220 gr subsonic from an 8.25" SBR........

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rb288
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220 gr subsonic from an 8.25" SBR........

Post by rb288 » Sun Aug 01, 2021 12:04 pm

I was loading some 220 gr subsonic loads for my 330blk.
I was using 11.7gr, 11.9gr, and 12.1gr of CFEBLK and 9.7gr, 9.8gr, and 9.9gr of H110.
I wanted to run at about 1050fps.
Out of my 16" ar, I was getting from 1125 to 1175 as my averages for the CFEBLK loads and around 110 to 1150 on the H110 loads.
These are all, substantially above what the manuals list.
But I can deal with that.
The main issue is that the same loads out of my 8.25" sbr average around 850 for the CFEBLK and about 920 for the H110.
Now all these loads are at the max end of the "recommended" levels.
So, my question...
Can I push those upper limits to try to get the sbr to about 1050, or am I tempting fate too much?
I understand the barrel length differences, and extrapolating the velocities in would fall in at about 25 to 30 fps per inch which is about right.
Accuracy was good for the sbr at 25 yards a solid 1 inch group.
Anyway, just wondering about pushing to boundaries for the sbr a bit.
BTW, there were no signs of any excessive pressure on any of the brass.
Also, they were shot through a SpecWar 7.62 suppressor.
Any thoughts would be greatly appreciated.
I may have been on the losing side, but, I'm not convinced it was the wrong side.

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Saxon
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Re: 220 gr subsonic from an 8.25" SBR........

Post by Saxon » Sun Aug 01, 2021 12:35 pm

what bullet are you using ? as a few listings show more then 9.9 for h110
same with cfe

BJK
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Re: 220 gr subsonic from an 8.25" SBR........

Post by BJK » Sun Aug 01, 2021 4:44 pm

RB288, You can determine maximum pressure for yourself if you have a mic' that can read to the .0001", that's to the tenth. Take a piece of brass and mark 2 points 180°across the case head (mark on the headstamp). You'll actually be measuring the case in front of the rim. Record that measurement. Now using that piece of brass load it. Fire it and allow it to come down to near the temp you measured it at. If you see any change in dimension on those 2 points you measured you don't want to go any further and it's strongly suggested to back it down. When the brass starts to flow at the case head you're near or above max' pressure. Don't do this with work hardened brass.

FWIW, I expect to need to do this with my 10.3" barrel also eventually (hopefully soon, my too busy definition of soon), so any data you get I'd appreciate having it posted here. If I get to it first I'll post somewhere. Hopefully I'll remember this post and put it here.

I want to get as much as I can out of my 300BLK handgun, I assume you do too, but I've always thought of this bullet weight/load to be a .45ACP in .30 caliber. But more is better.

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dellet
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Re: 220 gr subsonic from an 8.25" SBR........

Post by dellet » Sun Aug 01, 2021 5:53 pm

The data you are using is incomplete at best, complete garbage at worst.

This is a huge problem with load data for the cartridge. With heavy bullets you need to find data that max load is pressure related, and not fps related like you are using.

Here’s a good example of pressure max loads. Note the numbers you used are basically the same for the shaded numbers that define subsonic in a 16” barrel.

Image

There can be many reasons to have numbers that don’t match the book, generally it boils down to case capacity, lot variations with the powder, bore diameter. Adjusting 1/2 grain either way to match predictions is pretty normal.

The suppressor will also add a bit of velocity, take it off for comparisons.
300 Blackout, not just for sub-sonics.

HowardZ
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Re: 220 gr subsonic from an 8.25" SBR........

Post by HowardZ » Tue Aug 03, 2021 9:31 am

Hi rb288,

What exactly is the 220 gr bullet you are using?
For example 220gr Hornady ELD-X 3078 ?

What OAL are you using?

h

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Netpackrat
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Re: 220 gr subsonic from an 8.25" SBR........

Post by Netpackrat » Tue Aug 03, 2021 12:44 pm

The 330blk must have done a number on your 7.62 suppressor... :mrgreen:

HowardZ
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Re: 220 gr subsonic from an 8.25" SBR........

Post by HowardZ » Tue Aug 03, 2021 3:32 pm

*** DISCLAIMER ****
I have not tried these loads.
I might have some error using Quickload.
These loads might not be safe.
Nobody has tried them.
***

Well, I will tell you about an experiment I am doing with 5.56 NATO which - if successful, may be helpful with 300 blk subsonic.

December of 2019 I did not renew the range badge at my gun club. They raised the price to $200 per year, and I only go to shoot once or twice a year. So, I thought I'd skip a year. Then COVID hit. Now I am vaccinated, but the gun club does not pro-rate buying a range badge for half of a year, so I am waiting until the end of this year 2021 to pay.

In 2016 I purchased a stripped AR lower - I called it "Hillary Insurance".
Was told by the dealer I can make it pistol or a rifle - I made it a pistol.
In 2020 I purchased a 10.5 inch upper for it.

Shorter barrels supposedly have a huge amount of muzzle flash, muzzle noise, and vibrations in the air - due to high muzzle pressure and so much un-burned powder.

So, using QuickLoad - I figured out a load which should perform well.

55grHornadyGMX OAL=2.200 barrel=10.5 Brass=28.5grWater HERCO=(10.9gr 76.1% filled) 2247fps max pressure 52864psi, at muzzle 8944psi 100.0% powder burned. The GMX bullet needs the shorter OAL due to it's canalure placement.

55grHornadyFMJ OAL=2.250 barrel=10.5 Brass=28.5grWater HERCO=(11.3gr 74.8%) 2250fps max pressure 52354psi, at muzzle 9368psi 100.0% powder burned

This is slower velocity than using H335, but I see a pistol AR for under 100 yard use, so it is OK to me.
55grHornadyFMJ OAL=2.200 barrel=10.5 Brass=28.5grWater H335=(25.0gr 97.0%) 2613fps max pressure 53929psi, at muzzle 17069psi 89.4% powder burned

The goal is to reduce the muzzle pressure from 17069 psi, down to something more normal as found in 16 to 20 inch barrels.
It is also likely that factory 55 gr load will use a H3 buffer, but this HERCO powder load will require a lighter buffer, and possibly even a light bolt carrier. I have not found anyone at the club to sight-in this upper and test this HERCO load for me - so I plan to do it this winter after I pay for range use.

Now - to 300 blackout, Quickload displays:
220Gr Sierra HP MatchKing 2240 OAL 2.260 barrel 8.25 Brass 25.10grWater HERCO=6.5gr,73.9%full 1051fps max pressure 40732psi, at muzzle 3599 psi, 100% propellant burnt.

So, this load - theoretically - will give the desired subsonic 1051 fps velocity, with nice low 3599 psi muzzle pressure with no excessive flash, no excessive noise, no air vibrations. However, will it cycle the AR properly? and with what weight buffer, and what weight bolt carrier?

I can not find on the internet anybody using HERCO powder with any kind of rifle cartridge - seems to be only used for shotguns and handguns.

Personally, I plan on using H110 with 300 blk for supersonics, and have no plans for anything subsonic.

Anyway, I thought I will share the idea of using HERCO powder.
I do not know if it will function.
I do not even know how safe this is.

Regards,
Howard

P.S. Different barrel lengths use different gas port sizes. I assume manufacturers experimented and found the best gas port size for various barrel lengths based on using factory ammunition. I hope a HERCO load will cycle the AR properly after experimenting with different buffer weights and possibly a light bolt carrier?

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dellet
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Re: 220 gr subsonic from an 8.25" SBR........

Post by dellet » Tue Aug 03, 2021 6:55 pm

HowardZ wrote:
Tue Aug 03, 2021 3:32 pm
*** DISCLAIMER ****
I have not tried these loads.
I might have some error using Quickload.
These loads might not be safe.
Nobody has tried them
.
***

Well, I will tell you about an experiment I am doing with 5.56 NATO which - if successful, may be helpful with 300 blk subsonic.

December of 2019 I did not renew the range badge at my gun club. They raised the price to $200 per year, and I only go to shoot once or twice a year. So, I thought I'd skip a year. Then COVID hit. Now I am vaccinated, but the gun club does not pro-rate buying a range badge for half of a year, so I am waiting until the end of this year 2021 to pay.

In 2016 I purchased a stripped AR lower - I called it "Hillary Insurance".
Was told by the dealer I can make it pistol or a rifle - I made it a pistol.
In 2020 I purchased a 10.5 inch upper for it.

Shorter barrels supposedly have a huge amount of muzzle flash, muzzle noise, and vibrations in the air - due to high muzzle pressure and so much un-burned powder.

So, using QuickLoad - I figured out a load which should perform well.

55grHornadyGMX OAL=2.200 barrel=10.5 Brass=28.5grWater HERCO=(10.9gr 76.1% filled) 2247fps max pressure 52864psi, at muzzle 8944psi 100.0% powder burned. The GMX bullet needs the shorter OAL due to it's canalure placement.

55grHornadyFMJ OAL=2.250 barrel=10.5 Brass=28.5grWater HERCO=(11.3gr 74.8%) 2250fps max pressure 52354psi, at muzzle 9368psi 100.0% powder burned

This is slower velocity than using H335, but I see a pistol AR for under 100 yard use, so it is OK to me.
55grHornadyFMJ OAL=2.200 barrel=10.5 Brass=28.5grWater H335=(25.0gr 97.0%) 2613fps max pressure 53929psi, at muzzle 17069psi 89.4% powder burned

The goal is to reduce the muzzle pressure from 17069 psi, down to something more normal as found in 16 to 20 inch barrels.
It is also likely that factory 55 gr load will use a H3 buffer, but this HERCO powder load will require a lighter buffer, and possibly even a light bolt carrier. I have not found anyone at the club to sight-in this upper and test this HERCO load for me - so I plan to do it this winter after I pay for range use.

Now - to 300 blackout, Quickload displays:
220Gr Sierra HP MatchKing 2240 OAL 2.260 barrel 8.25 Brass 25.10grWater HERCO=6.5gr,73.9%full 1051fps max pressure 40732psi, at muzzle 3599 psi, 100% propellant burnt.

So, this load - theoretically - will give the desired subsonic 1051 fps velocity, with nice low 3599 psi muzzle pressure with no excessive flash, no excessive noise, no air vibrations. However, will it cycle the AR properly? and with what weight buffer, and what weight bolt carrier?

I can not find on the internet anybody using HERCO powder with any kind of rifle cartridge - seems to be only used for shotguns and handguns.

Personally, I plan on using H110 with 300 blk for supersonics, and have no plans for anything subsonic.

Anyway, I thought I will share the idea of using HERCO powder.
I do not know if it will function.
I do not even know how safe this is.


Regards,
Howard

P.S. Different barrel lengths use different gas port sizes. I assume manufacturers experimented and found the best gas port size for various barrel lengths based on using factory ammunition. I hope a HERCO load will cycle the AR properly after experimenting with different buffer weights and possibly a light bolt carrier?
I would say the highlighted sentences are a good indicator for you to consider, but I am all for experimentation. I just think it's a bad idea to drag someone else into it.

If you search the site there will be some bolt action or single shot loads. Search the net for Herco+300 whisper will turn some more. Getting it to cycle an AR without a lot of work probably isn't the best use of time and resources, but I would love to be proven wrong. Always fun to see new powders that can be used.
300 Blackout, not just for sub-sonics.

rb288
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Re: 220 gr subsonic from an 8.25" SBR........

Post by rb288 » Wed Aug 04, 2021 9:06 am

Ok, did some further testing.
13.0, 13.2, and 13.4 grains of CFEBLK
11.0, 11.2, 11.4 grains of H119.
8.5" sbr through a specwar 30 suppressor with a Gemtech adjustable bcg.
The bullet was a Berry's 220 grain spire point.
5 shot groups.

The CFEBLK loads got me to 1022 to 1140 fps with 1 inch groups at 25 yards with no pressure signs and full function.
The H110 loads got me to 1028 to 1085 fps with 1 inch groups at 25 yards.
But while the H110 loads functioned, there were a few FTE in each load and the bolt never locked back on the final shot.

CFEBLK at 13.2 grains and 1068 fps was the best group at <1 inch at 25 yds.
I am going to work around that load.
I may have been on the losing side, but, I'm not convinced it was the wrong side.

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dellet
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Re: 220 gr subsonic from an 8.25" SBR........

Post by dellet » Wed Aug 04, 2021 10:40 am

rb288 wrote:
Wed Aug 04, 2021 9:06 am
Ok, did some further testing.
13.0, 13.2, and 13.4 grains of CFEBLK
11.0, 11.2, 11.4 grains of H119.
8.5" sbr through a specwar 30 suppressor with a Gemtech adjustable bcg.
The bullet was a Berry's 220 grain spire point.
5 shot groups.

The CFEBLK loads got me to 1022 to 1140 fps with 1 inch groups at 25 yards with no pressure signs and full function.
The H110 loads got me to 1028 to 1085 fps with 1 inch groups at 25 yards.
But while the H110 loads functioned, there were a few FTE in each load and the bolt never locked back on the final shot.

CFEBLK at 13.2 grains and 1068 fps was the best group at <1 inch at 25 yds.
I am going to work around that load.
I would not rule out the H110 load yet. It might take some work, but in the end, if you can get it to function, it will be quieter, cleaner and probably more accurate than the CFE.

If this is a new assembly, I would not even begin any serious sub sonic load development until it has at least 200 rounds down range, 500 even better. The actions loosen up that much and when tight can cause reliability issues.

If you have room, move the bullet out, increase the COL, then add .1 grain of powder. This will keep the velocity about the same while adding gas to help carrier movement. It won't take that much from where you are now, to locking back on empty mag.
300 Blackout, not just for sub-sonics.

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