Large ES

[cat64]

What factors contribute to large ES vs. small ES. I went this weekend at the range and I choreographed my new loads for a 308 and a 7 mm SAUM. The 308 (Nosler Comp 175g with 43.5 Reloader 15) gave me an SE of 7 but the SAUM (just staring shooting this last week and I am at the first load trial) shot 35 respectively 40 ES (former Berger 180 Hybrid with 56.5 g of IMR 7828 SSC, and later same bullet and powder but only 56.0 grains).
Seating depth for the SAUM was into the lands first time and .010 jumped second time.

 

[Lapua40X]

The single greatest contributor to ES, IMO, is an unreliable chronograph or one that isn't set up properly

 

[chkunz]

The single greatest contributor to ES, IMO, is an unreliable chronograph or one that isn't set up properly

The biggest problem I see with the chronograph is that we have no way to calibrate them or test their accuracy. Yet we see folks that assume that they are good to one foot per second.

 

[cat64]

Well...are we surmising then they are useless? I got good results with the 308 and also feeding the information in the ballistic calculator (going backward if you wish) I was able to hit perfect elevation first shoot at 1000 yards. Must be some valid benefit to using them. I see many accomplished shooters on this site suggest as their preferred method (including during load development) using the chronograph.

 

[chkunz]

Well...are we surmising then they are useless? I got good results with the 308 and also feeding the information in the ballistic calculator (going backward if you wish) I was able to hit perfect alleviation first shoot at 1000 yards.

We depend a lot on knowing muzzle velocity, I am just pointing out a weakness in something that is critical.

 

[cat64]

We depend a lot on knowing muzzle velocity, I am just pointing out a weakness in something that is critical.
[/quote]

I understand. However, I am curious as to what determines such wide margins of discrepancy. I observed consistency between high ES and group consistency. The 308 with small ES was very consistent and grouped while the 7 mm was opening up (mostly windage wise) even at 100 yards (replicated at 1000 yards as well). Can the powder....or lack of finding the right "formula"...contribute to this?

 

[Lapua40X]

The single greatest contributor to ES, IMO, is an unreliable chronograph or one that isn't set up properly

The point I hoped to make is that the first thing to check is the chronograph to make sure it's set up correctly. There are many things (distance to muzzle, sunlight, etc.) that can cause some chronographs to be unreliable. If you're convinced that the chrono is not the problem then it's time to look at your load. Generally speaking, just about every element in the reloading process can contribute to ES issues.
I'm sure you can understand that if the reloader made the effort to go through the routine of preparing bullets for testing they'd waste a lot of reloading supplies while chasing chrono data that may not prove to be reliable.

Seating depth for the SAUM was into the lands first time and .010 jumped second time.

IMO, that's not enough of a spread in seating depth to provide meaningful data.

 

[cat64]

The single greatest contributor to ES, IMO, is an unreliable chronograph or one that isn't set up properly

The point I hoped to make is that the first thing to check is the chronograph to make sure it's set up correctly. There are many things (distance to muzzle, sunlight, etc.) that can cause some chronographs to be unreliable. If you're convinced that the chrono is not the problem then it's time to look at your load. Generally speaking, just about every element in the reloading process can contribute to ES issues.
I'm sure you can understand that if the reloader made the effort to go through the routine of preparing bullets for testing they'd waste a lot of reloading supplies while chasing chrono data that may not prove to be reliable.

Agreed. Thank you. Part of my dilemma stems from not having any "history" with that particular round and thus relying mostly on readings and what others have used with success. I know, the caveat is the famous by now saying...."not any two rifles are the same". I will try next H4350 and H1000 and see what data I can collect. Again thank you.

 

[Chuckhunter]

Cat, I have found that, at least in my experience that two things that greatly affect ES are making sure I have cases with the same or very close to the samee internal volume. That and also trying several different primers. In the case of my .300 SAUM, when I switched from Federal210's to Russian primers my extreme spreads dropped from the mid 20fps to single digets. I also generally speaking get slightly lower spreads being into the rifeling. I guess that would be 3 things. Just food for thought.

 

[Alex Wheeler]

I recently did a test of 6 difference primers, there was a very big difference in es. I have never been able to get the kind of ES that some claim. I have shot 5 shot strings with 0 es, but thats a fluke. I am pretty happy to get down to 10 fps ES consistently.

 

[fgregorio]

Cat 64,
You may find that your .308 might have the barrel on the load node and positively compensated.
Try this simple procedure.
Batch 25 cases of each caliber inside 0.1 gr for the whole batch.
Batch 25 projectiles inside 0.1 grains of each brand that you want to try for each caliber.
I suggest 3 brands per caliber if you want to get serious.
Measure the max oal for each projectile and select a jump between 5 thou and 15 thou.
Prepare the cases. Load 5 sighters. THEN, load the 20 rounds at 0.1 grain increments within the range that you want. Ex round 1-46.1; round 2-46.2 .....; round 20- 48 grains.

Shoot them in order through a chrony and have each poi numbered on the target.

You will find that there will be a spot of 0.4 grains to 0.7 grains that each velocity is very similar. Usually in that load range the hits will also group in elevation. Within the flat range pick the load in the middle.

Now you can interchange between projectiles and know which load to use for max accuracy. And lowest ES
Proof test each load+ projectile that gives you the tightest group.

Word of warning. If you change primer, seating depth you need to repeat the test. And, always combine MV with POI to make a decision.

 

[Dusty Stevens]

Hows it look on paper?

 

[Rustystud]

If the loads are consistent, and the conditions are consistent ES should be close. The worst factor in ES is one you can not see, you have to feel it. That is bores with tight and loose spots in them. Before you have a barrel chambered you should either slug it yourself or have it slugged by your smith.

About 9-10 years ago I was using a "High End" barrel ,maker. I was getting great barrels and my customers were burning up the records. Then all of a sudden I got five dud barrels in a row. I know of six other gunsmiths who ran into the same problem with this barrel maker. I contacted the barrel maker and he assured me there were no issues and he would replace the barrels. My comment was you already screwed me and my customers once, how could I trust him not to screw me again. I replaced all five barrels with another manufactures barrels and all five guns went to shooting in the .2s and .3s. Their ES was down under 9 fps. I later found out that all the "High End" barrel maker's experienced employees (lappers) had quit. Gordy told me to slug the barrels and I did, and all five had multiple tight and loose spots in the bore. Knowing what I know now I probably could have salvaged the barrels by lapping them. Hind site is 20/20.

If you are having and unexplained ES the first two culprit's I look at are tight and loose spots in the barrel. Second I look at the bullets used. I was using one of the most common 6mm bullets and was getting some unexplained flyers. I was running 6-9 fps ES then one round would go 60 FPS ES from the others. It was not OAL, diameter, or weight, it was about 500 of the 3000 bullets had a .030" longer bearing surface.

ES can come out of the woodwork and cause you many headaches.
Nat Lambeth

 

[dbramley]

Nat, where would you recommend buying slugs from. Did a search and didn't come up with much.