Friggin' bullet seating depth.

[ADIDAS69]

So SAAMI says 2.810 for a max length for .308 Winchester. If I just barely seat the bullet and then chamber the cartridge I get 3.002. Should I leave it there or are there dangers associated with too long a seating depth? I've always done what the hodgdon load data has told me (2.76 in this case) but I was listening to some yutz explain how he did OCW testing and seating depth was determined in the fashion stated above. Thoughts, feelings welcome personal experience a plus.

[ADIDAS69]

Note that this is an M24 long action chambered in .308 Win. and loads aren't meant for other guns. So magazine fitment is an issue. These long a@@ cartridges fit and feed very nicely in the long action.

[mikld]

The method you describe is for finding how long you can go with one particular bullet and just hit the rifling, max length for your bullet in your gun. Normally people will shorten this OAL .005", .010", or more. SAAMI specs is for manufacturers to make ammo that will fit all guns in production today. I have found the seating depth is last on my list for accuracy tweeks, and have made some very accurate ammo using the bullet manufacturer's OAL data....

[ADIDAS69]

Well I'm already down to trimming and re- pointing meplats, and figured now that vihtavori is available again I'd really crawl down the rabbit hole. When I run out of this batch of noslers I'm switching up to lathe turned projectiles. Thanks for the response, I couldn't personally think of why there would be any issues so I thought I'd ask.

[cdoc42]

If you chamber a round to seat the bullet you are likely to be just where the ogive meets to the rifling, which is not unusual for bench rest shooters. However, using this method without measuring every finished round can lead to inconsistencies based on variations in bullet manufacturing process and you can end up with a round that produces excess pressures. Thus, as stated above, you can seat a dummy round that way, then shorten it by 0.005, 0.010, 0.015" and so on until you reach your best accuracy.

[Mobuck]

"Note that this is an M24 long action chambered in .308 Win."
M-24 what??
"If I just barely seat the bullet and then chamber the cartridge I get 3.002."
How far are you jamming the bullet into the lands?
If this is supposed to be some sort of "super-duper" accuracy special, having a throat so far beyond standard is going to make ammo prep a tough Mother.

[ADIDAS69]

Mobuck: M24 is the designation given to military versions of what would otherwise be a heavy barrel REM 700. The lands are leaving little to no markings even after I applied layout fluid the the bullet. It is pretty accurate, with PRIVI factory ammo I can easily hold MOA out to 600 yards. With my reloads I do much better but I'm just trying to squeeze what is there to be squeezed in terms of accuracy.

Cdoc42: I am indeed seating bellow observed measurements.

[mehavey]

If one does as the OP described ... closed the bolt on a barely seated bullet
atop a normally sized case... you've jammed that round well into the lands
w/ neck tension.

Was that really what was done ?

[riverratt]

I've found me best accuracy with my bullets loaded less then .02 from the lands. However, you are reducing the bullet jump to the rifling which in turn raises pressures. I've personally only had 1 gun that a safe load at .05 off created obvious pressure signs at .015 so I had to back off the charge weight.

I'd strongly advise against keeping the same powder charge and loading rounds just off or into the lands as an over pressure may very well occur. Either start back at your starting load and work up with your new O.A.L or keep your charge and slowly change your O.A.L. watching for pressure signs along the way.

[ADIDAS69]

mehavey: your understanding of the procedure is accurate. The bullet was seated firmly. "barely" is not wholly accurate, three cartridges were prepared in this way and measured and then set back to 2.9800".

riverratt: regarding powder charge, I'm conducting an optimum charge weight test. creating 3 cartridges starting at 15% below suggested starting charge wait and increasing by one grain till I detect pressure signs.

[Chainsaw.]

What Mehavey is getting at is normally the procedure for this test is to reduce neck tension by a good amount on a case. By thinning the neck, splitting the neck etc. This way it takes very little force to set the bullet back into the case. In turn you get the true depth of the lands and are not "jamming" the bullet into them.

[Mobuck]

"Mobuck: M24 is the designation given to military versions of what would otherwise be a heavy barrel REM 700."

If so, that is a "short action" M-700--I've had one in my hands a "few" times. If this is actually a "long action", it is NOT an M-24.

[Sure Shot Mc Gee]

In your description it sounds like a near identical technique that's done to paper patched cast.
About such OAL w/jacketed. As I recall such extended length of barely touching rifling requires a reduction % of smokeless used. I would advise anyone. Without knowing just what that powder reduction figure is? {so to reduce excessive chamber pressure} its a good policy for any home reloader to follow their powder manufactures printed OAL/ Min & Max tolerances.

[jmr40]

If so, that is a "short action" M-700--I've had one in my hands a "few" times. If this is actually a "long action", it is NOT an M-24.

The M24 used by the Army is a "LONG" action rifle. They chose long actions in order to build 308 and 300 WM rifles on the same actions. It also aids in getting long high BC bullets loaded into the magazine instead of having to be fed one at a time.

https://en.wikipedia.org/wiki/M24_Sniper_Weapon_System

The M24 SWS has the "long action" bolt version of the Remington 700 receiver but is chambered for the 7.62×51mm NATO "short action" cartridge that has an overall length of 2.750 inches (69.85 mm). The "long action" allows the rifle to be re-configured for dimensionally larger cartridges up to 3.340 inches (84.84 mm) in overall length.

The M40 is the USMC version, they chose short actions.

https://en.wikipedia.org/wiki/M40_rifle

The M40 has always been based on the Remington 700 Short Action with .308 bolt face,

[F. Guffey]

So SAAMI says 2.810 for a max length for .308 Winchester. If I just barely seat the bullet and then chamber the cartridge I get 3.002. Should I leave it there or are there dangers associated with too long a seating depth?

I want to know the length of the chamber from the beginning of the rifling to the bolt face, I do not care what SAAMI says, I have no interest in what is printed in a reloading book. I start with all of the bullet hold I can get, I transfer the dimension of the chamber to the seating die and then adjust to 'zero' off the lands.

I am not the fan of 'the bullet into the lands', I want my bullet to have that 'jump'; I want my bullet to hit the lands 'a-running'. I do not want my bullets to hesitate when it hit the lands.

I was watching a T-V show; the subject was 'bullets', a tech from Sierra said they were pleased when they were able to get 10 shots off on a target with a group that was no larger than a quarter; and I thought that sounded familiar.

And I was pleased they did not make the quote about all that was necessary when sizing a case; they have been known to say the case can fit the chamber like a 'rat third in a violin case'.

F. Guffey

[zipspyder]

I just use max OAL or slightly less and call it good...I have an Ishapore Enfield .308 that will take anything but my Savage 11 is really picky.

[Jim Watson]

OAL/ogive to lands is a handloading variable. If you like to tinker with loads, that is just something else to fool with, there are no hard and fast rules that apply to every rifle and every bullet.

Jamming the bullet hard into the lands will elevate pressure somewhat, so the top load will be less than the usual maximum. But it might shoot accurately that way.
Then you have touching the lands, off the lands by .010", .020", .030" etc.

You are fortunate to be able to reach the lands at all; I have read of many Remington rifles with very long throats that won't do it.

Me? I am at .012" off the lands. I was going for .010" for that batch but missed it a bit. No problem, the load shot so well that I standardized on it.

You say you will go to lathe turned bullets. That will require you to start over, they behave differently. Barnes recommends a minimum .030" jump and powder charges for accuracy and maximum will differ. A jammed solid is not a good idea.

I'm conducting an optimum charge weight test. creating 3 cartridges starting at 15% below suggested starting charge wait and increasing by one grain till I detect pressure signs.

A waste of time, ammo, and barrel life. 15% below suggested starting charge is absurd, 25% below maximum. Start at the starting load, which is usually 90% of maximum. I think a one grain step is too coarse to find best accuracy. I would start higher, step smaller. I am sure there are texts with recommendations on the increments for different case capacities.

Philosophy. Post #4 sounds like your main interest is tinkering with loads. That is ok if you don't mind wearing out a barrel looking for that last smidgen on the target.
But if you want to hit targets, MOA at 600 is pretty good. I quit looking not much better than that and went F class shooting.

[RC20]

I may be able to put this in context. Its possibility not a given.

My brother bought a 700 in 30-06 with heavy barrel.

What he found was the throat was very long, suited to VLD bullets (which are very long), but not to regular bullets.

It sounds like the OPS gun is the same setup.

Regardless, you find where the bullet really is in relation to the lands, and then adjust the free bore from there.

Bullet seat depth of bullet diameter are recommend, so you want to be at least .308 bellow the top of the neck.

Also in my opinion you need to remove the boat tail (if there) from this as there is no support.

[T. O'Heir]

"...I get 3.002"..." That's the chamber length of your rifle. to the lands. Usually means you're into the lands at the ogive of the bullet. That'd be the off-the-lands starting point. OAL is not measured to the ogive. It's from the pointy end of the bullet to the flat end of the cartridge.
The whole off-the-lands stuff is an optional, entirely trial and error(there's no formula or norm for it.), load tweaking technique that doesn't get done until you've worked up a load.
An OAL for .308 2.800" works well.
"...dangers associated with too long a seating depth..." Its the OAL not the seating depth. Too long might give you magazine fit issues .

[hounddawg]

Just my method here but I start using SAAMI specs and do a ladder workup with whatever powder I am testing. Once I determine which load is giving me the best grouping I take and load 10 bullets @ .005 off the lands, 10 @ .010, 10 at .020, and 10 @ .030. Shoot them at 100 and call your shots, then see which performs best and adjust from there if nescessary

Different bullets do the jumps better and even that can change depending on the barrel. The 123 gr SMK's I am shooting in my .260 will shoot better at .025 then they will at .015, the little dogtowns I shoot in my 20 caliber like jumps of over .075, the .30 Berger 155.5 VLDs shoot best in one of barrels when they are dead in the lands with just a toenail in the neck. Same bullet in the bull barrel they like a .025 jump, go figure.

[Jim Watson]

I recall an article about load development. It was for BPCR but had a good point.
What do you do with leftover less accurate ammo as you continue to work up from your best yet?
Shoot it offhand, you need the practice anyhow.

[Mobuck]

My mistake, the rifle I used was the M-40 designate.

[HiBC]

What bullet weight are you using? More clearly,how much of the full cylindrical portion of the bullet is engaged to the neck?
In the extreme,if you are loading 155 gr boat tails longer than 3.00,you might be making a significant compromise.

Also,long throated reamers for heavy bullets are certainly a possibility. Throat erosion is another(Though you have mentioned good accuracy)

[cw308]

I shoot a Rem.700 308 cal. It started out as a LTR 20" brl. 1/12 twist. The rifle had so much free bore the bullet was almost at the end of the case neck to hit the rifling. Would just keep to OAL of 2.800 with a Sierra 168 MK using IMR 4064. The rifle shot very accurately. After 4000+ rounds I had a Rock Creek M24 5R 11.27 twist cut at 21" barrel installed & blueprinter, The new barrel has very little leade, it shoots best with a .002 jump with F/L case sized from head to datum .002 , I check with the RCBS Precision mic. I'll remove the firing pin assembly & plunger to test the round in the chamber. The M24 barrel is 1" thick with little taper, just love shooting the rifle.

[Unclenick]

ADIDAS69,

Alas, you have more work ahead of you. It is true that some guns like the bullet seated to touch the lands. Mid Tompkins told a long range rifle class I took that he and his whole family of long range champions "soft-seat" their bullets. That is, he sizes the case necks so the bullet has friction light enough that you can still push it in deeper or pull it out by hand. Not too loose, but not hard. He then seats them out beyond the throat of the gun by a little and allows the act of chambering the cartridge to complete seating. He and his family have an awful lot of gold medals between them.

That said, it isn't always best. The late Dan Hackett, writing in the 1995 Precision Shooting Reloading Guide, described a 40X in 220 Swift that he was loading for by 0.020" off the lands, thinking that was best. It shot half inch 5-shot groups on average, which, as a benchrest shooter he did not find adequate, but nothing he did could improve on that. Then one day when he was switching to a shorter bullet, he accidentally turned the micrometer adjustment on his seating die the wrong way and wound up with 20 rounds seated 0.050" off the land before he noticed the error. He debated pulling the bullets, but decided instead just to shoot them for trigger practice. To his astonishment, he had two groups that were 0.25 inches and two true bugholes in "the 1's" (0.10" to 0.1999 range)

Berger had a similar experience. You can read about it here. In some guns they've found their secant ogive bullets seat best jammed into the lands, but in others 0.020, 0.050, 0.080, or even as far as 0.125 off the lands do best. So you just can't know until you try.