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.

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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.

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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.

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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!

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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

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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

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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.

Alot of people are recommending to not use their non trigger hand under the butt.
I dispute that as I shoot all sorts of rifles regularly of my mobile bench or ute tray.
In quantifying that I have a rear sandbag that I squeeze to get my aiming point correct and I use (shock horror) Harris bipods exclusively.
All I can say my results do not reflect stringing when I do a lot of validation on my 720 m plate or 100m zero range either.
Loading bipods is also been proven to be a fallacy and I also subscribe to that theory as again my grouping capability doesn't improve with tension on my bipod as it allows for pressure variations compared to been static/neutral loading.
To be fair I also beleive that you shoot how ever you think you shoot your best.
I know when I get shooters to use my technique they can't beleive how steady they can hold their rifle and groups they can achieve.
M2C

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Originally Posted by andyanimal31

Alot of people are recommending to not use their non trigger hand under the butt.
I dispute that as I shoot all sorts of rifles regularly of my mobile bench or ute tray.
In quantifying that I have a rear sandbag that I squeeze to get my aiming point correct and I use (shock horror) Harris bipods exclusively.
All I can say my results do not reflect stringing when I do a lot of validation on my 720 m plate or 100m zero range either.
Loading bipods is also been proven to be a fallacy and I also subscribe to that theory as again my grouping capability doesn't improve with tension on my bipod as it allows for pressure variations compared to been static/neutral loading.
To be fair I also beleive that you shoot how ever you think you shoot your best.
I know when I get shooters to use my technique they can't beleive how steady they can hold their rifle and groups they can achieve.
M2C

Sent from my SM-A556E using Tapatalk

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Yep a bag under the butt, in my experience squeezing the bag with a light recoiling rifle can be very effective. However this is a 300 PRC and holding the fore end with a bag stabilizing the rear is far more effective when done right.

Bipods are fine, when used correctly. Loading a bipod when using a chassis can work but in my experience like you say it adds more variables espywith plastic stock rifles.

What I said was...try it the other way,nothing to loose. It seems to be most logical explanation for his issues. Be interesting to see results lol.

Does PRC stand for Problematic Rifle Cartridge? It appears every second question here is why won't my PRC shoot.

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Originally Posted by kiwijames

Does PRC stand for Problematic Rifle Cartridge? It appears every second question here is why won't my PRC shoot.

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I know a few 6.5prc's that go very well.
Also, a couple of 300prc as well.
I have in my safe a mates hells canyon I am doing load work on and started out with the 230Atips.
Now that's recoil! that's up there as just got an average can on it as well as a light rifle with an nx8 on it.
They are shit triggers, but an after-market spring helps.
I have dropped down to 212eldx and that helps.
It's is not a consistent grouper which is bloody frustrating as hate rifles that don't play the game!
Probably one of the most accurate rifles I have ever seen out of the box was a Rpr 300prc.
It still amazes me how well it shoots!

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Firstly I am not an expert but your results are pretty much described by "Mark and Sam" you tube. He does ELR shooting.

Short story is you most likely have an inconsistent muzzle rise/jump.

As others have said, hard surface and bipods aren't a great combo, a bag for a rear rest will also help.

Something that hasn't been mentioned is a bag rider to allow rifle to slid backwards without the butt dropping thereby lifting the muzzle.

He can explain it much better if you are interested.
https://youtu.be/2hh42VNxFkg?si=uoFOqKV6i5egpzJc

This ones a bit longer but deals directly with muzzle jump

https://youtu.be/l5aEqa2mWbI?si=AlL8xH8UexyfYraz

Does it progressively rise in vertical as you fire more shots or spray them all randomly?

If it’s random - borrow a mates bipod that doesn’t have pod spikes on it and try that. Reading your last post you mention spikes? Off the back of a wooden flat deck this stands out as an issue to me. Especially if you are muscling the gun and loading it up with force.

Gently gently with your shoulder just making light contact with the butt pad and loading the bipod ever so slightly. Thumb wrapped over the stock not resting on top. Light grip holding the stock the shoulder takes the recoil and your rest (bipod with rubber feet and rear bag) ensure the rifle recoils back nice and straight.

Something to consider anyway..

Interesting video.
Bottom line is bipods are not stable tend to move around when firing.

Shortish range only unless you practice a lot.

There are two points I want to suggest re shooting position. First you appear to have an accurate load so I would not alter that at all....

If you are trying to figure out whether the vertical stringing is technique or rifle then you need to eliminate your technique to find out if it goes away or not. Sandbag both ends of the rifle and do everything you can to hold it steady. NO MOVEMENT in the shooting position. If the strining still occurs then it is the rifle and not the technique.


If it goes away then change one thing at a time- go from sandbags to the bipod on a softer surface. Then a hard surface. And a sand bag on the Ute. Change one variable at a time to see when it starts to come back. Then that would be what I would address.

As mentioned earlier, breathing while firing can also cause vertical stringing. The fact that the speeds and lateral grouping are good implies to me that it is something that is happening when you are firing the rifle- be it bounce on the ute / bipod

Second point would be it is a larger cartridge...I had issues with my 375 H&H when I had it as the recoil caused me to develop a small flinch. That may be worth considering too..

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Originally Posted by Oldbloke

Interesting video.
Bottom line is bipods are not stable tend to move around when firing.

Shortish range only unless you practice a lot.

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You need to watch episode of nzhunter where they have dad's n daughters out after tahr..... It's eye opening just how good the" hug yourself" method can be with heavy rifle.

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Originally Posted by Husky1600#2

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.

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Wrong, you've been reading/listening to Mr. Foster too much.

This technique is very valid when using a bipod, ask these guys Attachment 259554Attachment 259555

IF your hunting rifle weighs as much...by all means.

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Originally Posted by Micky Duck

You need to watch episode of nzhunter where they have dad's n daughters out after tahr..... It's eye opening just how good the" hug yourself" method can be with heavy rifle.

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Or a light rifle in that case..

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Theres lots of different holds none of them right or wrong. The idea is to get comfortable behind the rifle and be able to manage the recoil. Body shape and injuries etc will make different styles suit different people

Well lads problem solved..
prone on the ground to get the spikes in the dirt and a better rear rest, and we have 5 shots into about .7 moa
A bit humbling but good to be sorted..
Lessons learnt are that you can get away with poor rests and technique in lighter recoiling rifles (groups were fine with the same technique in my 22 creed and 6.5 prc) but not in a big magnum.
And to always check the shooter first before tinkering with a load!

Appreciate the input gents

Absolutely STOKED to hear you have it sorted...now go enjoy using it with confidence.

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Originally Posted by Missalot

Well lads problem solved..
prone on the ground to get the spikes in the dirt and a better rear rest, and we have 5 shots into about .7 moa
A bit humbling but good to be sorted..
Lessons learnt are that you can get away with poor rests and technique in lighter recoiling rifles (groups were fine with the same technique in my 22 creed and 6.5 prc) but not in a big magnum.
And to always check the shooter first before tinkering with a load!

Appreciate the input gents

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Nice mate was thinking that would be the case.

To help get the nice tight groups with any light weight magnum, before pulling the trigger you need to consider your rest setup and how the rifle is going to react under recoil. I’ve never shot a good group with spikes and found that using them is too inconsistent for my liking.

Bit of an update here fellas.
After a fair bit of confidence building on paper and gongs, I’ve had the big 300 out hunting over the last month. 3 deer with it at 550y, 320y and 270y, all first round hits in the spot where I was aiming and with the exact same load I was having issues with back when I started this thread.
Elevation has been bang on since I tinkered with my shooting technique, starting to feel very confident inside 600y with this rifle. So thanks again to those that helped me get to the bottom of it!