Bullet Seating Depth

[Brian in Montana]

General question about seating depth; what does it effect more in the long run, the dynamics internal to the cartridge or jump of the bullet to the lands?

Obviously it effects both, but from a handloader's perspective, which is one to be concerned about?

 

[marksjeep]

That totally depends on the individual load. The specific bullet, the load, and the chamber will each affect which one (internal dynamics or jump to lands) becomes more relevant, and when.

 

[cahunter805]

The jump/distance to the lands IMO is more critical for accuracy.

 

[VikingsGuy]

From what I have read jump to lands & powder compression both have identifiable effects, but not much from reducing overall cartridge volume unless really deeply seating.

 

[Millsworks]

The seating depth will in most cases be something that will be more or less important in individual rifles and/or bullets ogive shape.
Load powder compression will also be a factor in creating or reducing pressure. But deep seating would have to be excessive to be a serious problem as long as loads are within max specs.
It usually will effect accuracy more or less depending on shape of the chamber and the depth of the throat.
In my experience, seating within 30 thousands is sufficient for decent performance. But certain bullets will require more or less space from the lands to give best accuracy.
Your magazine well length will many times limit your overall max length. Unless you want a single shot, the ammo needs to have a little space in the mag to cycle properly.

 

[Don Fischer]

From a handloader's perspective I try not to get hung up in stuff like that, way over my head. I do have specific way's I like to seat bullet's in anything. First off it has to fit in the magazine. If it doesn't, I make it fit. Then I like the bullet just off the lands, not a clue how far. If the round doesn't fit the magazine, good chance it won't fit to the lands either. So next think I look for is seating depth. I like the bullet seated a min of one caliber or to the junction of the neck and shoulder. If doing that pulls the bullet away from the shoulder, then I go with one caliber depth. Normally one cal depth will let the bullet get to the lands. If not, then I'll simply back up to the junction of the neck and shoulder. I think for the bullet to be well held by the case, it need's to be in a min of one caliber, I have nothing to back that up but it's they way I go. In the past I had an L61R sako in 7mm mag. It shot great with 139gr bullet's seated to the junction of shoulder and neck and right there was just off the lands. I preferred 160gr bullet's but they didn't shoot as well. So on a whim, I loaded up a dummy with the 160gr bullet seated to the junction of the shoulder and the neck and had a gunsmith ram the chamber to make it fit. I was using a load of N205 at the time and the load increased by 2 grs! Accuracy improved to a point where it was one of the most accurate rifle's I've ever owned.

It seem's to me that most chamber's are not cut deep enough to allow you to seat a bullet out like that. Rather they are configured to some mid range weight bullet! Go much lighter than mid weight and the bullet can't reach the lands many times. Go heavier for cal and the bullet intrudes on the powder space! I think that's where I picked up the extra 2 grs powder. From what I had to the new length, the bullet moved right a 3/8th inch.

 

[claybreaker]

Great question! I'm generally in the distance to the lands camp, buts I don't have any solid data to back it. As others have said its for naught if it won't fit in the mag.

I guess you could always have a group of cartridges that are longer, that are your "first shot" cartridges that never go in the Mag... but that brings its own set of issues that I don't want to deal with.

"...which is one to be concerned about?" Of course SAFETY is main concern, after that, as alluded to above to have enough seating depth to secure the bullet, to keep it from moving (in the mag) on the recoil from the other rounds, also secure enough so the bullet does lose any alignment (tilt) in the case during handling. One also don't want seat so close to the lands that the bullet runs the risk of "jamming" and getting stuck while in the field.

My 2 cents, .. on second thought, l likely not worth that.

 

[TimeOnTarget]

I like bullets seated long enough not to impede case capacity. This generally results in higher velocities IME. I've been able to achieve excellent results with seating depths ranging from touching the lands to .150 off in multiple calibers. I also require rounds to fit in the magazine.

Each rifle will be different as well a bullet choice. There really is no right or wrong answer to this as long as your loads are safe.

 

[Deleted member 16014]

Secrets of the Houston Warehouse is an interesting read. As it relates to this question, distance to lands and case neck tension were shown to be MUCH more important that powder charge. It's a benchrest heavy article, but there are applications for general reloading knowledge: http://precisionrifleblog.com/2013/10/18/secrets-of-the-houston-warehouse-lessons-in-extreme-rifle-accuracy/

 

[Don Fischer]

I wonder why new rifle's don't come with magazine's long enough to exceed the length to the lands? My old 7mm mag was a Sako and had plenty of magazine but for seating heavy bullet's like I wanted, the length to the lands was to short. Easy thing to have them reamed out to fit a dummy cartridge I put together by no way to lengthen the magazine if I had wanted to. Had a 6mm Rem in a 700 BDL. Magazine was to short to load 100gr bullet's to the lands. Never did like that rifle!

 

[Deleted member 16014]

I wonder why new rifle's don't come with magazine's long enough to exceed the length to the lands? My old 7mm mag was a Sako and had plenty of magazine but for seating heavy bullet's like I wanted, the length to the lands was to short. Easy thing to have them reamed out to fit a dummy cartridge I put together by no way to lengthen the magazine if I had wanted to. Had a 6mm Rem in a 700 BDL. Magazine was to short to load 100gr bullet's to the lands. Never did like that rifle!

In your 6mm example the mauser parent case is a short action/long action tweener in the 700.

 

[HSi-ESi]

This is one of the fun parts of loading to me - and I think the rifle really drives the answer. In my Tikka T3 (.300 WM) - the magazine really drives the OAL. I can't really run the OAL past the standard maximum - but it also shoots MOA. I have tried running bullets out so there is little jump to the lands just to experiment - and I didn't get any accuracy difference.

My Browning BLR 81 - jump to the lands makes a huge difference. I didn't have much room in the magazine for additional OAL, but when I switch from a 180 gr Partition Spitzer to a 180 Partition Protected Point - then my groups go from 1.5-2.0 inches to around 1.0 in @ 100. No difference in OAL, but the shape of the P.Pt runs the ogive much closer to the lands than the Spitzer.

I used to focus on powder charge, but in practice I would tend to say that case prep and bullet seating have more influence on accuracy.

This is where handloading really stands out from store bought ammo. It's not just components.

 

[AlaskaHunter]

Another safety concern is pressure.

With some rifle/bullet combinations,
seating too close the lands might result in excessive pressure.

 

[ccc23454]

I am a weatherby guy so i aint getting close to lands in majority of my rifles but still can usually find amazing accuracy. Find what your gun likes and go with it...

 

[Brian in Montana]

I was looking at a Hornady OAL gauge the other day. I'm very new at this but it seems the 3 things a handloader can really control that effect accuracy are case prep/length, powder charge, and bullet seating depth.

My interest is in loading for accuracy more than volume.

 

[Cerebral Stalker]

Every rifle is an individual and is unique. Control all three factors you mentioned, but play with them to see what your rifle likes, just be safe of course. That's the fun of reloading! I personally am starting to wonder if I am underrating my case-prep/brass quality. I am going to start paying closer attention to my brass. Hoping to get 3/4 moa accuracy every time out instead of every other time.

 

[Whiptail]

I was looking at a Hornady OAL gauge the other day. I'm very new at this but it seems the 3 things a handloader can really control that effect accuracy are case prep/length, powder charge, and bullet seating depth.

My interest is in loading for accuracy more than volume.

In my experience the three things that can really affect accuracy are:
1) seating depth
2) neck tension
3) concentricity /run out

powder and primers also have impact.

 

[Dougfirtree]

I wonder why new rifle's don't come with magazine's long enough to exceed the length to the lands? My old 7mm mag was a Sako and had plenty of magazine but for seating heavy bullet's like I wanted, the length to the lands was to short. Easy thing to have them reamed out to fit a dummy cartridge I put together by no way to lengthen the magazine if I had wanted to. Had a 6mm Rem in a 700 BDL. Magazine was to short to load 100gr bullet's to the lands. Never did like that rifle!

I agree. My rifle's magazine won't accept cartridges longer than .09 off the lands. Kind of a first world problem, but it does make me wonder what would happen if I could just go a little longer...