seating depth for an AR ?

rebs · September 29, 2013, 01:21 PM

I have loaded the same brand of bullet a 55 gr HP and seated them from 2.200 to 2.250 and see very little difference in accuracy. How can that be ? I would think there would be a big difference.

jepp2 · September 29, 2013, 01:24 PM

Quote:

I would think there would be a big difference.

Why? What is the OAL where you bullet would be touching the lands? The throat may be so long that 0.050" difference is negligible.

Might be the difference of being a long ways from the lands or a really long ways from the lands.

Nathan · September 29, 2013, 02:04 PM

The lack of difference is that at your long OAL is like lands - 0.050". So, your short OAL will be even further from the lands.

cryogenic419 · September 29, 2013, 02:21 PM

A thought...

How is the accuracy overall with this bullet you are using? Maybe the rifle isn't all that particular how its loaded.

rebs · September 29, 2013, 03:17 PM

I realize you cannot reach the lands in an AR chambered for 5.56 but I thought the OAL would have made a bigger difference. This bullets shoots 1" and under at 100 yds. I guess I just thought OAL would have made a bigger difference.

**Unclenick** · September 29, 2013, 04:00 PM

It can, but it's not a gimmie. Also, a number of people report getting more than one seating depth sweet spot with a bullet. Usually one is closer to the lands and the other somewhere around 1 caliber seating depth, but you can read about examples where it turns out to be way back from the lands (see item 3, here). Berger, for example, has found as much as an eighth of an inch or so back is necessary with their secant ogive VLD designs. The more common tangent ogive designs tend to be a bit less picky, and that's why Berger now has a hybrid ogive shape available. You might want to read Berger's procedure for finding a seating depth sweet spot.

rebs · September 29, 2013, 04:20 PM

the link for Bergers didn't work

**Unclenick** · September 29, 2013, 04:49 PM

Thanks. I fixed it. That forum's software has been changing what makes a link work. Sometimes wants "htm" and sometimes "html" at the end of the URL. Sometimes it wants an abbreviated post name included, sometimes not. This has broken a number of my saved shortcuts.

September 29, 2013, 01:21 PM	#1
rebs Senior Member Join Date: January 10, 2012 Posts: 3,881	seating depth for an AR ? I have loaded the same brand of bullet a 55 gr HP and seated them from 2.200 to 2.250 and see very little difference in accuracy. How can that be ? I would think there would be a big difference.

September 29, 2013, 04:00 PM	#6
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	It can, but it's not a gimmie. Also, a number of people report getting more than one seating depth sweet spot with a bullet. Usually one is closer to the lands and the other somewhere around 1 caliber seating depth, but you can read about examples where it turns out to be way back from the lands (see item 3, here). Berger, for example, has found as much as an eighth of an inch or so back is necessary with their secant ogive VLD designs. The more common tangent ogive designs tend to be a bit less picky, and that's why Berger now has a hybrid ogive shape available. You might want to read Berger's procedure for finding a seating depth sweet spot. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; September 29, 2013 at 04:47 PM.

September 29, 2013, 04:49 PM	#8
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Thanks. I fixed it. That forum's software has been changing what makes a link work. Sometimes wants "htm" and sometimes "html" at the end of the URL. Sometimes it wants an abbreviated post name included, sometimes not. This has broken a number of my saved shortcuts. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 29, 2013, 02:04 PM	#3
Nathan Senior Member Join Date: July 1, 2001 Posts: 6,331	The lack of difference is that at your long OAL is like lands - 0.050". So, your short OAL will be even further from the lands.

September 29, 2013, 02:21 PM	#4
cryogenic419 Senior Member Join Date: March 29, 2009 Location: NW Ohio Posts: 569	A thought... How is the accuracy overall with this bullet you are using? Maybe the rifle isn't all that particular how its loaded.

September 29, 2013, 03:17 PM	#5
rebs Senior Member Join Date: January 10, 2012 Posts: 3,881	I realize you cannot reach the lands in an AR chambered for 5.56 but I thought the OAL would have made a bigger difference. This bullets shoots 1" and under at 100 yds. I guess I just thought OAL would have made a bigger difference.

September 29, 2013, 04:20 PM	#7
rebs Senior Member Join Date: January 10, 2012 Posts: 3,881	the link for Bergers didn't work