300 BO 100 yards

[P1ZombieKiller]

@dellet


I am still getting Vertical on my 300 BO.
Load is 10.4 grains of A-1680 using 208 ELD-M at 2.200" OAL. (1st Target)
Load is 10.4 grains of A-1680 using Lehigh 200 grain Maximum Expansion at 2.117" OAL. (2nd target)


This is very typical of each 3 shots.
1st shot I can see as it is cold barrel.
Any suggestion on what to do?

 

[dmoran]

Looks like it could be a mechanical issue to me.
My suggestions:

• Check Rings & mounts
• Check Action screws torque
• Check scope for POI shift
• Look everything over very closely, and feel everything for movement

 

[dmoran]

On a second look at your targets above, looks to me like the bullet holes have excessive yaw.
Are you shooting straight in line with the targets, or at some angle?
Does the barrel have a fast enough twist rate for the bullets & velocity used?

 

[gunsandgunsmithing]

On a second look at your targets above, looks to me like the bullet holes have yaw.
Are you shooting straight in line with the targets, or at some angle?
Does the barrel have a fast enough twist rate for the bullets & velocity used?

The holes do look funny. Donovan may well be onto something.

FWIW, I assume you are trying to achieve two goals at once...subsonic and in tune. You might find what it like supersonic, then back way down.

 

[PhilKeil]

The holes dont look right to me either. I just checked my target I keep with the reloading data and with a 220 sierra mine are round. I have a 300 black with a 1-7 twist barrel on a AR 15.

 

[P1ZombieKiller]

i have also noticed this recently.... This rifle is about 10 years old, and I have not kept up with round count on this rifle. When I first got it, I was told to shoot lil gun in it... so that's what I did... for super sonic, it shot GREAT.... for subs.. it would shot great, then bad, then great, then bad.... I was loading the subs very long. But it never showed signs of the bullet not going in straight. I have noticed that on several targets. The barrel is 7.5 twist..... How can a bullet suddenly not be stabilized?

I had no concept of case capacity. When shooting 200 yards, and getting 12"-16" of vertical, I started researching.... that's when I found out a different way to look at it.

I took a fired case.... left the dead primer in it, dropped the same powder charge (10.4 of A-1680) then dropped a bullet in the case. Then measured OAL. This allowed a better way of telling when the bullet was resting on the powder.

Since then, this has been my recipe.

I have noticed that when I pick it up, I hear/feel a click in the front of the stock.
I am wondering if the barrel is not fully floating. Could this cause the vertical?

I just took it out of the current stock, and placed it into a new Magpul hunter 700 that I had set back for another project. I will go shoot it in the morning to see if this does any better.

All I want this gun to be is a subsonic hunting gun. so accuracy is relative... I would be fine with a 2" group at 100 yards subsonic.... but not 12" vertical string at 200? I think that is crazy. Are my expectations too high for this gun (for what it is)?

 

[P1ZombieKiller]

Looks like it could be a mechanical issue to me.
My suggestions:

• Check Rings & mounts
• Check Action screws torque
• Check scope for POI shift
• Look everything over very closely, and feel everything for movement

This has been checked, and rechecked.... I just placed a newer scope on this rifle hoping todo a little more, and that was looked at very closely.

 

[JimSC]

edit nevermind did not see you last post.

edit 2 - cures for vertical https://www.6mmbr.com/verticaltips.html

remembered a few years back I replaced all my firing pin springs after reading this article. One of my rifles had a vertical stringing problem that was nowhere as bad as your is but replacing the spring cured it. I then replaced two other rifles springs even though they shot fine

you can also tune vertical out with seating if you don't need magazine length

 

[dellet]

You have a couple things going on, velocity numbers would be helpful.

First round or two through a suppressor can be fast using a slow powder, you get more boost when there is powder and oxygen in the can.

The ELD load looks like it could just use some tweaking, But you need to treat sub's at 100 like a 308 and the same bullet at 600 yards plus. Take a look at a drop chart with a 5 yard zero see what 50 fps second does to point of impact, it's surprising.

The Lehigh load is a bit more complicated. Copper/brass solids and subsonic shooting is asking for trouble past 40-50 yards. The problem is the bullets are just not designed right to shoot at low pressure. Velocity is not the issue, probably not even twist.

You just can't get a proper gas seal with a copper bullet at 25,000 psi. You get gas cutting and zero obturation of the bullet. Chances are if you can recover one you will find a lot of carbon past the base and maybe even a depth difference in the grooves cut by the lands.

I would save the 1680 for heavy supers or something like a 22 Hornet.

Since you don't need gas to cycle, I would move up to a magnum pistol powder like H110/296 or even something faster like #9 or N105. You will accomplish a couple of things. Probably a 3-5 DB noise reduction and your bullets will have the pressure they were designed to be pushed down the barrel at.

1680 is good for reliable function in a carbine gassed AR for subs. Other than that it's loud and dirty. It's only other redeeming quality is mosquito control from the smoke and gas.

No reason that 2.5" groups at 200 yards aren't possible.

 

[P1ZombieKiller]

@dellet
Velocity with this combo in my 700 is 987fps.
Lapua Brass
10.4 grains A-1680
Hornady ELD-M 208 grain
Wolf SRM primer
2.200 OAL

10.0 = 900 fps
10.2 = 927 fps
10.4 = 987 fps
10.6 = 1025 fps
10,8 = 10.75 fps

Here are my load development targets from March. I do not think the scope is bad, and the bullet holes look much more "straight" than they have been looking. All targets were at 50 yards, and had point of aim at the center 1" square.

 

[dellet]

You really need the velocity for each shot, it is really critical with subs for diagnosing. Your targets make perfect sense with an ES of around 50. If they don’t have that, then maybe start looking at the rifle.

An ES of 50fps at 50 yards is around 1/4 of vertical, at 100 yards it’s worth about 1 1/2” of vertical.

Your targets at 50 yards with a 175 fps velocity spread and 3” of vertical would be a good way to confirm BC, without adjusting for conditions or low velocity, I would have had almost 2” of vertical spread where I shoot. You had about 3 1/2”.

ES outside of the low teens will kill you past 50 yards, and that’s kind of what I’m seeing in those targets. If you look at your 50 yard targets of 10.4 & 10.6 you have ragged hole groups and a vertical shift of less than 1/2”. About exactly what you would expect from 35 fps.

I would be working for a load around 1000 fps with as close to a single digit ES as possible. The ELD is pretty jump tolerant, some where between 10.4-6 and +/- .025” will probably find it.

 

[P1ZombieKiller]

@dellet On this day, and only 3 shots per group:
With 10.2 I am getting SD of 7 ES of 14
With 10.4 I am getting SD of 10 ES of 20
With 10.6 I am getting SD of 17 ES of 33

 

[dellet]

Were those numbers from the 50 or 100 yard target? It would be good to have a comparison of ES and vertical spreads.

If you can cut your ES in half it would be helpful. About half of your vertical with those numbers on 100 yard target is that 20 fps.

It’s hard to say exactly, but my best numbers and groups with 1680 seem to come with a bit more density to the load. I start with the bullet .010” into the powder and generally go deeper from there. I would probably seat that 10.4 load a bit deeper just to see what happened. It will raise both density and velocity a bit

Eventually you will need a larger sample group.

 

[P1ZombieKiller]

I changed stocks last night. I will also seat the bullets down .010" and .020" and see if it is any better. I will not have time to chrono today as I am going to run by the range before work.

 

[Oso]

Dellet...nice feedback!

Assuming velocity is fairly consistent, when I have seen vertical spreads like that then the checklist is:
1) Scope - is it tightened down in the rings and rings to the gun
2) Stock - is stock not free floated or rather is stock not rigid enough that it stops being free floating when in contact with the bag or bipod
3) Receiver - are the action screws not properly tightened, which is allowing action to slightly rock up and down from shot to shot. A good example of this is Ruger 10/22 (only 1 action screw so depending upon how you hold or support the rifle it is possible to create a vertical string and shift in POI from.
4) Suppressor - Is barrel profile to thin (older hunting rifles or light contour pencil AR barrel profile) can shift POI as barrel heats up quickly and lacks rigidity to offset.
5) AR (Specific Issue) - Who made the barrel? For instance, Radical Firearms made a series of barrels in which they attached the barrel extension to the barrel and then placed entire assembly into the salt bath, with the heat causing the metal to expand resulting in the barrel extensions becoming loose. The only solution was to replace the barrel.
6) AR (Specific Issue) - is barrel nut properly tightened down

I did some load testing with the Lehigh Max Expansion and Hornady Match 195gr. I tested loads using several different powders and several different rifles (all 1:8 twist) with different barrel lengths (AR15 8.5", AR15 16" , Bolt 18"). My take aways were:
1. Barrel Length - Longer barrel provided the best groups at all powder charge ... this is a given
2. Velocity - performance improved as velocity increased. I dialed in around 1080fps with solid results
3. Bullet - Lehigh did not perform as well... it was consistently 100-150 fps slower with same charge weight. Also, it did not group nearly as well.

 

[dellet]

The other dirty little secret is that no one really shoots Sub-sonic, It's Trans-sonic. You're shooting right into the turbulence that everyone else tries to avoid. Load development is tougher than most people think.

These were all shot off an Atlas bipod and squezze bag.

Here's a 200 yard group with a 208 ELD from a 1/10 18" twist AR, shot into a 10-15 mile an hour head wind at 1040 fps. 3" dot for reference. Stability was an issue with that slow of twist I think is around 1.3 on the stability factor.

240 Matchking, 1/5 twist 8" AR 200 yard load workup.

Load work up at 50 yards. I know this is the 8", not sure of the bullet, probably a 190 Nosler.

Same load sighting in at 200, 50 yards does not tell you much.

Wife's group at 200, Berger 230 Hybrid, out of a Handi-Rifle with a 3x spitfire off a front bag, 2" dot.

Vertical strings are a problem with subs. It's a challenge.

 

[Hoser]

I spent a lot of time playing with Berger 230s at 300 yards. Once I had a load down around 1030 fps I played with seating depth. Once I narrowed that down I had a solid accurate load with a really low ES.

I found that Vhit N-110 was the most accurate and still pretty quiet.

 

[Oso]

While testing subsonic loads I decided to go with CFEBLK and N110. I was targeting 1080fps using a 195gr bullet. I shot groups from an AR15 with 8.5" barrel and 16" barrel and also a CZ527 with 18" barrel. All guns had a 1:8 twist rate. Shooting was at 50 yards.

CFEBLK Powder with Hornady 195gr BTHP shot out of 18" barrel (yes - it refuses to right-side up the photo)

Vithavuori N110 with 195gr Hornady BTHP shot out of 16" AR15 and 18"CZ527.
Note: longer barrel groups better even though the round is slowing down. In fact the velocity out of 8.5" AR15 was only 16fps and 25fps slower for same charge weights as compared to the 16" AR15. However, the group sizes were noticeably larger.

Lastly, 195gr Lehigh Max Expansion (Vithavuori N110) group is large and 173fps slower as compared to the Hornday 195gr BTHP shot from same 18" barrel using same powder charge. Whether this is an issue of not getting as tight of a pressure seal due to the solid core Lehigh construction or possibly more barrel friction (more baring surface) causing drag that reduces velocity over the longer barrel).