300BO

504ranger

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Dec 8, 2011
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Tampa, FL
Guys hoping to get some load data from the folks that load 300BO. I saw a few threads for subsonic loads but can't seem to find any for supers (apologies if it exists).
I'm looking to load primarily for hunting (pigs mainly) and to play with accuracy (for fun). I've been running 110gr Barnes Vor-TX ammo for hunting and it seems to do well but I was hoping to see what other folks are loading with.
Primary rifle is a 12.5" Proof barrel (pistol length gas system with a 1:9 twist) in a Hodge Defense upper/lower with a Surefire SPS300 suppressor.
Other rifle is a 16" Rem 700 AAC-SD rifle in a Manners T4 side-folder with a Surefire SPS300.
Thanks so much and I'm new and in learning mode so go easy on me :)
 

padom

SuperMod
Staff member
Mar 13, 2013
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I run both 125 SMK and 125 TMK out of my 10.5" Ultramatch with H110. Both are extremely accurate with the 125 TMK being slightly more accurate but expand better. Did some unscientific testing with denim and wet phone books and the 125 SMK slightly bowed like a banana. Didnt expand or anything. The 125 TMK expanded like a 9mm Federal HST beautifully. Im getting just over 2100fps with the below 125 TMK/ 18.6gr H110 load out of my 10.5" barrel and have no problems consistently hitting steel out to 500yds.


 

504ranger

Private
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Dec 8, 2011
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Tampa, FL
I run both 125 SMK and 125 TMK out of my 10.5" Ultramatch with H110. Both are extremely accurate with the 125 TMK being slightly more accurate but expand better. Did some unscientific testing with denim and wet phone books and the 125 SMK slightly bowed like a banana. Didnt expand or anything. The 125 TMK expanded like a 9mm Federal HST beautifully. Im getting just over 2100fps with the below 125 TMK/ 18.6gr H110 load out of my 10.5" barrel and have no problems consistently hitting steel out to 500yds.


Stupid question but do I need bullets specific to 300BO? I've seen some bullets labeled as "Short Case" which I know is for 300BO but others I have not so it had me a bit confused.
 

Onyx Z

Private
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Sep 27, 2018
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300BLK specific bullets are typically flat base bullets. Generally speaking, flat base bullets are inherently more accurate, but for 300BLK, they don't give up case the volume for the boat tail. These "short case" bullets you speak of most likely have a flat base. Any 308 bullet will work though. Obviously lighter for supers and heavier for subs.

YMMV, but the Barnes solid copper bullets typically produces more copper fouling than a jacketed bullet, so you may need to remove the copper from the barrel more often. Typical jacketed bullets have gilding metal jackets (95% copper/5% zinc) to prevent/reduce copper fouling. I have some CFEBLK, but haven't tested it yet. Theoretically, it should reduce the copper fouling.

I know you are primarily looking for supersonic loads, but, your 1:9 twist barrel may not stabilize any of the heavier/longer bullets.
 

504ranger

Private
Belligerents
Dec 8, 2011
24
38
18
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Tampa, FL
300BLK specific bullets are typically flat base bullets. Generally speaking, flat base bullets are inherently more accurate, but for 300BLK, they don't give up case the volume for the boat tail. These "short case" bullets you speak of most likely have a flat base. Any 308 bullet will work though. Obviously lighter for supers and heavier for subs.

YMMV, but the Barnes solid copper bullets typically produces more copper fouling than a jacketed bullet, so you may need to remove the copper from the barrel more often. Typical jacketed bullets have gilding metal jackets (95% copper/5% zinc) to prevent/reduce copper fouling. I have some CFEBLK, but haven't tested it yet. Theoretically, it should reduce the copper fouling.

I know you are primarily looking for supersonic loads, but, your 1:9 twist barrel may not stabilize any of the heavier/longer bullets.
Perfect and thanks so much for the help ya'll have provided. Definitely feel better about buying bullets now after learning.
 

Snuby642

Major Hide Member
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Both my 300blk barrels are 1/7 twist, 16 and 10.5 inch.
They will both stabilize 200-220gr bullets "subs".

I would check the 1/9 short barrel without the suppressor in load development
to ensure they stabilize befor using the can.

My pet load is 12.1 cfeblk 220fbrn 2.1 coal slight crimp 1050fps in 16 inch barrel.
This is a 100 yd load and is consistant.

I didn't buy the 300 blk to shoot supers but since I have my sub load sorted out
I may try some loads like @padom suggests.

The cfeblk is working well for us.
 
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PBWalsh

Isaiah 40:25-31
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Feb 10, 2017
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For those of you running both supers and subs in the same barrel, what is a good utilitarian twist rate? Say for running 125 TMKs @ 2100 and then some 225 ELDMs @ 1000? Both loads suppressed of course.

Tinkering around with the idea of using subs for HD because of two reasons. 1) Same rough KE as a 45acp and 2) much less blast than a 5.56 out of similar barrel lengths. Plan on using a 10.5” barrel.
 
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Snuby642

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@PBWalsh
I have a 10.5 inch sbr in 300blk with a 1/7 twist
It runs super ?gr and sub 220s suppressed no problem.
2 16 inch bolt guns both 1/7 gtg.

I think most like a 1/7 for the big subs.
 

Datsrboi

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Not a load many run but it was cheap and on sale so I went for it.

Horandy interlock #3031 150gr sp
CFE BLK powder 21gr
CCI 450 primers

9 inch SBR 300blkout SOLGW barrel

I hit right at 1700fps on my chrono which is borderline expansion requirement of the bullet as I am told. I plan on using this for roughly 50yard useage only.
 
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Snuby642

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I figure you could double that yd.
Most mfg say "optimum" expansion @
 

pugnado

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I just started reloading for 300 BLK and I have no idea what I'm doing or where to start.
(Not first-time reloader, have made hundreds of 6.5 Creedmoor this year and still have fingers, just new to 300 BLK.)

So with that in mind I just went for whatever the Hornady manual recommends in their couple of paragraphs describing the cartridge before the load data sections.

For supersonic hunting bullets:

Hodgdon H110 14gn-18gn
Hornady 125gn SST bullet (much cheaper than their GMX bullet)

It's got a crimp cannelure, maybe I crimp, maybe not, depending on where the bullet ends up seating.
I'll use the same CCI 450 primers I use in the Creedmoor loads, because I'm lazy and want to stick to a common primer for all my loads.

I'll figure out paper target loads and subsonics later once I get a feel for it.
 
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Snuby642

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My pet load listed at Hodgdon .
12.1 cfeblk 220 rnfb.
Runs 1060fps in 16 inch barrel.
 
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Herstal 12

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Feb 18, 2019
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I use 16.8 gr lil’gun with anything from 147 -150 gr even pulled tracers as a plinker load. With the 125gr Sierra I use 17.6 to 18.3 gr of lil’gun at 2.03 aol. My 16inch barrel does not cycle with H110 at all either but runs 100% on lil’gun, go figure that one.
Hope this helps
 

Aimsmall55

Gunny Sergeant
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I’m running 8.2 grains of lil gun with 208 amax and 210 velds out of a 10.5” Seekins 1:8 upper. And a SAS ARBITER Suppressor. Very accurate and quiet.
I’m also running 19.8 grains of h110 with a 110 vmax and it’s super accurate. I’ve got a load for a 125 sst that I use for killing hogs but I can’t remember it off the top of my head. I think it’s like 17 grains of h110 or lil gun.
 

260284

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I run both 125 SMK and 125 TMK out of my 10.5" Ultramatch with H110. Both are extremely accurate with the 125 TMK being slightly more accurate but expand better. Did some unscientific testing with denim and wet phone books and the 125 SMK slightly bowed like a banana. Didnt expand or anything. The 125 TMK expanded like a 9mm Federal HST beautifully. Im getting just over 2100fps with the below 125 TMK/ 18.6gr H110 load out of my 10.5" barrel and have no problems consistently hitting steel out to 500yds.


I am wanting to build a 300 BO pistol before the next major election. Can you share the specs on your upper? How does it handle subs? I plan on running suppressed.

Thanks,

Keith
 

padom

SuperMod
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Mar 13, 2013
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I am wanting to build a 300 BO pistol before the next major election. Can you share the specs on your upper? How does it handle subs? I plan on running suppressed.

Thanks,

Keith
BCM MOD4 Thermofit upper receiver
FailZero NiB BCG
Rainier Ultramatch 10.5" barrel
BCM Large Latch Charging Handle
SA AGB

I dont run subs. Supers only.
 

Seandradamus

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I’m running 8.2 grains of lil gun with 208 amax and 210 velds out of a 10.5” Seekins 1:8 upper. And a SAS ARBITER Suppressor. Very accurate and quiet.
I’m also running 19.8 grains of h110 with a 110 vmax and it’s super accurate. I’ve got a load for a 125 sst that I use for killing hogs but I can’t remember it off the top of my head. I think it’s like 17 grains of h110 or lil gun.
All of this ☝ Is gold I use almost identical loads 8.2 LG with 220s or 225s and 20g of H110 or W296 behind Barnes 110 blacktips