Uneven lands...a problem...?

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Uneven lands...a problem...?

Post by Stix » 03 Jun 2018, 8:36 pm

So ive measured the lands in a new(ish) rifle today.

As i still dont have threaded cases ive checked the ogive measurement to be the same on several bullets for the test, & used the texta trick to see when the lands are contacting the bullet.

The short version is that out of 6 grooves, i get one mark on the projectile when JUST beggining to touch..
Then, seated another .001" further out, i get 2 marks (thats now 2 rifling ridges touching the bullet).
Then, another .001" further out, 3 rifling ridges out of 6 are touching the bullet.

Observations...
The 1st rifling mark is a fine, long mark along the bullet, plenty long enough to make out the 14 twist (ie; the mark is long enough to see it is 'angled' along the the bullets base to tip length).
The 2nd mark is just as fine, but not as long, yet is long enough to see twist.
The 3rd rifling mark is as if its marked the "chatter" from reaming on the bullet (ie; marks that appear left to right, the width ot that line of rifling, as bullet is viewed sitting on its base).

I did not seat the bullet out any further to see when the other 3 lands begin to touch.

I also dont have a concentricity guage to ensure concentricity, but i did however roll the pressed dummy & could not see any tip wobble.
The projectile is only a "superoo/Sierra 55 GK".

The rifle is a Tikka.
Its fired <60 rounds.
It may be of note that ivee noticed a high incidence of double grouping already with the rifle. (I realise this could be any number of things-loose bits-me etc, which i will check before i shoot it next).

So my concerns are obvioisly accuracy related...
Is this something to worry about... ?(is it normal?).
What should do...? (Deal with it/'Shoot' them even/try polish it even/try factories in it & send it back if it shoots greater than moa-(but it shoots 1" with basic handloads so will probably).

Any advice....???
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Re: Uneven lands...a problem...?

Post by brett1868 » 03 Jun 2018, 9:54 pm

How concentric is the projectile in the case? wouldn't have to be out much to see that result.
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Re: Uneven lands...a problem...?

Post by Stix » 03 Jun 2018, 10:52 pm

Thanks Brett.

Like i said, i cant measure concentricity due to not having a guage...but i coudnt detect any tip wobble on a roll test.

Given the difference in length of the marks on the projectile, i would have thought i would be able to see that much tip wobble...but then ive never measured concentricity before to be able to guage how much runout i can see with my eye... (?)

Ill try take some pics & post...
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Re: Uneven lands...a problem...?

Post by marksman » 04 Jun 2018, 7:59 am

what Brett says makes sence
how even is the thickness of the case neck
you would expect the case not to be concentric if there is a very thick and a very thin side? a banana
with an even thickness of the case neck the neck will be perfect to the chamber after firing but can be pushed off set just by sizing
but I would not be happy with lands not being even
if a new chamber it can be a burr
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Re: Uneven lands...a problem...?

Post by straightshooter » 04 Jun 2018, 8:34 am

OMG
A factory chamber that is possibly off center or off axis......unthinkable!
In a Tikka......impossible!
Well don't you know they are made by (take a deep breath and genuflect) Sako.

The sad news is that mostly factory rifles are chambered very quickly with reamers in various states of wear and clearances and the precision of the chambering will generally conform to a Pareto distribution that can be broken down to 10% very good, 80% average, 10% not good.
The comforting news is that a slightly dodgy chamber is not the sole determinant of accuracy.
By the way, when sample rifles are sent to reviewers for them to gush with praise, which end of the Pareto distribution do you think they are chosen from?
Now stop and think about why you pay many hundreds of dollars for a precision gunsmith (not a recycled blacksmith) to do a chambering job. It's not because he whacks the barrel in a machine and drills out the chamber in a matter of minutes or possibly seconds as the factories do. Everything is done carefully and slowly in as precise setup as is possible and may take a number of hours.
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Re: Uneven lands...a problem...?

Post by Gwion » 04 Jun 2018, 10:28 am

No advice on the chamber but i can't see it causing double grouping. This is more likely bedding or even technique or shooting setup.
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Re: Uneven lands...a problem...?

Post by Stix » 04 Jun 2018, 12:13 pm

Thanks marksman.

I didnt think of neck thickness...or a banana'd case... :roll: (in another rifle i first fired the cases with a 20 thou jam to try avoid this, but i didnt on this rifle :roll: ).
And i dont have a ball micrometer to measure the neck wall thickness.

Fwiw, i use redding dies, & when i neck size i leave the stem loose to self centre.
My initial very basic assumption is that the expander ball passing through the inside of the neck would iron out uneven wall thickness...but i guess thinking about it, the neck could easily spring back somewhat...is this correct...??

I realise it could be a burr, which is why i posed the question of a little polish, or to moniter it & potentially 'shoot' it off.
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Re: Uneven lands...a problem...?

Post by Stix » 04 Jun 2018, 12:25 pm

Thanks Gwion,
As i mentioned, ill check everything--remove the barreled action & check the lug & screw torque, & all optics mount fixings before i shoot it next.

I just thought id point out the double grouping in case it was a symptom of bullets entering uneven rifling, that anyone knew of...i get double groups every now & then, but with this rifle ive had up to 3 or 4 out of 6, four shot groups print a double on one page..so its excessive and something ill have check out further.
And the rifle is stock standard, so its not bedded as such.

Thanks for your input. :thumbsup:
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Re: Uneven lands...a problem...?

Post by Gwion » 04 Jun 2018, 12:41 pm

No worries mate. From my understanding, double grouping is more an issue of consistent return to two points of battery. A dodgy lede, as you have suspected, is more likely to cause the bullet to enter the rifling with poor concentricity which may effect stability and in turn cause random grouping rather than a consistent double group. But, as the other guys have said, it may just be the concentricity of your load. Theoretically, i guess it could also stem from how well the bolt face and/or locking lugs have been cut.

I'd be willing to bet you can eliminate the double grouping with a bit of attention to the bedding. I'd be starting there and seeing how well it shoots after that.

What is the rifle for and what sort of precision are you wanting from it?
If it isn't meeting your needs or crequirements after tidying the bedding and torquing down properly then worst case is about $400ish for a good smith to tidy up the chamber and maybe true the bolt face and lugs.
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Re: Uneven lands...a problem...?

Post by Stix » 04 Jun 2018, 1:26 pm

straightshooter wrote:OMG
A factory chamber that is possibly off center or off axis......unthinkable!
In a Tikka......impossible!
Well don't you know they are made by (take a deep breath and genuflect) Sako.

The sad news is that mostly factory rifles are chambered very quickly with reamers in various states of wear and clearances and the precision of the chambering will generally conform to a Pareto distribution that can be broken down to 10% very good, 80% average, 10% not good.
The comforting news is that a slightly dodgy chamber is not the sole determinant of accuracy.
By the way, when sample rifles are sent to reviewers for them to gush with praise, which end of the Pareto distribution do you think they are chosen from?
Now stop and think about why you pay many hundreds of dollars for a precision gunsmith (not a recycled blacksmith) to do a chambering job. It's not because he whacks the barrel in a machine and drills out the chamber in a matter of minutes or possibly seconds as the factories do. Everything is done carefully and slowly in as precise setup as is possible and may take a number of hours.


Thanks straightshooter..
I detect you have some issues surrounding folk who seem to think that because Tikka's are made in the Sako factory, that they will be perfect...?
Were they mean to you on the Tikka forum...? :D
(i suggest you see Bretts little footnote on each of his posts :lol: :sarcasm: )

Well im not one of those guys :thumbsup: ...& Ive not suggested that being a Tikka, & thus made by Sako, that it should mean the chamber & rifling should be perfect...in fact, i had a new Sako once that was so bad, i had a fight with various folk about it & refused to shoot it & i sent it back...!!

Here is some of what was wrong with it--
*it wouldn't sit in the barrel channel properly-every time you set it even in the stock it would find its way back to touching, or at least nearly touching the for end on one side, & that was from tinkering with a wide variety of screw torque settings, so you can imagine how much it would move when shot...!??!
*the chamber was so bad it literally had chunks ripped off the lands/start of the rifling,
*the barrel steel was so bad it looked like the moon in some areas with all the pitting & had a giant crater (pit) right on the inside edge of the crown that was already full of copper from factory firing,
you needed two hands with considerable force to push the mag in to allow for its release, not to mention the mag & bolt was scratched...
...AND...the inletting was so bad around the tang that i could have retired on the funds from renting the space out to a boat full of illegal immigrants....

So im well aware of the pitfalls of mass production...not to mention that in my post, i didn't elude to the fact that it shouldn't have any problems because its a Tikka.

Having seen in a few new chambers now, im well aware of what can be expected, & i looked into this one before it was shot & i dont recall it to be all that bad--certainly not polished silk, but not bad compared to whats out there.

The only reason this has come about is because ive never measured the lands in a rifle using a permanent marker on the bullet, & the marks the rifling left had posed some obvious thought processes & thus questions to someone who has basically just been a keen as mustard rabbit shooter for his entire life, & is now driven by just simply wanting to get better at this whole shooting thingo.
Its plainly obvious that there is not a great deal i can do about it, but it cant hurt for me to ask. :drinks:
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Re: Uneven lands...a problem...?

Post by Stix » 04 Jun 2018, 1:41 pm

Gwion,
Its just a hunting rifle. & It'll be used for long range head shots (for me 300ish) shots on bunnies/foxes etc.
As for accuracy, I want the best accuracy i can get....25" would be good, but i want at least a consistent .5"-.6" out of it or ill get rid of it.

Initial shooting seems to elude to it being capable of, or at least close to .25" with cheap Zmax proj's & either 2208 or BM2, but the double grouping is an issue...even when its not a double group, you can often see the the one flier out of a 4 shot group is often where it prints in double grouping in the medium end of charge weights.

It also doesn't seem to be getting the velocity it should, but i haven't hit the top end of loads with it yet.
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Re: Uneven lands...a problem...?

Post by Bills Shed » 04 Jun 2018, 9:43 pm

[
u]The short version is that out of 6 grooves, i get one mark on the projectile when JUST beggining to touch..
Then, seated another .001" further out, i get 2 marks (thats now 2 rifling ridges touching the bullet).
Then, another .001" further out, 3 rifling ridges out of 6 are touching the bullet.

Observations...
The 1st rifling mark is a fine, long mark along the bullet, plenty long enough to make out the 14 twist (ie; the mark is long enough to see it is 'angled' along the the bullets base to tip length).

The 2nd mark is just as fine, but not as long, yet is long enough to see twist.
The 3rd rifling mark is as if its marked the "chatter" from reaming on the bullet (ie; marks that appear left to right, the width ot that line of rifling, as bullet is viewed sitting on its base[/u]


Maybe I am reading this wrong but if you have just touched the lands and then only moved the projectile out three thou, how can you see a twist rate. It would only be a three thou mark. To have a rifling Mark, from base to tip the whole length of the projectile would have to be forced into the rifling.
I would suggest that the long thin mark along the projectile is from when you are chambering the round and the texta is being rubbed off and is NOT a rifling Mark. Once you have that sorted/ confirmed then check these other rifling marks. Something not right here!

Bill
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Re: Uneven lands...a problem...?

Post by Stix » 05 Jun 2018, 12:13 am

Good point bill...& thanks for the input...!!

Just to clarify, the marks are not the entire length of the projectile.
When i mentioned the marks from base to tip, i meant that is the direction they run, not the length of them. Sorry for not being more clear on that.

2 of the marks (the first 2 as described) are long enough to just notice they are on an angle, in that they run (in direction only, not entire length) from top right to bottom left, as viewing the bullet sitting on its base...or should i say, the marks are just leaning to the right closer to the tip of the bullet.
They marks also run through a circumference mark as left by the hornady .22 Cal comparitor (near enough to the ogive).
So this indicstes to me that they be rifling marks.

Ive tried to take pics, but cannot get anything clear enough to post, due to highly reflective finish & reflection of lights etc

But you are right on the point of length...the marks are longer than the distances i mention.

Ill have another go at some point.

I might even try it on a different rifle or 2 & see what results i get.

Thsnks again Bill... :thumbsup:
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Re: Uneven lands...a problem...?

Post by Stix » 05 Jun 2018, 12:18 am

Does anyone else get, or ever noticed different rifling marks becoming present at different bullet seated depths...
Or any difference (maybe in length) in the marks left on the projectile...?
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Re: Uneven lands...a problem...?

Post by Bills Shed » 05 Jun 2018, 8:09 am

Did it once but the COL was so long it did not fit in the mag. Made the COL to suit mag and it functions and shoots very well. I think we can get carried away with the chase for "more" . I asked myself if I needed it and the answer was no. Now I just shoot and cull just as effectively.

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Re: Uneven lands...a problem...?

Post by marksman » 05 Jun 2018, 12:52 pm

I think it will be a burr that hasn't been burnt off yet so if you just do a bit of running in
1-2 shots and clean then shoot, repeat, it will go away :thumbsup:
being newish it may have needed it and hasn't had it yet, the tikkas barrels are quality and lapped but sometimes lapping wont take the burr out
you have to burn it out, what I think anyway
do some fireforming and sighting before you go full on reloading :drinks:
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Re: Uneven lands...a problem...?

Post by Stix » 05 Jun 2018, 1:04 pm

I hear ya Bill... :thumbsup:
Ive done that for a long time now, but OCD got the better of me...
But im just wanting to load with consistancy.
I can reach the lands feeding from the mag with this rifle & have "roughly' measured it in recent past using the 'looser neck' technique so the proj can move, but wasnt 100% confident it was accurate..
So the last 2 loads ive shot were .020" off the lands to be safe.
Atleast now i know for sure where the lands are when i press out rounds, & i can start from .010" & go backward, &
(& as it turns out i was spot on the money with the last measurement used before, but this way is much quicker.
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Re: Uneven lands...a problem...?

Post by Bills Shed » 05 Jun 2018, 1:27 pm

Stix wrote:I hear ya Bill... :thumbsup:
Ive done that for a long time now, but OCD got the better of me...


That I understand, I think most reloaders carry the trait.
Have fun

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Re: Uneven lands...a problem...?

Post by Stix » 05 Jun 2018, 3:29 pm

Thanks marksman...ive wondered that myself, & you're most likely right.

I have done some running in regime, in shoot a few clean etc.
As it stands now, i cant get it to foul at all-not carbon nor copper...last lot was 28 rounds without a patch & it only took 2 patches & it was cleaner than the water in Gwions favourite trout stream...!!

Anyway, ive shot 50 odd rounds without a jam...thinking about what you've said maybe ill do some forming with a jammed bullet for the rest of the cases, then move to load testing again.

Then ill have the stress of OCD not allowing me to mix the first 50 cases with the 2nd 50 properly formed cases. :roll:

Another point ive thought about since, is that the extractor is quite strong on this bolt, & it really puts pressure on the case (obviously pulling the front/bullet end upwards while sliding rearwards), so some exaggerated markings may be left from dragging the case out before i can get my fat finger in the ejection port to push down on the case. :problem:

Ah well...thanks all for the input...when/if i have any discoveries ill update.
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Re: Uneven lands...a problem...?

Post by marksman » 05 Jun 2018, 9:28 pm

If the cases are not fireformed there is a good chance of the tilt when the bolt slips over the case
and you may get the marks on the projectile from extracting the case as it is pushed against the side of the chamber
I had thought about this
its to much hassle to take the plunger out so it may be worth waiting for your drilled cases before you worry to much about trying to be close to the lands
from what you are saying it is well and truly ready to find a load for
good luck with it :drinks:
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Re: Uneven lands...a problem...?

Post by marksman » 05 Jun 2018, 9:30 pm

Bills Shed wrote:
Stix wrote:I hear ya Bill... :thumbsup:
Ive done that for a long time now, but OCD got the better of me...


That I understand, I think most reloaders carry the trait.
Have fun

Bill


+1 ocd :thumbsup:
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