How much jump is too much?

[rockchalk06]

New rifle and I'm taking Jam measurements with the Berger 175 grain OTM. Jam is 2.306" off the O-Give. I'm using Erik Cortina's method from his video. O-Give 10 round average using 2.805" COAL nets me 2.160" average. That's a jump of .146" to get my COAL to 2.805". I have a little room to play with to run them in the mag, but that seems really huge to me.

Erik said he usually starts .020" off jam if I understood him correctly. 2.805" doesn't get me 100% of shoulder in the neck either. I've never loaded this far out. Hell, my Savage was only .076" jump to jam to be at 2.800".

Thanks in advance.

 

[straightshooter1]

New rifle and I'm taking Jam measurements with the Berger 175 grain OTM. Jam is 2.306" off the O-Give. I'm using Erik Cortina's method from his video. O-Give 10 round average using 2.805" COAL nets me 2.160" average. That's a jump of .146" to get my COAL to 2.805". I have a little room to play with to run them in the mag, but that seems really huge to me.

Erik said he usually starts .020" off jam if I understood him correctly. 2.805" doesn't get me 100% of shoulder in the neck either. I've never loaded this far out. Hell, my Savage was only .076" jump to jam to be at 2.800".

Thanks in advance.

IMHO, .020 off is indeed a good place to start. However, if you haven't read the set of articles here, you really should as it's great information.

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

 

[918v]

.020” off with the 175OTM doesn’t leave much bullet in the case. I jump that bullet .120-.130” and it shoots in the .2’s

 

[308Gunner]

Load to 2.8 and see if it shoots, have you found a powder node or are you wanting to start .20 off. I found a load that shot good and then I would work from there

 

[rockchalk06]

IMHO, .020 off is indeed a good place to start. However, if you haven't read the set of articles here, you really should as it's great information.

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

Holy shit man. Thank you for that link and info.

Crazy, I went .020", .030" and .040" jump to jam in my HMR 6.5 and didn't get good results the further I jumped. I stuck with .020". Sounds like I need to get back to the bench and work on some loads jumping .050" to .070" and see how the perform, because according to that data in the article, that seems to be the sweet spot.

Thank you

 

[rockchalk06]

.020” off with the 175OTM doesn’t leave much bullet in the case. I jump that bullet .120-.130” and it shoots in the .2’s

Thank you. That gives me some confidence knowing someone else is jumping it that far.

 

[rockchalk06]

Load to 2.8 and see if it shoots, have you found a powder node or are you wanting to start .20 off. I found a load that shot good and then I would work from there

I haven't fired it yet. Just getting some starting data to put together test loads to start out with.

 

[Formosan]

IMHO, .020 off is indeed a good place to start. However, if you haven't read the set of articles here, you really should as it's great information.

More Bullet Jump Research!

This is the 4th article in a series on some new research on bullet jumps. Here is a recap of the pr...

precisionrifleblog.com

Once you set your seating depth on the die, and say 3 of 5 bullets are at your desired depth, the other 2 are still too long. Do you just keep cranking them out or do you adjust the die and try and fix the 2 that are too long?

I'm loading 77gr SMKs and using Hornady custom dies and rarely do i get consistent seating to +/-.001 on half of my finished rounds. So im not sure how Erik in the video and others here can get such seating depth precision and accuracy.

 

[rockchalk06]

Once you set your seating depth on the die, and say 3 of 5 bullets are at your desired depth, the other 2 are still too long. Do you just keep cranking them out or do you adjust the die and try and fix the 2 that are too long?

I'm loading 77gr SMKs and using Hornady custom dies and rarely do i get consistent seating to +/-.001 on half of my finished rounds. So im not sure how Erik in the video and others here can get such seating depth precision and accuracy.

What are you measuring? O-Give or OAL?

 

[Formosan]

What are you measuring? O-Give or OAL?

o-give

 

[Gustav7]

Once you set your seating depth on the die, and say 3 of 5 bullets are at your desired depth, the other 2 are still too long. Do you just keep cranking them out or do you adjust the die and try and fix the 2 that are too long?

I'm loading 77gr SMKs and using Hornady custom dies and rarely do i get consistent seating to +/-.001 on half of my finished rounds. So im not sure how Erik in the video and others here can get such seating depth precision and accuracy.

1.) Set and confirm neck tension is where you want it. (I do this with pin gauges)
2.) Work your press consistently every time (this may take practice if you've never done it that way)
3.) Measure CBTO (ogive), NOT COAL

I just loaded 50rds last night on my Dillon 550 for the range this morning. I decided to measure every single one just to double check my process.
147 ELD-m for my 6.5cm.
48/50 were within +/-.001. 40/50 were within .001 total of each other.

To be fair, even high end calipers are technically only rated to +/-.001... so if thats what my less expensive calipers continually show, I'm happy. I doubt I could even shoot the difference that a few thou would even make....if it did.

EDIT: I used a Forster Benchrest seating die (not the micrometer one). I actually found with this die, a 1/4 turn is almost exactly .010" change in seating depth, and was very consistent through a seating depth test.

 

[rockchalk06]

o-give

Have you measured the O-Give of the bullet itself? In 6.5, I have only ran Nosler CC and SMK's in 140 and they were within a plus or minus of .0005 in the 30-40 I tested of each batch. Most were exact. Same with Berger OTM and Nolser RDF's in 30 cal.

That said, my shooting buddy is running 120 grain ELD's in his 6.5 and we found a plus or minus of .002 on a few bullets. I assumed they were spot on until we had some wacky length findings. He has another box of them coming to compare.

All of my seating is on Hornady Custom dies as well.

 

[Formosan]

Have you measured the O-Give of the bullet itself? In 6.5, I have only ran Nosler CC and SMK's in 140 and they were within a plus or minus of .0005 in the 30-40 I tested of each batch. Most were exact. Same with Berger OTM and Nolser RDF's in 30 cal.

That said, my shooting buddy is running 120 grain ELD's in his 6.5 and we found a plus or minus of .002 on a few bullets. I assumed they were spot on until we had some wacky length findings. He has another box of them coming to compare.

All of my seating is on Hornady Custom dies as well.

Not yet, but im going to give that a try and sort the odd ones out for a test.

 

[Jordanwickham]

I'm jumping 140 Berger Hybrids 115k off jam.
Idk which video you are referring to since he has two covering the jump topic.
I know in the second video he says start at 20k if you can, but you can also use mag length as your jam dimension. Jam on hybrids in my rifle is 2.278" which leaves about .117" of the bearing surface in the neck so effectively I don't care where the throat has eroded too and mag length of 2.170" CBTO is my jam number and I'm running 2.163" CBTO rounds. I've tested this round down to 2.133" which produced a .176" 3 shot but I have a wide seating node from 2.163"-2.148 that are all in the .3 so for my purposes no reason to test shorter than 2.133"

 

[Tokay444]

To answer the original question, for me, too much jump is when the bearing surface of the bullet passes the neck shoulder junction of the case. If I still need more jump at that point, it’s time to throat longer.