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Ladder Test Results...need help analyzing.

 
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  #8  
Old 10-07-2012, 01:20 AM
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Re: Ladder Test Results...need help analyzing.

Quote:
Originally Posted by Mikecr View Post
I just don't see anything useful there.
Why are the increasing charge impacts falling lower & lower?
I'm thinking maybe the order of the cartridges were reversed?
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  #9  
Old 10-07-2012, 08:07 AM
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Re: Ladder Test Results...need help analyzing.

They weren't. I can see how that seems possible, but unless my wife or nefarious two year old "helped" me by resorting, I loaded them with increasing charges and they went into the ammo box as I loaded them.

I will probably try other powders and/or bullets before setting my load on the minimum charge of H4350. There's a lot of empty space in there and while accuracy is paramount, the velocity I'm expecting to see from that charge isn't going to give me the energy to make this a viable load for deer beyond 500 yards.

I'm optimistic about finding something that will get the Bergers into the 2850-2950 velocity. I'm getting 2900 out of a 20" tube with 129s, seems reasonless to get around that with 4 extra inches of barrel and being able to seat the bullets significantly farther out.

2500 fps with the Berger 140s limits me to 550 yards to stay about 1800 fps and 1000 ft lbs.
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  #10  
Old 10-07-2012, 08:36 AM
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Re: Ladder Test Results...need help analyzing.

Never seen it upside-down. Did you keep barrel temps stable?
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  #11  
Old 10-07-2012, 10:08 AM
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Re: Ladder Test Results...need help analyzing.

Quote:
Originally Posted by Mikecr View Post
Never seen it upside-down. Did you keep barrel temps stable?

I would like to see the answer to this. I also often see increasing charges go down on paper instead of up. Doesn't make sense to me.
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  #12  
Old 10-07-2012, 10:44 AM
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Re: Ladder Test Results...need help analyzing.

It's common in ladder testing for SOME higher charge shots to impact lower by region.
Same with varying horizontal.
But not all & with such a strong trend right down the targets..

So I don't believe much of the results shown so far.
IMO, there are other factors invalidating this test.
Maybe bad primer striking, bad seating choice, varying barrel or powder temps, bad scope, bad rest/hold, big headspace variance, big neck tension variance, questionable organization.

Some things just need to be taken care of before benefiting from ladder testing.
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  #13  
Old 10-07-2012, 11:02 AM
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Re: Ladder Test Results...need help analyzing.

I use a modified ladder test in developing my loads. Testing via the ladder approach can use up a lot of bullets and barrel life. So I use Kirby Allen's method, then follow up with short ladder to confirm results.

Kirby Allen, a well-respected gunsmith on this site, develops his loads by finding the max powder charge where max velocity/pressure is achieved - usually exhibited by a slightly sticky bolt lift. He then back off two grains - and that is his load. This method has its share of critics, but I have found that in shooting a ladder test there is a node near the top or peak of the pressure curve.

So that is what I do. I load up a single round with a specific charge and then load subsequent rounds with a 1 grain incremental increase. When the bolt lift gets sticky, I stop. I then back off two grains and the load up enough rounds for a short ladder test. For example, if max load is 65 grains, then I back off to 63 grains. I then load a ladder test in .3 grain increments starting at 61.5 on up to 64.5. I almost always find a node somewhere within this spread.

I have found this method saves both time and money. To each his own.
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  #14  
Old 10-07-2012, 04:50 PM
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Re: Ladder Test Results...need help analyzing.

Quote:
Originally Posted by Mikecr View Post
Never seen it upside-down. Did you keep barrel temps stable?
Yup, and the bore wasn't shinny clean when the ladder was started. And I gave 2-4 minutes between shots so the barrel wasn't anything more than barely warm to the touch.

Quote:
Originally Posted by Mikecr View Post
IMO, there are other factors invalidating this test.
Maybe bad primer striking, bad seating choice, varying barrel or powder temps, bad scope, bad rest/hold, big headspace variance, big neck tension variance, questionable organization.

Some things just need to be taken care of before benefiting from ladder testing.
Let's discuss those things that need to be taken care of:

Savage Model 10 Predator Hunter with the action properly torqued using a FAT wrench into an aluminum bedding block. Barrel is a 24", probably varmint weight, fluted, 1:8 twist.

EGW base was torqued to 15 in lbs.

IOR V-TAC steel rings torqued to 65 in lbs to the base.

Rings were torqued to hold the scope at 12 in lbs and done in a rotating order from completely loose to tension, to torque spec.

Action was leveled from the Picatinny rail. Scope is a Vortex Viper PST FFP 6-24x50 EBR-1 MRAD and was leveled using a plumb line.

Front and rear rest were used.

I don't think there's anything missing on the rifle.

As far as the loads...all trimmed to the same length. All charges weighed on a digital scale to the 1/10th of a grain and measured twice if the pan didn't return to 0.0 on the scale after charging the case.

Bullets are Berger Hunting VLDs, loaded to 0.001 off the lands after measuring with a bullet comparator.

Bullets were seated using a Forster Ultra Micrometer seating die and were measured after seating to confirm seating depth of 0.001 off the lands.

Not a single issue from the primers, CCI BR2s, and the pockets were cleaned and flash holes inspected before loading.

Rifle was purchased used with less than 300 rounds through the tube and I have pictures of groups the rifle shot with other bullets (AMAX, which I don't want to use for deer) and it was used to ring steel plates out to 700 yards.

The rifle isn't the issue. I know it's just a Marine Corps rifle range, but I've shot expert 4 years in a row and never shot anything else.

I have another 260 that I put a 0.174" group together with, a factory Model Seven that only had a trigger job done.

No, I'm not a competitor or professional, but I know I can shoot, especially off a rest, at 300 yards.

Quote:
Originally Posted by azsugarbear View Post
I use a modified ladder test in developing my loads. Testing via the ladder approach can use up a lot of bullets and barrel life. So I use Kirby Allen's method, then follow up with short ladder to confirm results.

Kirby Allen, a well-respected gunsmith on this site, develops his loads by finding the max powder charge where max velocity/pressure is achieved - usually exhibited by a slightly sticky bolt lift. He then back off two grains - and that is his load. This method has its share of critics, but I have found that in shooting a ladder test there is a node near the top or peak of the pressure curve.

So that is what I do. I load up a single round with a specific charge and then load subsequent rounds with a 1 grain incremental increase. When the bolt lift gets sticky, I stop. I then back off two grains and the load up enough rounds for a short ladder test. For example, if max load is 65 grains, then I back off to 63 grains. I then load a ladder test in .3 grain increments starting at 61.5 on up to 64.5. I almost always find a node somewhere within this spread.

I have found this method saves both time and money. To each his own.
That's where I'd like to find a node for accuracy and the most velocity...I supposed everyone wants that.
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