Thanx for any comments/advice in advance. Have a m16 in .308 win. Have the Hornaday OAL guage to measure the base (bolt face) to ogive. I get 2.83 with Hornady 150 gn sp interlock #3031. Using 20 thousandths as a starting point to seat the bullet off the lands, (2.23 - .020) I seated bullets to 2.21. The bullet was seated WAY below the crimp ring, and left me with about 24/thousandths bearing surface. It is my understanding (confirmed by both Hornady and Sierra) that the bearing surface should be at least as deep as the caliber of the bullet (.308), which would be 1.992. Waaaay off the lands. Am I over thinking this? Are my calculations wrong? Anybody have a m16 in .308 they can measure for me??
The bearing surface of a bullet is what it is regardless of seating depth. That doesn't change.
Seating dept should be about the caliber of the bullet's bearing surface supported by the case neck. The boat tail will likely be well into the shoulder area (or slightly below). All you lose is power space - but longer bullets/heavier/more bearing surface need less powder to get to the maximum pressure, anyway. Some, like the .223 Rem, don't have enough neck but shoot well in spite of it.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
If your base to Ogive measurements at the lands is 2.83 then 20 thou off (.020) would be 2.63 Base to Ogive to get your .020 jump.
Correction 2.83 - .020 would be 2.81. We usually measure out 3 decimals...
I think 2.83" was his overall length. SAAMI COL for the .308 Win is 2.800"
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
This is the correct way to measure Base to OGIVE. You need to first verify distance to the lands then take this measurement and determine your seating depth to get your intended jump.
This is the Hornady OAL Gauge and a picture with barrel cut out showing the bullet in the modified case getting a measured distance to the lands. Last picture shows taking the measurement.
Thanx for the responses. 2.830 is the measurement of my chamber using the Hornady guage. Seating the bullet to 2.810 (-.020) puts very little of the bullet into the case mouth. I may be overthinking this. I understood bearing surface to mean how far the bullet seated into the case. No? Out of curiosity I measured a Federal 180 gn and got 2.105. That's a heck of a jump! Anyway, gonna go with COL for the time being.
No. What you are describing is seated depth. The bearing surface is the portion of the bullet that contacts the valley of the grooves in the barrel. The parallel part of the bullet. If you rolled a bullet across an ink pad and then a piece of paper the bearing surface would be what left a black stripe on the paper.
To minimize run-out (bullet wobble) you want as much of that parallel portion supported by the neck as possible.
Check how you are using the Comparator. I have a .260 Rem (same case as the .308 but necked down) and my base-to-ogive runs from 2.263" to 2.287" (touching the lands) depending on bullet. Yours should be similar. My .260 has a pretty small leade (from what I am used to) and I have to seat much deeper than tha magazine would allow. But I'm not trying to max out speed so I don't mind. I am currently using a 0.015" jump and with the boat tail bullets I use the bases are at or below the widest part of the shoulder. So I set my seating die for 2.248" to 2.272" (base to ogive) depending on the bullet.
This link is Hornady's on using the Comparator: https://www.youtube.com/watch?v=3kL0HIgqqjU
Your Hornady #3031 is flat based and you shouldn't have much worry setting at a spot other than the channelure. Think of it as the Interlock ring to limit expansion rather than a crimp groove. I never crimp bolt action bullets in place and my 140 gr Hornady SST have the chanellure groove almost 3/16" ahead of the case mouth).
PS - when you say your "chamber" is 2.83" that is .003" longer that a "typical" loaded .308 Win round is from cartridge head to bullet tip. Your "chamber" should be 2.1835" (length of empty case) to the case mouth plus some leade of another 0.25"+/- until the ramp of the rifling starts. Since the bullet is pointed the part that doesn't contact the barrel wall is ignored for base-to-ogive measurements.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
Sorry about the numbers. 2.235 is the correct length. Have measured many times. Watched the video you linked and I'm doing it correctly. I see in the video the "crimp" ring of his rounds is past the mouth of the case, similar to what mine are doing when I subtract .020 and seat to 2.215 base to ogive. My concern is not having enough of the bullet seated in the mouth. These are intended to be hunting rounds. I called Savage and they won't say what the base to ogive length is supposed to be, only to send rifle in if I think something is wrong. Going with COL for now. When I seat to COL, bullet seats to beginning of crimp ring. Don't mean to turn this into a reloading forum. Was hoping someone with a m16 in .308 WIn would measure their base to ogive.
You won't find two with the exact same measurement.... Post some pictures of what you have going on. I don't believe you have an issue or you may not be explaining it correctly. Either way we'll help you get there and do our best to help you understand.
I'm famous for not being able to accurately articulate either verbally or in writing what's going on in my head. Which is some cases is a good thing :) Standard disclaimer: Any confusion on my part is unintentional. Sometimes. I can, however, communicate accurately through interpretive dance. I'll post a video shortly called "Moustache-hair caught in beer can tab" in the humor section.
Can't help you there. Don't have a .308 or a Model 16.
But if that is what your leade measurement (Base-to-ogive) is telling you, and you can't pull the bullet out of the case with your fingers or push it in with your thumb you are probably good to go (with a bolt action).
Here's a simple test: lay one of your loaded cartridges on a flat surface and roll it. Does the tip of the bullet appear to be centered or is it "wobbly" as the case rolls? You may be getting run-out if not seated deep enough. If it spins true - good to go.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
Thanx, I'll give that a try.
I don't have a Savage in 308 but I do have a Remington 700 308 and it has a very long throat in it. You would have to look up the SAAMI specs for the 308 and see what it is. I think it calls for a long throat to accommodate long round nose bullets.
See below. But the base-to-ogive changes with every make and weight of bullet choice. And also whether the reamer Savage was using was fresh or had a few thousand barrels cut before it was replaced.
"They couldn't hit an elephant at this distance." Last words of Gen. Sedgwik
I have a 308 and still have the factory barrel measurements with Sierra 150 Pro Hunter. It is fairly close to the Hornady profile.. It measured 2.236 from case head to ogive where it hit the rifling so at 2.235 your barrel sounds about right.
Generally with a flat based hunting bullet I seat it so the base is even with the bottom of the case neck. Measure the ogive at this point and you should be good. Hunting bullets tend to be more forgiving when it comes to jump so if it exceeds the .020 it’s not really a big deal. If you seat them out to far you could have bullets slipping out in the magazine under recoil. So you might just have to seat them deeper and just work with charge weights until you find one that give you acceptable hunting accuracy.
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