450Bushmaster.net

Let me start this off by saying this is my first post here, so I'm glad to have finally made it out of the shadows. Lots of good information on this forum. I've got about a year of reloading experience, 6.5 Grendel, 9mm, 10mm, and now the 450 BM. I use the 10th edition Hornady book which has been fairly close to most of the charge weights and corresponding velocities.

That is until I loaded my first 450BM loads today. I'm using 250 grain XTPs, 300 grain XTP mags, new starline brass, CCI 41 primers, seating to the cannelure, and taper crimping to .476. They are fired from my 18" AR15.

I started the 250s at 37, 37.5, and the book max of 37.9. I realize these numbers are for the non cannelure 250 FTX, but they are more conservative than the 240 xtp mag. Groups shrank from about 4 inches to 2 inches and the SD dropped as well at max load, but my average velocity at 37.9 was just so of 2400 fps. That's a full 200 fps faster than the book. From what I can tell the fired brass looks (measures) similar to Hornady black.

Similar story with the XTP mags, with about 2000 fps velocity (100 fps over the book) and about 7 inches lower impact from the 250s.

Sorry for the long winded rant, I just want to make sure everything is safe. The book published max load had the best standard deviation and 3 shot group so I'd love to use that load if I'm not prematurely wearing out my brass/rifle.

Thanks!

What are the specs on the barrel? Maker, twist rate, gas system length.

It's a GLFA 18 inch, 1-24 twist, mid gas, thread protector, no brake yet.

Also, does everyone seat to the cannelure or just off of the lands?

Ok, reread your first post, somehow missed that your asking about the 250 XTP. Hornady says that the XTP's aren't rated for more than 45colt, they mention an overpressure problem. The XTP Mags are rated for moderate 450B loads.

As to the velocity increase, here's my thoughts. Hornady was using a Bushmaster 16" carbine gas length upper, which have looser tolerances, and they were most likely using the older Lilgun powder that was a bit slower than the current offering. So, running an 18" mid gas with the newer powder will give you gains, and if it has tighter specs, you will get a little more still. What you have to do is keep an eye on the brass.

Rklenke wrote:Also, does everyone seat to the cannelure or just off of the lands?

I'd use the cannuler as a reference and seat below it. The 450 has a generous amount of free bore so getting close to the rifling and keeping the oal to fit in the mag likely not going to happen.

Thanks, I'll have to try seating a little longer. I'm at 2 inch groups at 100 right now. Both the XTPs and the MAGs shoot pretty nice, both better grouping than the Hornady Black I was using as a control. I can't complain too much as this is a short range hunting rifle. Any other moderately priced hunting bullet anyone recommend?

225 FTX

You can actually load the 300gr XTP Mag to the lands in my rifle without exceeding the magazine space. IIRC, in my upper, I hit the lands around 2.22 COL. I used that as the basis of trying a slower powder than optimum for 300 grainers. The Idea was that by starting the bullet at the rifling, I would pump up the start pressure enough to get 1680 cooking. In practice, (see sig) it didn't work out that way and the 100yd 5-shot groups left a lot to be desired. Never wrote that one up. I have not encountered any other bullet that would reach the lands and still stay under 2.26 COL. Just thought I'd chime in on that.

With my 1:24 barrel, I found that with the 300gr XTP Mags and 300gr Speer Deep Curls, the faster I tossed them, the tighter they grouped. Started seeing pressure signs before getting them fast enough to tighten up to MOA. A faster twist barrel may be able to accomplish what I could not. Ditto on the 300gr SST/ML (FTX) bullets. They also wanted more speed than I felt safe delivering.

There are powders with burn speeds slower than W296/H110/300MP but faster than AA1680 that may be a better choice for the 300gr bullets. I always meant to try some H4227 because it was actually a temp compensated extruded powder, but never got around to it. Now they discontinued it, so we'll never know. IMR 4227 and ADI AR2205,though similar to H4227, do not have the temperature compensating ingredient in them. Ya' snooze, Ya' lose

Hoot

Welcome to the forum Sir.