t shoot factory ammo now, because I reload) doesn’t completely seal. In my opinion, running slightly over book is fine because it should have less bolt thrust than a mid book load that doesn’t seal. Just a FYI, I’m the only one that I know of that has broken a bolt, but that bolt came from a company who has known issues with Grendel bolts, and the 450B is thinned out even more. I ran a pretty heavy load on that one, yet I have 3 other bolts that I’ve beat on harder and for longer, without issue. So I wouldn’t worry about upping it a bit if needed.