7mm-08 – bullet seating OAL inconsistencies

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RonR

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7mm-08 – bullet seating OAL inconsistencies

Requesting some experienced advice please on some inconsistencies regarding OAL.

The depth has been set to try and achieve 2.800 on the nose and there are results up to 2.800 to 2.805. My understanding of how the Lee dead length seating die works is that this die seats based on the bullet shape (or ogive?) as opposed to the tip or bullet length. (please advise if that’s not correct)

The first line of questions I have is what is causing the variation? Bullet manufacturing tolerances or is it something else I am not recognizing? (The primers have been triple checked for flush or shorter.)

The second line of questions is recommendations for us in terms of accuracy. Should we tweak the length to 2.800 or use the original OAL? If we use the OAL as is out of the die, is it INcorrect to believe that this result would provide more accuracy? (…my thoughts being a more consistent bullet to rifle lands distance cancelling any bullet manufacturing tolerances from bullet to bullet…or is this logic wrong?)

Here’s some other details
- Lee dead length seating die, Lee o-frame press
- Hornady SST 139gr
- Federal cases and primers
- Bullets have been weighed to see if there is a relationship between bullet weight to shape and bullet weight to length and can’t find any correlation
- End goal is accuracy at the range for deer hunting this fall
- This is our 4th batch of reloads…so we are new to reloading. My son and I are shocked how much better the accuracy is over the pre rolled stuff…and now we are addicted :d
- Perhaps this amount of variation is too over the top for what we need...but we are trying our best to understand cause and effects
- Savage bolt action rifles



Regards
RonR
 
Likely something like neck tension is the likely culprit. Hrn bullets will vary in base to ogive length... like any hunting bullet but the odds of affect on your groups is slim.

When in doubt, shoot it and see the results. Group all those that are tight on OAL in 1 group... then compare to one with a wide range of OAL difference ie 5 thou max as indicated. You will quickly see cause and affect.... if there is any

In most hunting rifles, slight variations in a range of parameters will have little to no affect on your group.... the rifle system just isn't that sensitive.

powder charge will have a vastly larger affect on your results ... as can primers.

Enjoy your journey into reloading and I am sure you will see increasing performance. This journey really never ends ... nor will the improvement in all levels of the system.

Jerry
 
First of all, how are you measuring your length? Calipers? With or without a bullet comparator? Measuring with a bullet comparator is better than calipers alone as you are then measuring off the ogive rather than the very top, lessening the uncertainty associated with measurement. Also, try measuring the same loaded cartridge twice (or more) to see how much variation you get in your measuring technique.

Secondly, how accurate do you need for a hunting load? I have a 7-08 and have a hunting load that is about 1.25" at 100 yds. It sucks as far as my accuracy desires, however, it has worked very well this year (I have harvested two whitetails, both shot at under 100 yds and neither ran more than 40 m before toppling over dead). Given the limitations of my hunting load, my ethical range would be about 200 yds, which would still place my bullet within the kill zone of a deer.

Having said that, I continue to work with my load development to get a target load that will be much more accurate (I'm trying two different 139 gr bullets for that project).

Finally, as Jerry said, get out and shoot them to see how your OAL variations group. Perhaps they will be satisfyingly accurate for your hunting requirements as they stand.

Reloading is FUN and, as you state, you have already realized an improvement over commercial loads. Enjoy!!
 
If you're using a ring seater that bears against the side of the ogive then there's a few things you can check. First off measure a number of the bullets to ensure that they are consistent for length of the bullet itself. If the noses are slightly variable then it'll show up as variations in length when the bullets might be seated identically.

Next is to check the bullet ogive for consistency. To do that I'd figure out a way so that the bullets sit in the seating ring very consistenly and then measure the amount sticking out to the base of the bullet. The goal being that the amount of insertion should be identical so the case volume is identical.

Basically to figure out where the issue might be you want to trust nothing and check everything for yourself. Assume until checked that there might be variations in each and every item and each and every step. Come up with ways to measure each item and step to confirm the status.
 
Dynamic…it is caliper measurement. No comparator here and acknowledged on the right tool for the job. Duly noted on the 1.25” grouping for hunting. We are a little better than that right now thanks to advice from this forum and this is more than sufficient for our hunting requirements. Just trying to get the most of what we have and more importantly learn more.

BC…I have to apologize for the ignorance here in my reloading experience. I am having difficulty putting to practical the measurement techniques outlined.

Mystic…true to your post and have the results to confirm. Bullet seating depth not a factor for us at this stage in our reloading careers but powder charge is. BINGO. Jerry…if you could offer a little more insight please…I need to know a little more about hunting bullets. Without mentioning manufacturers, is it reasonable to think that a hunting bullet that I pay $1 ea for is more consistent in weight/length/measurement than a $.40 hunting bullet? Further on the neck tension point…I have got some inconsistencies with the once used federal cartridges I have in terms of weight and length. Our cases right now fit the “go” flat metal gauge from Lyman for cartridge length but vary a little up to .012 from the simple tools in my inventory. The variance in length may be the reason for the neck tension you speak of (aside from other factors of case hardness etc that I haven't experienced yet) thinking that the longer the neck the more tension there is…I would reason…but correct me if this is too far fetched to make any improvement at the range for us at this point. Your advice and time responding is appreciated.


Regards
RonR
 
RonR said:
...
Mystic…true to your post and have the results to confirm. Bullet seating depth not a factor for us at this stage in our reloading careers but powder charge is. BINGO. Jerry…if you could offer a little more insight please…I need to know a little more about hunting bullets. Without mentioning manufacturers, is it reasonable to think that a hunting bullet that I pay $1 ea for is more consistent in weight/length/measurement than a $.40 hunting bullet? Further on the neck tension point…I have got some inconsistencies with the once used federal cartridges I have in terms of weight and length. Our cases right now fit the “go” flat metal gauge from Lyman for cartridge length but vary a little up to .012 from the simple tools in my inventory. The variance in length may be the reason for the neck tension you speak of (aside from other factors of case hardness etc that I haven't experienced yet) thinking that the longer the neck the more tension there is…I would reason…but correct me if this is too far fetched to make any improvement at the range for us at this point. Your advice and time responding is appreciated.


Regards
RonR
Click to expand...

When you are looking at HUNTING bullets, you are paying for style of construction and material. The goal is to make a more effective way to dispatch game. Accuracy is not always a primary goal. Some premium brand bullets use to suggest bullets in the 1 to 1.5 MOA range were well within their accuracy spec.

Ironically, the basic cup core old style bullet is typically made better. Bottom line, choose the terminal performance you want... then find the best load to make that bullet and rifle shoot. As long as the accuracy is consistent enough to have a 100% hit rate for your style of hunting, the bullet is "accurate" enough.

If you want accuracy, work with "match" bullets... although some may not be ideal for game.

WRT to case length, try and trim them to a consistent length, even if it is a bit short. They will grow with firing so don't worry if short now. Does it make a big difference? No... not for what you are trying to do but if you worry about it, then it matters to you.

Pay more attention to proper neck sizing and turning. Anneal the necks if more then 3 firings (do this properly or just toss the brass). OAL of your ammo will vary .... period. The bullets you use vary so any measurement on length will vary too.

Get a good scale that can give consistent weights to within 0.1gr or better.... then test carefully to ensure the load is in tune AND you get the practise to deliver on that accuracy in the field.

Proper bedding, good solid base and rings... good scope.

I would worry more about shooting in field positions and trying to get 100% confidence vs tweaking your loads too much.

With factory hunting rifles, the gains aren't going to be world shaking. Get something that is consistent and practise getting that bullet on target each and everytime.

Jerry
 
Ron, most of the gist of my post is suggesting that the tips of the bullets may not be consistently shaped as to overall length of the bullet. So much of it was intended to suggest you need to measure them to see how consistent they are and to check that your bullet seating die is pushing against the side of the point instead of the nose of the bullet.

I'd also strongly second Mystic's suggestion that if you want match grade results then you need to use match grade components. He makes good sense with his separation between good hunting bullets and good match shooting bullets. It would be worth picking up a box of 100 proper match bullets to check that out.
 
Thanks Jerry for the terrific explanation. The most important parameters have been explained well and have been tested here. We are satisfied with the results we have and now have some smaller factors that we can work on and get better at. For kicks I will get some match grade bullets to see the difference sometime in the future. Noted on the annealing and the scale. I validate the convenient weight results of my electronic scale to the beam scale here that has that .1 grain resolution. I am already thinking about a better stock and scope already…but that’s a ways off.

Rockeye…your recommendation is consistent with what I have read here. It’s our aim to pitch them in the future but we had 180 or so from a few years worth from our rifles. I’ve noticed some variation in resistance already when seating primers so these will not have a long life. We’re using these to cut our teeth on.

BCRider…got it and as stated above will be apt to test match grade bullets.

Thanks all of you for your time.

RonR
 
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