In my very limited time as a reloader (2 yrs; .338 Win, .30-06 Spr, .22-250 Rem, .204 Rug) I have not seen seating depth make a big difference in the accuracy of a hunting load. POI may change, but I rarely experience a change in accuracy going from anywhere from .015 to .05 off the lands.

This seems to contradict most everything I have read. Just curious what other's real world experience has shown. I understand that seating to the lands has the greatest potential to improve accuracy, but I'm not really interested in doing so with a hunting load.

Care to share?

Hey NimrodRx

I was wondering the same thing so did a test with a 280AI. Same load different seating depths





Seating depth did not seem to make much difference in accuracy just POI. I later found a load that it liked much better




And it shoots just fine at .020" off.

Woods, Well done!


This confirms what most of us know, it does matter with most rifles. My most "sensitive" to seating depth rifle is my .30-06 Ackley... go figure.

Woods,
I did a lot of shooting the same way you did. But it gives confusion. Our statisticians underline that one cluster of four to even five shots only give no more than a slight indication. If your rifle shoots 1 MOA-groups average, your performance could be between 0.50 and 1.50 MOA. One should make some conclusions after, say, three to five 5-shot groups. And, if you look with a critical eye to your beautiful targets, I think the one 0.005" off is the best of the performances, march 8. How come? All the groups fall in the range of minus and plus 0,5 MOA.
The second group 0.020 off seemed to be better, but this one was taken another day (?) and with a different charge. This one is not comparable to the other groups.
Nice day,
Jan.

Hey Jan

I think you're right. These tests can be confusing and misleading. However these were 25 loads with the same case prep, powder load and bullet, and they were all loaded at the same time and shot at the same time in a round robin type method. Thus, I think they do give an indication that POI is likely to move with changes in seating depth.

This is one of the reasons I remeasure the bullet jump with each loading session. The throat is subject to slow erosion and the bullet jump will increase with time which will change the distance to the lands and thus the POI. In 100 shots it is not unusual for your throat to erode .010" depending upon several variables.

Yes the last photo was taken on another day and with a different charge.

I have never been able to duplicate the dramatic changes in accuracy and such that some claim. Sometimes moving the bullet jump will tighten up (slightly) an already good load (and sometimes loosen it up) but I've never seen it turn a lousy load into a one holer. In the real world of hunting, its effect would be a big nada.
It seems to me that folks (egged on by gun writers) will take a single aspect of the anal prep that a bench shooter does to his ammo and try to make a doxology of it.

Thanks all. Stillbeeman, that has been precisely my findings.

It's fun trying out new loads on a fine day when there's not very much on on the range. I like it and I just did the same as Woods last week when I had a day off. In my experience there is no general rule that accuracy is directly proportional to OAL. This may be the case, but you can't rely on that. To the contrary: the loads for my Swede (6.5x55) e.g. increase in accuracy with the seating depth (to a certain limit). And the Swede has a loooong throat.

As for statistics, +1 for what Jan said. My son, who is doing statistics in his math calculus course, enlightened me that if your rifle is technically able to hold 1 MOA, 64% of your shots will be in this range while 95% will be somewhere between 0.5 and 1.5 MOA. Mathematically, it would take you about 100 shots to make sure that a specific load will consistently group say 1 MOA. Thus I'll look with more ease at occasional inexplicable flyers when I called the shot right and know that I had given my best to produce an accurate load.

One more thing regarding the optimal number of shots for a test group: Speer's statisticians have found out that 7 is about the best number of shots; less would not be adequate, and more would be a waste. I'v tried it and it works quite fine.

Woods, curious to know why you did not try seating against the lands or even "jammed"?

quote:

Originally posted by eddieharren:
Woods, curious to know why you did not try seating against the lands or even "jammed"?

I only work on hunting loads and against the lands or jammed wouldn't work well in hunting situations. The bullet could stick in the lands and emptying the gun without firing could be a problem.

I measure the lands with 3 different tools and seat with a Redding Competition Seater but there are still enough variations in both the measuring and the seating that I would not feel comfortable loading any closer than .005".

I put them in the lands on my Varmint rifles,I know you cant do that for hunting as they will not feed in your magazine,or will they?????If you use a standard length action on a shorter Cartridge you can.Such as a 284 Win .in a standard length action.I do it just for that reason.It also les you use the heavier weight bullet.2 oz in extra action weight will not even be noticed. Just my

When talking hunting rifles forget the 5 shot groups.

IT'S WHERE THE FIRST ONE GOES THAT COUNTS.