Bullet Seating Depth

[alcor123]

I bought one of those Stoney Point OAL guages. Question is how much free travel should there be between the bullet ogive and engaging the rifling. Stoney Point recommends .020 to .040, but my guess is that they are errnig on the safe side because of pressures. A guy that used to work at my office (who shot in competition) recommended .010 to .012. Does anyone else have a recommendation and/or explananation of principles involved, i.e., pressures vs. accuracy?

[Sturm]

Great Question Alcor, I tend to read Rick Jamison more than I used to, after it took me awhile to figure out that he is pretty bright and his recommendation that I follow is .010" and I believe Layne Simpson makes the same recommendation. Both of these guys are writers for Shooting Times that I envy because it would seem they get invited on exclusive hunts far more often than I do!

[HSMITH]

There isn't any 'rule' for depth. You will have to try different lengths in your gun to see what IT wants. Some guns want the bullet right close and some want them back as far as .030" IME.

EDIT: Every time you try a new bullet you will need to go through it all again, as each bullet will also show a preference in individual rifles.

[Sturm]

That is a good point and I should have been clearer. Alcor, my take was that you were concerned with a minimum or proper amount of Freebore, so my response did only deal with the max. length at which to begin and of course you can tweak a load's length in the pursuit of accuracy. Some reloaders that have older rifles or ones with longer throats, crowd the lands of the barrel a little tighter and use .005" of Freebore. So, I gave an oppinion as a general guideline universally accepted in most reloading manuals. Of course, I could have said, it's in your manual, but I usually have more to say, obviously.

This does refer to OAL maximum and anything shorter is up to you so long as you don't seat too deeply. Pressure increases with a reduction of OACL. The individual rifle has an unique chamber. Pistols do as well and I load pistol ammo similarly, according to the chambers demands. I figured you already had a pretty good handle on that when you mentioned you had the Stoney Point gauge. I will not advise you to crowd the lands, so I think .010" of Freebore is a good place to start when you do change bullets. I believe you understand that I was in fact talking about the Max. OAL to start with, because the manuals recommend OALs similar to factory ammo knowing that the load may end up in many different brands of rifles, and chambers from one rifle to another by the same manufacturer can of course be different based on the machining tolerances an individual manufacturer allows during production.

[cdoc42]

It should also be pointed out that measuring your final cartridge over-all length should be from the ogive to the base of the case as opposed to the tip of the bullet to the base. When I note my measurements I mark them "OAL-OG" not just OAL.

As pointed out here, every time you change bullet brands you need to start all over because the ogive is likely to be in a different location. I have seen the ogive change in the same box of bullets with the same lot number!!! So don't assume since you've gotten an accurate load with, e.g., Hornady 130gr seated at .010" from the rifling that you needn't check that measurement with a new box of those bullets.

I measure my cartridges right after seating to be certain I'm where I want to be, especially if you're gonna seat to 0.005 to 0.010. If you're using a powder that pretty much fills the case, check that OAL-OG - the powder, particularly stick types, can bridge in the case as it drops and take up more space, retarding the seating as the bullet pushes into it.

I've not found any "magic number" to be best among the 12 or so rifles I load for. I start at 0.015" and if accurate, testing is over. If not, I load some at 0.010 and some at 0.02. I've not gone to .005 because I'm never sure my original dummy round is EXACTLY touching the lands when I set it up and I fear what I think is .005" might be right into the lands.

[flashhole]

If your seat die engages the ogive of the bullet, not the tip of the bullet, and the diameter of the seat stem opening is smaller than the diameter of the bullet, which it has to be to engage and seat the bullet, wouldn't the spacing between the ogive and the lands be constant regardless of ogive type and ogive tolerances? Seems to me the only difference would be how much bullet tip would extend into the bore but the spacing between ogive and lands would always be the same.

[HSMITH]

Flashhole, yes it would be consistent, but OAL from base to bullet tip can vary as much as .015" from what I have seen. What cdoc is saying is that you really don't know where the ogive will make contact with the riflng if you don't measure where the ogive is.

[cdoc42]

I'm not certain that the seating stem engages the ogive- it would have to have a pretty deep aperture and none of mine do. They seem to engage the bullet no deeper than just behind the tip, to avoid damaging the lead.

Manufacturing quirks and tolerances seem to be the bug. Nosler bullets have less variation than Hornady for me, until the SSTs came along. Barnes, I recall, made a statement one time recommending their bullets not be seated closer than 0.02 (or was it 0.20?) but gave no reason. I suspected it was ogive position variations that occur in the manufacture of pure copper bullets.

If you don't measure your "OAL-OG" not all your loads will be the same distance from the lands and any failure to get really tight groups might be thereby explained. That day.

[Sturm]

The seating stem engages the Ogive, except in cases where the seater is designed for a flatnose bullet, and truncated cone shapes with handgun bullets. The Ogive, or the tangent of a bullet is the only part of a bullet, besides the full diameter shank that is of concern with headspace, or freebore. Speaking of which, wasn't there a band in the 60's or 70's called the O-Gives?

[DAVID NANCARROW]

Well, I'll point out the obvious. Make sure the loaded length will fit in the magazine!

Also, be careful with free bored chambers such as Weatherby. Not that you could load to engage the rifling on them, but somebody is gonna try.

I have an old Rem VS in 308, and for some reason, the chamber is long, and I mean really long. Easy to load for-just set oal to the length of the magazine box and go get em. Accuracy is very good-I can hold hold a half inch group at 100 yards with 150 grain hornady soft points. My Stony point tells me that I am .050" off the lands with a 2.820" OAL, but for some reason I cannot explain, it works.

[B9mmHP]

Bullet Seating Depth.

First! I am by no means a professional reloader, but I do reload and read a lot about reloading in the three reloading manuals I have. I reread them often and review the Sierra Highpower Rifle Reloading tapes with G. David Tubb. I would suggest that every one should do the same. Every time I reread or watch the video I get something new out of them. (Maybe I’m just getting old) Sometimes I get knowledge from forums like this, and I hope that I can impart a little knowledge on.

Bullet seating depth is determined by the individual rifle and the magazine you are shooting not the caliber, no two guns have the same seating depth even if in the same caliber and brand name.

You should have the bullet seated to at least, to the bullet diameter to hold it in the cartridge and to seat and align properly. A “very” few thousands either way won’t make much difference if you need to, to get accuracy. If that doesn’t work, get different bullet.

You can not physically load an 110gr bullet to the same seating depth from the “lands” as you may be able to do with a 165gr bullet or larger. (See the above paragraph) Especially if the free bore is long as in a Weatherby and some others, and still maintain the bullet diameter to depth ratio. If you have a smaller caliber bullet, like in 22 calibers or 243 you may be able to raise the seating more if you shoot a single shot rifle and don`t beat up your ammo.

You should measure off the lands to the ogive and not the base of the bullet to get close to the seating depth, because the ogive is set, the base can very as in boat tail that is longer as apposed to the flat based bullet.

I have to hunt and peck to type much. So I suggest you read everything you can about reloading in books and tapes that were done by professionals.