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Old July 27, 2020, 08:52 PM   #1
reloader74
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Help with finding bullet jump

Trying to get .005”set back from lands. But when using Hornady ogive gauge with a fired form case I think the bullet is hitting the edge of the free space before hitting lands. 308 Hornady sst Bullet. Getting 2.740” oal. Tried seating oal to 2.800” but bolt will not close. Anyone have same issues. Gun is a savage 10PT-sr
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Old July 28, 2020, 12:11 AM   #2
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Reloader74 welcome to TFL

Quote:
Hornady ogive gauge
Do you mean the Hornady cartridge over all length gauge which is the one you use a modified case and insert it into the chamber and push the bullet forward with a rod ? Or the headspace gauge with bullet comparator attached which attaches to your calipers ? I ask because it's two different answers .
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Old July 30, 2020, 03:01 PM   #3
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Reloader74,

This is a total change of topic from the original thread. You need to start a new thread when the topic is different. You do it this way:



I will make your question it's own thread.

If I understand correctly, you are using the Hornady comparator on your caliper but not their Overall Length gauge. Instead, you are using an as-fired case with the neck split or otherwise set up for the bullet to slip into it with light friction. It is easy for the bullets to hang up and press into the case too far. It is also easy for the bullet to get pulled out of the case a fraction when you extract it. The best way I've found is to point the muzzle of the gun up and use your finger to gently seat the dummy cartridge, wiggling it as soon as you feel it begin to resist insertion to be sure the bullet slides past the mouth of the freebore portion ahead of the actual throat. A little light oil on the bullet can help. Once the bullet and case are fully in, do not pull them out, as that can pull the bullet out of the case neck. Instead, turn the gun horizontal and gently push it out with a cleaning rod pushed in from the muzzle. This will cause the least stress and get you the most accurate bullet location.
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Old July 30, 2020, 04:17 PM   #4
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A tip for removing the stuck bullet or it falls out of the case, use the appropriate sized wood dowel available at the big box hardware stores. They also come in handy for other items you may/may not get stuck in bore instead of using a cleaning rod around the muzzle.
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Old July 30, 2020, 06:17 PM   #5
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I seat a bullet long and stuff it in the chamber with my thumb. Tilt the muzzle up. Keep seating it deeper until the ctg drops from the chamber when you lift the muzzle. That’s zero jump. Quick, easy, and repeatable.
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Old August 2, 2020, 01:25 PM   #6
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Quote:
Tried seating oal to 2.800” but bolt will not close.
.308 Winchester???

Maximum overall loaded length with bullet is 2.800"

If you bolt won't close on that, it needs to go back to the factory.
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Old August 4, 2020, 03:13 AM   #7
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Personally, i'd throw the freak'n Hornady gauge away!
More threads with more issues using it than any reasonable need!

Use a fired case, size neck enough to hold bullet finger tight. Leave bullet seated long.
Carefully chamber. Do NOT pull the trigger.
Open bolt slowly, and extract cartridge.
Measure.
Do this 3 times to ensure nothing wonky on measuring. This is your to the lands with THAT bullet.
Subtract your desired distance (jump).
Go forth & reload.
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Old August 4, 2020, 05:33 AM   #8
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Quote:
Personally, i'd throw the freak'n Hornady gauge away!
More threads with more issues using it than any reasonable need!
Haha , although I own one and use it with good results . I have to agree with you that many have a hard time using it . It's not an easy tool to use .

What happened to the OP ?
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Old August 4, 2020, 11:11 AM   #9
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Quote:
Originally Posted by reloader74 View Post
Trying to get .005”set back from lands. But when using Hornady ogive gauge with a fired form case I think the bullet is hitting the edge of the free space before hitting lands. 308 Hornady sst Bullet. Getting 2.740” oal. Tried seating oal to 2.800” but bolt will not close. Anyone have same issues. Gun is a savage 10PT-sr
Where's the edge of the free space. Free space (freebore?) starts at the chamber mouth and its front end is where the rifling lands of the throat angle down 1.75 degrees to bore diameter.

Last edited by Bart B.; August 4, 2020 at 12:03 PM.
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Old August 4, 2020, 11:28 AM   #10
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Originally Posted by 44 AMP View Post
.308 Winchester???

Maximum overall loaded length with bullet is 2.800"

If you bolt won't close on that, it needs to go back to the factory.
If the factory chamber meets SAAMI specs, I think it's up to the rifle's owner to use ammo that functions freely in it.

There's no bullet ogive shape spec. SAAMI specs for 308 Win cartridge length is 2.490" minimum, 2.810" maximum. The rifling at the .310" diameter freebore front end starts angling down .090" forward of the chamber mouth. Bullet and chamber diameters have at least .002" tolerances.

All the Hornady SST pictures on Hornady's site show them seated so case mouths can be crimped into bullet cannelure. If their loaded 308 ammo is less than 2.81" long, Hornady may want it to easily function in SAAMI spec chambers.

https://www.google.com/search?q=horn...obile&ie=UTF-8

Try rounds with 2.700" OAL.

Last edited by Bart B.; August 4, 2020 at 06:00 PM.
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Old August 4, 2020, 12:42 PM   #11
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Are we talking about a hunting rifle here? if so this is simply much easier to accomplish. Size a case, FL or neck doesn't matter. Start a bullet about 3/4 way down the neck and try to chamber the round slowly, carefully! Slowly and carefully will let you feel the bullet rub on the rifling but not let the bullet stick if your gentle. You feel if, remove the round and screw down the seater a bit more. Keep doing that till you can no longer feel the bullet rub on the lands. Something that occurred to me over the years is that more people spend far to much time trying to make their hunting rifle a one hole match rifle! ya ain't gonna make it! Good match rifle in good hands is gonna beat you every time!
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Old August 5, 2020, 08:13 PM   #12
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Quote:
Originally Posted by std7mag View Post
Personally, i'd throw the freak'n Hornady gauge away!
Good idea considering the SAAMI 30 caliber chamber throat (leade) angles range from 47 minutes to 2 degrees 29.5 minutes. A given bullet will have several rifling touch point diameters across all 30 caliber chambers.

There's 2 flies in this ointment; custom chambers often have different leade angles and the case head is some thousandths off the bolt face when the round fires.

Hornady has made other reloading gauge boo-boo's.

Last edited by Bart B.; August 5, 2020 at 09:02 PM.
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Old August 7, 2020, 02:07 AM   #13
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Quote:
Originally Posted by std7mag View Post
Personally, i'd throw the freak'n Hornady gauge away!
More threads with more issues using it than any reasonable need!

Use a fired case, size neck enough to hold bullet finger tight. Leave bullet seated long.
Carefully chamber. Do NOT pull the trigger.
Open bolt slowly, and extract cartridge.
Measure.
Do this 3 times to ensure nothing wonky on measuring. This is your to the lands with THAT bullet.
Subtract your desired distance (jump).
Go forth & reload.
This is how I've been doing it for years but I back off .002". I tried experimenting with different spacing years ago but if I can, I always go with .002"... Your mileage may vary.

Tony
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Old August 7, 2020, 10:02 AM   #14
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Note the bullet touch point on the angled throat moves further down a 308 Win barrel about .001" every few dozen shots. Throat erosion is something we have to deal with if we want the same bullet jump to the rifling all the time. It's often called "chasing the lands." 30 caliber magnum barrels erode 2 t0 3 times faster.

Military 30 caliber bore erosion gauges whose tapered section diameter gets smaller .001" in diameter every tenth inch of length. It goes one tenth inch further into the throat for each .001" increase in diameter. It reads 5 at the receiver reference point after about 5000 rounds. Barrels in service rifles were typically replaced when it read 10 around 10,000 rounds. Match grade barrels used in competition got replaced when they read 3 or 4 for top ranked shooters producing best scores.

Last edited by Bart B.; August 7, 2020 at 10:37 AM.
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Old August 7, 2020, 11:00 AM   #15
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Quote:
Maximum overall loaded length with bullet is 2.800"

If you bolt won't close on that, it needs to go back to the factory.
I don't reload rifle ammo so I'll ask why not load a round at minimum OAL and work up to maximum and find the longest OAL that will work in that chamber. Regardless of what we want to believe no 2 chambers are identical. New tooling verses half worn to I should replace the tool will give varying chamber dimensions. Reamers, cutters wear.
My 9 mm Springfield 1911- OAL 1.120 works
my Tangfolio 9 mm - OAl 1.069 works anything longer and I'm into the lands
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Last edited by Don P; August 7, 2020 at 11:09 AM.
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Old August 7, 2020, 12:13 PM   #16
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Don , simplest answer is you never work to the lands only away Because seating closer to the lands raises start pressure. Meaning if you already have an established load that is close to max pressure and you are .060 off the lands . If you start adjusting your seating depth closer and closer to the lands , start pressures will rise higher and higher the closer you get possibly putting you over maximum allowable pressure since you were already close to max at .060 off the lands . So if you were looking to do seating adjustments the first thing you do is find your max coal . Start your load development there once you have a charge you like you adjust seating depth away from the lands Avoiding those pressure spikes
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Old August 7, 2020, 05:08 PM   #17
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Quote:
Don , simplest answer is you never work to the lands only away Because seating closer to the lands raises start pressure. Meaning if you already have an established load that is close to max pressure and you are .060 off the lands . If you start adjusting your seating depth closer and closer to the lands , start pressures will rise higher and higher the closer you get possibly putting you over maximum allowable pressure since you were already close to max at .060 off the lands .
Berger says just the opposite. They say seating the bullet farther out increases case volume

from page 149 https://www.bergerbullets.com/wp-con...13/03/COAL.pdf

Quote:
Figure 1: When the bullet is seated farther out of the case, there
is more volume available for powder. This enables the cartridge
to generate higher muzzle velocity with the same pressure.
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Old August 7, 2020, 05:15 PM   #18
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Lots of competitive rifle shooters soft seat bullets long so they are set back a few thousandths when chambered. Cutting the powder charge 1% fair the well compensates for pressure increase, but I never did because I think it's enough to matter. Their jump to the lands is always zero; another variable eliminated.

The tighter case necks grip bullets, the more pressure it takes to start moving them. 308 Winchester handloads may take 80 psi, 7.62 NATO service ammo is at least 800 psi.

Last edited by Bart B.; August 7, 2020 at 05:55 PM.
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Old August 7, 2020, 07:18 PM   #19
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I don’t see a conflict in What I said . Infact they may be saying more volume equals more space for powder equals more pressure equals more velocity . In theory that makes my point even more meaningful If you seat the bullet out and jam it in the lands that is going to raise start pressure and then because you have more case volume you’re gonna go ahead and put more powder in there too , sounds like a recipe for disaster
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Old August 7, 2020, 10:28 PM   #20
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MG, re read the article. The same amount of powder with the bullet seated longer equals more space equals less pressure or at least that is how I read it. In my way of thinking when the bullet encounters the lands whatever running start it has is moot, pressure is still going to spike at that point to overcome the resistance. The extra case volume provided from the longer seating depth negates any pressure spike. To be fair however Hornady and most of the internet wisdom agrees with you. I try not to run my ammo at the ragged edge anyway. I shoot for accuracy and find little or no benefit in a few extra FPS
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Old August 7, 2020, 10:40 PM   #21
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Quote:
The same amount of powder with the bullet seated longer equals more space equals less pressure or at least that is how I read it.
That's only if when you seat longer you still have at least a .020 jump . Seating into the lands raises pressure far more then increasing case volume reduces pressure because you don't have that running start , the bullet is already stuck in the bore . I would much rather seat deeper into the case reducing case volume with a max charge then seating into the lands with that same max charge . I hope Unclenick comes along and helps me out cus I feel I'm not explaining it well but I strongly believe what I'm saying is accurate .
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Old August 7, 2020, 10:53 PM   #22
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oh, you are explaining your point just fine. I am just pigheaded and feel the best hamburger is made from sacred cows lol.
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Old August 7, 2020, 11:00 PM   #23
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Haha , thanks
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Old August 8, 2020, 06:56 AM   #24
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that is why I love this forum. Makes me think, question my own perceptions, research and educate myself etc. I found these late last night, some may find them useful and educational

Precision Rifle Blog has a four part series of articles on bullet jump, how to find, pressures, etc

https://precisionrifleblog.com/2020/...est-practices/

https://precisionrifleblog.com/2020/...d-development/

https://precisionrifleblog.com/2020/...a-barrel-wear/

https://precisionrifleblog.com/2020/...elopment-data/
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