Suggest a blackout load for an sbr

[greyling22]

I have a 1:7 twist 8.5" sbr blackout and I'm going to load a hunting round. I've bought some of the Barnes tac-tx 110grn black tips, which are expensive enough I'd rather not use more than I have to in load development.
I have h110 and 1680 for powders. Probably going to use h110. My hangup is on the short barrel. I've never loaded for an 8" rifle barrel before. All data I'm finding is for 16" barrels. Barnes says use 18-20 grains, hogdon 18.4-19.4.
Should I step that down a bit for the short barrel? Like 16-17 grains? Or just stick around 18? I'm currently thinking try 4 at 17.5, 4 at 18, and 4 at 18.5 and keep whatever seems to work the best. Does that seem reasonable? (Reloads at nearlty a dollar a round. Woof. I miss my cast lead wheelweight bullets already)

 

[jmorris]

Either powder will be a good choice I use H110 most often because I have more of it in stock. Use the same loads as you would a longer barrel, they will just exit slower.

You could go below “starting loads” but I would expect it not to run, it might though if it’s also suppressed.

If I were in your shoes, I might start with a bullet of the same weight that costs less than $34/50. There are some 110gn JHP’s for sale here for $19/100.

http://castboolits.gunloads.com/sho...inter-308-110gr-JHP-bullets-(factory-seconds)

Would let you “test and tune” for half the price.

 

[beeenbag]

I don't change my loadings based on barrel length, the shorter barrel will reduce your velocities, no need to further reduce them by downloading.

 

[luzyfuerza]

True enough that safe loads aren't based on barrel length.

Addressing your other issue: the cost of the TAC-TX bullets. I could never bring myself to spend the coin on the 110 grain Barnes TAC-TX bullets. I knew that I would end up buying a bunch to do load development, and I didn't want to do that. Also, at the time, there were no TAC-TX bullets to be found. So, I did the next best thing: bought 20 factory loaded TAC-TX rounds to get a data point on how they might do in my 10.5" SBR.

I wasn't overwhelmed. The Barnes factory ammo yielded a five round group of 2 3/8" at 100 yards. This quelled my interest in these bullets for the moment. (BTW, the best factory loading that I shot through my gun was Remington's 120 grain OTFB, which turned in a five-shot group of 1 1/8".) (YMMV, small sample size, and all similar caveats apply).

I next sampled loads using a variety of other bullets and powders, and found the best results in my upper with AA1680 under a 168 grain Sierra BTMK (no surprise there) and a 125 grain Sierra ProHunter. I started building my new house before I could ever finish a full load work-up with the ProHunters though.

The match king certainly isn't suitable for your hunting purposes, but the ProHunter might be. I don't know how well it would perform at the velocities you could achieve in your 8.5" barrel and at the distance that you might shoot, but it is much cheaper than the TAC-TX, is widely available, and appeared to work well in my gun with AA1680.

When I pick up the 300 BO again I think that I'll work some more on the ProHunter with AA1680, but in the meantime, I would just use the Remington OTFB factory loading.

 

[mcb]

My brother has shoot 2.7-inch groups at 250 yards with hands loaded Barnes 110gr TAC-TX bullets. Him and his youngest son have both killed deer with them. I have had similar good accuracy in my 300 BO though I have not stretched then much beyond 100rds due to the low magnification I am running. That said I am still getting ~1MOA accuracy from them.

 

[Kaldor]

125gr Speer TNT Varmint - about 17 cents per
https://www.midwayusa.com/product/2149663126

Generally are right around 1 inch in my rifle with 19gr of W296/H110

 

[cougar1717]

Should I step that down a bit for the short barrel?

Just stick around the starting charge with H110.

Take the caliber and firearm out of the equation for a moment. Should a person reload specifically for barrel length? Generally, no. The powder that is the fastest in a shorter barrel will be the fastest in a longer barrel (as long as the barrel isn't too long that it actually slows the bullet down). There are always minority situations, like not wearing yourself out with 357mag in an 1-7/8" revolver, but this situation isn't one of them.

We can add in the expansion threshold argument. Will the terminal velocity at the expected distance be high enough for the bullet to expand? It should. Light for caliber bullets mean velocity and Barnes has 300BO specific bullets with huge tips. It's not like long range expansion is the goal here.

Then, add in the powder. Should a person download H110. Very simply - no. That powder needs to operate at near max charges as the starting loads indicate. Hodgdon's 110gr Vmax data shows a starting load that is only 5% below max. I get that the v max is different from the copper Barnes, but the principle is there to not download H110.
Even Barnes' data shows this: https://www.barnesbullets.com/wp-content/uploads/2016/03/300AACBlackoutV6ForWeb.pdf as it isn't significantly different from Hodgdon's.

The next consideration is cycling. Even the starting load should produce enough gas to cycle, so this typically isn't a concern. There can be variations in gas port size, gas block fully over the barrel port, etc. In most cases, this isn't an issue for a starting load of powder in an AR. But it would be, for instance, if you used Trail Boss since Hodgdon also has data for that.

Other considerations: H110 has a hangfire risk if downloaded below starting loads. When I was just getting into reloading, the main concern is to just be safe, right? So, I'm loading for 357 magnum with H110, 125gr bullets, and mag primers. (I didn't know any better.) As a new reloader, I'm looking at all the different data and a little confused by the differences. Where should I start? So I found the lowest charge and was under that to be safe, you know. When I go out to test my loads, I experienced a hangfire on the lowest charge weight reloads. It's a little scary to pull the trigger, and see the hammer drop. Then,nothing happens for a split second, and then, the gun fires. I realized what I had done. All the rest of the other loads functioned as they should. Most of the time, going below starting charges is not a big deal, but with H110, it is.

 

[greyling22]

I've used the Sierra prohunters in my 16" upper. They shot great, but I struggled to get the velocities needed for them to expand right. I've been plinking around with a 160 grn lead bullet, but I wanted something more lethal for swine. Thus the TAC-tx. I've hear the ax might be a decent bullet too. though it is designed to explode at high velocities, some people report that it expands like a regular soft point at the lower blackout velocities.

 

[jmorris]

I used 125 gn nosler BT’s out of my 8.5” barreled 300 blk, on the only pig I have shot with the caliber. It was at a full run and didn’t even make it across the lane I shot it in.

He was a little one though.

 

[AshMan40]

I have a 1:7 twist 8.5" sbr blackout and I'm going to load a hunting round. I've bought some of the Barnes tac-tx 110grn black tips, which are expensive enough I'd rather not use more than I have to in load development.

I have a near identical set up in my AR (8.5" Nitrided 1:8 twist barrel; pistol gas SBR; H2 buffer). My rifle LOVES the 110gr TAC-TX! I've placed 5rds into a 1" group @20yds... standing unsupported! That may not be great for some, but for me that was outstanding!

I initial loaded the TAC-TX over IMR4227 which is where I saw the above grouping. But since then I've switched to H110. My best 110gr TAC-TX load with H110 is over 19.0gr. Above this I started to see pressure signs. My notes say I loaded to COAL=2.250". At this length the rounds fit well in AR mags but very little of the bullet is in the case. It basically seats only the length of the neck.

As a substitute for the expensive TAC-TX bullet I also load Hornady 110gr V-max over H110, but to a shorter COAL (2.050"). Even with the shorter COAL my load data shows the same 19.0gr charge of H110. While the bullets are similar this round had never been as accurate as the TAC-TX in my rifle. But the V-max is much less expensive and easier to find.

As always, work up your loads from lower until you see pressure signs. I think you will find the TAC-TX is an almost ideal round for 300 BLK.

 

[greyling22]

I loaded 5 at 19 and 5 at 19.8. we will see how they shoot and go from there.