When the OAL to the lands is to long for the Cartridge?

[bravo2zero]

I used a stoney point oal gauge with a 140 grain boat tail sierra bullit in my 6.5 284, and if I keep the bullit .002 off the lands the length is to great for the bullet to be seated in the cartridge. Is this common, or do I need to go to a different bullitt.
If I use a 142 grain bullitt the distance is even greater.

 

[jofus]

do you mean to deep or to shallow

 

[olympian]

The length is too great, so when the bullet contacts the lands, the bullet is not touching the case neck. I am assuming this is the situation from the description, and that the cases are not trimmed too short.

You can try the 142gr., but it is not likely to help your situation much. Try shooting the rifle with the bullets seated such that a reasonable amount of the bullet is contacting the neck. It might group fine. If it does not group such that it meets your expectations, then start being concerned about re-chambering or other costly undertakings. Keep in mind some rifles and pistols, e.g. Thompson Center's TCU series, shoot fine with this condition.

 

[jofus]

140 or 142 sierras tend to shoot better off the lands like .010" to .020"

 

[DonL]

Hi There,
You may want to give 140 grain Hornady A Max bullets a try. My chamber was cut for 142 gr. Sierras, but when setting up the overall cartridge length for the A Maxs they ended up considerably deeper in the cases. I have used a Sinclair bullet seating depth tool for years to determine oacl. I take 3 different bullets from a given lot and take 3 measurements with each bullet to come up with an average to determine oacl. With what I consider to be good VLDs the differance from shortest to longest is never more than .010". I just sent a box of VLDs back to a well respected bullet manufacturer because after checking 2 different 3 bullet groups the closest I could get any group was .036" from shortest to longest.
By the way, for those of you that are thinking that a bullet comparator measurement would have caught this drastic differance in the bullets it didn't. They were within .005" using a comparator.
I hope this helps you.
DonL

 

[spclark]

Sierra's bullets, compared with some other makes, typically have shorter ogives. Loading them to touch, or "into" the lands, in many chambers may seat them pretty far out there. You need only .060" - .100" of a bullet in the neck to hold them in the case; seat 'em out too far & they won't stay in your case necks.

Depending on the caliber, Sierra's usually shoot fine even with as much as .040" of a "jump" to first land contact.

If you can't get 'em to stay in the necks with a jump, try another brand of bullet. Berger, JLK / Swampworks, Hornady, Lapua, etc. all provide bullets with longer ogives that will seat with more of their bearing surface in the case necks in your chamber.