Measuring Bullet Seating off the Lands

[Michael J. Spangler]

ok that's what i needed to know, so the tip is very inconsistent but further down the bullet it's more consistent right? even though we're not hitting the major diameter with the seating plug, it's consistent enough to give good results?

reading all of this just makes me wonder why die manufacturers won't make the seater plug to sit just below the major diameter. seems like a gap in the market.

then again i don't have much practical experience with the consistency that the run of the mill dies are giving right now.

i love learning new stuff. thanks again

 

[mmmooretx]

I will pass one of my learning curve items on dies which happens to be on a 6.8 mm SPC AR-15. Because the bullets are shorter errors tend to get amplified. I was using RCBS SB dies and was getting variability of .008" while changing nothing. What it turned out to be was the cone inside the seating die was contacting the ogive further up (closer to the bullet tip) that caused the instability since the bullets had some minor variability there. Go with the competition grade seating dies that have the micrometer style adjustment. I get 3/8" groups at 100 yards with my 300 Win Mag and Forster seating die. Forster has stopped making the 6.8 seater so I got the Redding "S" competition seater and the cone that contacts the ogive is further back on the bullet and I get much better groups.
I am ready to try the Berger 210 gr. hunting rounds in my 300 win mag and did not have good luck at .008 off the lands. I found a thread at Berger and they recommend .030-.040 off the lands for finding your rifles sweet spot. I have talked to people that like them .015 into the lands and .080 off the lands. Your rifle will let you know. Use the ladder method to narrow your search, and save ammo. Only change one variable at a time, powder weight or OAL (distance from lands). I tend to find powder first then OAL second.
Good luck!

 

[LRHWAL]

I was getting excited seeing that Michael Moore had joined the NRA, but now I know why that may "M" in the middle may be the most important "M" in the USA...

 

[GCF]

When Berger recomends holding them off the lands, how exactly do I measure this ?

New guy here. What I just started doing to determine COL to Lands, is first teflon tape (single layer w/ slight overlap) from the base up, the bullet in question.

Next, I hand seat it in a clean / fired / unsized case.

Slowly, fully chamber the round w/ the bolt, & then slowly extract the case.

If done right, the bullet will be lightly stuck in the lands - by the teflon tape, & can be gently tapped out w/ a cleaning rod.

A clean "shoulder" should be formed in the teflon tape, that when re-inserted into the fired case neck - & measured, will show you "exactly" how deep the bullet was seated when "on the lands". Pretty easy to figure various seating depths for desired distance off lands, from that point.

When I figured this method out (blind hog finds acorn), is seemed overly simplistic. Seems to work though...

Kinda' wonder why I never though of it before... ;-]

Give it a try, & let me know what you think.

Gary

 

[Toons]

Not necessarily, although I always work up loads with an OAL gauge and a comparator. The Stony Point (Hornady) gauge is inexpensive, reliable and easy to use. Of course the second COL check, as already pointed out in this thread, is making sure the cartridge also clears the magazine, feeds up the ramp and, hopefully, ejects as an assembled round. For me, use of the gauge is to assure consistent assembly and safe operation.

One advantage the Hornady unit has over some of the home brewed OAL gauges that are based on slip fitting a bullet into a case neck is that measurement is controlled by a pushrod that passes through the case. So if the lands grab the bullet and pull it forward when extracting the gauge, this is corrected when the bullet heel is seated back against the pushrod when the measurement is taken.

Bullets with extended ogives often make getting near the lands impossible as bore diameter is reached so far up from the bullet's nose, a cartridge assembled to 0.020" off the lands would be too long to cycle through the gun. When I load for the .300 UM I don't exceed 3.600" and finesse charge for accuracy. A 0.020" movement that results in a 500 psi shift in pressure can be duplicated with a 0.2 tenths grain change in powder charge with a similar impact on accuracy as would result from moving the bullet toward or away from the gun's lands. I know we all have our own theories to apply for maximum performance.

Just a thought.

Joe,
I'm fairly new to reloading, working up a load on my RUM using the ELD-X. I've had very sporadic groups, starting with the 220, then the 212, and settled on a 89gr charge using H1000 and 3.6 COL, 3005 FPS off of a chronograph. I stopped at 3.6 since that's the limit of the magazine and the reloading manual, but decided to measure the distance off of the lands, and got a surprising 3.866". That's a huge jump compared to what most posts are shooting for, so I loaded longer rounds based on the Berger method and my group at .050 off the lands had 3 bullets touching out of 5 (1 of which I know I pulled). So, best accuracy is a 3.81 COL, which turns me into a single shot rifle. I'm fine with that for a 3/4" MOA vs double or more at 3.6 COL, but I'm concerned with over pressure. None of my cases look to be damaged. Any other signs I should be looking for?