Gentlemen,

I am starting to get organised with my reloading and scanning my targets into the computer rather putting them in a box and eventually loosing them.

I've noticed an odd effect on one of the load development targets I shot for my Sako varmint .308 where it appears that as the charge weight increases, the POI shifts to the left.



The load is BL-C(2) powder, RWS cases, 125gr Sierra PH, Federal magnum primers and I picked an arbitrary OAL of 2.700" based on having about a calibre's worth of shank in the case.

The groups are shot at 200 yards and charge weight is increasing from left to right in .5gr increments from 51.0 to 52.0 grains. Assuming the fliers are me, need to confirm by loading up another ten each of the 51 and 52 grain loads, these both seem quite good and chrono at around 3150 fps. They were actually the first three homeloads I shot with this rifle and I am almost tempted to call load development at an end already!

The question is what would cause the horizontal stringing?

I can understand vertical stringing in relation to charge weight and different bullets or powders causing the POI to change appreciably in any direction but charge weight?

Does this indicate something untoward in the bedding or barrel?

With thanks,

GH

Which way was the wind blowing?

That's not at all unusual.

I just shot some 330 yard groups increasing charge by .2 gr.

POI shifted more to the right as I went up

Most barrels move like a lamb's tail when fired, especially the thinner ones. The harmonics of this movement depend on the load and bullet weight.

This does typically not affect precision which is confirmed by the excellent groups you got.

You might want to do further reading on "loading ladder", not sure if the spelling is right.

The odd fliers are not you, check that the extractor is not touching the back of the barrel. The horizontal shift of impact is usually caused by the locking lugs of the bolt not bearing evenly.

quote:

I am almost tempted to call load development at an end already!

Amir,

Having experienced your Sako Varmint personally - I'd suggest you're chasing Fairies about the Pinhead here.

If I was obtaining results as depicted w/the left & right groups with 125 grain flat based bullets at 200 meters; I'd cancel my contract with the R&D department staff, tweak the 1st & 3rd load, go shooting and then toss a few Beers with the Boys afterwards (we know the Drill).

Humor aside, the rifle obviously shows a preference for the left & right groups or the "special" wind was kicking up at Bisley when you touched off the middle group; which I doubt - your barrel most probably does not appreciate your efforts with 51.5 grs. w/that bullet.

I'd repeat the 1st (left) & 3rd (right) loads, loading 12 or 15 of each to get a better sampling and get on w/life ..... select the best results of each, tweak, if required. I think you've already hit the sweet spot.

Try adding an inexpensive Lee Factory Crimp Die to your arsenal, give those loads a nice 75%-80% crimp (not too tight) and enjoy.

POI can shift as the barrel heats up.

Good question.

I have experienced horizontal stringing in my 270win. I wanted to use RL22 with a Barnes 130TSX since I was getting 3,200fps with it, but also had horizontal stringing, from 58gr to max. I even re-bedded the rifle to try and fix it, but to no avail.

I switched to IMR 4350 and H4831sc and eliminated the horizontal stringing, but lost about 75fps.

quote:

Originally posted by Ol` Joe:
Which way was the wind blowing?

It was almost dead calm, with the occasional light breeze from 1 o'clock to 5 o'clock.

I did my best to dope it but the groups were shot within 10 minutes of each other and the wind didn't change.

quote:

Originally posted by rcamuglia:
That's not at all unusual.

I just shot some 330 yard groups increasing charge by .2 gr.

POI shifted more to the right as I went up

quote:

Originally posted by DUK:
Most barrels move like a lamb's tail when fired, especially the thinner ones. The harmonics of this movement depend on the load and bullet weight.

This does typically not affect precision which is confirmed by the excellent groups you got.

You might want to do further reading on "loading ladder", not sure if the spelling is right.

Thanks Dirk, I has a look at the ladder method but haven't given it a go yet. The barrel is the standard Sako varmint profile so pretty thick. It is fluted however, might that make a difference?

quote:

Originally posted by Gerard:
The odd fliers are not you, check that the extractor is not touching the back of the barrel. The horizontal shift of impact is usually caused by the locking lugs of the bolt not bearing evenly.

Thanks Gerard, The action is a 3 lug Sako so I don't think the extractor touches the barrel face. How would I go about checking the lock up?

quote:

Originally posted by Gerry:

quote:

I am almost tempted to call load development at an end already!

Amir,

Having experienced your Sako Varmint personally - I'd suggest you're chasing Fairies about the Pinhead here.

If I was obtaining results as depicted w/the left & right groups with 125 grain flat based bullets at 200 meters; I'd cancel my contract with the R&D department staff, tweak the 1st & 3rd load, go shooting and then toss a few Beers with the Boys afterwards (we know the Drill).

Humor aside, the rifle obviously shows a preference for the left & right groups or the "special" wind was kicking up at Bisley when you touched off the middle group; which I doubt - your barrel most probably does not appreciate your efforts with 51.5 grs. w/that bullet.

I'd repeat the 1st (left) & 3rd (right) loads, loading 12 or 15 of each to get a better sampling and get on w/life ..... select the best results of each, tweak, if required. I think you've already hit the sweet spot.

Try adding an inexpensive Lee Factory Crimp Die to your arsenal, give those loads a nice 75%-80% crimp (not too tight) and enjoy.

Thanks Kapitan, as you know this rifle is turning out to be pretty accurate. Guess what though.....it hates (3-4") Privi soft points....

I'll try the 51 and 52 grain loads again and decide whether it's worth playing with seating depth.

What does the factory crimp die do? ( Aside from crimp, before you start, what's the effect?)

quote:

Originally posted by 243winxb:
POI can shift as the barrel heats up.

The barrel was cool before each group was fired. It was like -2C that day and the barrel hardly warmed up.

quote:

Originally posted by k-22hornet:
Good question.

I have experienced horizontal stringing in my 270win. I wanted to use RL22 with a Barnes 130TSX since I was getting 3,200fps with it, but also had horizontal stringing, from 58gr to max. I even re-bedded the rifle to try and fix it, but to no avail.

I switched to IMR 4350 and H4831sc and eliminated the horizontal stringing, but lost about 75fps.

Was the horizontal stringing a problem with the eventual load or just during load development. I don't think my issue is a problem unless it is a result of something that would be a problem.

I bet you have a left hand twist rifled barrel

Barstooler

quote:

What does the factory crimp die do? ( Aside from crimp, before you start, what's the effect?)

http://www.accuratereloading.com/crimping.html

quote:

How would I go about checking the lock up?

Just take a look at the back-side of the locking lugs on your Bolt - you'll easily note if they're bearing evenly.

quote:

Was the horizontal stringing a problem with the eventual load or just during load development. I don't think my issue is a problem unless it is a result of something that would be a problem

In my case, I believe it to be a powder/bullet issue. I tried the combo in Remington and DWM cases and had the horizontal stringing. Switching powders solved it for me.

Take a look at just about any calibers data in this forum's reloading section...you can see group changes(and velocity changes) with powder amount changes, step by step, that should give you a clue that ANY change in powder amount, bullet or bullet seat will produce a change in POI and/or group size...I've seen POI/group changes in as little as .1 gr in a few of my very accurate, benchrest capable rifles... moreso with small cases than with larger ones.

Some changes can depend on just how close you weigh(or NOT weight) your powder charges...get sloppy and you can have a .1-.2 range.

POI changes also depend on just how anal you get with your bullets and brass...and that means weighing the bullets to within .1 grain, and measuring the ogive and sorting into .1" variations...pretty much only for the competition shooters, but for my medium long range rifles, 300 out to about 500, if you want to keep hitting, then you will do the mind numbing things.

The level of "tuning" of your rifle and scope must also be taken into account...yours seems pretty well set up.

It is fairly easy to get ~1" - 3/4" groups with a good rifle/barrel and many times down to 1/2", but to get to that bughole group and STAY there takes a lot more work...on ALL the components.

The quest for that "perfect" load and pinpoint accuracy is an ongoing thing...you may quickly find that load or it may take some doing...many shooters find that load for their rifles but it may or maynot work in another rifle...BUT...from them on that load is "boss" and however that shooter got there is "THE" way and proselytizes from then on...not necessarily bad, but it can get in the way of looking at other "thingys that might actually be the cause or at least contribute.

Vertical or horizontal stinging can be cause by powder amount and/or type or bullet seating or the bolt touching the barrel face or abutting the lugs non-uniformly or barrel heating, sand shifting in your bags, barrel touching something, how you hold the rifle...the whole gamut...and everyone has their favorite causative factors to bandy about.

It's all about barrel harmonics and just about ANYTHING can impact those vibes.

If you're confident about your shouting and your rifle system then get to work on the ammo.

You picked an arbitrary seating of 2.700" for that bullet and those groups are in the 1/2" groups size already...I have a few rifles that get ALL the treatment and STILL won't go below about a 4...makes me totally crazy but those are small cals, 17-22, they shoot several bullet brands and weights just as accurate and are on platforms that aren't worth tossing more money at...and they take plenty of sageratz out to ~300 yds so I can't complain.

You can quit now and be happy or...what I would do...check to see what the seating is in relation to the lands and maybe go in/out 0.005" or 0.010", first weigh/ogive sort your bullets...killing three birds with one shot so to speak...a couple of 4-5 shot groups will tell another story. I just depends on how much "analosity" you are willing to go through as to how far you will go.

I would rather be whacking ratz than targets so when I hit a 1/2" group at 125 yds on my range I use that load for hunting, but STILL work up a few 3 shot groups to test, just in case I might hit that "perfect one"...

By the by, I've always had very good luck with Horn 130 SP, Sierra 125 SPT and 135 MK's and Speer 130 HP's in all my 30 cals for varminting.

I worked up a Speer 130 HP/H4895 for my father back in the early 60's, that does bugholes in a Rem 788 at near max pressures...I tried Varget when it first came out and it's a toss up which does the best, and the same goes for RL15.

You might glass bed that beautiful thang just in case....wish I had it and you had a feather up your kazzoo and we'd BOTH be tickled... Hahahahahahah

I bought a 6PPC Sako way back when they first came out and shot some amazing groups with it for almost 20 years with factory AND reloads until "stuff" happened and I had to sell it...never got around to buying another one...just kept building my own.

LUCK

Possible cant issues

But they don't usually show up at 200 yards