Very interesting sp6x6.Thanks for the info!
Seating bullet depth
- Thread starter baydog
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jimbires
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westcliffe01
Well-Known Member
If I'm loading a new bullet for the first time, then I always do a little "discovery" to see if the magazine is going to limit the OAL or if it is the chamber/throat. So on the first one I load, I load it to the MAX OAL that I know the magazine will feed. Then chamber it to verify whether it is touching the rifling or not. If it is already touching the rifling, then I continue to seat progressively deeper until I reach the point that I can chamber it without shortening OAL.
I make note of this dimension to know to always stay under that value, otherwise you have the risk of sticking a bullet in the rifling and leaving it behind when unchambering the round. That can make a mess or blow up your rifle, depending on the next action you take (don't try chambering a second round behind it !!!)
The Savage centerfire magazines are very generous for cartridge length, much more so than AR type magazines, so often it is not the magazine that limits the OAL, but the chamber.
Depending on the bullet, optimum seating depth is usually from a few thou off to as much as 0.030" so knowing where contact occurs is a good starting point. I will find a good barrel/charge node first, then fine tune seating depth, then possibly fine tune load a bit more.
I make note of this dimension to know to always stay under that value, otherwise you have the risk of sticking a bullet in the rifling and leaving it behind when unchambering the round. That can make a mess or blow up your rifle, depending on the next action you take (don't try chambering a second round behind it !!!)
The Savage centerfire magazines are very generous for cartridge length, much more so than AR type magazines, so often it is not the magazine that limits the OAL, but the chamber.
Depending on the bullet, optimum seating depth is usually from a few thou off to as much as 0.030" so knowing where contact occurs is a good starting point. I will find a good barrel/charge node first, then fine tune seating depth, then possibly fine tune load a bit more.
boomtube
Well-Known Member
So, you're saying you're a reloading expert that didn't know some cartridges have necks shorter than caliber and, by default, your reading or logic comprehension converts that to 10 thou? WOW ha ha ha
jimbires
Well-Known Member
So, you're saying you're a reloading expert that didn't know some cartridges have necks shorter than caliber and, by default, your reading or logic comprehension converts that to 10 thou? WOW ha ha ha
your the expert .
here is the info sp6x6 is talking about .
[/QUOTE
Wow Jim there it is in black and white. I understand this is a starting point but this is at least a good safe starting point for depth..Great info !
Thanks Jim
baydog
Ok this what I got going on. Trying to get to know this new gun. It's a new Sendero 300 RUM..To some it ain't so big but to me it's a big *** gun And I'm trying to ease myself into the guns full potential and gain confidence in the gun and myself shooting it. Been asking a lot of questions and everyone has been very helpful and I thank you all for answering them..For the last 5 days I 've shot 5 rounds through the gun each day. I know I'm going catch hell for using the load that i have been shooting but like I said I'm trying to get to know the gun and gain confidence in the gun and myself shooting it...I used 94 grain of Retumbo powder and I had a open box of 165gr. Sierra bt. bullets and wanted to use them up and work my way up to the 200 gr.Nosler Accubonds I plan on being the load I stick with. I have a box of 180 grain Nosler Ballistic Tip That I 'm going to use up too while experimenting trying to find a load that works best for me and the gun. The picture with the least amount of holes in it is @ 50 yards to get the gun zero in on paper. That target had 5 rounds thrown at it. Then I moved back to 100 yards and that is the picture with all the holes in it. I shot 5 rounds a day for 4 days at the same target, so it's suppose to be 15 holes in that target. Some holes were shot through a couple of times. The OAL to the lands is 3.747 but i had to sink the bullet in to 3.600 so the cartridges would fit in the magazine. The holes in this target that have a small circle around them are all 165gr. bullets with 94gr. of Retumbo with a OAL of 3.600 but the holes with a small line pointing at them were shot the last day. The difference in the last day and the last 5 bullets are that i seated the bullets in deeper .50 making the OAL 3.550 and this OAL seemed to shoot higher and more consistent group. So what I've learned from this is that some Bullet Jump turns out to be a good thing to me where I thought it would be a bad thing and always tried to get as close to the lands as I could. I'm sure I'll find that some guns like it close and some don't but this one seems to like some Jump. So now I believe I have a better understanding of bullet depth and having to hammer it out for each gun and probably each bullet weight for the gun...So now I'm hoping to tighten my groups up now by trying different amounts of the Retumbo. So I guess it's back to the hammer to find the sweet spot for powder to tighten my groups up....Am I anywhere close to being right as far as now to tighten my groups it will take a fine tuning of the amount of powder to use??..
Thanks for your time and help
baydog
Thanks for your time and help
baydog
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boomtube
Well-Known Member
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.
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.
longrangebo
Well-Known Member
- Joined
- Oct 8, 2005
- Messages
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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!
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 *** 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
LaHunter
Well-Known Member
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
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
boomtube
Well-Known Member
"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.
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.
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