Inconsistent results from ladder testing

)Stephan

)Stephan

Member
Dear boys & girls,

For this being my first post in this Forum I will shortly introduce myself.
I've been shooting for about 10 years now, taking part in several national and smaller matches in germany.
Shooting keeps to be my favourite sport after many years and one could say I'm quite interested in Benchrest and other accuracy-dominant disciplines.
Proudly owning a BR50 rimfire gun I quite often participate in Matches and love it like nothing else.

Now this topic will be related to centerfire rifles, in my case a trued Rem700 Action with a .338 neck--chambered Shilen Barrel cal.308Win, McMillan Fiberglass Stock and Nightforce NF 42x optics.
Although I believe to run into the same problems with my other guns, I'd probably say this is my most accurate one.


So now to describe my observations in short terms, my group sizes from ladder testing tend to be very inconsistent. E.G. My best load from the last week will often not be the best group from the actual week.
Let's say it's just +/- 0.3grs of powder.

I have observed this for quite some time (some years maybe?) and feel quite frustraded as you can imagine. Well of course I read a lot of literature and Forums regarding probably every accuracy-related topic yet, but nothing seemed to eliminate the cause up till now.

So for example, taking into consideration Tony Boyers book and several other BR or long range related books i tried all of the following:
Neckturning, Bushing Dies, individual charge trickling, shooting in the same temperature, all kind of barrel cleaning methods, several powders/bullets/primers/cases, ... I don't know what to check next.
I have also tried several scales for powder charges, but nothing really helped.

What I can say is that bullet concentricity etc. is minimal and also I try to keep all other tolerances the same (currently shooting Lapua brass).

But what annoys me the most is, that the difference from charge weight is really minimal from one week to the other..

Have you ever encountered something alike?
And can you give any advice?

Cheers,
Stephan

P.S. I'm FL resizing my cases with a .335 Bushing and use a Wilson seater.
Also i set back the shoulder by ~.002 and the bullets are touching the lands (they are not pushed back in the case while closing the bolt, but have uniform touch-markings).
In addition to that I tried moly (self coated) and non moly.
Additionally I tried neck sizing and many different dies..
 
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You have me confused...
You do not shoot "groups" in ladder testing.

Skip the full length sizing and go to neck sizing only.
.001-.002 neck tension for a start....are you at the lands ??

Are you keeping track of temp and using wind flags ??

Did you weight sort the brass, uniform the primer pockets.

Seating the primers to the bottom of the pocket ? and then a small crush in place.

(see the primer test thread)

What bullets ? How are they sorted ?
 
CMaier, sorry I made a mistake there.
Of course I did not shoot for groups, but for horizontal and vertical spread. (I did not change the point of aim / I did not compensate for wind)

And yes, I do have a set of 6 windflags.
Neck tension is about right, should be around .002 or a little less.

I added some pictures to demonstrate what I was talking about:

This picture is showing the result from ladder testing N150, on the left there is 44.4grs (I do shoot round-robin).
Shooting 5 rounds at 100meters with minimal wind resulted in a .196MOA group
image.jpg
One can see, that there is only a little vertical spread - so I testet that load the week after.

image.jpg
Sadly I do not have a picture of the week after, but from last week (it looked just alike).
Now the left group is shot with 44.4grs of N150,
The other ones are n135 and do show a lot of vertical stringing.
Now regarding that 44.4grs group i wonder where that vertical came from.
Shooting at just 100m this looks like it was shot during some strong wind, if not worse.
But actuall the conditions have been quite similar (temperature & windspeed/direction)
Also, there gas been some horizontal spread.. But the grous of N135 do only show a lot of vertical (2nd group from the left, the last shot fired introduced some horizontal.. Maybe a flyer or the fouling started to do it's part)
Maybe..

EDIT:
Do you have a tip on bullet sorting and how to check for ruined cases?
Sadly I do not "feel" anything on the bolt as it is quite snug even without a case/cartridge.
(What does Tony mean by "Throw your brass out if it clicks?)


I am using k&m tools a lot as they are widely available in germany (neck turner, primer pocket uniformer, expander die for neckturning and primer seating tool)
Also tested shooting free recoil from a Rock BR and Edgewood Minigater (used for my BR50 rifle typically).. I assume that free recoil will not be a thing for 308Win as the rifle jumps around a lot
 
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I'm assuming that Tony means at the top of the extraction stroke, the bolt hangs such that you have to push it past the hard spot.....the last little spot before the bolt opens. That particular "hangup" doesn't cause your rifle to shoot poorly but rather goofs you up in other ways during competition. It does, however, indicate that your load is a bit much....generally speaking.

I read and re-read your previous post and something you said needs clarification. What exactly do you mean when you say your bolt closure is "quite snug" even when the chamber is empty?
 
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Wilbur, thank you very much for explaining this!

Now for future testing I threw all my used cases out (they will be used for prone rifle shooting...) and weighted, headspaced, trimmed and neckturned 50 new Lapua cases..
Taking a look at that N135 it looks quite promising as there is only minimal horizontal spread.. so I will try some bullets with that for now.

Maybe regarding OAL (Base-to-Ogive if you want), is there a Problem if the bullet is seated "long" for touching the lands?
The barrels twist is 1:12 so I could go up in bullet weight a bit (I used 168grs SMK for this test, also have 185grs Scenar and some other brands.. I stopped using Bergers as I did not get the rifle shooting with them either and the Scenars are really affordable over here)
 
I didn't add to my post quickly enough.....What do you mean when you say your bolt closure is "quite snug" on an empty chamber?
 
By "snug" I mean it does need a little push to go down.
But it's not like you need to force it, maybe just a little tight all the way.
The bolt lugs habe been reworked, but the BR rifles I know close without any help if there is no case in the rifle.

(This is why I do set back my shoulder by .002" - I can not check for headspace with just a case and "the feel of it" while closing the bolt. I did read somewhere that .002" might be best in that scenario)
 
Are you sure the bolt is not touching the barrel? A little black smoke will tell that tale. Alternatively, you can remove the spring assembly and the bolt should simply fall closed.
 
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i am with wilbur.
Fix one issue at a time, then work on loads and accuracy.
stop sizing to -.002, fix the problem.
 
Guys, thank you very much! I just stripped the bolt and inserted it without the firing pin - this alone did sfeel better, but it did not close by itself with a case inserted just now.
But asking Google told me to remove the ejector plug & spring (and to leave it out) - so I did try that and it worked!

Now I do know, that pushing the shoulder back by .002 is way to much! There is no resistance at all!

Cheers,
Stephan

P.S. Maybe I can give some Feedback on wednesday!
P.P.S. I do shoot 300meters for competition, the middle ring is about 1" in diameter - so i need groups smaller than that ?
 
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So I fireformed my cases today and after that tuned my FL die to size the case correctly - I did read Tonys book again for the tuning process.

Now this really opened my eyes, my calipers tell me that the shoulder only needs to be set back by about .0004" for this rifle!
Next week I can do some ladder tests again.

Cheers,
Stephan
 
First of all welcome. Second, if your bolt is hard to close you may want to try some different grease on the lugs. Also put some on the threads of the cocking piece and the ramp that pulls the firing pin back when cocking. This may ease the pressure a tad
 
Dusty Stevens said:
Also put some on the threads of the cocking piece and the ramp that pulls the firing pin back when cocking. This may ease the pressure a tad
Click to expand...
This is a good idea, thank you! I did that Prior to todays shooting.

Today on the range I noticed 2 things:
1st.: The cases that I FL-sized on wednesday have been inserted in the chamber without the firing pin assembly again. On closing the bolt I noticed that it was quite tight and maybe that is because of case springback?
For that reason, I set my die to go only a litte deeper. Most cases were too loose by then, the bolt just fell closed. But maybe 30min later the bolt gave me a good feel again... strange.

2nd: How do you prepare your rifle for Shooting after cleaning the barrel?
I started today with loading N135 & Lapua 155grs Scenars with a light starting load. From that point on I increased the load stepwise by 0.3grs to find the max pressure. Some steps later I encountered my first signs of overpressure, so I moved back by 0.6grs and defined that as max load.
After that I shot my ladder using round-robin style - it worked quite well and gave me some ideas what the rifle likes.. So after maybe 35 shots overall accuracy was decreasing rapidly - because of that I decided to clean the barrel and go on after that..
This is what I did (using a bore guide of course): maybe 20 passes of a bronze brush with shooters choice, then a tight patch with shooters choice on a patch jag and after that a rolled up patch with shooters choice to scrub the bore.
The Patches after that have been clean/white - the barrel was also free of oil.
What happened then shocked me a Little, the first case fired gave me obvious signs of overpressure (bolt markings on the case, also the bolt was very tight to open). I tested again with -0.3 grs and still the same. After taking another 0.3grs away it was okay again. What happened here?
Maybe my problems with ladder testing are caused by the cleaning procedure? Regulary I use oil to conserve the bore for lets say some days and I use grease if I will let the rifle stay a longer time. Before Shooting I use one patch to get it out again. Looks like something is wrong here? How do you do it?

Thanks again,
Stephan
 
Weather on different days affects your loads differently. One day your load is fine the next its over pressure. So if youre a proponent of ladder testing you must do another one on each day if the temp/humidity has changed at all. Now you see why pure accuracy shooters work up loads on the fly and have never heard of round robin except in elementary school. I suspect your load was borderline hot then went over the limit on the next trip
 
I am aware of the weather fact. The overpressure showed today just after cleaning. So weather and humidity should be the same. That's why I asked.
 
You may want to run a patch with a little dab of lock eeze on it after youve dried the bore and chamber completely. Nothing dripping wet just a light film. Evidently your bore was real sticky and held the bullet back after cleaning. Lock eeze is a graphite lock lubricant found at napa. Could be different names at different stores. And be sure you shoot 3-4 shots to foul the bore before you start taking official shots again.
 
Thank you, I will do that! Actually you made me search for "dry firing" a lot and it seems as people do not recommend it. So I will get a tube of Lock-eeze later (local bike stores sell it).

Another thing, I did say that after FL-sizing the cases somehow changed in form after that.
Now today I just entered them in the chamber again to see what happened the last days an I wouldn't believe it, they changed again (this time only a few...).
So some cases on wich the bolt just fell closed are good now. And some good cases have gone bad (too loose or tight).
So this is a problem for me as I can only load on the range while training. I can't do that at matches. Also I need 20 cases for the match and some additional sighters and foulers.. I am going crazy over here - that cases have all just been shot 2 times and they were threated exactly the same.

Can this be because of my sizing procedure? I use a Redding Type-S (not made for mychamber but off the shelf) with a TiN bushing. Also i use imperial sizing die wax.
Maybe I use too much wax? Maybe not enough? I think I do sizing in a repeatable and constant fashion..

Talking about the FL die, it does not feel tight, maybe the body of the case gets a little bit oversized but not much.



Well thinking about the fact that all my cases are sized the same every 10 feel different in the chamber, maybe this gives velocity spread and causes bad results?
Actually it does look like I do know why my ladder tests differ from day to day, even with the same temperature.
Actually I have read a post in this forum where somebody said he loaded some rounds on one day and shot a half of it then and the other half later - this gave him a 60fps spread from the 2 days..

So thinking of that, I am going to chrono every shot the next time.

Does a heat cracked or worn out barrel also show high spreads of velocity?
I am thinking of getting a new one, but I have the same problem on new battrrels so probably this does not help...


P.S. Probably neck tension did also change .. I don't know yet, but I am at a level to believe that right now
 
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Id try some new brass and do some annealing. When sizing only get lube on the body not on the neck or shoulder at all. Very light wax! Your cases are alive.
 
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