Help! 3 shot or 5 shot group

davide montini

davide montini

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Eh fellow sport shooters
I’m asking all for there advice ......here goes
Folks I’m right bugged up about this one ....so please tell me what you think
I’m trying to get develop a load for my rifle so I can get my dope for. Up coming PRS shoots .....
So should I use a 3 shot group load
Or a 5 shot group
Christ almighty !!! I get nice groups 3/4 “ or say 14,15,mm size groups when shooting a group of 3 .........
But when I go for the 4,...5... shot they open up....for f@&k sake!!!!
So should I base it on a 3.. shot group or 5
I did .3 grain steps ....3 different powder!!!...Dio Cane!!!!!!!!!!!!
Also it’s a semi .....fnh (ya I know it’s not a bolt,....I like semi’s).....7.62x51 fnar.....
And no I did not do a round robin style type of dan newberrys load testing ....
Any advice help folks is greatly appreciate
Davide
 
First you need to ask why they are opening, is your barrel getting too warm? Try to let the barrel cool a little before taking the next shot.
 
My advice is go for 7 shot groups. Then never fire the last two... that way you don't get all excited


5 round groups for development.
 
If I recall correctly, I believe 4 x 10 shot groups were fired in acceptance tests for military ammunition lots. It is straight forward statistics. Shoot three shot groups and fool yourself into having valid information about where the next 10 shots will go. Or, go with what numbers say and use 10 shot groups to predict where next three will go. Up to you.
 
For prs there is no time to let your barrrl cool down between shots so that’s not gonna help you. As far as how many shots to fire to test a load 3 won’t cut it and even 5 is a little slim, you want your ammo to stay consistent for long strings or fire, I run ten rounds or more when settling in on a load all run past a lab radar. As stated above first you need to figure out why your group is opening up after 3 rounds.
 
Depends on the range you are expecting to shoot at. Within 200 metres. 3 shot groups should do. Fatigue can be as big a factor as anything, including barrel warming, wind changes and the quality of your rest for 100 metre sight in. If you are trying to sight in at greater distances, everything gets more critical. You can drive yourself nuts trying to adjust back and forth if you are trying to adjust your point of impact within a cm at 100M.
 
I think of it this way.. .

How many rounds are you going to fire in a typical stage? 3, or more than 3? If more than 3, and your load repeatedly shoots bad beyond those 3 rounds, you are knowingly putting yourself into a position where misses in shots 4-10 may be a misread of wind, a pulled shot, or maybe it was just your load..
 
I do 5 shot groups but the top PRS shooter (Matt B) does 3 rounders. His logic is that it tells him what the gun is doing without human input.

He also validates at long distances so his process is probably more involved than just a few 3 shot groups.
 
So I used 3 different powders .....and I got the nice three shot group ...I’m like ya this is it ...shot 4 open up shot 5 open a bit more and like bloody hell!! I knew it was going to open up......
I’m using a magneto speed to see and the velocity is in the high 2400....to 2600 .....I’m not trying to kill my gun but I’m starting to wonder if I start to go beyond 400 meters will it have enough steam to make it out to 600?????
I’m using 155 sierras hpbt
 
The funny thing is that when I go do some loading for my bar in 2506 .....I used this method shooting a three shot group to see what gave the tightest group.....found it .....plugged in the numbers into isnipe ...it gave me all my dope .....one day I tried it at different distances .....and I pooped my pants at how accurate it was!!... and it’s a hunting round ...go figure ?
And here I’m using what a lot of people used or have claimed to be what they are using ...
Hmmmm I’m scratching my head here and I’m puzzled ....I can’t see where I’m going wrong
This is why I asked for some help on here
Thanks people
 
I have shot thousands of rounds in rifle and ammo testing. With a good scope I can see the group form. The first 3 shots are random and have nothing to do with the final (10 shot) group.

A 10 shot group is a fair representation of what the rifle and ammo will do. It needs to be repeated a couple times to confirm it was not a fluke.

3 shots in almost the same hole does not mean the next 7 will be close. 3 shots is only useful if you knew they showed the extreme of the group. But you don't.

I developed ammo using 10 shot groups and then had someone else shoot a 20 round group to confirm the load was ok (for match ammo).

This is a 20 shot test (308) shot at 525 yards. One of the Nutz here has a concrete bench set up behind the 500 yard firing point. It takes awhile to shoot a 20 shot test (a minute or so), so there is some lateral shift with wind. I mostly look at the vertical of a group.

RAIL GUN 308 AT 525.jpg
 

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So how big are your 5 round groups? I hate to say it but you're shooting a semi, not a bolt gun with a high end match barrel. There's no reason to believe that any load will give you sub-moa performance. If you've tested all these different powders and bullets, well I hate to tell you but your best groups are most likely the best groups that the combo of you and your rifle are capable of.

Personally I use 3 round groups for load testing, at least initially, to get an idea of what charge I want to be around for whatever my target speed is. More or less like an OCW but with 3 round groups (all shot while using a chrony). From there I'll have a better idea of where I need to be looking. If doing load dev for something that has a long barrel life, like a .308/.223 I'd do my follow on testing with 5 round groups. With something like a 6 or 6.5mm I do follow on testing with 3 round groups. I prefer 2x 3 round groups of each powder charge, I find it takes the human error out of it more. You can also compare the poi of your 2 groups and get an idea of how it shoots over longer strings. Then verify as you check your dope at distance.
 
Initial test with 5 shot groups, count only the best 4 (1 shot for human error) to see what looks promising BUT then confirm with 10 shot groups. You won't end up with many 1/4" groups but have a better verification of what the rifle really will do. I don't remember the author, or who said it first, "ACCURACY isn't what you once did, it's what you can do on DEMAND". (Col Cooper?)
 
big boar said:
Initial test with 5 shot groups, count only the best 4 (1 shot for human error) to see what looks promising BUT then confirm with 10 shot groups. You won't end up with many 1/4" groups but have a better verification of what the rifle really will do. I don't remember the author, or who said it first, "ACCURACY isn't what you once did, it's what you can do on DEMAND". (Col Cooper?)
Click to expand...

So shoot 6.... then discount one to human error.... but really that is faulty logic as any one of the rounds could be the human error shot.

All rounds fired count.

The rifle is only as capable as the shooter and vice versa.

Load development you should eliminate all human error by utilizing a sled or brace.
 
if your 4th and 5th shot is ruining your group try this, two shots with 7.62, 40 with 22lr, then another two, then another 40, then your 5th, see if you have a bedding problem, human problem or ammunition problem.
 
After load development and sight in I shoot from a standing offhand position. I have started shooting 50 rnd groups with rimfire. Fatigue plays a huge factor, especially for the groups after #1. I think I will go down to 3 rnd groups from the centerfires shooting offhand. Many hunting rifles heat up and spread the shots after 3 or so. Blasting long strings standing costs $$ but hasn't changed much for me lately. Slowing down a getting learning from each string is my goal. (No, not semis) Unless you spend the $ for a rifle that shoots the same hot, long strings in a short time don't tell you much. Keeping track of bench group size over time is a sound indicator of a rifle's accuracy too. Like other posters said, if your task demands x shots in x time, then shoot it in practice. Hunting rarely demands more than 2, almost never more than 3, so my methods work for me.
 
Like other have said, I would suggest watching conditions (wind, barrel temp, mirage in your scope, etc) and more likely, pay attention to your breathing, the amount of pressure you're putting on the grip, the butt, the forend, the position of your rifle in the rest, etc etc. Also, once you get a good 3 shot group, you may be thinking about that more than the next shot. Maybe force yourself to take a 30 second break between each shot, or something like that.

I have rifles that just don't shoot well once they warm up - maybe check that the stock isn't putting pressure on the barrel anywhere.

It could be so many things .. so try to change just 1 thing at a time so you can rule them out.

I'd shoot 5 shot groups, then when you narrow it down to a couple of good loads, shoot more.
 
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