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I've read some discussion in gun magazines about some bullets requiring deep seating in cases and that this takes away powder space. Usually this is stated as a negative. For larger cased cartridges reloading manuals show that most powders don't come close to using all of the case capacity. So for those cartridges does deep seating of long bullets make any difference? What good is the case capacity if you can't put powder in it? Just trying to understand things a bit better. Thanks for any help. David | ||
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While reduced case capacity is one part of the issue with "deep seating," most people are concerned with getting the bullet close to the lands for optimal accuracy--sometimes resulting in the opposite question, "how little bullet needs to be in the case?" But this too is not a guarantee as some guns/bullets shoot better seated further off the lands. R | |||
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It's actually not a negative at all if you are using one of the loads that leaves a lot of empty space in the case. However, if you want to use one of the loads with slower powders that fills up the case under the bullet, then it could get in the way of using that load. Most of my rifles seem to like slow bulky powder that fills up the case. | |||
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IMHO , this is something gunwriters like to fantasize about being relevant. Comparison of different cartridges/bullets from the perspective of looking at them " on paper ". Actual results are that deep seating will raise pressure somewhat due to reduced case volume. Yeah, even though the space is not filled with powder it still matters pressure wise. How much it matters to the actual bullet choice and maximum velocity attainable with a given pressure is less important than the performance of the bullet. ( A fancy way of saying " use what works, and don't sweat the small stuff ".) I would gladly trade a little velocity for the correct bullet. Travis F. | |||
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If you wanted to use the heaviest bullet in a particular bore diameter in your rifle, you would elect to have the bullet seated to be level with the base of the neck, so that the bullet has the best chance of being correctly aligned, and the full usuable case capacity is utilised providing a powder with the correct burning rate is selected. However, usually rifles are throated so that the base of the bullet in the middle of the bullet weight range for that calibre is at or near to the base of the case neck,then obviously the heavier and longer bullets will then project below the case neck. I have found that acceptable accuracy is still usually obtainable in these situations and as an example I recently accuracy tested and chronographed the Nosler 115 grain BT in a my 25/06 AI, and consistently obtained sub 0.5 moa groups from a slightly compressed load (63.0 grains) of Hodgdon 1000 and a velocity of 3,255 fps. In this instance this bullet is projecting about .080 inches below the base of the neck, as I had my gunsmith throat the rifle so that the base of the Nosler 100 grain BT bullet would be level with the base of the neck. Currently there is very large number of powders commercially available covering a wide variety of burning rates, so even with cases with a capacity of up to 100 grains (and maybe larger) you should be able to select a powder that will give you a minimum of air space in the case. To achieve the goal of 100% loading density, I measure the amount of powder it takes to fill the case to the base of the neck with the three basic powder types, and then look at one or more of the burning rate lists to see which powders are likely to be most suitable. To give you an example, a fireformed resized case in the newer of my two 25/06 AI takes: 71.1 grains of water to fill to the top of the neck 61.5 grains of long cut extruded powder (IMR 4831, 7828)to fill to base of the neck. 63.5 grains of short cut extruded powder (H1000, Re 22 etc) to fill to the base of the neck. 66.0 grain of ball powder (H870, Ramshot Magnum, etc) to fill to the base of the neck. Hope the above information helps. Brian. | |||
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Quote: Hey David, They write about those things because they are at a total loss to come up with something which will make a useful or worthwhile article. ... However the article did get you looking at a Load Manual, which to me means that totally worthless article was not as worthless as I give them credit for. Articles that create opportunites for "thinking" seem to be in short supply. The part that I'll probably have trouble getting across, is you have the "cart slightly before the horse" so to speak. First off, two things will determine the "actual" Seating Depth of the Bullet(s) - the distance to the Lead and the length of the magazine, not the Overall Length seen in the Manuals. To state the obvious, your loaded Cartridge must fit inside the magazine with enough clearance for the cartridge to move freely. And it must also be short enough that you can close the Bolt on it. The final "length" of the cartridge is not something you get out of the various Load Manuals. You measure this distance for each new box of Bullets(even if they are the same Part#) in the Barrel using any of the various Methods available(I like the old Cleaning Rod Method) and you must also measure the magazine. This Seating Depth will vary slightly from firearm to firearm, even made side-by-side on the same manufacturer's production line. Once you know the MAX Seating Distance, you shorten the Seating a bit and then begin developing the Load from below. ... The information in the various Load Manuals is specific to the firearm they developed their Loads in - only! When we use that data, it is only for a "Reference" and our Final Load will rarely be exactly the same as found in the Manual. Which gets us back to your original question. Once you know the Seating Depth for your firearm with a specific Bullet, you can look in the Load Manual and get a "general idea" about which Powder will fill the Case to the Bullet Base. But, you may get Pressure Indications as you Develop your Load before you get enough Powder in it to reach the Bullet's Base. If so, you can either change to a slightly slower Powder, or reduce the amount of the current Powder. Or the opposite may be true. You may run out of Case capacity before you reach any Pressure Indicators at all. You can accept that Load, or redevelop with a slightly faster Powder. ... Good observation on your part, but it is not something to concern yourself with at all "IF" you follow proper Load Development procedures and think of the Manuals as Guidlines only. Best of luck to you. | |||
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Thank you all for your input. You learn something new all of the time. David | |||
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The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Bullet seating depth question
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