Bullet seating length. How are you doing it?
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  1. #1
    Sidewinder
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    Bullet seating length. How are you doing it?

    Important note, I'm not asking how do I do this, more of how do you do it?

    I've read where guys will seat 1 round a little longer than OAL. Then chamber the round so the rifling seats the bullet the rest of the way. Take a measurement then seat the bullets to that length. Others will shorten it 15-30 thou. The Lee 2nd addition states this. They also add, "There is no universal agreement on this". Which I found very fitting in a lot of ways!

    So, what are your methods?
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  2. #2
    Sidewinder
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    No longer than recommended cartridge LOA, but usually so my roll crimp fills 2/3 - 3/4 of the bullet cannelure.

    I only use a LEE FCD on .45-70, otherwise, to LOA but usually where I can crimp into the cannelure. Last few .45-70 rounds I loaded were .010" shorter than recommended LOA.
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    Distinguished Master
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    I size a case, trim to length, and chamfer the case mouth. Then I ream the I.D. of the case neck (I use old or spare cases for this test) to the diameter of the bullet I am shooting, so the bullet is a slip fit. I goop up the base of the sized bullet and the inside of the case mouth with bullet lube, and gently seat the bullet "long" in the case neck....the bullet lube will help secure the bullet. The I put the bullet into the chamber and slowly push the cartridge into the chamber until it is just short of seating. Then I gently close and lock the bolt on the cartridge, then slowly extract the cartridge as to not upset the bullet. Then I take a micrometer and measure the OAL. I normally reduce that length by .005 as a starting point......................keep in mind though, a firearm will only allow a specific maximum length cartridge to cycle so that would be the next step in the process...you may have to shorten the OAL of the cartridge to allow it to cycle in your firearm.
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  5. #4
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    Depends a lot on what I'm loading and why.

    For a lever action rifle, or a semi-auto, I load to factory specs. It absolutely has to cycle through the action.

    For short action bolt action rifles, like my Rem 700 in 308 Win, I load to factory length. If I go longer, the cartridges won't fit in the magazine.

    If I've got some length to play with... Like in a Rem 700 long action - or with my Ruger single-shot rifle - then I will mess with the seating depth trying for better accuracy. Some bullets seem to shoot best with quite a run to the lands, others better when they're nestled right up against the rifling.

    First though, is reliability. It absolutely has to feed properly. And extract without pulling the bullet and dumping powder inside the rifle! I've seen that happen.

    Guy

  6. #5
    Gun Wizard
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    I'm not a benchrest precision shooter or anything like that, I just seat bullet to COL in spec for caliber for cartridges like 243, 308, 30-06 and or seat as far as is needed to crimp at cannalure for calibers that need cannalure in tube fed guns
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  7. #6
    Certified Gunnut
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    Note, this is only useful for loading individual rounds into a bolt action receiver. Many 22 bolt action target chambers are milled so that the (lead) .22 bullets begin to engrave the rifling when the cartridge is fully in battery.

    For a center fire rifle, there are gages that will help figure this out for you. The rifle's bolt is removed and the gage and bullet are inserted into the chamber. The case will headspace on the bottleneck. Basically, there is a threaded bolt adjustment mechanism going through a case that will allow the bullet to be held either more shallowly or further out. I mad my own using a fired case is so that neck tension is not an issue. The bullet is coated with Dykem or black marker so that as the adjustment is turned out, marks can be seen on the bullet ogive when it begins to engrave on the rifling. I used a nut to lock the bolt against the head of a case drilled and threaded to accept the bolt, and I cut and polished the forward end of the bolt where it would contact the bullet.

    The through bolt is adjusted out in steps until the engraving can be seen. After that, you need to have a way to measure the over all length from a fixed point on the bullet ogive. When you set up your reloading die, you will use this measurement for bullet seating.

    Potentially, it is possible to seat your bullets long of the jam length, and allow the camming action of bolt closure to push the bullet back into the case neck as the ogive contacts the lands. However, with this approach neck tension would need to be closely controlled. It would require neck turning and/or reaming to closely control neck tension, otherwise variation in neck wall thickness could prevent the round from being seated into battery. (Bench rest shooters often use custom cut chambers with the chamber neck sized for a certain reamed cartridge wall thickness. Tolerances are so close that the cartridge neck will only stretch within the elastic recoil of the brass before it contacts the support of the chamber wall. The cases are totally formed to the chamber, and the case necks need not be resized to hold the bullet at the next reloading.) As you can see. These are very specialized situations.

    Bench rest shooters will sometimes seat their bullets so that they begin to engrave on the rifling when in battery. They use neck tension only to hold the bullets, no crimp. As a caution, realize that with this method many times, when the round is extracted without firing, the bullet will remain lodged in the rifling, and the powder charge will be spilled into the action making a mess. They sometimes refer to this over all length as the "jam length". It may be that resistance against the lands is more consistent for powder combustion than a crimp. On the other hand, there is some thought that internal powder combustion pressure may be higher at bullet jam length than it is for a crimped bullet allowing some bullet jump before meeting the rifling.

    Weatherby, in it's day, cut the chambers for their magnums to have a generous free bore or bullet jump before encountering the rifling. This was done to lower maximum pressures during powder combustion. This was done despite the understanding that overall accuracy could suffer. Accuracy shooters use much smaller intervals on the order of 0.005-0.020" bullet jump in hopes of maximizing accuracy.

    FWIW, I eventually gave up fussing with the variable of optimum bullet length (optimizing free bore and bullet jump) as I was not shooting bench rest, and I could not measure a bullet length related decrease in group sizes with my rifles. Any improvement is likely to be less than 0.2" of group diameter at 100 yards. For this to be significant, I would suggest that your outfit already be able to consistently group to 0.5" at 100 yards before working on this additional confounding variable. It will take a lot of time and work.
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    Certified Gunnut
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    I load to the specified COL or a little shorter for bullets without a cannelure. Depends on the gun that the rounds are going into. I set the COL based on where I can crimp into the cannelure when present. I load to just shy of the COL for pistol rounds.

    I have never set the COL as they would bench rest shooting. I do measure the COL for each for each bullet style in all rifles that the round will go into to and make sure that the COL does not result in the bullet touching the lands.
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  9. #8
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    One thing for sure.....we can make this rocket science or not. For those interested in the pursuit of "supreme" accuracy the techniques of the competitive Benchrest game are a must...but, for those just looking for decent accuracy to put meat on the table, the normal process of loading and working up a good consistent group/load can suffice. Set a goal and go for it, and, use whatever means need be to get there.
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    Flat Top - yup - adjusting the overall length for best accuracy is much discussed, but... Often the rifle won't let that length be adjusted much.

    Two of my most accurate rifles have magazines which limit my handloads to factory length cartridges, or very close. One is a Krieger barreled 308 Win, Remington 700. That rifle is very accurate - but, I gain nothing by changing the seating depth.

    The other is a 6mm Creedmoor, Ruger Precision Rifle. Good grief that thing is accurate! But there's no point in trying to "load long" because then the ammo won't fit in the magazine.

    Both are very accurate rifles, and I just load them to factory length.

    Happy Thanksgiving All!

    Guy
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  11. #10
    Marlin Marksman
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    For the 44 Magnum lever rifle, I crimp 3/4 of the way up in the groove with jacketed bullets.
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