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Bullet seating depth in casing
- Thread starter Usmc_0331
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As far as you want as long as you understand how you will need to remove powder the deeper into the case you seat.
One needs to be aware that as bullets are seated deeper, pressure increases . . . especially if a bullet is seated deep enough to actually compress the powder. If the powder load is already producing pressure near or at maximum, deeper seating can easily then produce pressures well above maximum (quite a few reloaders will go above maximum to get as much velocity as possible, but need to be very careful about doing so). As long as the bearing surface is making good contact with the neck, you can go as deep as you want.
Most precisions shooters, for accuracy's sake, don't like to seat the bullets where the bearing surface touches the area where the donut forms at the neck-shoulder junction on reloading, which means they will typically seat the bullets long. But, some of this may depend on how one prepares the case to deal with the donut issue.
Depending on the cartridge and bullet, you might want to seat them shallower to reduce bullet jump and gain accuracy. Please include some details about the specific cartridge, bullet, and powder load you are thinking of. Also whether you're using a bolt-action or semi-auto rifle.
For example, I'm hand loading 6.5 Creedmoor with 41.0 grains of H4350 powder and 140 gr Hornady ELD-Match bullets. The cartridge over-all length (COAL) of my reloads is longer than the Hornady factory ammo with the exact same projectile. The bullet in the factory ammo is jumping 0.047" in my rifle. My reloads are jumping about half that distance and the 5-shot groups are much tighter.
For example, I'm hand loading 6.5 Creedmoor with 41.0 grains of H4350 powder and 140 gr Hornady ELD-Match bullets. The cartridge over-all length (COAL) of my reloads is longer than the Hornady factory ammo with the exact same projectile. The bullet in the factory ammo is jumping 0.047" in my rifle. My reloads are jumping about half that distance and the 5-shot groups are much tighter.
I would argue that it's NOT the jump that is working for you, but it's the seating depth. If you keep loading to that same seating depth as your throat erodes making your jump longer, your groups will remain good for some time . . . . maybe even for the life of your barrel.
It’s bolt action chambered in 375 ruger. I have been looking at 300 grain mth bullets from cutting edge. The majority of 375 bullets for the 375 ruger seem to be 1.5 in in length. The mth bullets are 1.8 in in length. As far as powders imr 4350 seems to be a win with other loads
That applies more to pistol than rifle, the deeper you seat the further you are from the lands and the less the pressure until you really start to compact powder.
I looked up the Cutting Edge 300 gr MTH bullet. https://cuttingedgebullets.com/375-300gr-single-feed-mth-match-tactical-hunting
It has an overall length of 1.723". While this is longer than some of the other .375 bullets, keep in mind that this bullet has a with a long, pointed nose that can likely extend into the throat without engaging the lands/rifling. Compare this bullet's shape to the projectiles you are presently using. I suspect the additional 0.223" can likely be tolerated unless you have a specific reason for maintaining the COAL of .375 caliber cartridges that use shorter (stubbier) bullets.
My reloading book lists the .375 Ruger as having a maximum case length of 2.580" (min of 2.570") and a maximum COAL as 3.340". Assuming the maximum COAL and case lengths, 0.76" of your 300 gr Cutting Edge bullet is allowed to extend beyond the case.
Sorry, I have to agree with Spife7980 on this one. Rifle powders are slow burning compared to handgun powders. The peak pressure in a rifle occurs in the first couple of inches. With seating depths we are dealing with changes that are measured in hundredths and thousandths of an inch. One graph puts the peak pressure in a rifle barrel occurring at time = 0.5 millisecond.If you're talking about the peak pressure, you're simply wrong about that.
The newest Hornady reloading book (11th edition) does not list a 375 Ruger bullet heavier than 300 grains.
Very well, here’s a link to them. I haven’t been able to find reloading data on it at all.
Creedmoor Sports - Precision Reloading and Shooting Gear
Shoot and Reload with the Pros! Creedmoor Sports has served the Precision Shooting Community for over 40 years in Centerfire, Small-bore, Air Rifle and Pistol Disciplines.
www.creedmoorsports.com
Your screen captures prove my point. The peak of the red curves (max pressure) occurs after the projectile has traveled somewhere around 2 to 2.5 inches. (sorry, I can't make out all the details on your screen capture graphs.) So the bullet has left the casing and traveled more than its entire body length before maximum pressure is reached. Bullet jump is measured in hundredths of an inch. So the bullet has fully engaged in the rifling (effectively sealing the gasses behind itself) and begun traveling about 2" down the barrel before maximum pressure is achieved. Yes, pressure ramps up quickly, but it doesn't peak until well after the bullet separates from the casing.
That looks like some pretty neat information. What software was used to generate the data? Is it an online program?
Did you notice that the A-tip's intended application is target/match shooting and not hunting?
For more information about the lands and bullet seating depth, check out this YouTube video from Ultimate Reloader. Gavin demonstrates three methods of measuring where the rifling starts in your Ruger 375. With a bolt action rifle it is much easier than a semi-auto.
Having that information allows you to determine the allowable COAL for your rifle. Eric Cortina says: Take the lands dimension, subtract 0.020" and consider that as the maximum allowable length. Then make several rounds at that COAL and at every 0.003" shorter than that. Shoot 5-shot groups at each COAL dimension and see which COAL produces the tightest groups.
(In my specific case, I made cartridges with COALs of 2.827", 2.824", 2.821", 2.818" and 2.815")
Keep in mind, this is done by precision shooters looking for highly consistent 5-shot groups, smaller than 1/2 MOA. If you click on my user picture, you'll see a 6.5 Creedmoor 5-shot group at 100 yards using Hornady 140 gr ELD-M that was seated with a COAL of 2.824". Factory ammo (with the exact same 140 gr ELD-Match projectile) has a COAL of 2.800". For scale, the grid squares are 0.25" and the blue circle is 1" in diameter.
The point is, when you seat deeper the peak pressure increases (as does the velocity) as well as decreasing the barrel time. What's concerning about pressure is the safe limits of peak pressure. When peak pressure occurs doesn't matter much . . . maybe, unless one is loading cartridges to be jamming the bullets into the lands. (BTW: click on the picture to enlarge it for viewing details better)
The software is QuickLoad and is not an online program. It's an imported program from Germany and because of it's nature, the rules don't allow for it to be accessible on line. But, you can get it here. There is very similar program, Gordon's Reloading Tool, that's free and can be had here.
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