Thread: A question for the sharp shooters..

Hey fellas,

I’m battling my way through a load development for a new 300 prc.
I’ve stumbled on to a load that has good speed and SD of around 6fps over 15 shots over a garmin chrono.
I’ve fired 3 five shot groups with this load, and all three have been exactly the same - horizontal dispersion of less than 10mm but vertically stringing about 2-4 inches across each group. If I overlayed the targets they would all be in the vertical line but a 4 inch string.
The fact there is a good SD and horizontal spread is so good makes me want to persist, so is there anything I can do to shrink the vertical string? Could it be something with the load (seating depth etc) or rifle (action screws etc). Or do I give up and carry on in another direction?

The rifle is braked with one of Greg’s terminator brakes so I’m not going to be able to reduce muzzle jump more than that. Also only about 30 rounds down a new barrel.

Any advice would be great!

Seating depth

Go too far and it will start to string horizontal

Stop at the point it prints nice tidy small groups

Well seen as though your velocity is so darn close together and your not wobbling around like flagpole...it only leaves two things. 1# your breathing Vs trigger break...eg breathing in n out normally moves Xhair up n down through the bull. So maybe not doing the pause breath on half exhale when fire? Of rifle jumping on bipod?? Possibly try firmer hold on forend vs toe of stock... Nothing to loose trying it.

Originally Posted by Micky Duck

Well seen as though your velocity is so darn close together and your not wobbling around like flagpole...it only leaves two things. 1# your breathing Vs trigger break...eg breathing in n out normally moves Xhair up n down through the bull. So maybe not doing the pause breath on half exhale when fire? Of rifle jumping on bipod?? Possibly try firmer hold on forend vs toe of stock... Nothing to loose trying it.

I think Micky is probably onto something there, something to do with the rest or hold, what is your method of holding the rifle? Have you tried more than one method of holding the rifle?

If its a hunting rifle, shoot a group off a decent bag, no bipod. And hold the forend, like youre hunting, not the LR or PRS type hold with your off arm tucked under the butt.

Groups have been shot lying across the flat deck of the ute on a bipod, spare hand tucked under the butt of the rifle. A good solid rest, but nothing at all to stop the front of the rifle jumping. No one likes admitting it could be shooter era and to be fair I hadn’t really thought of that… but it would make sense and I need to rule it out.
I’ll have a crack over the next few days prone off the ground where I can get the bipod spikes into the ground and load some weight onto it to stop the rifle jumping (that’s how I’d typically shoot when hunting). Part of me hopes that doesn’t solve the issue but I’ll report back on how it goes!

Good on you. I HOPE it sorts it out and you can get on with enjoying that accuracy potential.

Originally Posted by Missalot

Groups have been shot lying across the flat deck of the ute on a bipod, spare hand tucked under the butt of the rifle. A good solid rest, but nothing at all to stop the front of the rifle jumping. No one likes admitting it could be shooter era and to be fair I hadn’t really thought of that… but it would make sense and I need to rule it out.
I’ll have a crack over the next few days prone off the ground where I can get the bipod spikes into the ground and load some weight onto it to stop the rifle jumping (that’s how I’d typically shoot when hunting). Part of me hopes that doesn’t solve the issue but I’ll report back on how it goes!

Bipod on solid surface with nothing holding the forend is a recipe for what you are seeing.

One other factor to consider, I was shooting groups off the flat deck of my ute once, terrible groups, I didn't realise old mate was leaning and moving against the front end of the ute during the process, so if you have anyone along to 'help' when you are shooting off the back of your ute, make sure they aren't in the ute or leaning against it while you shoot. One other thing I have noticed about shooting off of the back of a ute, is that if the engine is running, especially diesel, it will affect accuracy. I doubt you were shooting groups with the engine running but I mention it to rule out all options.

If shooting off the ground with the bipod still doesnt fix the issue, try what Husky suggests, shoot off a solid sand bag. While not a great way to simulate hunting shots, it will tell you if the stringing is caused by shooter position or something at the loading bench. If you can confirm it is shooter position, at least you won't be chasing tails at the bench trying to troubleshoot a non-problem.

You could start ruling out shooting error by shooting some groups from different rests, or even with another rifle with the same rest as the first rifle, and compare your groups.
In basic marksmanship, a vertical group is typical from the butt slipping in the shoulder slightly.

Get your hand out of there and onto the fore end. Stick a sand bag under the butt of the rifle.

I believe you're making a "hand sandwich", no good for accuracy from what I've seen.

Bipods on hard surfaces can cause vertical stringing. I use a piece of dense foam if I'm using bipod on a hard surface

Bag under butt, left hand on the top of the scope (this will not put so much weight onto the fore end if the fore end is a little flexy). A bag under the butt to support that, a pad or something squishy under the bipod legs to cut the bounce down...

Loading a bipod can be a bit fraught as well, can be very hard to control all the extra factors that it can influence such as fore end flex. If you can get a sandbag or something and run without the bipod for the purposes of testing thats an option.

Today I did some pretty shitty target shooting with my Hornet on a bipod, on a floor mat, on the bonnet of my ute. On Friday ( low wind forecast) I'll ditch the bipod for a sand bag or similar.
Alway listening and learning, thanks.

Get someone else to shoot the same load and see what they get, equally a bipod on a hard surface will bounce. Also trying a grain less and a grain more should showroom difference. Even from same load try 3 of each seating deeper by 20 thou forn3 or 4 seating depths. That should give you a base to draw some info from

Originally Posted by Jus

Get someone else to shoot the same load and see what they get, equally a bipod on a hard surface will bounce. Also trying a grain less and a grain more should showroom difference. Even from same load try 3 of each seating deeper by 20 thou forn3 or 4 seating depths. That should give you a base to draw some info from

Why fook around with load??? It seems to be very good if can elimtthe verticle but. With such tight ES it's not velocity related so WTF would you change charge weight??? Until shooting form has been eliminated he would just be wasting components.