What am I doing wrong - inconsistent seating depth?

[juststarting]

Hi All

I am reloading for a .308 and getting inconsistent overall length after seating projectiles.

About half seat at around 70.8mm - just an arbitrary length I had that worked well, so tightened everything up on that. Around 70.83 - 70.86. However, the other half seats at around 70.94-70.93mm.

I haven't changed anything on the press or die and tried to apply the same pressure.

I would also assume that I am using .308 168gr Woodleighs, if that makes a difference. I would think that brass length makes no difference, as long as it's within spec (mine is around 50.81-50.86mm). Using RCBS dies 'RCBS 308WIN SEAT 15' die and Partner press.

As far as I can tell, I am applying consistent pressure and press is firmly mounted.

Any suggestions?

[No1Mk3]

G'day juststarting,
From your post, your maximum deviation is .004" (0.11mm, as you don't use arshins!) This is very good for a commercial press, and I would be happy with that. One possible cause could be the seating punch, does it push on the point of the bullet or on the ogive? Have you measured a quantity of projectiles to check for variation? Remember, Woodleigh are a hunting bullet not a long range precision item and may vary that 0.11mm. Your press may have that much cumulative error in it's pins etc. If you want to get seating to a variation of 0.05mm or less, you are going to have to spend large sums of money on benchrest level equipment, if you want to, you could try re-seating the longer ones a 2nd time, Cheers.

[Gwion]

Are you measuring to the ogive or to to bullet tip? I should probably know from your stated length but I've been up since 330am.

[Wm.Traynor]

To put it another way, the shape of the ogive varies from bullet to bullet. That makes each bullet's length vary and that is why your OAL varies. Shoot them and see how they group

[Baldrick314]

Get yourself a comparator unit that measures off the ogive of the bullet. Bullet tips vary in length considerably. The true measurement you want anyway is the distance from the leade of the rifling to the ogive since that's where engagement happens. The bullet tip location is practically inconsequential.

[Old Fart]

Tip variation is my guess for the apparent discrepancy too.

juststarting your die seats the bullet using the ogive, not by pushing the tip, I suspect upon closer inspection the bullets are seated more uniformly than you're finding assuming you're measuring tip to base.

[heeple]

Crack it, JS?

[juststarting]

I'll be doing some reloading this week, I'll measure things a bit better and see if it's the projectiles or just expected error margin... Stay tuned

[Ariat]

Sounds like the tips.

Just line a few bullets up on a table and look along them and you can see how inconsistent they can be.

[juststarting]

Apologies all, forgot to measure everything for this thread. Next batch this week, will try to figure it out.

Life is a bit hectic right now :/

[5Tom]

Definitely try getting your hands on a bullet comparator. I've yet to get one myself, but in my experience loading Sierra 180gr soft points and measuring from the tip is proving too inconsistent. Bullet variation has been up to 12 thou difference and that's just the bullet alone.

I have also found that I can squeeze an extra 2 to 3 thou just by making sure the primer is seating 100% in the pocket.

[Bourt]

Life is a bit hectic right now :/

More important that a forum? I don't believe it!

[juststarting]

Alright, so now with data...

Essentially, COL after seating a batch of projectiles (from the same batch) seems to be slightly inconsistent.

I am loading for 308 bolt action, using RCBS dies. Once I am happy with the length, I tighten the die in place and off we go... I try to apply the same lever pressure consistently.

I was told earlier that this is due to bullet inconsistencies, based on data it seems to be the case.

COL data table here:
http://myshootingjourney.com/2016/07/07 ... epth-data/

They all shot fine. Nevertheless, still keen to understand the root cause of this variance.


Thanks

[bigfellascott]

just shoot the bloody things and stop worrying about crap! Ya not some high end Olympic shooters so don't get sucked into all that crap

[Oldbloke]

just shoot the bloody things and stop worrying about crap! Ya not some high end Olympic shooters so don't get sucked into all that crap

Um, I think in this case BFS has a point. Isnt the 308 for pigs and deer sized game? If so the size of the target is almost the size of a foot ball. So 1.5 moa is plenty good enough. Bet your getting better than that now. And in a hunting situation (and I mean on foot in the bush, not spotlighting from a car or ute) there are plenty of hunters who cant shoot that accurately anyway.

[juststarting]

just shoot the bloody things and stop worrying about crap! Ya not some high end Olympic shooters so don't get sucked into all that crap

I am certainly not a high end shooter and don't you worry, I definitely 'just shoot the bloody things' Definitely don't care that much about hunting rounds. Care a little more about target rounds, but not a lot more. Nevertheless, since I reload, I am interested.

All clues/answers/advice point to COL being the same at ogive, while the tips of the projectiles having some inconsistencies. Maybe some day in the distant future I will buy a comparator. For now, I think I am ready to put this one to bed.

[Adelaide]

Hi I am also having the same issue. I am using a comparator, All cases have been trimmed and neck turned. Dies are Foster Benchrest ,Press a Bonanza and I am still getting a variance of up to .10mm. Additionally when seating I have tried rotating the cartridge in the press a couple of times ( once just as the bullet is initially seated and then twice more during the process) . I am also trying to use as consistent a stroke and pressure. Any advise would be greatly appreciated

[Stix]

Hi I am also having the same issue. I am using a comparator, All cases have been trimmed and neck turned. Dies are Foster Benchrest ,Press a Bonanza and I am still getting a variance of up to .10mm. Additionally when seating I have tried rotating the cartridge in the press a couple of times ( once just as the bullet is initially seated and then twice more during the process) . I am also trying to use as consistent a stroke and pressure. Any advise would be greatly appreciated

What is the inconsistancy you are getting exactly...?

Is it the length of the loaded round as measured by the comparitor set...?

If so, i get it too...i think its due to inconsistencies between the shape of the bullet (each one may vary from the other), & the point at which the seater die pushed the bullet in.
If these 2 things are different (comparitor size & seater size being different), youll get inconsistancies.

Thats one reason...many others could be the case with the press etc...

I sometimes get up to 7 thou difference over a lot of 50--still cant figure out why or how i get such a variation though--my variation is always the same--my rounds get progressively longer the more i press out, no matter the round im seating or which die im using, which leads me to believe its in the press gradually freeing up somehow...

[Adelaide]

Thanks for the response, I have just remeasured and the variation is between .02-08 mm Its the length of the loaded round as measured by the comparator.

[marksman]

measure your bullets and batch them before seating them
neck tension can also be a problem
https://blog.ammolytics.com/2019-02-02/ ... t-one.html

[SCJ429]

What bullet are you using?

[TassieTiger]

Some good help above.
I’d add my 2c.
The 308 Hornsby comparator insert is $10-12.
If your only reloading the one size - buy it to put your mind at ease.
Have you measured your chamber so you know max seating depth ? How did you measure it? If you used the candle/carbon method or cleaning rod method, it’s very easy to over / under measure by .5mm or more.

I’m convinced my press has more than .1mm built into it - depending on how it’s feeling...

[tophet1]

Are you actually trying to fix an accuracy problem ?
If its only seating depth your worried about try a L.E.Wilson seater die. (The type you hit with a rubber mallet to seat the projectile). They will improve run out as well, and eliminate the flex in a press.
Accuracy is a slippery slope of $$$ spent.
Remember, if your not annealing cases, commercial projectiles will get variance anyway.

[Adelaide]

Thanks for all the great advice. Always in search of better accuracy and could not understand the variations . Do you think they will effect accuracy?

[Adelaide]

I am using Nosler Ballistic Tips

[in2anity]

An extreme spread of 4 thou of variance, measured off the ogive won't translate to a huge ammount of inaccuracy (relatively speaking ofc). Remember, the standard deviation would be a fair bit lower - lengths are probably mostly within 2-3 thou of each other. I mean it's not ideal for a static kind of precision setup (say f-class or benchrest comp), but for everyone else, I'd be looking at other areas first, like neck tension. FWIW I'm coming from a club-level Fullbore/Service Rifle perspective, which occasionally includes scoped-rifle, bipod matches.

[SCJ429]

I am using Nosler Ballistic Tips

They are a hunting bullet, so I expect you are not jamming them into the lands. if you are loading them to fit a magazine, i would think that 5 thou differance in the ogive lenght isnt going to affect you too much. Nosler usually are not too bad but you could try batching them. How are they shooting? what is your accuracy goal?

[in2anity]

Yes I agree SCJ - if he’s jumping them a distance, that can be detrimental to accuracy. I had the same problem with short bullets. My remedy was be to increase neck tension somehow, in an attempt to better standardize ignition. I did this by polishing down the mandrel in a collet die. Groups came in after that.

Adelaide have you tried seating one 20 thou off the lands? You may have to single load it to do this test.

[SCJ429]

The seater may also be hitting the plastic nose of the bullet instead of the ogive, you could try a different seater insert or a different seater designed for VLDs.

[marksman]

The seater may also be hitting the plastic nose of the bullet instead of the ogive, you could try a different seater insert or a different seater designed for VLDs.

or drill out the seater stem a bit deeper,
jam or jump 20 thou and you will not have any problems with inconsistent seating depth
it does depend on what your rifle likes, some like to be just on touch