Wondering if I am Missing Anything

[370bc]

Happy holidays A.S. members!
I have been working on several different loads for my kimber montana that has been glass bedded 243 with a 1-12 douglas barrel with about 300 rounds through it. I am wondering if I am overlooking anything in my load developments.
In general, I do an OCW test for a load combination and I usually find one that is sub MOA @ 100 yards. Several have been half MOA. Most are just over MOA. The experience that I am having is these combinations either do not transfer to the 200 yard range, and mostly they do not stay repetitive in group size. (half MOA).
I am using a concrete bench, wind flags, low wind conditions, 4.5-14 LR Leupold. The trigger is right at 2lbs.
I have had sub MOA's with berger 88 varmint, 70 tnt, and 55 Bal tips, 75 sierra hp. Always keeping barrel cool. Front and rear rests. I have shot 1/4'' groups in the past with other rifles. I know this isn't a AI with a NF scope, but I was hoping for finding a repeatable, half MOA load with my set up.
I just recently segregated brass by weight and neck thickness with no noticeable improvements. Concentricity +/- .003.
Does this sound like operator error or that I have reached my limits?
Thanks everyone!

 

[BoydAllen]

So....what have you done with seating depth, and how do you clean your barrel?

 

[jcampbellsmith]

A structured approach is needed and I've run across the following on another forum:

Start by making sure every screw is tight, the crown looks good, etc. and then proceed as follows:

Deep clean the barrel to remove any fouling, clean the bolt and lug recess..and test fire a group
Check with someone else pulling the trigger..and test fire a group
Check a number of different factory loads..and test fire a group for each
Remove the stock, check if anything has altered with the stock (barrel touching, bedding, crap between action and stock) reinstall stock..and test fire a group

Check a different moderator..and test fire a group
Check a different scope..and test fire a group
Once you've eliminated all these variables get a reputable gunsmith to check the barrel with a borescope.
Sell it.

Regards

JCS

 

[370bc]

cleaning after 25- 30 shots with wipeout.
I do have another scope to try. My 4.5-14 does not have thin crosshairs (boone & crockett ). The 6.5- 20 does.
I check for parallax with the side focus. (Im a bell AO man).
I have only done moderate depth checking, (88 bergers ), the 55's and 70's are too far from rifling.
Great ideas.

 

[bheadboy]

+1 on the above,

add, I would take a carefull look at the bullet jump, take a starting point of say .020 then try a ladder test with one powder and primer combo.

repeat with another powder,

if any powder begins to tighten, then adjust the jump by .05 up and down and see what happens

also, in the sizing operation, check to see if you are pushing the case sholder back more than .003, that is enough.

Bob

 

[370bc]

I am setting shoulder back no more than .002 w type s bushing style full sizing die.

 

[370bc]

My best groups are with the 70 TNT and 55 bal tip. Seating depth still matters even tho I'm 600 miles from the lands? I have not done a complete seating depth check.

 

[BoydAllen]

One of the great experimenters in short range benchrest, Jerry Hensler, now working in rimfire exclusively, gave me some invaluable information that I will try to pass on, without messing it up too much. Just like there are powder nodes, there are seating depth nodes, both in and out of the rifling. If you think about that a bit, I think that a bulb will come on. In the Burger manual, and I think mentioned in posts on the internet, is a method for working up jump seating depth with VLDs. It is worth be coming familiar with. I think that the jump seating depth nodes are about the timing of the bullet's passing through the crown so that the motion of the muzzle has it in the most favorable position. If you are going to jump, Also, I think that concentricity and neck tension uniformity are more important than if you are seating into the rifling.

 

[Tim Singleton]

i haven't had good luck with the OCW approach.

This is my opinion only and what works in my equipment.
Seating depth is a very critical part of load development for accuracy. Developing a load based on seating depth and charge has given the best results for me

I would find the lands with a dummy round. Then do testing from just touching going into the lands .005 at a time for hunting rifles and .003 at a time for target barrels
If the bullet design prefers a jump follow the same as above but come off the lands .005 at a time
Load the above in a middle weight powder charge and the same test in a upper powder charge window.

IMO, the best potential of a barrel can't be found without finding the seating depth it likes for the particular bullet being used

 

[Tim Singleton]

The Berger FB 80gr is a great bullet for a 12 twist

 

[CJ6]

Start from scratch....CLEAN IT, Recheck EVERY bolt and screw for tightness. Prep your brass (clean/trim, uniform the pockets, weight-volume sort (get 10 cases as close in weight- volume as possible)use these cases throughout testing, anneal them. With the loads you currently have used (I'd start with the heaviest bullet) change 1 and ONLY 1 thing at a time (eg. seating depth), then do a ladder test with the powder charge, then primer test. Make sure your rifle "rests" in the same spot (RTB) for each shot, pay attention to what and where pressure is applied to the stock when shooting (keep it consistant).

 

[370bc]

I have tried the 80 berger and had success. The BC of the 88 is a deal breaker for me tho. Yotes in the flatlands of Il are closer to 300 yards than 200. I haven't done a fair test with seating depth for any of the bullets I have tried.
I have changed depths, just not as detailed as berger suggests to test.
I measured my TNT's to the lands. It measures 2.970''. If I measure the amount into the neck, it is .166''.
That is .77'' away from the standard suggested depth of diameter of bullet which is .243''. Am I correct with this .243'' at least into case?

 

[370bc]

Will do.

 

[Tim Singleton]

I have tried the 80 berger and had success. The BC of the 88 is a deal breaker for me tho. Yotes in the flatlands of Il are closer to 300 yards than 200. I haven't done a fair test with seating depth for any of the bullets I have tried.
I have changed depths, just not as detailed as berger suggests to test.
I measured my TNT's to the lands. It measures 2.970''. If I measure the amount into the neck, it is .166''.
That is .77'' away from the standard suggested depth of diameter of bullet which is .243''. Am I correct with this .243'' at least into case?

I know that seems to be the rule of thumb. A bullet diameter length in the case. I've heard it a lot don't know where it comes from

My ppc neck is .280" long and with my .045 freebore and 66 gr fb bullets are about half way down the neck maybe a little more
It shoots great there
You won't know with out trying new things, IMO .166" in the case is plenty
Having the 70 gr flat base bullet touching the lands.then finding the depth the barrel likes is way more important for accuracy than maintaining some figure of case engagement

Try it and see

 

[CJ6]

In a magazine fed rifle .166 (bullet in neck) may/may not be enough to hold the bullet properly , single feed ok, just not sure with the magazine feed.

 

[Brians356]

I check for parallax with the side focus. (Im a bell AO man).

Not sure what you mean - does the scope have side or AO focus?

How are you checking for parallax error?

 

[CatShooter]

The rig you have should not be giving you this much of a headachee.

Is the glass bedding original from Montana, or did you (or someone else) do it. Last year I bought a 22-250, $1,200 rifle with less than 200 rounds through it for $500, because "... it had a bad barrel" and shot 3"+ groups. The best I got was 2.5", until I pulled it apart.
It turned out that the glass bedding was badly done... rebedded, it really shoots 0.3" to .4" groups, same everything else.

Parallax is high on the suspect list, especially with side focus scopes - make sure that you always adjust the parallax by turning the side focus knob from the infinity end, and if you overshoot it, start again from the infinity end.

It has to do with spindles and forks. Read this for why:

http://www.snipercountry.com/Articles/Parallax.asp

Don't try to change so many variables - pick one bullet (the TNT has a solid reputation), and a good powder, like H-4350, and work with that.

The 243 is a fairly accurate cartridge and the Montana is a good rifle, but this is not benchrest rig, so don't waste time with techniques that are for trimming the last 0.005" from groups.

You did not mention what brass and what dies you are using - those are important.

I am not a fan of OCW - more often than not, it can send you off on wild goose chases.

 

[Brians356]

... make sure that you always adjust the parallax by turning the side focus knob from the infinity end, and if you overshoot it, start again from the infinity end.

Also, make sure you adjust parallax, not focus. "Target focus" and "parallax error" are separate and independent variables.

 

[CatShooter]

... make sure that you always adjust the parallax by turning the side focus knob from the infinity end, and if you overshoot it, start again from the infinity end.

Also, make sure you adjust parallax, not focus. "Target focus" and "parallax error" are separate and independent variables.

"Target focus", and "Parallax" are two different names for the very same thing. It is only one adjustment, either on the objective or on the left side of the turret.

 

[Brians356]

"Target focus", and "Parallax" are two different names for the very same thing.

Not true. They are separate and independent.

It is only one adjustment, either on the objective or on the left side of the turret.

That's true only after the objective and ocular (eyepiece) have both been focused precisely on the reticle plane. But more often than not, if someone (not you, of course, CatShooter!) simply focuses the target image, there will still be parallax error. I invite all who read this to go out and test that for themselves.

Parallax error is zero only when the target image is focused on the fixed reticle plane. When this has been accomplished, there will be no apparent motion of the reticle on the target image when the eye is moved around behind the ocular lens. You cannot and should not rely on target image focus to check for parallax error, because if the ocular (eyepiece) is not also focused on the reticle plane, the target image will still appear out of focus. Under this condition, if you do adjust the objective for sharpest target focus, the target will no longer be focused on the reticle plane, and you will have reintroduced parallax error.

The only condition under which parallax error will be zero and target image sharp is when both objective and ocular have been focused on the reticle plane.

The easiest way to adjust for both zero parallax error and sharp target focus is to (making no assumptions about the scope's adjustments whatsoever):

1. Adjust objective (side focus or AO) for zero parallax error (no apparent reticle movement on target - ignoring target focus.)

2. Adjust ocular eyepiece for sharpest target focus (and, coincidentally, reticle focus - since they are now in the same plane).

Note: Once you get the eyepiece thus focused on the reticle plane, and locked, thereafter focusing the target image for sharpness should also minimize parallax error, but I never trust that on the bench when testing accuracy - I always move my eye around behind the ocular to make damned sure there is no parallax error.