OK, here is my reloading mystery of the week...

I am working up a hunting load for my .260 Remington using the following components:
twice fired Remington brass, sized full length
Hornady 129 grain SST bullets
Alliant RL-19 powder (corrected from original post)

I am loading four cartridges at each charge weight on my single stage press. Each change in charge weight is 1% of the MAX load, or 0.5 grains. I started with the lowest load and increased the charge every four rounds. Note, I could hear powder crunching when I seated the bullets.

I set the seating die to give me an OAL of 2.780" and double checked the first three cartridges before proceeding.

When I checked the OAL of the last cartridge it was about 0.010" too long. I checked the first cartridge again and it was correct. A cartridge from the middle of the run was about half way between. I figured that something came lose while I was working so I readjusted the seating die to get me back to 2.780" and ran the cartridges through again, this time "last loaded" to "first loaded". MISTAKE #1 - I did not measure as I went.

When I'd run them all through I rechecked the OAL. Now my "first loaded" are about 0.010" too short... My repair was to use the kinetic bullet puller to "lengthen" the rounds and then reseat them to the correct OAL, measuring carefully. And yes, I am now a bit concerned about neck tensions.

I checked the lengths of ten bullets from the same box and found a variation of +0.002" to -0.003" from the average length of 1.319". Using a Sinclair comparator I found a variation of +0.002" to -0.002" from the average of 0.668".

At this point my theory is that the different amounts of powder compression resulted in different amounts of "spring back" from the pressure of the seating die. What do you folks think?

This is not uncommon with compressed loads. If you are not loading to an OAL which places bullets very close to the lands or near the limit for your magazine, I wouldn't be concerned.
You will probably also find that these cartridges continue to "grow" in OAL for a few days. When you remeasure them a week later they may be another .005" to .010" longer. The entire batch will most likely "settle in" at a very consistent length for each charge weight. Once they reach equilibrium, they should stay put.
I had this happen regularly with compressed loads for my .204. I was concerned at first. I took a batch of cartridges that had "grown" like this and tested to see if they would continue to grow when exposed to recoil in the magazine. I would fill the mag and fire all except the last round, repeating this process until this final cartridge had seen the recoil from 20 rounds. The OAL did not change. (Pleasant surprise)

I had a run of luck like that on hornady's a few years back-the loads would not stay consistant length(oal),after much frustration and cussing I found the reason.I had to make a bullet ogive length guage.Found out that the ogives up to the surface that the lands ride on was varying in length!These were on .224"match 68 gn hpbts too!I quit using them and went back to sierras-problem solved!YMMV

How much Varget are you using ???
I didn't think a max charge of Varget in a .260 would create a compressed load. But then again that is a rather long bullet.

If memory serves me correctly your loading for a Model 7 or 700 Remington.
If I'm correct your magazine should accommodate up to a 2.825 OAL
If it turns out to be a compression issue lengthening would be an easy fix.

Every time I've ran into these issues it has always been tracked back to the ogive.
Your comparator should be .264 (groove dia.) while it's possible your bullet seater is locating at .256 (bore dia.) on the ogive. If the curvature of the ogive isn't consistent this could account for the discrepancy.

Noslers are notorious for this, they mix batches of bullets that come from different dies, however I've never seen it as an issue on papper.

TRBLSHTR wrote:

:( I had a run of luck like that on hornady's a few years back-the loads would not stay consistant length(oal),after much frustration and cussing I found the reason.I had to make a bullet ogive length guage.Found out that the ogives up to the surface that the lands ride on was varying in length!These were on .224"match 68 gn hpbts too!I quit using them and went back to sierras-problem solved!YMMV

This was my first thought too but PS said he measured on the Sinclair comparator and I think that measures to the Ogive.

Mike if you did not measure to ogive check that. it may be ogive to tip variation you are measuring and your seating die is contacting a point somewhere near the ogive and the bullets are slighlty different taper to the tip causing the problem.


BTW TRBLSHTR SMK's will vary base to tip length up to .010" too. drawing the tips on a hollow point is not an easy parameter to control, but since "jump" is from ogive to throat anyway OAL is really not an important measurement beyond fitting in the magazine.

I have found on my .308 and .223 when I compress Varget, I reach a point where I can't drive the bullet in any further and my OAL is longer than I have the dies set for. The powder won't compress anymore and I have to use less Varget to achieve my desired OAL.

Chambered, you hit on a mistake in my original posting, which I've corrected. This load used RL-19 powder, not Varget as I first posted. I'd used Varget in the other test load I was setting up this weekend.

These loads are for the Ruger M77 Compact. The Hornady manual called for an OAL of 2.775" but I decided to try 2.780" and have plenty of magazine length to spare. The comparator ID is bore diameter, 0.256". The seating stem ID is tapered so its hard to measure but I get about 0.230" at the most. I considered an ogive problem but what are the odds that it was be progressive through the batch?

PS, I've run into the same thing with compressed loads. They sometimes "grow" longer. Even with a medium crimp from a Lee FCD.

I sure appreciate the input from you all. I didn't crimp these loads at all. If the test looks promising and the "growing" continues I'll try some with a crimp into the cannelure. Right now the bullets are seated to just above the top of the cannelure so I can increase OAL a hair, crimp and try again.

After I posted I got thinking about the comparator and whether or not it was bore or groove diameter. Bore did make more sense !!!

If it were me and hearing what guys are saying about OAL growing........ I'd lengthen OAL from the start of load development, since the room is available in the magazine.
If you do that you'll need to figure out how far off the lands you are first to ensure no issues arise from shifting things forward.

The next suggestion I'd make is to measure the loaded rounds with the comparator and see how much fluctuation you have there, it's the measurement that matters most.

As for the batch issue......I haven't messed much with the SST's, but I know it's a common practice for the industry to mix bullets into one batch from different dies.
I've gotten up to 4 different groups of bullets in 1 box of Ballistic Tips, it's very common to have 2 groups.

I had 2 boxes of 130grn sp from hornady the first box was very accurate seated to the canalure the 2nd box had it in a different place!!!

Pumpkinslinger wrote:

..... The comparator ID is bore diameter, 0.256". The seating stem ID is tapered so its hard to measure but I get about 0.230" at the most. ....

On another note - This revalation has led me to use a comparator to set my seating dies between lots of bullets and bullets of different designs. depending on the draw consistency of the tip of the bullets, you cannot use OAL as a valid measurement of Off the lands distance. OAL will really only tell if it will fit in the magazine box.

Dawgdad wrote:

On another note - This revalation has led me to use a comparator to set my seating dies between lots of bullets and bullets of different designs. depending on the draw consistency of the tip of the bullets, you cannot use OAL as a valid measurement of Off the lands distance. OAL will really only tell if it will fit in the magazine box.

I use the direct method of determining maximum OAL (touching the lands) for each bullet by test fitting a case and each bullet in my rifle. Without going into details it involves a case with a drilled primer hole, a brass rod with a tight friction fit collar that can slide along the rod and a neck that grips the bullet firmly but allows it to be pushed out of the neck with firm pressure on the rod. Once I have the bullet against the lands with the case fully seated in the chamber I measure the OAL and then repeat to check for error. I then seat at least .010 deeper. Now all this depends on consistency of the distance from the ogive to the tip of the bullet. What I gather you are saying is that I can't count on this consistency. My question is how much do I need to allow for the differences in ogive to tip within a batch or between batches of bullets.

Whenever I change something like OAL I start at my beginning load and work back up and check for any signs of trouble. If the ogive to tip decreases more than .010 from my original measurement for that bullet then this process isn't foolproof. I don't mind spending money on a comparator but didn't see a need for one until now.

If you go over to neck sizing you will find tha case will take the same load without compression - I found almost 2gr increase in capacity with .270 cases.
Using a comparator will always give a more precise & repeatable measurement than from the bullet's tip & makes changes in bullets simpler.

Here are my measurements, after all the fiddling around. "Comp" is the comparator measurements. I found it interesting comparing the OAL with the comparator numbers because some loads that were short or long on OAL were the opposite on "comp". Now I plan to quit tinkering and just go shoot the things and see what happens.