Loading to the Lands

L

Lef T

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Southern Ontario
I'm not seasoned in the art of reloading for rifle and I'm
concerned that maybe I've watched one too many G.David Tubb's
Videos.
So,I've got a Stony Point and a Sinclair OAL gauge and I wish to find
an OAL based upon the ogive of my rounds touching the lands and then
backing it off by 4/1000 of an inch.
Here's what I don,t understand.
I take my box of Sierra MatchkingHPBT bullets and each bullet will give me a varying Oal reading using the Sinclair or Stony Point.
I'm measuring the OAL with a Starrett set of calipers,so my readings should be accurate.
The Sinclair OAL tool will give a longer OAL reading than the Stony Point.
EX..Stony Point.....2.350
Sinclair 2.399
Now I can start again with a different bullet out of the same box and get totally different readings again.

Here's some reading for a Savage .222 using a different bullet out of the same box each time
2.156
2.165
2.200
2.212
2.235

How do I know which reading to trust.
Do the match bullets vary this much.
Take it easy on me.
I'm trying to learn.
Thanks
 
The tip (meplat) of each bullet will vary from one to the next. Generally when I've measured the distance from the base to the ogive of many SMK's, and they usually only vary by 0.0005 to 0.001" (one-half of one thousandth to one thousandth of an inch. Meanwhile, the length from base to tip may vary by three or four thousandths.

The best method is to set the distance to the lands with the gauge, then measure with a bullet comparator which rests on the ogive of the bullet, rather than the tip.
 
Try taking a neck sized unprimed case and inserting a bullet so that it is longer then your final OAL. Insert in the chamber and close the bolt. Hopefully when you eject it (gently) it will be the perfect length to rest against the lands. Now use a collet crimper to lock it in place and use that bullet to set up your seating die.
If you are not sure what is going on in the chamber with regards to where your bullet is seating, smoke a bullet over a candle and then chamber upon extraction you will clearly see where your bullets ogive is in relation to the lands.

Knowing the length is not as important as knowing that your loads consistently engage (extent of engagement most likely argued elswhere LOL) the lands.

Sorry I just reread your question and see that you want to back off the lands 4 thou. Any reason not to go with collet neck sized, trimmed brass and contact with the lands?
 
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What you want is the COL, measured to the ogive, not the tip. Afterall, you are trying to seat the ogive 4 thou shy of the lands. The relationship of the tip to the ogive can vary, but with good bullets the relationship of the ogive to the base of the bullet should be constant.

You need one of these..............

http://www.sinclairintl.com/cgi-bin/category.cgi?category=RESDTCO&item=09-600&type=store


Zero you caliper on the comparator, and then insert the test round, and measure the distance from the base of the case, to the ogive. This is the distance you want to replicate when you make your reloads.
 
Thanks for helping me out here guys.
As to backing off the lands by 4/1000ths of an inch I thought that
would be better than seating it right into the lands.
As I said,I've been watching too many Tubbs videos.
I do have a Sinclair bullet comparator(just arrived) .
This is all new to me.
If I use the Sinclair or Stony Point Oal gauges with the bullet seated,ogive to the lands I will get varying Oal readings,because of the
varying lengths of the bullet from base to tip.
Doesn,t that kind of make these gauges redundant?
It's not telling me the measurement of when the ogive contacts the lands.
I'm going to study my Sinclair comparators now.
Geez,I feel like a newbie all over again.
 
Without a comparator, the best method is to take the OAL, and then measure the length of THAT bullet.

When setting your die the next time, find a bullet of the same length to use first, or add/subtract the difference of the bullet you do use.

Really a comparator is the best tool, and not very expensive.

As for the redundancy of the OAL gauges, it only becomes an issue if you're loading very close or touching the lands. If you're loading 10 or more thousandths off, a difference of 2 or 3 likely won't be noticeable.
 
As to backing off the lands by 4/1000ths of an inch I thought that
would be better than seating it right into the lands.
Click to expand...


Ultimately what you are trying to accomplish (for accuracy) is consistent pressure between rounds. This is accomplished by: using cases of the same volume, using the exact same powder charge, having consistent crimp or neck tension and (opinions may vary)having the bullet resting consistently against the lands.

All those fancy tools are nice but smoked unprimed cartridges have been used to excellent effect for many years. It wont tell you how far off the lands you are but it will tell how engaged you are.

Word of warning rounds that engage the rifleing (even lightly) do have a slightly greater chance of becomeing unseated upon extraction.

One other idea is to use a moly coating spray on your bullets and load per normal. Then cycle the rounds and the moly will show you which rounds are engaging the rifleing and which are not. divide in two piles, go to the range and compare.
 
Just do what David Doyle says and forget about this 4/1000 stuff.
As he says, if you seat them hard into the lands you could pull the bullet out if you exract it without firing.
 
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