Secant Ogive Bullets: Seating Into the Lands

[beartooth91]

When I was 14 years old, and knew all there is to know about reloading, I mistakenly seated some Sierra 100 grainers too far out for my then-new Remington 700 ADL .243. One day, out in the field, I tried to chamber a few of them and they wouldn't go. In frustration, I put one in and gave the bolt a good, hard, shove. The rifle went off. It was pointed at the ground, so, the only thing hurt was my ego. Thirty years later, after getting back into shooting and reloading, I am real careful about my measurements and never seat a bullet closer than .010" off the lands.
But, I do shoot some of the Hdy AMAX's and read these like to be seated at or into the lands. I've been trying to read everything I can on how to do it, though I don't understand the touching vs. jamming. The first part seems straightforward: adjust my load development practice with jammed bullets at the beginning - at the minimum recommended charges. Some of these pro shooters are seating the bullet .015" past what they measure. I've experimented a tiny bit with dummy rounds and the bullet gets pushed further into the neck when chambering. I'd like to try this with some of the AMAX's. And these would be range loads.
But, going back to that day, thirty years ago, how does one safely chamber a round that's seated a bit beyond the rifle's measured COAL? (I'm guessing shoving the bolt closed isn't the answer.)

Mark

[stomp442]

I have yet to have a rifle that liked the bullets touching or jammed into the lands. .025-.030 off the lands has always worked for me.

[darkker]

+1 to stomp

If a shell "goes off" when you slam the bolt. That really has nothing to do with the OAL, as it does an improperly adjusted trigger.

Touching = at the supposed point where the bullet contacts the lands.
Jammed = bullet at the same point as above, only the contact causes the bullet to be seated deeper into the case.

There is no practical difference between the two.

[82boy]

I will have to say that in most cases I jamb bullets into the lands, in almost every rifle I own. I find that it works and the guns shoot there best there. When we are talking about jambing the bullet into the lands you go from touching to 5 ,10, 15 thousands jamb, at this length the bolt will close with about the same feel as not jambing at all. If you have to ram the bolt in then you doing something wrong.

[CJnWy]

Never been a big fan of jamming bullets into the lands in anything but a bench gun. If the round is not shot the bullet can stay in the barrel and make a mess!!
Have found the Amax to do just as well off the lands....Some as much as a 1/2" off
The round years ago went off because you jared too light of a trigger not because you jamed the bolt!

[beartooth91]

So, how does one tell, by looking at the bullet, whether or not its a secant-ogive or tangent-ogive design? I read that most match bullets are the tangent ogive type. A few, like the Hdy AMAX and Berger VLD are the secant type. I have some Speer 145 BTHP Match bullets, for my 7mm-08. I've read that most of the Speer bullets are the tangental design. **If** I understand correctly:
If the bullet nose arc radius is greater than the bullet shank diameter its the secant design.....I think.....? If true it explains why they look long and pointy.
One of the definitions of spitzer includes something about tangent ogive. My .284 Speer 130's BTSP's look like the tangent ogive type. But, this .284 145 BTHP Match looks to have a much longer arch radius, compared to the Speer 145 BTSP. It looks, to me, like it may be the secant type.....?

All of my shooting is range, informal benchrest. That's why I'm interested in the answers to these questions.
Thanks

[Apache]

Excellent article for secant and tangent:

http://www.riflebarrels.com/articles...et_weights.htm

[82boy]

well maybe this will help
http://www.accurateshooter.com/balli...ogive-bullets/

and this
http://mathscinotes.wordpress.com/20...shapes-part-1/

and this
http://www.appliedballisticsllc.com/...lletDesign.htm

Amazing what you will find using a search engine.

[82boy]

throw in a couple of picture and you may have something.
http://images.search.yahoo.com/image...mb=Bqi009M7anR

http://images.search.yahoo.com/image...mb=Bqi009M7anR

http://images.search.yahoo.com/image...mb=Bqi009M7anR

http://images.search.yahoo.com/image...mb=Bqi009M7anR

[r3dn3ck]

A-max's touching the lands resulted in unacceptable pressure spikes for me. Shoving them .010 deeper in the case with a seater die solved the problem. I would recommend you play with seating depth last and just make sure that your ammo chambers easily. If it doesn't you've got a safety issue. You'll never see a competitive shooter (well not a good one anyway) forcing a bolt into battery.

[Iklwa]

Hello,
I am sure you already have an answer to your question but I just stumbled across it.
Hornady makes a very fine measuring tool whereby using a modified case (for sale by Hornady), you use the intended projectile in that case and lightly seat the bullet against the lands of the rifling. Then, you snug down an adjustment knob and extract the tool and bullet from the chamber.
Now you have a cartridge that can be duplicated by measuring with a second Hornady tool and set the projectile depth at whatever you desire with repeatable results.
Comparator:
https://www.amazon.com/Hornady-B14-Lock-N-Load-Comparator-Inserts/dp/B000PD01OC/ref=sr_1_2?hvadid=78134096170307&hvbmt=bb&hvdev=c& hvqmt=b&keywords=hornady+comparator&qid=1551470752 &s=gateway&sr=8-2&tag=mh0b-20
OAL Gauge:
https://www.amazon.com/Hornady-C1000-Lock-N-Load-Length-Straight/dp/B000PD01SI/ref=sr_1_2?crid=3MZ8KCLZX4TXK&keywords=hornady+oal +length+gauge&qid=1551470833&s=gateway&sprefix=hor nady+oal%2Caps%2C246&sr=8-2
Modified Case)s):
https://www.amazon.com/Hornady-B204-Lock-N-Load/dp/B000PD1X3U/ref=sr_1_fkmrnull_1?crid=3LTFATPEUWX00&keywords=7m m+rem+mag+modified+case&qid=1551470885&s=gateway&s prefix=7mm+rem+mag+modified+%2Caps%2C233&sr=8-1-fkmrnull

[Stumpkiller]

Stoney Point was making that tool back when this thread was created. ;-)

Be VERY careful working up a load when seating a bullet so it contacts the grooves. That increases the pressure significantly.

[Ryfulman]

The only bullets I’ve had to jam were some vld type,like the nosler rdf junk. As far as the amax is concerned every rifle I’ve ever loaded them for shot best with a 20-30 thou jump. I’m referring to 308 due to that’s the only amax left.
I establish chamber length using a dummy round and always seat according to the length from the landscape.
Try a 20 thou jump and work from there.