AR thumpers

[BD]

I thought I'd start this thread as a place to talk about shooting cast in the large bore ARs. I'm still in the early stages of cast boolit work ups for my .450 bushmaster, and I haven't hit the magic load so far. My 300 grainers are grouping about 3" to 4" @ 1,950 fps. I tried ten 230 grain BD acps at about 1,500 fps on Saturday, and I got about the same group at 100 yards that I get with a 1911 , maybe a little better, but not much. i also tried some Lyman 457193s sized down to .452 at about 1,000 fps over Unique. they shot way low, but stayed in 3 1/2".

Good news is no leading. A little plating on top of the carbon at the rear of the bolt, but no real crud in the gas system, and easy clean up.

Anybody else having luck? What have you tried? What are you sizing to?

There's a forum started just for the .450 B at:

http://450bushmaster.net/

It's more of a general discussion forum, not specifically cast boolit related. However there are a couple of guys interested in using boolits.

BD

[rockrat]

3" is about all I got with my 450B. The best boolit was the RCBS 45-300 sized to .454". Tried the LEE 340gr and got about 4". Also, the Lee 45-300pistol boolit, but it casts at .452" and would really like to try one about .454". A Saeco copy of the 457191 size to .454" would only do about 4" so far. I think that they might like a harder boolit.

Working with my 50 Beowulf right now. The 330 NEI boolit for the 50AE will only go about 4", but the Lee 50-440 today went 2" @1739fps @100yds--best group so far.

[BD]

I've been using water dropped wheel weights. Maybe I should try some heat treated? I have some lino in the barn at home in Maine, but only wheel weight alloy with me in NY. Have you recovered any boolits to have a look at the heel? On .450B.net a guy who had tried some sabots, (with no luck), was saying that recovered sabots had a small semi-circle melted out of the heel that matched the diameter of the gas port. Could be possible that the gas port is taking a bite out of un-checked boolits as well as I did find some lead plating on the rear of the bolt and bolt carrier after shooting plain base on Saturday.

BD

[rockrat]

I would think water dropped WW's should be fine to 2000fps or so. Haven't recovered any boolits, but unsure how the gun would like plain based boolits. I can see why the sabot would have the melted part. The hemispherical base of the sabot along with the gas port even for a fraction of a second should be enough.
The 45-300 is gas checked and did better than the plain based ones. Only gas checked also in the Beowulf. Something like the Lee 45-310 boolit, but around 280grains , would be perfect for the 450 Bushmaster

[BD]

The 300 grain mold Dan cut for me weighs 293 grains lubed and checked. So far I haven't done any accuracy loading, I'm just loading spreads 1 full grain apart to get within a decent pressure range. I'm hoping to do some more this weekend.

BD

[dk17hmr]

How well does it run with Keith style bullets?
I like the theory of the 450B better than the 458 socom. Because all the bullets you could use by sizing.

[BD]

I haven't tried any keith style bullets as I'm a fan of the full diameter front band, RNFP style. The .450 B has proven extremely accurate with the Hornady FTX bullets, I'm hoping that I can find the formula to achieve that with cast as well.
BD

[BD]

I went to the range today with 60 rounds, 30 using H110 under the MM 293 grainer, and 30 with WC 680 under the same boolit. I'm still feeling my way around, going up @ one grain increments, playing with the crimp and the difference between small rifles primers in the hornady brass vs. large rifle primers in cut down .284 brass.

Some progress! 33 grains of H110 under the 293 grainer in cut down .284 brass primed with Federal 210Ms gave me an average velocity of 1866 fps with an extreme spread of 27.65 and an SD of 8.9. The first five round mag went .98" Of course, as sometimes happens with me, when I saw this I managed to throw a couple of fliers out of the second mag for a 10 round group of 3.5". 34 grains of H110 opened things way up again so I'm gonna feel around between 32.5 and 33.5 in tenth of a grain increments. This is something I can work with.

1870 fps is a little slower than I was hoping for, but I think it'll still put down anything on this continent under 200 yards.

I have to say that this set up handles this round really well. I think I'd be pretty sore if I'd have shot that load work up in a lever gun. The 5" diameter tunnel I dug in the clay bank, deeper than I can reach, was somewhat satisfying as well.

The barrel is clean and shiny after 60 rounds. No sign of leading, but the brake is coated with lube. The WC 680 left burnt granules in the tube as always. Could be I need to lube only one groove. If you had a choice, would you pick the groove just in front of the check, or the groove just behind the front drive band, (which also doubles as the crimp groove) ?

BD

[dpaqu]

This is a great thread. Would the 450 bushmaster be the best upper from a Cast Boolit/reloading point of view?

[BD]

I'd say the jury is still out on which of the thumpers is easiest to achieve accuracy with. The .450B is certainly an easy platform to deal with, brass is available and it has the largest choice of boolits and bullets to play with.
BD

[crabo]

Any updates?

[Tad Houston]

[QUOTE=rockrat;the Lee 50-440 today went 2" @1739fps @100yds--best group so far.[/QUOTE]

What was your load for this in your beowulf? I have that mould, and want to try it- Thanks!

[rvpilot76]

What is the twist rate on your 450 Bushmaster?

[hammerhead357]

I am glad I found this thread. I have been thinking of building an ar thumper and was trying to decide between the 450b and the 458 socom. Anyone have opinions of the pros and cons between these two???
I would like to hear everyones thoughts on this..
Thanks....Wes
I should have added that I want to use this mostly for cast boolit use.

[StarMetal]

I've been using water dropped wheel weights. Maybe I should try some heat treated? I have some lino in the barn at home in Maine, but only wheel weight alloy with me in NY. Have you recovered any boolits to have a look at the heel? On .450B.net a guy who had tried some sabots, (with no luck), was saying that recovered sabots had a small semi-circle melted out of the heel that matched the diameter of the gas port. Could be possible that the gas port is taking a bite out of un-checked boolits as well as I did find some lead plating on the rear of the bolt and bolt carrier after shooting plain base on Saturday.

BD

Correct me if I'm wrong but don't the sabot have a cupped base like a shotgun shot wad? If so it's not doubt there is a semi circle cut out of the base because when that thin portion which is the side wall of the cup recess is over the port the gas just punches it right out. I doubt the gas cuts a plain base. I also don't think the gas pressure is real high right there. I have the gas pressures inside the gas tubes that come from Colt.

Joe

[jblee10]

dk17hmr, my 450 Bushmaster will feed rcbs 45-270-saa bullets well at 1927 fps. I don't see why an accurate load couldn't be developed with a SWC. Maybe with a gascheck.

[brstevns]

Anything new with lighter wieght bullets say 200-230 gr.