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Bullets shoot badly
I have owned my 300 blackout for almost 2 years now. I have reloaded a wide variety bullet types and aware how differently they perform at the shooting range. Got a good deal on these Subsonic Rainer 180 gn bullets. Was at the shooting range sighting in my thermo imaging scope. I thought I was fairly well sighted in when I switched to these Rainer bullets. The Rainer bullets were all over the paper target. At first I thought it was my scope but switched over to the 150 gn Hornady bullets and started shooting nice tight groups again. What's the deal on these Rainer bullets, is it the blunt tip, bullet weight? Maybe this is why we go to the shooting range.
When I'm wild hog hunting I don't trust my reloads. I use Remington hollow points available at Wal-Mart for $16/box
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Sometimes one must be a very good detective to figure reloading mysteries out.
With a cartridge like the 300BO there are lots of mysteries.
First, that cartridge can accept bullets from 100-200 grains, so the first thing I would ask is "what is your rifling twist?"
Even between the 30-06 and .308 there is a difference in rifling twist to enhance performance with the intended bullets. There are numerous charts and references correlating twist rate and bullet weight published by the bullet manufacturers. There used to be a chart in the Siaria book but someone stole mine and I have not replaced it.
In fact, I have an old Spanish Mauser in 7x57 mm. It will only shoot bullets of over 170 grain weight due to the tight 1/9 rifling twist. Modern 7x57 mm rifles are made with a slower 1/12 twist and stabilize the 140 grain bullets that are now commonly loaded in factory rounds. My rifle keyholes those bullets at 25 yards.
The AR rifle issued to troops and built by one and all now has a normal 1/7 twist to stabilize the longer 60-75 grain bullets used in the NATO spec rounds. If you wish to shoot the old 50-55 grain loads, or the 40 grain pills, it is best to have a 1/9 twist like the old original M16 barrel from days of yore. There was a reason for that unstable bullet but we will not go there right now.
The first thing I would do is find the rifling twist of the barrel and match bullets to the rifle rather than picking a slug because it looks good or you just want a different weight bullet. If 150 grain slugs do well in the rifle use 150 grain slugs. There are only about a million choices in 150 grain .30 caliber bullets from each and every manufacturer that ever made a slug!
Your 300BO is a massive trade off cartridge. It is normally selected simply because it works on the AR lower with no modifications. That was its entire design parameter. It has exact limits due to cartridge capacity, pressure limits, bullet size and shape, and cartridge over all length limits and reaches its ballistic potential at a fairly low level.
There is no stretching the bullet in length due to the magazine restriction. All weight increases must intrude on the powder capacity. You increase bullet weight and you reduce velocity. Finally you get to a point where the greatest weight/length bullet reduces the velocity to below the sound barrier. That was the intended bullet the designers anticipated for use for the .300BO. Those are the rules as they now stand in physics mode.
Working at that maximum trade off point is the intended purpose of the cartridge. It was never intended to be a heavy bullet hunting round for the AR. It was developed to give the military a sub sonic round that would work through a suppressor on an AR platform. They did not actually care if that bullet was a 150 or a 175 or a 220 grain weight. They just wanted a bullet heavy enough to be impressive to the test audience and give maximum energy on target, sub sonic to work through the silencer, and still short enough to hold the necessary powder load and not exceed magazine length.
They presented the cartridge as a military cartridge and reloaders were not their specific target market. The design was not expected to see use in every 30 caliber bullet weight available, just the specific load that met their parameters of subsonic functioning through an AR magazine with sufficient knockdown power inside 100 yards. It would then be made by the thousands for the military with no one knowing the exact powder/primer/bullet maker or combinations.
When the military failed to pick up the cartridge in a big way it was offered to the civilian market so the designers could recoup some of their investment. So that may be why your 150 grain factory rounds work and your 175 grain reloads have problems.
Those limitations are the reason I do not own a .300BO upper. If I am not going to use a suppressor the cartridge has absolutely zero benefits for me over and above either 30-30 or 7.62x39, .308, which are better performers in each bullet weight category. The AK round gives higher velocities with bullets up to 150 grains and the 30-30/.308 gives better performance with bullets above 150 grains.
It is the same in almost all caliber choices for the AR. That magazine length restricts bullet weight and velocity potential. Each time I consider a different caliber on the AR platform I run into that limitation and it stops me cold in my tracks.
When they offer an upper that involves a .223 blown out to a straight wall 9mm I will once again review the situation!
But enough of my rambling. Just check your barrel twist rate. If it is 1/10 or 1/12 it will work best with the mid-range bullets at the velocities you are limited too.
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What you are saying is buying bullets based on cost is the wrong approach. I figured as long as the bullets were .30 cal and I adjust the powder charge I would be good to go. I think my 300 blackout has a twist rate of 1/8.
Here is another bullet that shoots poorly in my 300 Blackout. These are 110 grn. I bought a bunch of these because they were cheap. I usually order 100 ct at a time. The last time I made a mistake and ordered 200. I think these are M1 Carbine bullets. I know a guy at the shooting range that loves M1 Carbines, maybe I'll give them to him.
I also have a bullet mold for the 300 Blackout, I think that cast bullet is over 200 grn. Shoots terrible. At 75 yards some of the bullets actually "key hole" through the paper target. So now I have a bullet mold collecting dust.
Just goes to show you need to ask the right people the right questions.
Thanks Kyrat
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No one ever tells anyone what a military gun/cartridge combination is designed around because it is never really expected to be used in anything but that platform.
The .300BO was specifically designed as a pistol round, around use in a 9" barrel with a 1/7 twist. With a suppressor, which screwed into the end of the barrel it would have been the same length as a standard carbine but most of the length would not have been rifled. Using it in a rifle actually detracts from its performance. I am surprised they work as well as they do.
Those carbine bullets did not stand a chance in that cartridge! Anyone that reloads for about any other .30 caliber can use them. I used to reload the soft point carbine bullets as varmint rounds for my 30-06. They do not make good long range rounds but they will sure flip a ground hog off a stump across the garden patch from the back porch. That hog looked like a Chinese acrobat!
What I would do, if I had a .300BO w/loading dies and all the trimmings, would be to buy some 150 grain round nose soft points intended for the 30-30 and see how they worked. You can get them fairly cheap too.
They should make it through the over all length and cycling problem OK, and they would stand a better chance of expanding at .300BO velocities than most other .30 caliber slugs. 30-30 jackets are super thin. They might even shoot to where you look.
If you go over to Cast Boolit forum you can probably trade off that heavy .30 mold for some kind of goodies. They are always swapping stuff.
Unless you think you might get a .308 or 30-06 rifle some time. With cast bullets the heaviest bullet wins, since they all have an upper velocity limit that can not be exceeded, and a 30-06 was designed around and is set up for 200-220 grain bullets flying at 2200-2400 fps. The original 30-03 bullet for the '03 rifle shot a 200 grain slug. They changed the military loading in '06 and again around 1927.
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