Weighing .17 WSM for accuracy improvement
I saw in an earlier post that one fellow had weighed his .17 WSM ammo and sorted it by weight as a method to improve accuracy of groups. Being from the reloading world, that seemed to be a plausible method of getting tighter groups. I wondered if the variation was in the bullet/propellant or the case? Figure the hardest component to get consistent is the propellent, right?? I know that to be true with reloading but also know that cases do, sometimes vary in weight. With that in mind, I have decided to conduct a bit of an experiment and invite others to join in. My plan is to weigh and sort each unfired cartridge and to shoot them for groups on a clear, calm (no wind) day. I am looking to compare the accuracy results to my earlier groups at 100yds and 200yds. Following the range session, I plan to weigh the empty brass to see how much the brass cases vary alone. Yeah I know that there will be some residue in them but whatever.
If I can find some more ammo, I will also fire some groups without weighing them for comparison, but at present, ammo is still in too short supply for me to do that. So, will have to just compare to the early groups and look for measurable improvements or not.
So far, I have weighed one box of 49 rds. Here are the results in grams:
4.345g = 1
4.350g = 4
4.355g = 6
4.360g = 8
4.365g = 17
4.370g = 8
4.375g = 5
I also hope to see if my split cases are coming from any specific group of rounds. i.e. Are only the heavy cartridges splitting? or not? Am making the current assumption that the heavy cartridges will be the ones with the most propellant. Weight of the once fired brass should help to confirm this. Will note the weights of all the split cases since they may lose some weight when fired if pieces fly off. My experience with quality ballistic tips is that bullet weights are very consistent and variation is less than my scales would measure with rare exceptions. Wish us luck. I will post the results good, bad or ugly.
:cool:
Irish
Weighing bullets to improve accuracy
Well, I finally had time to go to the range this evening to test fire the cartridges that I weighed and sorted into groups which weighted the same. The results were better and worse. Here is what I recorded:
.17 WSM 25g ballistic tip ammo
The gun did post its best group ever for me at 100yds. This was a three shot group of 0.687", which was recorded shooting some of the heaviest cartridges (more on this later). Of the five total groups fired, four of them were worse than my best 100yd group of 1.010" which was recorded earlier shooting random cartridges from the box. In fact three of the groups fired at 100yds were worse than my best group recorded earlier at 200yds, which was 1.410".
From what I see the cartridge weight variance is NOT all from variance in powder charge. I weighed the fired brass and with exception of the heaviest group which were all identical, and which fired the best group, all of the others varied from 0-0.015grams. Some of my groups resulted in two shots that were touching or nearly so, with one that was way off lower, by as much as 1-2 inches (presumably due to a light powder charge and heavy brass case). So weighing the rounds can and will generate a few improved groups but will also potentially result in many groups that are worse than they might have been. There is no way to tell if a round's weight varies due to heavy or light powder charge or heavy/light brass casings until you fire them. Even my best group which had brass that was all identical, exhibited vertical stringing which is likely due to velocity variance (pic below). Again, with only five groups fired, it is only interesting observations from limited data as this stage. But I could not have asked for more ideal conditions to fired accurate groups today. Temps were in the mid 70's and zero wind and I had the range all to myself. So, no distractions.
As a comparison, I fired four groups with my Remington 700 varmint in .223 just for grins and three of them were sub MOA. In fact all three were <1/2 inch at 100yds with the best being 0.333" center to center. The one bad group was 1.125" stringing vertically and was fired with Black Hills 55g FMJ, which is not exactly match grade ammo. The vertical string implies velocity variance. The two best groups were recorded with old hand loads from the Dillon using Nosler 55g ballistic tips. My point is??? Both the shooter and the B-mag are capable of printing some decent groups when supplied with decent precision ammo. But weighing the ammo is not likely going to be the answer until somebody makes .17 WSM ammo with better manufacturing tolerances in at least the brass if not also the powder charges.
Irish
http://img.photobucket.com/albums/v3...WSMphoto-1.jpg
Weighing bullets to improve accuracy
Quote:
Originally Posted by
plinkin
I really haven't said anything until now but I don't see how weighing them in grams is going to really help. since there is approx 15.45 grains per gram and I was getting a .6 grain spread on the 25gr ammo and 1.3 grain spread on the 20gr ammo and I noted POI and velocity change with the 25gr I tested.
Just saying.
Plinkin, your point is well taken. I am not sure that it matters either. My scales can weigh in both grains (to a 1/10th) or grams (to 0.001g). I sort of arbitrarily selected grams. I doubt that it matters that much. Plus, from what I have seen so far, we might be better off not weighing them at all. I see little benefit in obtaining four or five tightly spaced shots only to then get a huge flyer since there is no way to predict when the flyer will occur. Yes, we will obtain on occasion some impressive groups under controlled conditions but the more shots included in a group, the greater the odds of getting the flyer to spoil the group. Anybody who shoots a tight 10 shot group using weighed ammo is a lucky dog for sure. If my math is right 1/10grain = about 0.006 gram. Since the readout on my scale measures down to the nearest one-thounsandth of a gram, it seemed to be a more precise measurement, but I doubt that everyone's scale is the same as mine. And, regardless of the scales or the units of measure, the variance is not all from powder charge variations so, it is not going to work in my opinion. I do plan to try it some more, just for grins to see if overall average groups do improve and break out my chrono to get more data but my optimism is not so high anymore.
As you work on this, if you find results that counter my opinions expressed here, I would love to hear about them as my gross lack of ammo is still hampering my fun so far.
Irish
