More seating depth questions

[Mike6158]

I just measured distance to the lands (Stoney Point gauge) for two bullets in my Sendero in 7mm mag. All measurements were repeatable (4 times for each bullet) to .001 so I feel pretty good about that.

The first bullet that I measured was a 140 gr. Sierra Gameking (#1905). OAL measured (to the lands) was 3.480. At this length the bullet was barely in the case and it fell out easily. Of course this was the Stoney Point case but seating depth of the bullet into the case was under 1/4". It doesn't look like I can completely follow the aforementioned testing guidelines of .010, .050, .090, and .130 off of the lands as seating .010 and possibly .050 will not allow for very much neck tension. At least I don't think that it would. Any thoughts?

The second bullet was a 150 gr Nosler Ballistic Tip (#28150). The OAL was longer but was deeper into the case. COL was 3.554. I think that I can seat to the full test range mentioned in the earlier post with this bullet.

Am I wasting my time trying to seat hunting bullets in the sweet spot?

 

[Moman]

I don't think you are wasting your time. It sounds like your chamber is a little throaty, many if not most factory guns are. I would try your test with the 150's but also consider moving up to a 160. It will be a longer bullet and give you more bullet contact in the neck. The problem may end up being that these could be too long to fit in the magazine if you are going to use it as a repeater.

 

[Mike6158]

I don't think you are wasting your time. It sounds like your chamber is a little throaty, many if not most factory guns are. I would try your test with the 150's but also consider moving up to a 160. It will be a longer bullet and give you more bullet contact in the neck. The problem may end up being that these could be too long to fit in the magazine if you are going to use it as a repeater.

Thanks. I've got a few hundred of each bullet. I guess I'll load the 140 gr's to manual specs and use them to site in and stocking stuffers I should have put a "which bullet is best for the 7mm mag" post up.

This is my first 7mm magnum (or any belted magnum for that matter). My other rifles are a couple of .308's (two AR's and a VTR), an old .270 (great rifle), and a couple of home built AR15's with Shilen match barrels. I also load 6mm and .243 for my boys (now grown men). Around here the deer are small and a 55gr bullet in an AR15 will drop them so I gravitated to a lighter (140gr) bullet for the 7mm. I should have done more research I guess.

I bought the Sendero with the idea of learning to shoot at a bit longer range than normal. Maybe out to 600m - 1000m. I say learning because I recently walked over to our 300m range to "have a look" and figured out pretty quick that my factory ammo shooting buddy that can't place a shot accurately at 100m is lying his *** off <--- Texas term for being untruthful when he talks about taking game out to 300m - 400m. It's easy to claim it... not so easy to do it well.

Thanks!

 

[Mike6158]

I don't think you are wasting your time. It sounds like your chamber is a little throaty, many if not most factory guns are. I would try your test with the 150's but also consider moving up to a 160. It will be a longer bullet and give you more bullet contact in the neck. The problem may end up being that these could be too long to fit in the magazine if you are going to use it as a repeater.

Want to know what I just "discovered"?

Being kind of hard headed and having a free Sunday morning, I decided to do a bunch of measuring, load up some empty cases, and see if I can figure this thing out. At the end of all of the preeee-cise measuring and funiggling I finally had a round loaded that, by my preeee-cise measurements, was .010 off of the lands. I stuck it in the magazine and it fit (albeit a little long). I chambered it by hand. As I was pushing the bullet in I notice some "soft" resistance toward the end. lightbulb My preeee-cisely loaded round that was supposed to be .010 off of the lands was touching the lands before the bullet was seated and the bolt was closed.

So... I used a version of what you posted ^^ only I didn't split a case. I use micrometer seating dies so I can make fairly precise adjustments to the seating depth easily. I took a black magic marker and ringed the ogive, inserted the bullet, closed the bolt, extracted the bullet, and looked for marks. They show up clearly. I adjusted the die down in .005 increments until the marks were barely visible and I called that "touching the lands. I measured that with the MIC gauge and adjusted down from there.

Any flies on this method?

 

[Innovative]

Check out this article about finding the best seating depth.
OAL

- Innovative

 

[boomtube]

"Am I wasting my time trying to seat hunting bullets in the sweet spot?"

I'm puzzled. Where do you think the "sweet spot" is?

 

[Innovative]

boomtube .....

Finding the optimum OAL for maximum accuracy usually requires you to reduce the distance that the bullet travels before it contacts the rifling. This also helps maintain concentric alignment between bullet and the bore, so that your bullet gets a good start down the barrel.

Setting the OAL correctly for your "particular" chamber is the cheapest accuracy improvement there is. Experienced shooters know that this is one step to improve rifle accuracy. The optimum length of accurate handloads will almost always be quite a bit longer than factory loads. Do your reloading at the shooting bench . . . . or al least seat your bullets there. Be sure to take accurate measurements (back from the bullet ogive), and keep good records.

[This came from the article at the link above.]

- Innovative

 

[Moman]

Nice article Larry, I've read it once before on your website. Mike, a couple things you can do. One, I always make sure the throat area is clean before measuring. I've had some weird results with a slightly dirty throat. Another is to take a couple different bullets and write down the measurement to the lands. Save these bullets and OAL measurement and you can remeasure later down the road to keep track of throat erosion.