Seating Depth

[Brian in Montana]

Doing some load development with my new .270 (Weatherby Vanguard Wilderness - I plan on doing a little review on it after a little more range time with it). My first round was using H4831sc and 130gn Federal TBT's. It didn't produce very good groups, a couple were about 1.8". I was thinking of just scrapping the project and trying something else, but decided I'd take the opportunity experiment with seating depth, something I haven't done much of in the past.

I was thinking I'd take the load that produced the "best" group and work load some other 5 shot batches each with the bullet seated .02" longer than the last. So my question is, should I work in longer increments, like .05", or even shorter? Considering my equipment, I think I'd have trouble try to work with less than .02.

 

[Pelican]

I’m my opinion, .05 is too course of an adjustment at one time. .02 would be my choice. Did you happen to do a ladder or OCW test or did you just shoot individual groups?

 

[Brian in Montana]

I did a 12 shot ladder test using a Magnetospeed, then follow up with 5 shot groups derived from the flat spots in the velocity data. My best loads in 7-08 and .308 have come from this method.

 

[N2TRKYS]

I've gotten tighter groups by just changing primers.

 

[Pelican]

Have you determined how far out you can seat bullets before you reach the lands or if the magazine length limits how long your rounds can be? Weatherboard rifles in the past had a lot of freebore which made seating some bullets close to the lands impossible without being too long to fit in the magazine. I don’t know if the newer weatherbys are the same or not. Sometimes seating bullets out farther helps tremendously, other times it doesn’t. Good luck.

 

[Scott85]

I wouldn't worry with it because of the freebore the weatherby has. I would load to 3.34 for an overall case length and then change powder, primers and grains.

 

[mtmuley]

Load mag length. mtmuley

 

[Losing_Sanity]

Doing some load development with my new .270 (Weatherby Vanguard Wilderness - I plan on doing a little review on it after a little more range time with it). My first round was using H4831sc and 130gn Federal TBT's. It didn't produce very good groups, a couple were about 1.8". I was thinking of just scrapping the project and trying something else, but decided I'd take the opportunity experiment with seating depth, something I haven't done much of in the past.

I was thinking I'd take the load that produced the "best" group and work load some other 5 shot batches each with the bullet seated .02" longer than the last. So my question is, should I work in longer increments, like .05", or even shorter? Considering my equipment, I think I'd have trouble try to work with less than .02.

Thanks for posting this discussion, I am very interested in the answers...

You address a real good question and one I have thought of myself from time to time. Since I don't know, doesn't the depth of seating the bullet into the neck matter fore consistent and correct pressure within the case?

I have a .270 that if I extend the bullet to the lands, there is very, very little amount of the bullet itself seated into the neck of the case. Especially with spitzer boatails. Because it "just don't look right", I always seat it farther without coming close to the lands. I still get good groups, but nothing I'd bet the farm on.

Is there a minimum seating depth in regards to the case and bullet, aside from reaching the lands?

 

[mtmuley]

Is there a minimum seating depth in regards to the case and bullet, aside from reaching the lands?

Caliber length in the neck of the case. Guess a better way to put it is the caliber diameter is the minimum length recommended to be seated in the case. I'm to the point sometimes. mtmuley

 

[Blaser270]

All of the things mentioned above will “affect” your group size in one way or another, some more than others. What stands out to me is that ur using a magnetospeed for load development, which i presume attaches to your rifle barrel. Attaching anything to the barrel changes the barrel harmonics that are touched off when the powder ignites and the bullet travels down the barrel. Thats because the magneto has mass. The only way you get tight groups is if the bullet leaves the barrel at the same point in the harmonic motion every shot, and with a magneto attached, you might find a load that “works”, but it’ll chang when the magneto is removed. Hold on to the magneto for a quick velocity check. Borrow a Chrony for load development and do your ladder again.
Cheers...

 

[Brian in Montana]

I don't shoot groups with the Magnetospeed attached. I just use it for velocity data. I'm well aware it changes the harmonics of the barrel.

 

[Fire_9]

I’d go with .010” adjustments

 

[Don Fischer]

Doing some load development with my new .270 (Weatherby Vanguard Wilderness - I plan on doing a little review on it after a little more range time with it). My first round was using H4831sc and 130gn Federal TBT's. It didn't produce very good groups, a couple were about 1.8". I was thinking of just scrapping the project and trying something else, but decided I'd take the opportunity experiment with seating depth, something I haven't done much of in the past.

I was thinking I'd take the load that produced the "best" group and work load some other 5 shot batches each with the bullet seated .02" longer than the last. So my question is, should I work in longer increments, like .05", or even shorter? Considering my equipment, I think I'd have trouble try to work with less than .02.

Go for it! I don't know any reloader that quit's looking for better group's even though they have say a half inch rifle. Got to improve on that and hard telling what will do it. Now something you might consider, say your getting 1/2" group's. Have you got the shooting skills to actually claim than the hundredth of an inch improvement is due to the load? Often we'll chase thing's we'll never catch!

 

[Dougfirtree]

I usually change by .025 and I've seen dramatic changes from playing with seating depth. I play with it on virtually every load I create now and I generally improve on performance by doing so.

 

[antelopedundee]

The easiest way to accurately change seating depths is to get a Redding seat die and replace the seater plug with one of their micrometer types which you can get off of eBay for $35-$40 plus a little shipping. And hopefully no sales tax if you're lucky.

I'd start with maximum length and seat deeper rather that tuther way round.

 

[std7mag]

I usually check COAL to the lands.
Need 1 fired case.
1 bullet.
Micrometer.
Bullet puller.
When i have COAL to lands, i check to make sure it will fit into magazine.
Cup & core bullets seem to like 0.020" off the lands.
VLD (at least for me) 0.005" off the lands.

 

[brockel]

I start at the lands or mag length and then seat deeper by 0.040” until I find something with potential and then tweak around that length with powder charge and OAL but only one variable at a time

 

[N2TRKYS]

By in large, Nosler's listed COAL has been very good for me.

 

[antelopedundee]

With a new bullet I start with the bullet out too far [make sure first that the unprimed case will chamber with NO resistance] and gradually seat it deeper until it just chambers with a bit of resistance AND that the bullet stays in the case when I eject it. At this point I know I'm on the lands so I'll check to make sure that it fits into the magazine. Don't really see a need to know what the actual COAL is. I'll set this aside as a dummy round for future use. At that point I'll shoot some and play with seating depth if necessary.

 

[Brian in Montana]

By in large, Nosler's listed COAL has been very good for me.

That's generally what I do, just go by listed COAL. Seems to work just fine. I got interested in messing with seating depth a while back but I've never really done much with it. The only time I've ever loaded to magazine length was this past spring when trying Ramshot Big Game in my 7-08 with 139grn Hornady Interbonds. I seated to mag length in that case just because I thought the secant profile was going to give the bearing surface a pretty long jump to the lands, so I loaded long. I haven't messed with it since, but that produced a real good load. Its 1 MOA and zipping out there at about 2920 fps.