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  #1  
Old 11-23-2016, 03:08 PM
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Bullet seating question



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I'm familiar somewhat with how to find the maximum seating of the bullet related to ogive contact with the lands on a specific bbl. What I'm unclear on, is what would be considered maximum outward seating of a bullet in a given case regarding the safe or structural integrity of the loaded cartridge. I'm working up a 284 Win load for a custom built rifle which has the chamber cut with a throat longer than I'm compfortable getting within .020 away from lands with certain bullets. I'm loading lighter bullets than the builder planned for.

My question here is this:
How far out in the neck is too far to seat a bullet? My sence is that I ought not seat bullet any further out than the base of the bullet even eith the base of the neck. That would allow full bullet to neck contact for the entire length of the neck. In the case of a 284Win, the neck is relatively short, so this would seem especially so in this case. The cartridge is used in a bolt action box magazine, bullets are hunting loads.
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Old 11-23-2016, 03:19 PM
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Sounds like you are on the right track. You also need to take the maximum length that will fit in the magazine. But that likely won't be at issue since you are loading lighter bullets.

You might want to rethink the whole lighter bullets idea since they may not be stable in your rifle. Generally a custom rifle is built for a particular weight of bullet and lighter weights might not work well.
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  #3  
Old 11-23-2016, 04:10 PM
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I have a long throat in my 6BR, and it is a bit of a problem. If you go to a lighter bullet you should stick to a flat base bullet. You certainly can seat further out than lining the base of the bullet up with the bottom of the neck. In my 6BR I have seated as far out as having only 0.100" in the neck. What I found however is that at some point a shorter light bullet simply will not shoot. A 68 grain flat base Berger Target in this gun will easily shoot down to or less than 1/4" at 100 meters. However I could not keep a 62 grain Berger Target bullet under 2" at 100. At some point you seem to just drop off the cliff. I don't believe it is a stability issue as the short light bullets need the least amount of twist. I think what happens is the bullet gets cocked sideways in the throat before it gets into the rifling, and never straightens out going down the barrel. When it exits the muzzle the bullet remains cocked, and does not fly straight.

I only size about 2/3 of the neck, so for me it is pointless to seat all the way back to the bottom of the neck. I find 1/2 to 2/3 of the neck holding the bullet is ideal, and in some cases I have gone to 0.100" as mentioned earlier. The loads are somewhat fragile though. You can easily grab the bullet with your fingers and wiggle the bullet out!

Last edited by Ron AKA; 11-23-2016 at 04:14 PM.
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Old 11-23-2016, 07:47 PM
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There is no minimum amount of bullet that has to be in the neck. I have a rule of thumb that as Ron has said with flat based bullets I will seat them out to the point of having at least 1 caliber in the neck. in your case .284. With boat tails I will go to where the boat tail meets the bearing surface of the bullet and the neck meets the shoulder. That way you don't get a pinch point of pressure in the neck wall.

Another point that I have found is that the further you seat bullets out, generally the more runout (bullet wobble as you roll it) you get. I have tested that seating my 223 .010 deeper makes lower runout in the whole batch.

Sometimes you have to just jump bullets. Bullets with tangent ogives generally are jump tolerant especially compared to VLD's (secant ogives). Note that a-Maxes are VLD in nature though Hornady doesn't call them that.

David
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Old 11-23-2016, 07:51 PM
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Thanks for the replies. I haven't started yet, but I plan at some point to try resizing the necks only, going about 3/4 of the way down. However since these are hunting rounds fed from a magazine, they need to be fairly robust. If the neck sizing that far does not give me a solid hold on the bullet I will forgo that technique.

The bbl twist is suitable for the lighter bullet I will be trying, and the overall length of that bullet is .009" shorter from ogive to base. That difference in length can be made up in how deep I seat with enough neck remaining to hold the bullet well I think.

I'm using a 140 gr boat tail as my main bullet right now. Have been shooting this bullet well now in this rifle for 20 years. Have that bullet seated so that the start of the boat tail is about in line with the bottom of the case neck. Distance from ogive to the lands is a whopping .076". I generally get 3/4 to 1" groups at 100 yrds though.

So all this also applies to another calculation I'm playing with. I've ordered up another rifle to be built to my specs, also in 284 Win. Since I plan to shoot 120-140 grn Sierra hunting bullets in it, I'm trying figure out how I'd like the 140gr cartridge lengths to be, and how much longer I want the bbl throat cut to. I'm thinking the throat ought to be something like .010 from ogive to lands with the 140 gr loaded to use the entire case neck. That gives me a little play forward and reareard to find the sweet spot without giving up much in either neck contact or case capacity.

Last edited by 284wahoo; 11-23-2016 at 07:55 PM.
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Old 11-23-2016, 09:07 PM
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Bullet Seating

Assuming this isn't a single shot, yes? If it were, you could easily seat out further than the "1 bullet diameter" rule. (which for most purposes is certainly a good rule of thumb.)
Once you start working with one in the chamber and more in the well, you need to be sure that bullets aren't creeping forward from the recoil. At that point you might want to consider a Lee Factory Crimp tool into the equation.
I generally get better accuracy without a crimp, but under some circumstance, and for hunting loads, they do have their place.
FWIW, as they say, Your results may vary.
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Old 11-23-2016, 10:39 PM
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My recollection is that the rule of thumb is to seat 1/2 bullet diameter in the neck as a minimum. I go below that. Also keep in mind that many neck lengths of various calibers are only 0.25", so for many cartridges you could not even seat a full bullet diameter, even if you use the full length.

If it is not too late, and you are doing a custom build, I would suggest doing the .284 in a long action rather than a short action. It will let you seat the long low drag bullets so they do not stick back into the case, and use up case capacity.

Last edited by Ron AKA; 11-23-2016 at 10:41 PM.
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Old 11-23-2016, 10:58 PM
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Quote:
Originally Posted by Ron AKA View Post
If it is not too late, and you are doing a custom build, I would suggest doing the .284 in a long action rather than a short action. It will let you seat the long low drag bullets so they do not stick back into the case, and use up case capacity.
The 284 I currently have is built on a Rem Model 700 short action, with the blind magazine lengthened. I'm able to seat the 140 gr bullets I use well out into the neck with no clearance issues, and no case capacity loss. The new rifle is planned to be dedicated to shooting 140's or lighter, so I think I will be making all use of the case capacity ok. That rifle will be using a custom made action sized to the cartridge as well.

So what is this "1 bullet diameter" rule?
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Old 11-24-2016, 10:14 AM
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Quote:
Originally Posted by dstoenner View Post
There is no minimum amount of bullet that has to be in the neck. I have a rule of thumb that as Ron has said with flat based bullets I will seat them out to the point of having at least 1 caliber in the neck. in your case .284. With boat tails I will go to where the boat tail meets the bearing surface of the bullet and the neck meets the shoulder. That way you don't get a pinch point of pressure in the neck wall.

Another point that I have found is that the further you seat bullets out, generally the more runout (bullet wobble as you roll it) you get. I have tested that seating my 223 .010 deeper makes lower runout in the whole batch.

Sometimes you have to just jump bullets. Bullets with tangent ogives generally are jump tolerant especially compared to VLD's (secant ogives). Note that a-Maxes are VLD in nature though Hornady doesn't call them that.

David
"Pinch point of pressure in the neck wall". That is a very interesting statement. Can you ellaberate please? Is this a concern unique to boat tails? Is it a concern any time the boat tail is seated above the neck base? How does it manifest?
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Old 11-24-2016, 10:57 AM
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Originally Posted by 284wahoo View Post
So what is this "1 bullet diameter" rule?
Never heard of it. I have heard 1/2 of a diameter as a minimum. The neck length in a 284 Winchester is about 0.285, so you would have to use the whole length to follow that one diameter rule. Not at all necessary. To shoot different bullets, with boat tails and flat base, and the very long low drag, you need room to adjust to each bullet.

My target would be to keep all bullets of interest with the base or start of boat tail no lower than the start of the neck, and a minimum of half the neck in. As mentioned before you can stretch that some, for target use anyway.

As dstoenner mentions, the VLD bullets will often do well with a jump, while the newer Hybrid Bergers like to be seated closer to the lands. Some more info here.

A .284 Winchester is a nice cartridge by the way. I would plan it for more than a 140 grain to take advantage of the 168 and 180 grain low form factor bullets that are on the market though. 140 grain is a nice bullet weight for a 6.4x284, but a little light for a 7mm. Ballistics suffer.

Last edited by Ron AKA; 11-24-2016 at 11:01 AM.
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Old 11-24-2016, 12:30 PM
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Quote:
Originally Posted by 284wahoo View Post
"Pinch point of pressure in the neck wall". That is a very interesting statement. Can you ellaberate please? Is this a concern unique to boat tails? Is it a concern any time the boat tail is seated above the neck base? How does it manifest?
If you seat the boat tail so that the boat tail junction is up in the neck, then you get the triangle donut shape. It is this sharp point shape that concerns me. Point shapes and pressure can do strange things. Where as if the junction of the boat tail with the bearing surface and the shoulder to neck, then you have a much broader angle and less stress.

I am an electrical engineer, not mechanical so maybe it is much ado about nothing. It is something that I have avoided in my reloading. I only have about 15 years of reloading making me a youngster compared to others here.

David
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Old 11-24-2016, 12:41 PM
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Quote:
Originally Posted by Ron AKA View Post
Never heard of it. I have heard 1/2 of a diameter as a minimum. The neck length in a 284 Winchester is about 0.285, so you would have to use the whole length to follow that one diameter rule. Not at all necessary. To shoot different bullets, with boat tails and flat base, and the very long low drag, you need room to adjust to each bullet.

My target would be to keep all bullets of interest with the base or start of boat tail no lower than the start of the neck, and a minimum of half the neck in. As mentioned before you can stretch that some, for target use anyway.

As dstoenner mentions, the VLD bullets will often do well with a jump, while the newer Hybrid Bergers like to be seated closer to the lands. Some more info here.

A .284 Winchester is a nice cartridge by the way. I would plan it for more than a 140 grain to take advantage of the 168 and 180 grain low form factor bullets that are on the market though. 140 grain is a nice bullet weight for a 6.4x284, but a little light for a 7mm. Ballistics suffer.
The 1 caliber minimum in the neck is my rule based on finding that I had large runout when I tried seating less. By keeping at least 1 caliber, I could get a resonable amount of my seated loads to be 3 mil runout or less.

Actually I shot Berger hybrids in both my 260 Remington and my 6BR. I seat my 140 hybrid for my 260 at 2.950 COL. This is seated to within .025 of the lands so that if the line has to go cold, I can eject the round without issue. According to my spreadsheet, I can go to 2.992 before I exceed the boat tail neck junction rule I have already talked about. Then it would just start jumping more. According to Bryan Litz, who created the hybrid design, they were made to be jump tolerant and therefore more flexible than the VLD type of design.

Berger did come out with a paper that said you need to test a VLD for your chamber and rifle. Not all chambers like a jam or small jump. Some like a big jump. They recommended testing at -.010 (jam), .010, .040, .080. .120 to see where you could maybe tune for better results.

One thing for sure in reloading, there are no absolutes.

David
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  #13  
Old 11-24-2016, 02:27 PM
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Quote:
Originally Posted by dstoenner View Post
I am an electrical engineer, not mechanical so maybe it is much ado about nothing. It is something that I have avoided in my reloading. I only have about 15 years of reloading making me a youngster compared to others here.
I am a mechanical engineer and I would suggest it is not something to worry about. Even with a flat base bullet I only resize 2/3 of the neck so that last 1/3, at least in theory has a slim space around the base of the bullet. Those are my most accurate loads.

That said it is widely recognized that for short range (100-200 meters) flat base bullets are more accurate than boat tail. Boat tails only start to out perform flat base when the distance increases and resistance to wind effects becomes more important than pure precision. The tail of the bullet is very important to accuracy, and my understanding is that flat base bullets are easier to make consistent than boat tail. Flat tail bullets also have a pressure ring of increased diameter at the base that probably increases the fit in the barrel to ensure a bore concentric start to the path down the bore.
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Old 11-24-2016, 06:24 PM
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You folks are pitching me some very helpful feedback, thanks again.

In response to the comment of getting the new rifle built to handle the bigger 7mm bullets...my current rifle is like that now, I wanted to maximize the second 284 for the lighter bullets.

I find it particularly good to learn that boat tails are prone to be less accurate at 200yrds and under than flat base bullets. I'm intending to use the lighter bullets in flat base configuration, and expect to seat these further out in the neck than the 140s. Sounds like that will work out good.
I will need to re-read your comments again a few more times to be sure I mine all the nuggets of good info.

Last edited by 284wahoo; 11-24-2016 at 06:32 PM.
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Old 11-24-2016, 08:06 PM
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Finding match grade bullets that are flat base and 140 grains and less is going to be your issue. Berger makes no flat base bullets at all in 7mm. I don't think Lapua either. Sierra make some flat base, but not match quality. Hornady I see one V-Max at 120 grain, but again, not really match quality.
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