Does seating depth a have this large impact on group size?

[Mikecr]

Bart, you're wrong in your generalizations about seating affects.
Seating is the single largest load development adjustment in our bag. Far larger than powder, primers, or bullets.

For others, don't count on a 30thou window. I've yet to see any load that forgiving -that shoots worth a ****.

 

[Canadian Bushman]

I typically move seating depth .005" for a fine tune on a load that shows promise.

Ill move .01" if i cant make sense of the results of the smaller increments.

 

[Bart B]

Bart, you're wrong in your generalizations about seating affects.

Not according to my observations. I'm not blind. Which means we've both done something different that the other doesn't know about.

If you see a difference, so be it.

 

[HunterGreen]

I bet you previously had rifle perfectly fouled up.wondering if you cleaned that barrel sparkling shine ?

That would be the greatest effect on accuracy.

 

[Bigeclipse]

I bet you previously had rifle perfectly fouled up.wondering if you cleaned that barrel sparkling shine ?

That would be the greatest effect on accuracy.

Funny you should say that but I am beginning to think that is another huge factor in what happened. I cleaned the crap out of it with the bore eliminator which removed a LOT of copper fouling. I'm wondering if this barrel likes a bit of copper. Time will tell

 

[HunterGreen]

Funny you should say that but I am beginning to think that is another huge factor in what happened. I cleaned the crap out of it with the bore eliminator which removed a LOT of copper fouling. I'm wondering if this barrel likes a bit of copper. Time will tell

Bigeclipse, it's a proven fact, glad you now know the reason.

Next time you hit the range, (I can't over state this) record your first clean cold bore shot. You must take your first shot as if the world depended on that shot pretend that you can change the course of history with that first shot. Now shoot three to five shots let the barrel cool down and note where these shots are impacting. Keep shooting at least 20 rounds between cool-down periods and note their POI.

Wrap it session, apply moist cloth with hoppies cleaner and (JAG) not brush, run it down (1) time, let it sit till you get home and run dry patches. (Note, this will not remove copper, only powder residue that traps moisture and cause rust). Next day if possible, take your first copper fouled cold bore shot like the world depended on it.

Now you can pause and admire your exact point of impact has not changed. The only time your point of impact will change is with these two situations, shoot at least 20 rounds rapidly but accurately and notice if your groups maintain size or open up. secondly, accuracy will be limited because copper fouling will eventually put resistance on your bullet down the barrel flight path, this well increase pressure and your velocity will decrease between 22-70 or more feet per second and your groups will open up, at that point you must remove some copper out.

 

[Bart B]

HunterGreen, I've never had a barrel change bullets' point of impact with either of those sessions. What might I be doing different?

Mine shot to point of aim from the first shot to the last one 30 or more rounds later.

All my barrels shot bullets a few fps faster after they fouled.

 

[Mikecr]

I don't even think a bore taken to white metal with oil left in it throws shots like seating changes I've seen.
I'm pretty sure I could take my 223 rounds for a Cooper from consistent <1/4moa to a full 1moa with nothing more than seating adjustment. And I honestly can't think of any other adjustment, that's not an actual problem, that could make this gun shoot 1moa or worse.

On copper;
The ONLY thing close to bad as very wrong seating, is copper fouling out.
IMO, the is nothing 'good' about copper.

 

[Mike 338]

I can't speak for anyone else but Berger's recommendation for seating depth testing for load development has changed the way I do things. I test the bullet as far out to as deep as I can seat it. I usually seat no further out that maximum magazine length because I want a repeating rifle. I wouldn't be to sure that seating your bullet out as far as you can get it will give you the best groups. I have some that will only shoot with a "big" jump.

 

[Rich Coyle]

I can't speak for anyone else but Berger's recommendation for seating depth testing for load development has changed the way I do things. I test the bullet as far out to as deep as I can seat it. I usually seat no further out that maximum magazine length because I want a repeating rifle. I wouldn't be to sure that seating your bullet out as far as you can get it will give you the best groups. I have some that will only shoot with a "big" jump.

One of my rifles prefers .180". That is almost 3/16". If I didn't know about changing overall length I would not realize it can fire good groups. Another one prefers .015". Without testing we will never know what the rifle prefers.

 

[Mike 338]

One of my rifles prefers .180". That is almost 3/16". If I didn't know about changing overall length I would not realize it can fire good groups. Another one prefers .015". Without testing we will never know what the rifle prefers.

Exactly... I used to change seating depth 3-5 thousandths. Now I start in 40 thousandths increments and find a rough seating depth. I go back later fine tune the depth adjustments in small increments but you gotta find the general area where it wants to shoot. I have a 338 Win Mag that shoots 2-1/4" at max mag length but shoots .6" with a .200" jump. I found that big jump to deliver the best accuracy even when using different powders so long as I used the same bullet.

 

[Rich Coyle]

Exactly... I used to change seating depth 3-5 thousandths. Now I start in 40 thousandths increments and find a rough seating depth. I go back later fine tune the depth adjustments in small increments but you gotta find the general area where it wants to shoot. I have a 338 Win Mag that shoots 2-1/4" at max mag length but shoots .6" with a .200" jump. I found that big jump to deliver the best accuracy even when using different powders so long as I used the same bullet.

I, too, now start with .040". I used to make .005" changes. If I did that with the magnums the barrels might wear out before I found the sweet spot.

 

[Mikecr]

You guys are right.
Now consider that most reloaders(by far) simply pick a seating depth.
They just just pull one out of their butts, a book, or based off herd notions (like "VLDs shoot best against lands").
I wonder how many have determined their guns won't shoot well, without ever finding out.

I believe the next big advancement in load development will involve striker tuning.
Believe it or not, you can change grouping with firing pin and/or trigger adjustments. You can open groups, close them back up, and open again, just as you can with primer changes, but without changing the primers.
Primers don't just 'go off'. There is a reason a particular primer works best for you, while worst for me.
Well, maybe in ~20yrs. I can't afford to define it.

 

[Marble]

My experience learning that seating depth matters..

I loaded berger 95s in my wifes .243 Finally got consitant .6-.7 groups. Went and loaded a dozen or so and took her out to shoot. It was horrible, probably 2"+.

Got home and check the OAL and it was .0030-.0040 short and different from what I had originally loaded. I loaded a bunch more bullets and double checked the deating depth and I was good after that.