220 swift round test results. Opinions needed

Ccctennis · December 27, 2014, 01:13 PM

I did my first big load development test this week with my 220-swift. I used a round robin system that I read lots of reloaders use. I need help deciphering some of the results. Here are the powder charges and group size:
Powder varget. Bullet hornady a-max 40 grain. 100 yard test. .4 increments.

36.8 gr. .6 inch
37.2 gr. 1.0 inch
37.6 gr. .75 inch
38.0 gr. .9 inch
38.4 gr. 1.5 inch
38.8 gr. .5 inch
39.2 gr. 1.0 inch
39.6 gr. 1.4 inch
40.0 gr. 2.0 inch
40.4 gr. 2.0 inch
Some questions I have regarding the test.
1. What is the next step in continued testing loads?
2. What do the up and down sizes really mean? Does it mean with barrel harmonics that my rifle shoots better with lighter powder charge and a heavier one. 36.8 and 38.8?
3. Do I take the best two or three weights and shoot more or do I tinker with coal?

Roughedge · December 27, 2014, 01:34 PM

If the 38.8 is consistent I would stick with that unless you are going for one hole groups. I have some 220 brass I no longer need if you pay shipping its yours if you pm me.

Bart B. · December 27, 2014, 04:12 PM

How many rounds per group did you shoot?

Those in the 37 to 38 whole grain spreads may well be equally accurate if you shot 20 to 30 rounds in a single group. There's typically a 5% spread in charge weight that will shoot equally accurate in most barrels when tested the traditional way shooting a hand held rifle atop a bench. Human variables play a big part in the accuracy one gets.

It's obvious that the heavier ones didn't fare as well as the lighter ones.

Shoot 15 shots with a 37 grain charge then 15 more with a 38 grain charge. If one's at least 10% bigger than the other, that's the one that's probably least accurate. Otherwise, accuracy's the same for both charge weights for all practical purposes.

603Country · December 27, 2014, 04:25 PM

When you get finished doing it Bart's way, I'd give that 38.8 gr load a good workout to see if it's consistent.

And, if you have any IMR 4064, try it. That has long been a winner in the 220, and that's what I have used for years, though lately R15 gets a lot of praise.

pathdoc · December 27, 2014, 07:55 PM

The aim with these systems is to find a range of charge weights within which your group size is acceptable for your purposes AND the point of impact doesn't change much between charge weights. If you can find three adjacent charge weights that do that, you pick the middle weight and can be confident that variations (either in charge weight or in ambient temperature) won't upset your applecart on the day.

Your 0.5 inch group is great, but ask yourself what happens 0.4 grains either side; the groups grow quite substantially. On the other hand, if you could go 0.2 grains either side of that and not get much change in POI or group size, you would be on to a really, really good thing.

In your shoes, and without being able to see what the changes in point of impact were like, I'd be playing with 0.2 grain intervals between 38.6 grains and 40 grains to see whether the small group was a fluke and what happens in the immediate neighbourhood. The 38.4 grain group looks like an outlier; everything else below 39 grains is sub MOA, and you might want to re-shoot that one. Above 39.2 looks like a waste of time.

boondocker385 · December 28, 2014, 01:21 AM

I too would go down to .2 increments. I will second the use of 4064 if you aren't happy with varget.

FrankenMauser · December 28, 2014, 03:21 AM

If you used 3-shot groups, I would retest the charge weights around 38.6 gr with at least 5-shot groups (10 would be better), in 0.2 gr increments. To me, that looks like the butter zone, with the 38.4 group being a fluke (operator error - we all do it

).

If you used 5-shot groups, or better, I would try a different powder or seating depth.

In my experience, powders in the Varget burn rate aren't too great for the Swift. I had better luck with powders that were a little slower. ...Or a lot slower - my best loads used Winchester 780 Supreme.
I don't know what you're using, but I also had a 26" barrel to make the most of the slower powders.

Bart B. · December 28, 2014, 04:15 PM

If you shoot five more groups with the 38.8-gr. load and they're .5" groups or less, it's the best. Otherwise, the biggest group best reflects that loads accuracy.

Saint Dennis · December 28, 2014, 10:56 PM

Re-read the directions on the test. It is not group size necessarily but a common point of impact on adjacent charge weights. When you find the best three, choose the middle one and play with seating depth and maybe slide up and down half a grain to find the one that groups the best in your rifle. The common POI is the point of the test, not so much small group size. One three, or even 5 shot group does not tell you that much. Too many variables and luck involved.

December 27, 2014, 01:13 PM	#1
Ccctennis Member Join Date: April 22, 2013 Posts: 65	220 swift round test results. Opinions needed I did my first big load development test this week with my 220-swift. I used a round robin system that I read lots of reloaders use. I need help deciphering some of the results. Here are the powder charges and group size: Powder varget. Bullet hornady a-max 40 grain. 100 yard test. .4 increments. 36.8 gr. .6 inch 37.2 gr. 1.0 inch 37.6 gr. .75 inch 38.0 gr. .9 inch 38.4 gr. 1.5 inch 38.8 gr. .5 inch 39.2 gr. 1.0 inch 39.6 gr. 1.4 inch 40.0 gr. 2.0 inch 40.4 gr. 2.0 inch Some questions I have regarding the test. 1. What is the next step in continued testing loads? 2. What do the up and down sizes really mean? Does it mean with barrel harmonics that my rifle shoots better with lighter powder charge and a heavier one. 36.8 and 38.8? 3. Do I take the best two or three weights and shoot more or do I tinker with coal?

December 27, 2014, 01:34 PM	#2
Roughedge Senior Member Join Date: January 24, 2011 Location: Monroe,NC Posts: 669	If the 38.8 is consistent I would stick with that unless you are going for one hole groups. I have some 220 brass I no longer need if you pay shipping its yours if you pm me. __________________ The man that die's with the most stuff win's!

December 28, 2014, 03:21 AM	#7
FrankenMauser Senior Member Join Date: August 26, 2008 Location: In the valley above the plain Posts: 13,774	If you used 3-shot groups, I would retest the charge weights around 38.6 gr with at least 5-shot groups (10 would be better), in 0.2 gr increments. To me, that looks like the butter zone, with the 38.4 group being a fluke (operator error - we all do it ). If you used 5-shot groups, or better, I would try a different powder or seating depth. In my experience, powders in the Varget burn rate aren't too great for the Swift. I had better luck with powders that were a little slower. ...Or a lot slower - my best loads used Winchester 780 Supreme. I don't know what you're using, but I also had a 26" barrel to make the most of the slower powders. __________________ -Unwilling Range Officer -Unwilling Match Designer -NRL22/PRS22/PRO -Something about broccoli and carrots

December 27, 2014, 04:12 PM	#3
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	How many rounds per group did you shoot? Those in the 37 to 38 whole grain spreads may well be equally accurate if you shot 20 to 30 rounds in a single group. There's typically a 5% spread in charge weight that will shoot equally accurate in most barrels when tested the traditional way shooting a hand held rifle atop a bench. Human variables play a big part in the accuracy one gets. It's obvious that the heavier ones didn't fare as well as the lighter ones. Shoot 15 shots with a 37 grain charge then 15 more with a 38 grain charge. If one's at least 10% bigger than the other, that's the one that's probably least accurate. Otherwise, accuracy's the same for both charge weights for all practical purposes.

December 27, 2014, 04:25 PM	#4
603Country Senior Member Join Date: January 6, 2011 Location: Thornton, Texas Posts: 4,039	When you get finished doing it Bart's way, I'd give that 38.8 gr load a good workout to see if it's consistent. And, if you have any IMR 4064, try it. That has long been a winner in the 220, and that's what I have used for years, though lately R15 gets a lot of praise.

December 27, 2014, 07:55 PM	#5
pathdoc Senior Member Join Date: February 12, 2013 Posts: 669	The aim with these systems is to find a range of charge weights within which your group size is acceptable for your purposes AND the point of impact doesn't change much between charge weights. If you can find three adjacent charge weights that do that, you pick the middle weight and can be confident that variations (either in charge weight or in ambient temperature) won't upset your applecart on the day. Your 0.5 inch group is great, but ask yourself what happens 0.4 grains either side; the groups grow quite substantially. On the other hand, if you could go 0.2 grains either side of that and not get much change in POI or group size, you would be on to a really, really good thing. In your shoes, and without being able to see what the changes in point of impact were like, I'd be playing with 0.2 grain intervals between 38.6 grains and 40 grains to see whether the small group was a fluke and what happens in the immediate neighbourhood. The 38.4 grain group looks like an outlier; everything else below 39 grains is sub MOA, and you might want to re-shoot that one. Above 39.2 looks like a waste of time.

December 28, 2014, 01:21 AM	#6
boondocker385 Senior Member Join Date: March 6, 2013 Posts: 640	I too would go down to .2 increments. I will second the use of 4064 if you aren't happy with varget.

December 28, 2014, 04:15 PM	#8
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	If you shoot five more groups with the 38.8-gr. load and they're .5" groups or less, it's the best. Otherwise, the biggest group best reflects that loads accuracy.

December 28, 2014, 10:56 PM	#9
Saint Dennis Member Join Date: March 31, 2008 Location: Minnesota Posts: 97	Re-read the directions on the test. It is not group size necessarily but a common point of impact on adjacent charge weights. When you find the best three, choose the middle one and play with seating depth and maybe slide up and down half a grain to find the one that groups the best in your rifle. The common POI is the point of the test, not so much small group size. One three, or even 5 shot group does not tell you that much. Too many variables and luck involved.