Help with getting ES down.

[Sika Slayer]

I have a 7mm Rem mag Sendero. I have been getting nice groups with it at 100 yards but when I run it through a chronograph I haven't been able to get below 30 fps difference over five shots. I am using 162 gr A max's, fifteen thou off the lands. I am neck sizing using a simplex collet die. I have tried a couple of different powders, different charge weights
CCI BR and CCI magnum primers. new and once fired brass.
But nothing I have tried has brought the ES down for me.

 

[brentc]

Retumbo? What do your long range groups look like?

 

[SA1000]

Two of the creedmore I've had did the same thing with A maxs.I switched to berger and got low es.That may have just been my guns but you could try it and see.They grouped ok with the A maxs too.

 

[cowboy]

A lot of chrony's have a + or - % of error of 1%. A rifle shooting 3000 Fps could have an acceptable accuracy range of + or - 30 fps for a total acceptable range of 60 fps. Try to find someone with another chrony - set them back to back and see if it truly is your ammo.
PS: I could care less what a chrony says - stretch your yardage out as far as you can and your target will tell you how much your velocity is varying.

 

[roninflag]

what rifle ? what powder??

 

[J E Custom]

Everyone has there way of reducing SD's And ES's so all I can do is give you what I do in hopes it will work for you.

If I have a weapon that has high SD's I always start with things that are physical and correctible.
First = I prep all of my cases (Size, trim and weight sort them) to make them as consistant as possible.

Then I weigh all of the bullets (Sometimes you will find 1 or 2 grain differences) and sort them by weight to load them in batches.

Now that the brass and bullets are as close to the same as I can get them I look at the primers and powder combinations (Some powders require hotter primers and depending on the volume of powder, sometimes a milder primer will improve SDs) I found this to be the case on my STW. It produced lower velocities with large rifle primers but better SDs than the magnum primers that increased velocities but also increased SDs.

Poor SDs are an indication of a poor combination of components. When you make a change, only make one change at a time so you can see/read the effect it has on the SDs.

I also look for a powder that has a case density near 100% at maximum pressure. Excessive air
space in a case can change the burn rate of powder. Also look for primer seating consistency this can also have an effect on primer performance.(If you have a primer that seats with little or no effort DISCARD IT.

Checking the performance of your chronograph against another is a good idea also.

Unfortunately there is no magic method/formula for improving SD's so just address one thing at a time and you should find a way to get it into the low teens or better yet single digits.

Good Luck

J E CUSTOM

 

[deadidarren]

the best thing i did to get my ES down was buy a magnetospeed

went from 80+ to below 20 , on one rifle a Sendero 7mm rem mag

it is just 13fps now .

 

[FearNoWind]

IMO, there are some very good pointers listed here. JE Custom's plan of action is one that I would endorse whole heartedly.
Depending on the machine, a chronograph's outputs can be misleading. If you're results came from a Magnetospeed or LabRadar I'd have more confidence in the numbers than if they came from one of those that you have to position ten feet in front of the muzzle on a cloudless day.
Assuming your chronograph outputs are accurate, I would guess that your ES is laying out an SD of about 12. For a hunting rifle that's not terrible; not the most desirable, but close to acceptable IMO. Try the routine that JE suggested and I think you'll find you have better performance.

 

[desertbull]

make sure your chrono is out at least 15 feet, 20 would be even better.

 

[Dr. Vette]

If you're results came from a Magnetospeed or LabRadar I'd have more confidence in the numbers than if they came from one of those that you have to position ten feet in front of the muzzle on a cloudless day.

In reality, as already noted, 15 feet away is better, and they perform much better on a CLOUDY day where the sun doesn't mess with them. I've proven this to myself time and time again. Best day is overcast, but early morning before the sun gets above the trees is OK too. Sunshine inflates the speeds and causes more variance in the numbers.

And yes, I have a Magnetospeed but since it does change the group location (and maybe the grouping) I save it for final measurements.

 

[RockZ]

In my 7rem mag with 160AB I'm getting a great ES with Ramshot Magnum.
To find a decent ES I just load at the range until I find the max load then test backwards for a load with an ES of 10 or less. The. I really go to work. Maybe even trying different primers.
Sometimes a certain powder doesn't work with my setup..even though it works in the same caliber in another rifle. If no success with one powder I'll try another suitable powder.

 

[barefooter56]

I have a 7mm Rem mag Sendero. I have been getting nice groups with it at 100 yards but when I run it through a chronograph I haven't been able to get below 30 fps difference over five shots. I am using 162 gr A max's, fifteen thou off the lands. I am neck sizing using a simplex collet die. I have tried a couple of different powders, different charge weights
CCI BR and CCI magnum primers. new and once fired brass.
But nothing I have tried has brought the ES down for me.

Sika Slayer,
The SD is the one you need to pay the most attention too as it affects vertical dispersion. What was the SD on the "good" group you shot? There is a very good article by Jerry Engleman on German Salizars website that puts chronograph testing into perspective as far as what to pay attention to and what not to pay attention too and testing to confirm at distance. Jerry shot PALMA for quite a few years and knows what he is talking about. Very good read.

 

[eshorebwhntr]

PS: I could care less what a chrony says - stretch your yardage out as far as you can and your target will tell you how much your velocity is varying.

Amen. Chronographs are just tools. The reason you care about what they say is because it should reflect what your bullet is doing down range.

Good/Low ES/SD = Minimal vertical stringing at distance

 

[LoneTraveler]

Using a chronograph is just part of the proving of a load. With a good bench and rest set up, I lay a target on the bench and mark the shots by number and velocity. Variables will start showing quickly. Because of barrel twist some slow load bullets will hit low right or Left and fast loads will hit target high and opposite. By keeping a good shot logg on the target will tell you a lot. The biggest variables I have found in ES is Primers, From make to make or lot to lot. The other problem is using powders that leave space in the case for powder to shift around from shot to shot. Good luck in finding the cause.