.450 Bushmaster
Ambrose
Member Posts: 3,164 ✭✭✭✭
I have an interesting situation with this cartridge. Excessive extreme spread. I have three rifles: A Ruger American (22" barrel), a Mossberg Patriot (20"), and a Ruger 77 (24"). So far I've fired 63 five-shot groups: 36 from the American, 14 from the Mossberg, and 13 from the 77. Nine of those groups were with Hornady factory loads. A third of those groups had an extreme spread over 100, including 3 of the 9 factory load groups. I shoot over a double chronograph set-up with a PACT and an Oehler 35P so I'm getting 3 readings with each shot. I don't think my chronographs are the issue. I've tried 6 different primers. I started with Remington 7 1/2 and got an average ES of 130 so went to Remington 6 1/2 and it improved to 85. Trying an even more "delicate" primer, I tried Federal 100, a pistol primer; 73 (but I've only fired one group with that one). The worst I've tried is the CCI 450, a magnum primer @ 227! I am using mostly Lil'gun powder with Hornady 250 FTX bullets. I am wondering if the small rifle primer is not hot enough to light the quantity/volume of powder used in this cartridge. I'm temped to cut down some .284 Winchester cases to see if a large rifle primer levels off the ES.
Anyone else noticed this issue?
I think this is a near ideal deer cartridge (except for the recoil!) for moderate range. The muzzle energy beats most .30/06 factory loads and it punches a big hole.
Comments
How do your loads compare with the loads above?
How do your 'triple' chronograph readings compare to the velocities shown above.
Have you checked the case lengths?
I have found loads right at book max with 1680 and the 250FTX shoot great, I have not chrono'd them but they shoot around 1.5" five shot groups at 100 yards in the AR platform and the Encore. That is good enuf for deer.
I saw that article in Shooting Times and tried the 37.5/AA4100 load and got 2102 fps with 36 SD. My jug of AA4100 must be a bit slower than theirs.
I am using 38 of Lil'Gun and getting 2347 fps with 36 SD.
The factory loads were the earlier brown box Hornadys. I got 2250 fps and 30 SD.
And, yes, I measured cases and had an AHA moment when I found variations so, thinking like you probably are, sorted them to reduce differences in firing pin strike. Didn't seem to make a difference in extreme spread.
Since the Shooting Times article featured a Ruger American, the comments I'm making in THIS post are reference to my Ruger American with 22" barrel. I have used only Hornady cases in this rifle: I have Starline brass but haven't used any yet in this rifle.
I didn't notice before, but the SD's that Shooting Times was getting are not that much different from my results.
I was initially more concerned with the Extreme Spread as opposed Standard Deviation. But without the information in your second post it was going to be a cat chasing mouse trying to solve the question.
I built several dozen of these rifles chambered for the .450 Bushmaster when the first craze hit the internet. Keeping this short, most of the owners found the same or similar situation as you. I started tearing rifles apart looking for the cause until I realized that this cartridge was the cause all along. It was not created to be as most of our other cartridges but rather made to fit a bunch of stupid rules which government officials decided fit their definitions of a hunting cartridge. Chalk it up to the crazies running the asylum.
The end result was, without redesigning the cartridge and without Hornady's support, we were stuck using their half baked solution. It's essentially a short range thumper cartridge with barely reasonable accuracy.
Your loads are in the ballpark with the published data and with what I found basically. After wasting way too much powder and too many bullets, I arrived at the idea that the cartridge itself has too much capacity to warrant finding only two powders which filled the case, yielded any sort accuracy and burned completely in those shorter barrels.
Out here I carry a lever action rifle and revolver chambered for the .454 Casull. Maybe not as much velocity but the same big hole with enough energy to kill a deer at short to moderate range. Works great on Javelina, too!😉😊
Best.
I note that the .454 Casull uses small rifle primers, too. What are the extreme spreads for that cartridge in your rifle? Do you think that cutting down .284 Winchester cases to try large rifle primers would be a worth while experiment?
I spent some time discussing this with Dick Casull years ago. I tested both and arrived at the same point Dick did:
I use the Small Rifle Magnum primers with the H-110 powder. I did not get the improved results I expected from using the LR primers. I'd have to do some real digging to find my ES data for this cartridge, sorry.
Best.
If you are ever able to locate your ER data on SR vs LR primers I'd be very interested in learning about it. I have a rifle ( an A-bolt) in .284 and, over the years, I've accumulated much more brass than I'll ever need or use. So it shouldn't bother me to cut down a batch to see what develops. Of course, the possibility exists that the case walls would be too thick to be usable but I'd know that from the first modified case.
My first .450 was a Ruger American and I thought I might be getting light firing pin strikes. So I switched from Remington 7 1/2 to 6 1/2 and got what appeared, at first, to be an improvement. Then, later, when I got a Mossberg Patriot, and then a Ruger 77, I got the same wide ES no matter what primer I used. I guess chronographs are not always a blessing.
Not long ago, I read an article wherein the writer theorized muzzle blast was responsible for wide ES from the .450. So he set up a baffle in front of his chronograph screens. I was thinking of trying that until I realized I've shot a lot of rifles that have generated much more muzzle blast than the .450 is capable of without the wide ES.