Questions on initial load development for bolt action subsonic .300 BLK

[Wilc0]

I come to you guys in need of some clarification and confirmation;

I've been entertaining myself with a little project gun lately. I've got a Rem 700 SPS in .300 BLK that I want to work up a consistent performing load to throw subsonics out as far as I can (repeatably). Most of the information that I come across online seems to be restrictive due to most pet loads being developed with the necessity to A) Fit in an AR mag, B) Cycle an AR gas system, C) Be as quiet as possible, or D) Minimize cost per round. Since I either don't need to worry about or care about any of those factors, I need to find out where to start in developing a subsonic load with the lowest variance and spread that I can.

For now, the projectile I want to push is the 230gr Berger Hybrid.

From what I've read, most subsonic loads are running either 1680 or Lil'Gun with CCI400 Primers. But a few (of the many) questions I have are; Is there something that would be beneficial for me to try that most .300 BLK shooters can't due to their gas guns? Should I be trying to maximize powder volume in the case? Would a faster or slower burning powder yield more consistent MV? I've seen threads on various forums of people swearing by magnum primers for improved consistency, is there any merit to this?

Thanks to anyone for reading, especially if you have an answer to any of my questions.

 

[spife7980]

I have a 16” ruger ranch. Loading cfeblk, I figure what could be better than a powder with the cartridge in the freaking name?

I think trying to maximize volume is important. I tried 4198 with 220 Sierra round nose. It would give serious pressure signs around 950 fps with little changes and wasn’t at all consistent. Could have been my neck tension and I think a bunch of tension can help too. My misfortune with 4198 led me to wander the powder aisle at cabelas and I saw cfeblk. I didn’t even knew it existed but grabbed it right there.

In federal American eagle brass I have found 12.1 gr of cfeblk is pretty much a max load with anymore and I notice slight pressure signs on the 220 and it coincidentally puts it right at 1050 fps which is exactly what I would want. I have the bullets seated pretty deep in the case but it compressed. Shakes a fair amount. I did a primer test and the 450, br, rem 7.5 didn’t do any better than my standard 400.

I wasn’t a fan of the sub Sonics for hunting so I made a supersonic round with a 150 game king. 19.4 of cfeblk is right at a compressed load giving my 1999 fps but isn’t giving me any pressure signs. I tested a fair amount above that but it was so compressed when seating my bullet was out .02 out further before I realized that it wasn’t just my press acting up and I had too much powder. Shot them testing higher gradually since they were loaded and I was 3/4 of a grainish away from pressure.

Both of these put three shoots touching, though strung in a line, at 100 in consecutive weeks so that was good enough for my hunting round testing.

Also this, for target lighter bullets could be the answer. https://forums.gunhive.com/topic/395/new-ts-customs-300blk/2

 

[TripleBull]

Spife, your microphone keyboard has an echo, lol!

 

[spife7980]

Spife, your microphone keyboard has an echo, lol!

All better, I shot that second voice in my head.

 

[isofahunter]

My 300blk sub loads use 170 gr Sierra Pro Hunters with BlueDot and a 90gr Hornady XTP with Trail Boss. If you use a can make sure to test without can first to make sure bullet is stable coming out of barrel. Subsonic 300blk with a can are a hoot!

 

[quietmike]

VV N120 and N110 are great powders for heavy subs in a bolt gun.

http://up.sur-la-toile.com/iFsk

 

[Wilc0]

I have a 16” ruger ranch. Loading cfeblk, I figure what could be better than a powder with the cartridge in the freaking name?

I think trying to maximize volume is important. I tried 4198 with 220 Sierra round nose. It would give serious pressure signs around 950 fps with little changes and wasn’t at all consistent. Could have been my neck tension and I think a bunch of tension can help too. My misfortune with 4198 led me to wander the powder aisle at cabelas and I saw cfeblk. I didn’t even knew it existed but grabbed it right there.

In federal American eagle brass I have found 12.1 gr of cfeblk is pretty much a max load with anymore and I notice slight pressure signs on the 220 and it coincidentally puts it right at 1050 fps which is exactly what I would want. I have the bullets seated pretty deep in the case but it compressed. Shakes a fair amount. I did a primer test and the 450, br, rem 7.5 didn’t do any better than my standard 400.

I wasn’t a fan of the sub Sonics for hunting so I made a supersonic round with a 150 game king. 19.4 of cfeblk is right at a compressed load giving my 1999 fps but isn’t giving me any pressure signs. I tested a fair amount above that but it was so compressed when seating my bullet was out .02 out further before I realized that it wasn’t just my press acting up and I had too much powder. Shot them testing higher gradually since they were loaded and I was 3/4 of a grainish away from pressure.

Both of these put three shoots touching, though strung in a line, at 100 in consecutive weeks so that was good enough for my hunting round testing.

Also this, for target lighter bullets could be the answer. https://forums.gunhive.com/topic/395/new-ts-customs-300blk/2

Interesting read about the lighter projectiles, I guess I just assumed that the heaviest and highest BC projectile would yield the best results but I had questions about performance at subsonic speeds; namely would the longer bullets have stabilization problems? I got a copy of Applied Ballistics but I'm only on chapter 2, I'm hoping there is some more insight to this deeper into the book. I'll be sure to look at some of the CFE BLK pet loads around on the net and maybe try iterations out, thanks!

My 300blk sub loads use 170 gr Sierra Pro Hunters with BlueDot and a 90gr Hornady XTP with Trail Boss. If you use a can make sure to test without can first to make sure bullet is stable coming out of barrel. Subsonic 300blk with a can are a hoot!

Have you had more success with the lighter or heavier projectiles? I'm wondering if I'm starting in the wrong spot by wanting to throw 230gr Bergers =/. Good call on stabilization testing without the can, I've got a SiCo Omega 9k that I've been using for this rifle that is absolutely a bag of giggles. I'm hoping to have it out of NFA-jail by september but at least I get conjugal visits with it at the range.

VV N120 and N110 are great powders for heavy subs in a bolt gun.

http://up.sur-la-toile.com/iFsk

Thanks for the link! I hadn't considered N110 but after reading that and doing some searches around the web it seems like it might be a great contender for achieving a consistent MV.

 

[isofahunter]

The default is big heavy bullets but I tend to wander off the reservation and look over the hill. I shoot a lot of coons off deer feeders and pig pipes and go tired of the ice pick like wounds where the coon would run off and die. They do not go far when hit with the 90gr xtp, usually pop and flop. The 170 is for bigger stuff and my reason for this bullet selection is flat melpate transfers energy and penetration better in my experience. both shoot to same point of aim out to 100 so depending on what shows up I can pick my load and shoot.

 

[quietmike]

^^Agreed.
Lighter bullets require less powder, so less gasses for your can to deal with. The 90xtp is stupid quiet.

 

[Wilc0]

The default is big heavy bullets but I tend to wander off the reservation and look over the hill. I shoot a lot of coons off deer feeders and pig pipes and go tired of the ice pick like wounds where the coon would run off and die. They do not go far when hit with the 90gr xtp, usually pop and flop. The 170 is for bigger stuff and my reason for this bullet selection is flat melpate transfers energy and penetration better in my experience. both shoot to same point of aim out to 100 so depending on what shows up I can pick my load and shoot.

Copy that, so I suppose I'm not starting in the wrong spot because I'm only hunting steel gongs

^^Agreed.
Lighter bullets require less powder, so less gasses for your can to deal with. The 90xtp is stupid quiet.

Figured as much, I was just curious if the lighter rounds would be easier to achieve the most consistent MV's for some reason. I'm pretty much ignoring audible report as long as the round is subsonic, and I'm willing to pay into a high cost-per-round to develop a "match quality" sub load. I don't always have the real estate to shoot far with my other rifles so that's what this rifle is for; lobbing subsonics at ranges <500yd

 

[isofahunter]

Keep in mind long sleek bullets need speed to be stable. The bullet you are considering might not like being subsonic. I would not buy 500 bullets until you test them. You might consider trying a heavy round nose or flat nose bullet too, they might be more stable for distances you are shooting. Good luck and keep us posted.

 

[Wilc0]

That's was one of my concerns too, but I'm not very knowledgeable on the subject. I'm hoping the 1:7 stabilizes these long bullets, but I bought 200 for testing so I'm not too terribly deep into my pockets with them. If they don't work out I'll try exactly what you said and start lobbing shorter OAL projectiles, trading drag for stabilization. I'll be sure to do a writeup

 

[softcock]

The default is big heavy bullets but I tend to wander off the reservation and look over the hill. I shoot a lot of coons off deer feeders and pig pipes and go tired of the ice pick like wounds where the coon would run off and die. They do not go far when hit with the 90gr xtp, usually pop and flop. The 170 is for bigger stuff and my reason for this bullet selection is flat melpate transfers energy and penetration better in my experience. both shoot to same point of aim out to 100 so depending on what shows up I can pick my load and shoot.

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exactly ... I love the 90's xtp's and speer 110 HP's . I use Viht. N-320 and much better transfer of energy . am using 4.4 grain N320 for the 110's . stupid quiet also with the tiny amount of gas byproduct for the Can to handle .
.