Thread: 300blk Loading Tips

I know there is a fair bit of info on the forum already (I've been searching through all the threads) but most of the reloading info is spread through multiple threads.

I've bought a Howa Mini action 300blk and wanting to set up a few different loads, unlike most cartridges there is an insane variety in projectiles, powders, seating depths, and rifles the 300blk is used in so there seems like no obvious load to try as a first step.

I'm planning on using 2205 and will obviously work up my own load but is there a seating depth/COAL that is a good idea to try?
Usually I'd try mag length or .020 off the lands but depending in the projectile these two measurements will vary widely.

I've got some 190gr Subx bullets I want to try and will get some 125gr TMKs. I also want a cheap subsonic load I can use for long range plinking, probably with 150gr bullets.

Any info you guys can share will be greatly appreciated.

cheap 150grn= Roberts cast jobbies...and they up there with the best for all round subsonic use too.....

Originally Posted by Micky Duck

cheap 150grn= Roberts cast jobbies...and they up there with the best for all round subsonic use too.....

Are they the ones that used to be advertised on Trademe?
I can't see them there anymore.

You probably won't get the stumpy little 110's and 125's 0.020 off the rifling with any amount of bullet left in the neck. Just go with whatever length the manual suggests for your particular bullets. Seat out further if you want - you're just sacrificing neck tension - the bullets are all jump tolerant so no point messing around much with seating depth really.

Start high and work down with subs. No risk of overpressure with such light charges (even at "max") but there is a risk of a stuck bullet if starting too low.

If there's a cannelure, there's your seating depth sorted. Seat to it and crimp. Treat 300blk like a 357 or 44 Mag in the sense that a magnum primer and a crimp is necessary to get good ignition.

You'll probably end up with some bullet munting levels of compressed loads with 2205. Lil Gun or H110 are denser and tend to avoid that.

Other than that... It is just a bottleneck centrefire rifle cartridge so follow the same SOP as you would for the others.

Originally Posted by Pommy

You probably won't get the stumpy little 110's and 125's 0.020 off the rifling with any amount of bullet left in the neck. Just go with whatever length the manual suggests for your particular bullets. Seat out further if you want - you're just sacrificing neck tension - the bullets are all jump tolerant so no point messing around much with seating depth really.

Start high and work down with subs. No risk of overpressure with such light charges (even at "max") but there is a risk of a stuck bullet if starting too low.

If there's a cannelure, there's your seating depth sorted. Seat to it and crimp. Treat 300blk like a 357 or 44 Mag in the sense that a magnum primer and a crimp is necessary to get good ignition.

You'll probably end up with some bullet munting levels of compressed loads with 2205. Lil Gun or H110 are denser and tend to avoid that.

Other than that... It is just a bottleneck centrefire rifle cartridge so follow the same SOP as you would for the others.

Are you saying the H110 will be better for supers?
My initial plan is to shoot 90% subs for just general target shooting and work up a super load when/if I want to do any hunting.

Originally Posted by Beetroot

Are you saying the H110 will be better for supers?

I am saying that the seating forces that you get as a result of compressed loads can visibly damage projectiles.

When you come to loading supers, H110 and AR2205 both give good speeds but AR2205 is bulkier which leads to heavy compression up around max - somewhere you'll need to be IMO, given blackout's pretty pedestrian speeds.

Modifying your seating stem to match the bullet profile helps... a bit. My experience is with the 110 VMax, not the 125 TMK.

AR2205 fine for subs albeit a bit louder and dirtier at such low pressures vs faster powders like AP70N.

Originally Posted by Beetroot

Are they the ones that used to be advertised on Trademe?
I can't see them there anymore.

I am casting some at present trying to conserve my lead supply until lockdown lifts, If you want some let me know,
Email robs.reload@gmail.com

Originally Posted by shooternz

I am casting some at present trying to conserve my lead supply until lockdown lifts, If you want some let me know,
Email robs.reload@gmail.com

@Beetroot - the listing is back on Trademe but Rob has kindly provided his contact email above.

Originally Posted by shooternz

I am casting some at present trying to conserve my lead supply until lockdown lifts, If you want some let me know,
Email robs.reload@gmail.com

Cheers, ill flick you an email.

Originally Posted by Beetroot

Are they the ones that used to be advertised on Trademe?
I can't see them there anymore.

yes...from Tokoroa.

yes you can shoot such a huge variety of projectiles, I used to shoot a lot of pull out 7.62 fmj's out of mine for plinking and service rifle but my loads were about 2000 fps and have't tried them as subs but should be good plinkers. Cast projectiles also work well so if you don't want to cast there are plenty of pre-made ones around.

Robert’s 151gr .308 cal shot from a .308 subsonic round @1100fps.

Large nanny standing about 25m above me, facing away and browsing on steep ground facing uphill. In behind the ribcage low down, through the liver and across the vitals making a nice hole through the aorta and hilar, found in join between #1 offside rib and spine. DRT. Looking at the way it expanded, not too hard to imagine this cutting a nice hole as it spins. The hole through the arota was a thumb’s width. Massive internal bleeding - when I opened up the thoracic cavity a torrent of the stuff gushed out over my boots.



I can’t find my travel plug so can’t get my scales switched on to weigh it. It has shed a bit of weight but not a lot.

If you are using these bullets on goats and you want to drop them within a reasonable short distance, then it’s best not to shoot them in the traditional manner, standing broadside and through the front lungs. There’s not enough resistance on a goat to get these bullets to do the necessary work. So when broadside, the best target is the high shoulder with spine, lower neck or head. However as mentioned above if they are shot along the length of the torso then these bullets do a surprising amount of damage and goat will not go far.

Regarding accuracy, me and the wife were out a couple of nights ago shooting rabbits with the Browning BLR and these 151gr. I’ve put a Zeiss 3-9x on that rifle so we can judge holdover more accurately… we had no difficulty smoking rabbits out to 75m, the farthest bunny we saw. It is tremendous fun shooting rabbits with these bullets.

Originally Posted by Flyblown

Robert’s 151gr .308 cal shot from a .308 subsonic round @1100fps.

Large nanny standing about 25m above me, facing away and browsing on steep ground facing uphill. In behind the ribcage low down, through the liver and across the vitals making a nice hole through the aorta and hilar, found in join between #1 offside rib and spine. DRT. Looking at the way it expanded, not too hard to imagine this cutting a nice hole as it spins. The hole through the arota was a thumb’s width. Massive internal bleeding - when I opened up the thoracic cavity a torrent of the stuff gushed out over my boots.



I can’t find my travel plug so can’t get my scales switched on to weigh it. It has shed a bit of weight but not a lot.

If you are using these bullets on goats and you want to drop them within a reasonable short distance, then it’s best not to shoot them in the traditional manner, standing broadside and through the front lungs. There’s not enough resistance on a goat to get these bullets to do the necessary work. So when broadside, the best target is the high shoulder with spine, lower neck or head. However as mentioned above if they are shot along the length of the torso then these bullets do a surprising amount of damage and goat will not go far.

Regarding accuracy, me and the wife were out a couple of nights ago shooting rabbits with the Browning BLR and these 151gr. I’ve put a Zeiss 3-9x on that rifle so we can judge holdover more accurately… we had no difficulty smoking rabbits out to 75m, the farthest bunny we saw. It is tremendous fun shooting rabbits with these bullets.

Great photos Flyblown, All the recovered bullets I have seen all expand like that; the ones given back to me have expanded to .400" at least, Friwi has shot doubles with them
a few times while culling goats, It is only the lack of shock that lets them down, They are better killers at speed push them to 1600fps makes a big improvement.

Anyone had a play with the 230gr cast boolits from the Lee mould?

H110 I found really only likes fast supersonic loads with light bullets in the 110-120g range. I found it very inconsistent with heavier bullets and it's a powder that like in 357 Magnum, it likes to be loaded near max to work well.

Lil Gun works well in the mid range it seems. I use it a lot for 150g bullets.

CFE BLK goes well with heavier bullets and is probably ideal for subsonics.

I'm doing a lot of 300 Blackout stuff on my Youtube channel so feel free to check it out. Same user name. Right now in the middle of doing a series on 150g Hornady FMJs. Coming up I have a variety of bullets I'll be working with and doing video series on for 300 Blackout. Right now no plans for subsonics but open to doing videos on it if there is a demand for it.