OAL question for 308

B

Ballisticrat

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I'm in the process of working up loads for my Sako A7S. I'm using fire formed brass with Hornady 150 gr SP Interlock bullets. I'm also using Hornady'sOAL length gauge without the bullet comparitor. I'm hoping to get close without it by using OAL measurements. I don't have a Hornady reloading manual yet.
Here's my quandry.
When I measure the cartridge length to the lands I'm coming up with 2.869".
This is leaving my crimp groove .137+- above the neck. I've read that once your bullet ogive touches the lands you should back off slightly, but to get back to the crimp groove is quite a leap.
Brass has not been trimmed. Once fired Winchester.
The Lee manual says 2.810 OAL, Winchester White Tails measure 2.709. If I seat to the crimp groove I'm at 2.750 leaving me .119" off the lands. Is this too far a jump?
Do Sako's have longer throats?
Any thoughts would be appreciated.
 
Don't worry about the crimp groove. Sakos do seem to have a long throat. I have 2 sakos and can't come close to the lands with a 180gr bt.
 
Yes Sako has long throat. I also have a WWII rebareled Eddystone that has a long throat.

I don't worry about the seat groves, I just load them to what works with the lands for best accuracy.

You can hold them back and crimp, your hunting accuracy won't suffer much if any. 2" group at 100 is plenty good for anything but real long range shots hunting.


The comparator you only really need if you are bench shooting of some type.

Each mfg has its own ogvive shape so you can't cross compare, the mfg will have a good average for rifles but can't suit all rifles (so they go with safe

You can also just get it to the crimp groves.

Weatheby went with long jumps to keep pressure down in their OEM magnums and they shoot fine.
 
Thanks guys for your input. Okay, I'll not worry about the crimp groove and proceed.
Any recommendations about how much I should back off the lands?
 
I seat that bullet to the cannelure and don't crimp, so that's what I would try first with your rifle.
 
In 39 years of reloading I've never crimped a rifle bullet in .17 Rem, .22-250, .223, 6mmPPC, .243, .25-06, .270 Win, .270 WSM, 7mm Rem Mag,.30-06, .300 WSM, .300 Win MAg and .338 Win Mag.

My understanding is the cannelure - or "crimp groove"- stops the bullet from expanding any further, assisting deeper penetration. It's a manufacturer's design necessity, not a handloader concern. In fact, at one time I noted the position of the cannelure had been changed by Hornady in the .270 or 7mm bullets I had been using (I forget which caliber now). I wrote to them just to bring to their attention they should have made some kind of notation on the box for those handloaders who DO use the cannelure as a seating target, but I never had a response from them.

My first rifle was a .270 Rem Model 700 and the throat was so long I could not seat ANY bullet close to the lands without the seating depth being less than the bullet diameter. A 100gr Speer HP would fall out of the case if I tried to get to the lands at all.

As noted in the above posts, all manufacturers have a different ogive position which is really where you should be measuring your seating depth, not using the overall length from case base t bullet tip. If you experiment with the same weight bullet from Speer, Hornady, Sierra, Berger, Barnes, etc., and make them all the same overall length from base to tip, they will all be a different distance from the lands, and your most accurate finding will be chance.
 
All good responses. Especially interesting about the cannelure not being a crimping groove.
Okay, I'll forget about the cannelure position and seat my bullets wherever they give me the best performance.
This forum is great. I can always trust to get good info based on experience. A valuable resource that's greatly appreciated.
Thanks again.
 
Actually the crimp cannelure just locates the bullet so you don't seat deeper than the bullet bearing surface. It's a nuisance for the manufacturer in that it is hard to roll it into the bullet without distorting the bullet and adversely affecting its balance. It does indent the core, but doesn't stop expansion. Take a look a a cutaway of a Hornady Interlock, and you will see the interlock ring, which holds onto the core during expansion, is substantially below the cannelure.

Usually you don't need a crimp. Some argue it helps with semi-autos to resist feed ramp bullet movement, but I've never seen it make a difference there with jacketed bullets. If you have lubricated lead bullets in a magazine or in a revolver it makes a difference. Crimping can increase start pressures, which can help slow powders ignite more consistently, but it's usually best to avoid powders too slow for your bullet weight.

Ballisticrat, just seating your bullet so the crimp cannelure is at the level of the case mouth is a good starting point. The bullet manufacturer knows what works with it. The 2.810" figure is a maximum for fit into and feed from a minimum length .308 Win magazine. It has nothing to do with ballistic requirements, either interior or exterior.

If your bullet doesn't shoot well for you, then you can think about varying seating depth. Look at Berger's information on this subject for VLD's and treat it as a starting point for a non-VLD bullet. If you start out seated in contact with the lands, reduce powder charge 10% from the maximum you use not touching the lands in order to make up for the pressure difference that results from throat contact, and then start adjusting seating depth.
 
@cdoc42,
Just went back and read your response again. So if you're not crimping, then is it safe to assume that you have a standard for your neck resizing?
 
All necks are ideally sized for about 0.001"-0.0015" interference fit with the bullet. Much more than that doesn't add appreciable grip, as inserting the bullet merely stretches the brass by the extra amount, leaving about 0.001"-0.0015" maximum elastic range of interference grip. It's all plenty for hanging onto a bullet. You can improve consistency of that grip by turning a bore brush inside the case mouth to remove carbon before seating the bullet.
 
Bear in mind that you won't get close to the lands, in a great many .308 rifles, with 150 grain bullets - unless you seat them very shallow. They simply aren't long enough. So, I wouldn't worry about this issue with the 150's. I simply seat to the bottom of the cannelure for my .308's, when using 150's.

With heavier bullets, such as 165-168 grainers or heavier, seating close to the lands becomes an issue....and should be addressed.
 
"...don't have a Hornady reloading manual yet..." You don't need a Hornady manual just because they made the bullet.
"...stops the bullet from expanding any further..." More about holding the lead core and jacket together.
"...I'll forget about the cannelure..." Good. Just seat to 2.800" with no crimp and you'll be fine.
"...seating close to the lands becomes an issue..." That isn't and never will be an issue. It's one load tweaking step and that's all.
 
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