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Seating bullet depth

 
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  #22  
Old 03-05-2014, 02:36 PM
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Join Date: Oct 2007
Location: Mountians of SW NC, near Asheville
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Re: Seating bullet depth

Magazine reading web gurus "know" a lot but understand little and it gets sorta funny.

Seating a caliber deep started in black powder cartridge days because case necks were long, soft and thin. Reloaded lead bullet ammo with shallow seating often ended up with such light grip the bullets would work loose and fall out in coat pockets. Now, more than 100 years later, the obsolete reccomendation carries on because the well read "experts" know the old rule of thumb but not why; "a caliber deep" sounds really well informed - I guess. It would be really funny if they didn't insist on confusing others even tho they haven't a clue what they're talking about.

There is no seating depth rule but that of common sense; anyone suggesting seating 10 thou would benefit from a measure of common sense. Today's case necks are thicker and harder than 100 years ago, they can obtain sufficent jacketed bullet grip for routine handling when seated as little as 1/3 a caliber deep for short to mid-length bullets, a bit deeper for long bullets (Barne's bullets run long for caliber). And, if the magazine allows it, thinking that seating bullets deeper than bullet-to-neck contact obtains anything useful is plain dumb.

If knowing all that is all it takes to make me a reloading expert, that's exactly what I am.
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  #23  
Old 03-05-2014, 03:59 PM
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Join Date: Oct 2005
Posts: 103
Re: Seating bullet depth

You have to try differant lenths, see what your gun likes, If you have ever been to a benchrest shoot you will see everyone with portable presses, they have shims that go from on the lands to 30thou off. Now this is benchrest but it can change day to day , even relay to relay . For hunting and target practice it is different . See what you gun likes and stick with it . No set rules! Buy the way touching does increase preasure!
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  #24  
Old 03-05-2014, 09:37 PM
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Join Date: Jan 2014
Posts: 67
Re: Seating bullet depth

Quote:
Originally Posted by boomtube View Post
Magazine reading web gurus "know" a lot but understand little and it gets sorta funny.

Seating a caliber deep started in black powder cartridge days because case necks were long, soft and thin. Reloaded lead bullet ammo with shallow seating often ended up with such light grip the bullets would work loose and fall out in coat pockets. Now, more than 100 years later, the obsolete reccomendation carries on because the well read "experts" know the old rule of thumb but not why; "a caliber deep" sounds really well informed - I guess. It would be really funny if they didn't insist on confusing others even tho they haven't a clue what they're talking about.

There is no seating depth rule but that of common sense; anyone suggesting seating 10 thou would benefit from a measure of common sense. Today's case necks are thicker and harder than 100 years ago, they can obtain sufficent jacketed bullet grip for routine handling when seated as little as 1/3 a caliber deep for short to mid-length bullets, a bit deeper for long bullets (Barne's bullets run long for caliber). And, if the magazine allows it, thinking that seating bullets deeper than bullet-to-neck contact obtains anything useful is plain dumb.

If knowing all that is all it takes to make me a reloading expert, that's exactly what I am.
Ok so 100 years ago the necks on the cases were softer so they really had no choice but to seat the bullet deep but now the necks aren't as soft as a matter of fact they are harder which started people experimenting with not seating the bullet as deep until it got to the point to were some people are touching the lands or are off the lands .002 Some guns may like it close and we can do it now without the worries of the bullet falling out of the case while in you pocket. So there is no better way to find bullet seating depth than trying different depths...And now we can extended out up to 1/3 of the diameter of the caliber or can be seated in the neck the full length of the case neck or even compressed loads if your gun likes that. It's the guns decision...Is that about right???

Jumping to the targets that i posted, the bullets that I made to a OAL of 3.600 Verses the bullets that had a OAL of 3.550 was really not a real fare comparing test because I shot 3 times more of the 3.600 OAL then I did of the 3.550 OAL's but what I did see is that all five that were seated deeper shot higher and seemed to be a more consistent group. So using the common sense you mentioned tells me that if they shot higher then the ones that aren't as deep will shoot further. Is this maybe because the bullet set deeper is building or taking more bullet start pressure to release the bullet and because of the higher pressure it's giving the bullet a harder kick in the ass and thats why they are shooting higher which to me is a good thing because higher to me means further then the bullets that aren't as deep and could be creating more consistent groups too??..In other words thats proof that extending the bullet out as far as possible isn't always the best...Do you agree that now I need to start working on powder charge to tighten my group??

Thanks for your time and help

baydog
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  #25  
Old 03-06-2014, 12:56 PM
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Join Date: Sep 2012
Location: N.E. Louisiana
Posts: 54
Re: Seating bullet depth

In my limited experience (only about 2 years of handloading), I have learned there are very few hard rules on seating depth. For a given bullet, you can read different forum posts about where to seat it and they will range from being jammed into lands to .2" off lands. As a hunter, I will never want to seat the bullet touching the lands. What I have had success doing is start about .015" away and gradually work back away from lands.

For example, I am in the process of evaluating the Nosler ABLR 150 grain bullets in my 7mm rem mag. I worked up to the mv that I wanted at approximately .015" jump, but could only get about .75 MOA at 200 yards.
At the same powder charge, at approximately .030" jump, I recently shot a
.25-.30 MOA 3 shot group at 200 yards.
Then at .40" jump, the groups opened back up to about 1 MOA.

It just takes time and try to minimize other variables while evaluating seating depth.

Good Luck
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  #26  
Old 03-07-2014, 12:52 PM
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Join Date: Oct 2007
Location: Mountians of SW NC, near Asheville
Posts: 1,596
Re: Seating bullet depth

"Ok so 100 years ago the necks on the cases were softer so they really had no choice but to seat the bullet deep but now the necks aren't as soft as a matter of fact they are harder which started people experimenting with not seating the bullet as deep until it got to the point to were some people are touching the lands or are off the lands .002 Some guns may like it close and we can do it now without the worries of the bullet falling out of the case while in you pocket. So there is no better way to find bullet seating depth than trying different depths...And now we can extended out up to 1/3 of the diameter of the caliber or can be seated in the neck the full length of the case neck or even compressed loads if your gun likes that. It's the guns decision...Is that about right???"

Exactly. Seating depth, as such, isn't the issue so it's not a question of some magic book seating depth or any rule of thumb; as handloaders we should be loading for best performance and that includes seating! The max length question is what's practical as the longest for YOUR normal handling/feeding AND for your own magazine and chamber length. Within that max, it's up to your rig and your load for what actually works and shoots best.

IME, most factory rifles and common (off the shelf) bullets shoot best with a jump between maybe 20 and 60 thou. "Most" means not all, some like no jump, some like even more jump than 60 thou; there's absolutely no way to guess and changing bullets will require another series of tests because there's no consistancy to it.

As long as we're into this, I doubt that seating into the lands does much for centering a bullet into the bore, SAAMI chambers have too mich slack for displacing the rest of the case off axis for just centering the ogive to do much for alignment. Instead, I believe the real effect from seating depth is controlling the initial powder burning curve sufficent to affect how the barrel harmonics work out. For rifles, seating long greatly accelerates the initial start pressure:time slope of the burn; seating deeper slows that initial burn rate and reduces peak pressure. Therefore, tuning a hand load requires finding the correct powder charge for the best burn for your rig and load AND seating then tweeks the initial and peak burn.

Contrary to another "conventional wisdom" accuracy rule of thumb, I've found that loading down from max pressure does not automatically improve accuracy UNLESS the chosen powder burn rate is too fast. Accuracy counts but so does speed, if I had wanted a .223 instead of a .22-250 or a .30-06 instead of a .300 Win that's what I would have bought! All powders burn most consistantly within a fairly narrow pressure range. The ideal powder and charge is one that reaches the design pressure with a small air space left (i.e., a high loading density). If I can't find an accurate high density load for a powder at or very near normal top velocity for my cartridge and bullet weight I change powders until I do.

Last thoight; being outside the normal pressure range is hazardous because powder burn rates get squirrelly from one round to the next when the pressure is either too low or too high. Meaning an overload that was 'safe' a moment ago just may not be safe the next time it's fired.

Last edited by boomtube; 03-07-2014 at 01:27 PM.
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