So I've been able to nail some single digit SD's here recently but the lowest SD doesn't always produce the tightest groups. If that's the case, what can I look at in my loading technique to improve the group size? Is SD simply an indication of precise powder charge and primer depth? Does neck tension primarily affect group size?
SD vs group size
- Thread starter Ape_Factory
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I have a bit. I haven't wanted to get too far down the rabbit hole but figured neck tension/crimping may have more of an overall effect vs. seating depth.
I've tested two loads, same everything except for the charge, and sometimes the higher SD will have the smaller group. Have to go back and look at my notes but testing Sierra TMK69's in 223, I had one SD around 9 and the other was 4.6. The SD9 group was smaller.
I've tested two loads, same everything except for the charge, and sometimes the higher SD will have the smaller group. Have to go back and look at my notes but testing Sierra TMK69's in 223, I had one SD around 9 and the other was 4.6. The SD9 group was smaller.
Velocity SD's (like velocity ES's) only tell you how well you're doing with your loading (including neck tension issues, like consistency in the tension) and really says little about group size as there are so many other factors involved with group size.
Some things to look at to improve group size:
Harmonics: fiddle with seating depth, mount a tuner and set it for your barrel's harmonics, experiment with different ways of holding your gun as that too can affect harmonics
Wind Reading: use flags when practicing, learn to read wind from the surrounding vegetation, learn to read wind off of mirage (if that's ever an issue)
Shooting Mechanics: work on trigger pull, "drive" the shots, check proper site view, etc.
Check Equipment: make sure things like sights, scope, rail, barrel, action screws etc. are all tight and torqued to proper specs.
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Ok so I should stick with the loads that produce the best SD regardless and work on other variables to lower the group size?
In terms of barrel harmonics, both my current rifles are AR's, 16" barrels. Not sure how much my grip affects harmonics. I do use a cheap bipod and I think that's my weakest link as I can't load it by pushing forward as the feet just slide on the wood shooting table. My left hand is wrapped around and on the bean bag at the rear. Trigger technique is something I definitely had to learn and I've been working hard at it.
I have achieved very small groups at 100 yards in the past with varying loads and off the shelf ammo, under a mil, so it sort of surprises me when I see say a set of five rounds at a certain charge produce a tighter group despite having a higher SD. I usually know when it's "me" vs another variable.
It was quite windy out there and the targets were bouncing around but still not enough to really throw off the group size, IMO. Plus I was only shooting 100 yards.
Funny you should mention equipment. Today I discovered my 308 had "loosened" the scope mount rings and I have a feeling it's why some of my loads haven't been grouping as tightly in the past. Never had that happen before but I haven't been using loctite on any of my scope mount rings. That's about to change.
I'll keep at it, appreciate the feedback!
In terms of barrel harmonics, both my current rifles are AR's, 16" barrels. Not sure how much my grip affects harmonics. I do use a cheap bipod and I think that's my weakest link as I can't load it by pushing forward as the feet just slide on the wood shooting table. My left hand is wrapped around and on the bean bag at the rear. Trigger technique is something I definitely had to learn and I've been working hard at it.
I have achieved very small groups at 100 yards in the past with varying loads and off the shelf ammo, under a mil, so it sort of surprises me when I see say a set of five rounds at a certain charge produce a tighter group despite having a higher SD. I usually know when it's "me" vs another variable.
It was quite windy out there and the targets were bouncing around but still not enough to really throw off the group size, IMO. Plus I was only shooting 100 yards.
Funny you should mention equipment. Today I discovered my 308 had "loosened" the scope mount rings and I have a feeling it's why some of my loads haven't been grouping as tightly in the past. Never had that happen before but I haven't been using loctite on any of my scope mount rings. That's about to change.
I'll keep at it, appreciate the feedback!
When it comes to group size, SD's just don't tell you much of anything. So, in terms of group sizes, ignore SD's (but not with regard to your reloading). In fact, ES's are more important than the SD's and unless ES's are really bad, they're not going to show much at 100 yds (unless your shooting something like a .22LR
).The effects from a grip depends on how one grips it. Everything touching the rifle affects the harmonics to some degree. Things touching the barrel or mounted on the barrel has the most effect. The pressure you put on the butt to load your bipod effects harmonic and so you need to be very consistent with that . . . the same goes for your cheek weld pressure (not just position).
Harmonics is a bigger issue than SD. One can have cartridges that produce somewhat high SD's, yet the load is more in line with the harmonics resulting in better groups . . . especially at only 100 yds. With off the shelf ammo, it's a crapshoot.
Even at 100 yds, a mild wind an make a significant difference, depending on group sizes one typically gets . . . and a lot depending on its direction (like I hate wind at my back).
I've never used loctite and from problems I've heard from several people who've done so, I'd not recommend it. The problem I've heard reported were often due to inability to remove the screw or breaking the head of the screw off . . . and we're talking about Loctite Blue. Torquing them down properly and checking them once in a great while when cleaning the gun is what I find the safer way to go.
Anyway . . . good luck and good shooting.
Not really
For ammo for short range shooting ES means very little.
If your regularly shooting 1000 yards and beyond it really starts to matter.
My favorite AR load has terrible ES but it doesn’t matter at the ranges I shoot it at.
what's your standard loading practice? or steps involved?
We are assuming a gas gun, right?
if your loading is good, and powder measuring is good, then play with seating depth.
seating depth changes can change Optimal barrel time (or whatever) a little and really make a load become more consistent in SD/ES.
shoot an OCW then play with seating depth as needed.
We are assuming a gas gun, right?
if your loading is good, and powder measuring is good, then play with seating depth.
seating depth changes can change Optimal barrel time (or whatever) a little and really make a load become more consistent in SD/ES.
shoot an OCW then play with seating depth as needed.
I keep seeing people say “play with your seating depth” or “then I fiddle with my seating depth”.
Is there a set procedure that you are recommending, by omission?
I start .020" off the lands. I determine this distance using the Sinclair Seating Depth tool.
Others use the Hornady or Stoney Creek tool, but this method requires the use of a modified case, which is essentially a fired case with a threaded hole where the primer pocket is.
The Hornady tool requires the modified case for each caliber, whereas I bought one Sinclair tool and can use it for pretty much every caliber I load for.
There are other methods, but I've found these to be the easiest for me.
Using one of these methods, I determine how far I can seat a bullet in a case while the bullet is touching the rifling in the barrel. This is called the distance to lands.
I start seating bullets .020" off the lands.
ill then load up five rounds at this length, all the same charge weight.
Then, I'll load five seated .040 off, five at .060" off and five at .080" off.
Fire all the rounds and see which seating depth was noticably smaller in size. Then load five more at that seating depth and confirm that it does shrink the group size and that it wasn't just a fluke.
Now, other guys may load in .010" increments, some at .005" increments, and some at .003" increments.
This is just what I've found works for me. And quite honestly, since I've started buying custom barrels, more often than not, .020" off has worked well enough and I don't waste time and money to find something better.
Here are links to the tools referenced in my post.
Sinclair:
www.sinclairintl.com
Hornady:
www.midwayusa.com
Note that Hornady makes two, a straight and a curved. The straight is for bolt action rifles, and the curved is for semi autos.
Sinclair:
All SINCLAIR INTERNATIONAL Products for Sale Online - 236 Products
Brownells has 236 SINCLAIR INTERNATIONAL products for Sale Up To 91% Off including Reloading, Tools & Cleaning, and Gear.
www.sinclairintl.com
Hornady:
Hornady Lock-N-Load Overall Length Ga Bolt Action
The Hornady Lock-N-Load Overall Length Gauge is one of the best kept secrets to accurate reloading. This tool allows reloaders to quickly and easily...
www.midwayusa.com
Note that Hornady makes two, a straight and a curved. The straight is for bolt action rifles, and the curved is for semi autos.
Nice, I will note that. I have used Bergers seating depth instructions with good results on Berger bullets but I always wonder if people have other ways. I will try this when working up my 6.5 cm with Hornady 140s
In a gasser I test at mag length to find the powder load.
So for 223 it would be 2.260
Then for seating depth I'll go .005 shorter to .255, .250, and .245.
With say the 77gr smk the group wont change much but the sd/es will show more stable somewhere along that range.
At least that's what I've found, milage of course varies.
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