Subsonic 300 blackout balistic help

[P1ZombieKiller]

I need some help from you guys that have bigger brains than I do (which means most everyone out there).

I am trying to use JBM ballistic calc ( http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi ), and I don't know how to input the data I know to get the data I want to know. They ask all the questions, but I am not sure where to input my info. I need someone that is super familiar with that calculations (or maybe even quick load which I do not have access to) to help me punch in the right info in the right place.

I have a bolt action rifle in blackout. My kids use this gun shooting super sonic rounds for deer. I have it zero'd at 100 yards with that load/bullet combo. I want this to be my "ZERO POINT". I use a 2.5-10 Leupold mark4 with M2 turrets (1/2" clicks so it's 30 moa per single revolution). It has ZERO STOP so no matter what I do playing around with subs, I can always go back to my kids hunting load zero point very easy.

I want to get the right info to place in the calc to get my subsonic loads charted so I can have a custom turret created (or even a piece of tape added above the marking on the current turret).

What I do know:
Remington 700 action
Ken Farrell 20 MOA rail
TPS low rings
Leupold Mark 4 2-8 scope

Supersonic load:
Hornady 130 grn SP running at 2220 fps
Zero'd at 100 yards

Subsonic load:
200 grn SMK running at 1050 fps
at 50 yards I come UP 6.0 MOA and I am dead on.
at 100 yards, I come up 12 MOA and I am dead on.

How can I make a chart from 30-200 yards (in 10 yard increments) for my subsonic loads?

Or even better, at what distance is impact for +8 MOA, +10 MOA, + 12 MOA, +14 MOA (etc) out to 30 MOA

 

[FeMan]

The problem is that you cannot use a standard BC in these ballistic programs for transonic bullet flight (below around 1,300 fps). In order to use the program and get reliable results at your velocities you would need to develop a custom drag curve. The best way to get what you want is to go out and shoot groups at the distances and make your own drop chart based on field results. Once you get below about 1,000 fps the drag on the bullet drops way off and gets fairly constant, not changing with velocity much. That should make it easier and more reliable to guesstimate the drop in between yardages if you want to only shoot a few distances for measured drop and fake the rest.

 

[gary0529]

I shoot the 300 Whisper exclusively in subsonic territory with 2 different custom hunting bullets-never got the Sierra 220 or 240 to open at subsonic velocities- and have not yet found an app or program that works anywhere near as good as just going out and shooting a few at the ranges you anticipate using it.
My personal limit is 150 yards.
I have dope on my loads out to 200 yards and that works for me.
It can get expensive especially when using the $1+/each bullets but I then KNOW what to expect when I pull the trigger.

Hope it helps.

By the way, what kind of results are you getting with the Sierra bullet on deer? What loading to maintain subsonic ?

Thanks,

Gary

 

[gary0529]

PS on previous post-

I am using a bolt action custom on a Rem XR action with a 16" 1-8 twist

 

[P1ZombieKiller]

I don't use the SMK on deer (any more). I have shot a few deer with them, but unless you catch a rib or plan your exit into the shoulder, it's a .308 hole in, and a .308 hole out (on the first 2 deer I have shot). After that I started planning my shots the complete opposite of what you would THINK the shot should be. Wait till they were quartered away and have the exit point in the front shoulder.

I just want to play with the 200 SMK's and hunt with the Lehigh's. I usually limit my subsonic hunting to less than 50 yards. This takes most of the guess work out. The Lehigh's have plenty of expansion at subsonic speeds.

I was hoping that once I shot he SMK's a hundred or so times, I could shoot the Lehighs a few times, and make an additional chart with that would give me MOD (Minute of Deer) for the Lehigh's.

 

[P1ZombieKiller]

My 16.5" barrel is a 1:7.5 and 8.5 grains of Lil Gun gets me right at 1050 fps.

 

[Tozguy]

I have a bolt action rifle in blackout.


Remington 700 action
Ken Farrell 20 MOA rail
TPS low rings
Leupold Mark 4 2-8 scope

Supersonic load:
Hornady 130 grn SP running at 2220 fps
Zero'd at 100 yards

Subsonic load:
200 grn SMK running at 1050 fps
at 50 yards I come UP 6.0 MOA and I am dead on.
at 100 yards, I come up 12 MOA and I am dead on.

I am very interested in knowing the level of accuracy (or should I say precision) you are getting from both your loads with a bolt action. The idea of building a target rifle in 300 BLK has been haunting me.

 

[P1ZombieKiller]

I am very interested in knowing the level of accuracy (or should I say precision) you are getting from both your loads with a bolt action. The idea of building a target rifle in 300 BLK has been haunting me.

I do not know what your definition of a target gun is, but I do not consider the blackout a target cartridge. I consider it a hunting or plinking cartridge.

My gun shoots .50" - 1.00" groups at 100 yards with supersonic loads (3 shot groups with the occasional .25" group).
It shoots 1.00" - 1.50" groups at 100 yards with the subsonic loads (3 shot groups with the occasional 2 shots touching).

What I am trying to accomplish is to keep the supersonic gun ready for my kids to hunt with, and yet have a turret thatcan double for me playing with the subsonic loads at any point of the year.

 

[P1ZombieKiller]

Its also a lot o fun to shoot. When the zombie apocalypse happens, this will be my go to gun.

 

[Tozguy]

Wes, thanks for the info.
My definition of a target rifle is one able to hit small mosquito sized zombies at 100 yds. 3 times out of 4.
Is there be anything you would do to get smaller groups with the subsonic load?
Regards

 

[Tozguy]

PS on previous post-

I am using a bolt action custom on a Rem XR action with a 16" 1-8 twist

Gary, might I ask you also what level of accuracy (size of groups) you are getting with that rifle?
I understand that you are loading for hunting but do you have an opinion on how it would group if it was loaded strictly for accuracy?

 

[P1ZombieKiller]

Wes, thanks for the info.
My definition of a target rifle is one able to hit small mosquito sized zombies at 100 yds. 3 times out of 4.
Is there be anything you would do to get smaller groups with the subsonic load?
Regards

I don't think this cartridge is capable of doing that and I would say impossible of hitting it once at subsonic speeds.

 

[Geno C]

I would have to disagree. I have and have seen other blackouts that are very accurate. My load of H110 under 220gr round nose is sub 1/2" very consistantly at 100 yards. I won't even post pictures or the groups I get with 155gr bergers because no one believes it possible with this round. Check out long rifles inc. and talk to Chad about a couple blackouts that are target worthy.

Mine is a savage target action with a 16" rock creek barrel. Shot through a Thunderbeast 30p1

 

[P1ZombieKiller]

I would have to disagree. I have and have seen other blackouts that are very accurate. My load of H110 under 220gr round nose is sub 1/2" very consistantly at 100 yards. I won't even post pictures or the groups I get with 155gr bergers because no one believes it possible with this round. Check out long rifles inc. and talk to Chad about a couple blackouts that are target worthy.

Mine is a savage target action with a 16" rock creek barrel. Shot through a Thunderbeast 30p1

if this is the case, TOZ better call this guy and find out that secret, as this case/bullet combo is not known for that.

Mean while.... can anyone help me with those calculations?

 

[Geno C]

I apologize for the side track.

I have not found a ballistic calculator that has worked insistently with subs. My. DOPE charts are just that; drop observed on previous experience.

 

[P1ZombieKiller]

I am going to the range tomorrow. I will take the blackout to play with in between working sessions. I will shoot some 3 shot groups, and post them here. One thing to consider is I am only using a 2-8 power scope, so that should factor into the larger sized groups.

 

[Tozguy]

Please excuse me for sidetracking your thread. Looking forward to seeing your groups, have great day at the range.

 

[P1ZombieKiller]

Mother nature and the weather man did not agree today. Mother Nature won. 39 degrees and Thunder sleet is not something I like to go shoot in. Maybe in a couple of weeks.

 

[P1ZombieKiller]

I was looking for some old info, and stumbled across my old thread about subsonic loads in my 300 BO. Just wanted to update this for future reference (I often do this for historical reasons in case I cant put my hands on my notes easily).

Shot the 300 BO the other day as I am dedicating this rifle to subsonic only. Took a 25 yard zero start, shot 10 rounds (5 at target 4 and 5 at target 5). Great targets.

Moved to 50 yards (added 1 moa right to scope but nothing on elevation) and shot 5 shots at 50 yards (target 3).
Moved to 100 yards, and aimed at target 3, however the 7" drop caused it to hit target 2. This was by design. You can see that I dropped one WAAAYYYY low, however you can also see the piece of brass with the missing case neck and that would explain the shot thrown out.

Over all I am very pleased with this grouping, and I am not beginning the journey of gathering my calculations for shooting out to 250 yards subsonic.

Remington 700 SA
300 black out
Mark 4 2.5 - 8 M2 turrets
Douglas 1:7
200 grain SMK @ 1050 fps
LC range brass (but will be switching over to Lapua when these rounds are all shot up).

 

[Kings X]

Wes,
I put in a 100 yard zero. 1050 speed. Max range 300. Min range 20. Increments 10 yards.
Jack with the BC until I got your 6 moa drop for 50 yards. BC used is .315. That gives you your 200 grain chart. Add the 12 moa to your Zero Stop setting. Then do your math for your 8,10,12,20,30 chart.
See you know at the Zero Stop you need 6 for 50 yards and 12 for 100 yards. My chart says 20 moa is 210 yards - so you add 12 moa to that = 32 moa from ZS is 210 yards