Heavy Cast Subsonic Bullets (500 grain) Range Report

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Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Rklenke » Tue Mar 05, 2019 7:02 pm

Having fired everything between 230-300 grain in my 450BM, I figured it was time to try out what the SOCOM fanboys are always raving about. Through seemingly endless internet searching, I could not find a single source document or forum about shooting heavy bullets in the 450BM that didn't end in "The 450BM was designed for lighter, faster loads" which always seemed to be a conversation killer. That being said, I've got my steel toe boots on, let's go bowling!

The gun:
18" AR15 GLFA barrel, mid gas, 1:24 twist, (90% confident of a .451 bore size)
Standard carbine spring
H2 Buffer
FA profile BCG

The bullet:
Lee 459-500-3R 2 cavity aluminum mold
Dropped at 490 grains with straight wheel weights, air cooled, .459
Loaded to 2.3 in twice fired Starline brass. Case mouths required a good bit of flare. Seating depth is required to be long due to the very narrow taper of this bullet, which is designed for the 45/70. This also does not allow us to get a very good taper crimp as the case mouth with the bullet seated at 2.3 is not on a portion of the bullet that measures at .452. My standard crimp is .474", however, I believe these were crimped to .470" and was still not a great grip on the bullet. This bullet requires you to have a magazine that will allow for an COAL of 2.3". Seating any deeper will further reduce the effectiveness of the crimp. I am not set up to use a side-crimp, however, I bet it would be extremely useful here.
Finished bullet double.jpg
Finished bullet double.jpg (107.52 KiB) Viewed 1376 times


The process:
I currently only own a .451 sizer die, so I elected to size first, then powder coat. The sizing process required a layer of Hornady Unique lube, and did require some force. I wiped off the lube and had to mildly sand the bullet base as going from .459 to .451 left a small extruded ring of lead at the base. They were powder coated using standard methods and measured at .452-.453 after PC. I am extremely new to casting and powder coating, so I can say for certain there are probably other factors I left out such as water quenching, age hardening etc.

The good stuff
I fired three groups of three: 21, 22, and 23 grains 1680 after my very first shot at 19gr gave me 807 FPS. I started with a clean bore and did not use a fouler shot.

Group 1: 21gr 1680
1: 994 - case stuck halfway extracted
2: 943 - no extraction, bolt full forward
3: 943 - no extraction, bolt full forward
AMV: 962 FPS
The first two essentially hit the same hole.
21gr1680.jpg
21gr1680.jpg (35.58 KiB) Viewed 1376 times


Group 2: 22 gr 1680
4: 1059 - case stuck halfway extracted
5: 980 - no extraction, bolt full forward
6: ERROR - case stuck halfway extracted
AMV: 1022 FPS
Tightest group, impact shifted .15" inches up from 21 gr load
22gr1680.jpg
22gr1680.jpg (45.12 KiB) Viewed 1376 times


Group 3: 23 gr 1680
7: 1188 - case stuck halfway extracted
8: 1111 - case stuck halfway extracted
9: 1123 - case stuck halfway extracted
AMV: 1143
Impact shifted .8" up from 22 gr load. Slightly above subsonic speeds.
23gr1680.jpg
23gr1680.jpg (47.12 KiB) Viewed 1376 times


Conclusions: I'm not too worried about the rifle not cycling as I have a decent bit of mass in the bolt/buffer that I can remove to help cycle. I have to do this to run 225gr subs in my 7.62x39, so I'll try that out next time. I need to get a .452 sizing die. I think that will help increase the pressure and bit and help with cycling. We'll see if I change my mind on sizing pre powder coat...I probably won't due to the lead movement. I'll probably try one and just melt it down if it doesn't work. I'm going to stick with the 23 gr load and continue to mess with the other variables. In about a year when my suppressor comes in, I may have this load down pat. Let me know your thoughts and I'll keep making adjustments until we get it right. Other powders on hand: LilGun, H110, SWBO

Ryan
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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Hoot » Wed Mar 06, 2019 5:35 am

Nice looking boolits! if you increase the diameter as you plan, you will have to reduce your charge a little bit to offset the increased pressure. For sure go back to 21gr 1680, possibly 20. Decent groups for cast boolits too! Not that I'm an authority on cast boolits but I did stay in a Holiday Inn Express once. ;) You may have to go with a faster powder to get it to cycle. I seem to recall cast boolits needing faster powders. The down side to that is keeping you case fill at a safe level.

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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Rklenke » Wed Mar 06, 2019 7:12 am

I did forget to mention that these were fired from 22 yards, so I expect those group sizes to open up a bit, but I'm still happy where they are at. I'll repost groups at 100 yards when I can get out to my neighbors range.
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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Texas Sheepdawg » Thu Mar 07, 2019 6:17 am

Welcome. Good post. We will be watching your progress. And yeah a LeGendre side crimp would definitely help you here.
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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Rklenke » Sat Mar 09, 2019 2:05 pm

I got to shoot some more today, none at 100 yards yet, so I was just looking for ability to cycle and some points on FPS. I loaded a single round each of 24, 25, 26, and 27 (which should be very close to case capacity of 1680). I didnt chrono these, just looking for bolt hold open on an empty mag. Each 24-26 had a clean extraction, and 27 held the bolt open using the carrier (not full back on the bolt lugs). These were all fired in my original setup with std power carbine spring and H2 buffer. I swapped those out for my 1oz buffer and reduced power spring and went back to the 23 grain load to see if the subs would cycle; good extraction only, didn't pick up next round. Off we go to 26.5, 27, 27.5 with the light buffer, details below:

Created: 03-09-2019 01:43:42 PM
Description: 450BM 500HC 26.5 1680
Notes 1: light buffer and spring
Notes 2: OAL 2.3
Distance to Chrono (FT): 10.00
Ballistic Coefficient: 0.430
Bullet Weight (gr): 490.000
Shots
# FPS FT-LBS PF
3 1345 1968.59 659.05
2 1336 1942.34 654.64
1 1340 1953.98 656.60
Average: 1340.33
StdDev: 4.51
Min: 1336
Max: 1345
Spread: 9
True MV: 1343.87

Created: 03-09-2019 02:03:30 PM
Description: 450BM 500HC 27.0 1680
Notes 1: light buffer and spring
Notes 2: OAL 2.3
Distance to Chrono (FT): 10.00
Ballistic Coefficient: 0.430
Bullet Weight (gr): 490.000
Shots
# FPS FT-LBS PF
3 1336 1942.34 654.64
2 1343 1962.74 658.07
1 1329 1922.04 651.21
Average: 1336.00
StdDev: 7.00
Min: 1329
Max: 1343
Spread: 14
True MV: 1339.53

Created: 03-09-2019 02:21:42 PM
Description: 450BM 500HC 27.5 1680
Notes 1: light buffer and spring
Notes 2: OAL 2.3
Distance to Chrono (FT): 10.00
Ballistic Coefficient: 0.430
Bullet Weight (gr): 490.000
Shots
# FPS FT-LBS PF
3 1339 1951.07 656.11
2 1362 2018.67 667.38
1 1339 1951.07 656.11
Average: 1346.67
StdDev: 13.28
Min: 1339
Max: 1362
Spread: 23
True MV: 1350.22

There was no discernible difference between those three loads and I only had one shot pick up the following round and chamber it. They all seemed to shoot as accurate as before, and were absolutely punishing on my steel. For now I'm going to hold off on burning more bullets and 1680 until my .452 sizer comes in to see if that will push me over the edge and help with cycling (besides the couple I have loaded up for 100 yards. All of the brass was very clean, no sooting.

Blue cast.jpg
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Rifle and range.jpg
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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Hoot » Sat Mar 09, 2019 5:18 pm

Judging from the direction you're going, I'm not sure you'll be able to keep those honkerillas subsonic and still get full cycing with a mid-length gas system. I haven't read of anybody getting full cycling with a mid-length gassed 450b rifle and subsonics, regardless of weight. They sure are handsome though!

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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Rklenke » Sat Mar 09, 2019 5:32 pm

I think you're right there. Unless the suppressor can add enough back pressure to cycle it, these may be super sonic only. The can will for sure allow the supers to cycle, not sure about the subs though.

Other options are powder, lightened carrier, and opening up the gas port and putting in an adjustable gas block.
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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Hoot » Sat Mar 09, 2019 5:49 pm

Rklenke wrote:I think you're right there. Unless the suppressor can add enough back pressure to cycle it, these may be super sonic only. The can will for sure allow the supers to cycle, not sure about the subs though.

Other options are powder, lightened carrier, and opening up the gas port and putting in an adjustable gas block.


Or buy one of those inexpensive 450b barrels, rotate an unwanted block to close off the mid-length port and drill either a carbine or pistol length port. Save the other barrel for when the subsonic spell wears off. ;)

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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Rklenke » Sat Mar 09, 2019 6:13 pm

Unfortunately, I want a rifle that can do both with minimal configuration change. If they won't run, I won't shoot them. Luckily the mould was only 25 bucks. These bullets would really shine in the bolt action guns, so hopefully this is useful for someone. I'll keep testing, loading, and shooting as it's always enjoyable regardless of the result.
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Re: Heavy Cast Subsonic Bullets (500 grain) Range Report

Postby Hoot » Sat Mar 09, 2019 9:17 pm

Rklenke wrote:Unfortunately, I want a rifle that can do both with minimal configuration change. If they won't run, I won't shoot them. Luckily the mould was only 25 bucks. These bullets would really shine in the bolt action guns, so hopefully this is useful for someone. I'll keep testing, loading, and shooting as it's always enjoyable regardless of the result.


The chase is the best part of the hunt. If any boolit will cycle an AR based 450b, that's it. May take trying a lot of different powers to find the magic recipe. Borrow or swap powders you don't have with friends. At least the boolits are recyclable!

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