Ogive to base – 4 different bullets – requesting interpretations of findings

[RonR]

Ogive to base – 4 different bullets – requesting interpretations of findings

We have a few different projectiles on hand for fire forming and load development for hunting. This was the first time determining the ogive to base measurements to derive starting seating depths for the 4 bullets.

The following are the values for my rifle ogive to base measurement

Hornady SST – 2.227” ogive to base (OAL base to tip 2.860”)
Sierra GK HPBT – 2.272” (2.765”)
Sierra PH SP – 2.243” (2.748”) lead tip*
Nosler BT – 2.309” (2.885”) both values surprising**

These are my interpretations, and please advise if these are not correct
- The difference in values is related to the different bullet ogive/designs
- If a person used 2.800” as COAL (from Nosler loading manual for 7mm-08) that the SST is .060 short from the lands ( see above OAL measurement ) , HPBT a .035 “jam” into the lands, SP .052 jam and the BT’s are .085 short of the lands.

If the interpretations are correct I have the following questions

1. What is the acceptable amount of jam? .035” and .052” seems alarming to me.
2. What do you hunters use as a value to start with short of the lands for bullets like above? I have read here and watched a few videos ( that looked like professionals ) that .020” jump was the place to start. Any jam wasn’t suggested for hunting or hunting bullet accuracy…but please share
3. Are the “jump” or “jam” values above translatable to intended manufacturers seating depths for accuracy? I.e. The Sierras intended to have little to no jump and SST and BT’s should have more space.
4. Is no 3 irrelevant because it’s rifle specific regarding bullet seating depths?
5. Are the measurements indicated in range of what's expected...err another way to ask...anything alarming?

To note
- Savage 7mm-08
- All bullets 140gr except for SST 139g
- Using a collet die to provide the proper bullet neck fit and then insert into chamber…I read that on here and who ever shared that should take a bow. Seriously, what a tip. Jerry if that was you THANKS! All other methods, at least to me, had too many opportunities for error.
- 5 tests for each bullet, same cartridge and same bullet for each test (20 tests total)
- Hornady comparator system used to derive ogive to base
- Caliper measurement for OAL.
- Nosler BT’s being used to develop hunting loads with Accubonds. The other bullets are to experiment, develop experience and add to trigger time to improve our marksmanship.
- Novice reloader and just trying to develop knowledge and reloading skills that translate at the range and into the field.

Appreciate your time.

Regards
RonR

 

[Keithjohn]

I put a post like that on once . What I do is select what bullet I want and with a fire formed brass I set the collet little by little UNTILL the bullet can be pushed into brass by chambering ( with no primer ) and enough neck tension that the bullet comes out with the shell . Then I set the bullet back a few thou from where the rifle lands were found . Then. You should be able to pull the bullet out by hand (pliers ) and keep the brass and use for other bullets again starting way long and chambering to find the lands with that bullet profile . Hope you understand my wording
Start with the bullets way long . You have found your own OAL , the manual s are for all rifles and have room to move
Look up "heydays " thread best ever reloading tips , it has good info

 

[RonR]

I put a post like that on once . What I do is select what bullet I want and with a fire formed brass I set the collet little by little UNTILL the bullet can be pushed into brass by chambering ( with no primer ) and enough neck tension that the bullet comes out with the shell . Then I set the bullet back a few thou from where the rifle lands were found . Then. You should be able to pull the bullet out by hand (pliers ) and keep the brass and use for other bullets again starting way long and chambering to find the lands with that bullet profile . Hope you understand my wording
Start with the bullets way long . You have found your own OAL , the manual s are for all rifles and have room to move
Look up "heydays " thread best ever reloading tips , it has good info

I missed that post but you pretty much described the process I used to derive the numbers. Thanks for the tip.

So you space off the lands by a couple of thou...what bullets are you using (anything posted above?), cartridge you are loading, and how is the accuracy?

Regards
Ron

 

[Keithjohn]

I shoot a 7mm , have tried all bullets . I got best groups with chinchaga, Berger,hornady , nosler accubond . They were all good but the ones with highest bullet coefficient are best at longer ranges

 

[yodave]

the OAL given in the reloading manuals are purely based on the maximum length that will fit and function in every magazine out there, they have nothing to do with the chamber specifications or bullet jump or jam. It's always best to tailor your handloads to your rifle and keep your ammo sorted to what rifle it was designed around.
As a general rule of thumb I run a 10 thou jump on everything, so long as it will fit in the mag and cycle cleanly.
If you go to the bullet manufacture's website they may have a OAL that more closely relates to their particular bullet, but again in most cases it is the max mag length, just remember that moving the bullet farther into the case then the tested OAL can and will increase pressure, so always start low and work your way up to max published data

 

[Keithjohn]

The Bergers were an exception in my guns as far as bullet jump .I had to try lots before finding what works best (pain in the but and lots of bullets )
The chinchaga from a guy in Alberta work as good or better at long range
Good point by yo Dave about the pressures, can't take anything for granted

 

[Mystic Precision]

Treat each bullet as a separate entity... which they are.

Set the ogive of EACH bullet to be 10 to 20 thou OFF the lands. Assumes that the OAL will still fit in the mag... if not, then the OAL for the mag is the length to go by.

This is a hunting rifle and jamming can lead to serious problems in the field.

Yes, each bullet will need a different setting on the seating die

Work up loads for each bullet and tune for best performance. Accuracy is likely to be similar but may use quite different loading.

Enjoy...

Jerry

 

[RonR]

the OAL given in the reloading manuals are purely based on the maximum length that will fit and function in every magazine out there, they have nothing to do with the chamber specifications or bullet jump or jam. It's always best to tailor your handloads to your rifle and keep your ammo sorted to what rifle it was designed around.

Thanks Yodave...that's exactly what I am learning. This exercise has indicated that if a person doesn't understand what he's doing, it can be BAD.

As a general rule of thumb I run a 10 thou jump on everything, so long as it will fit in the mag and cycle cleanly.
If you go to the bullet manufacture's website they may have a OAL that more closely relates to their particular bullet, but again in most cases it is the max mag length, just remember that moving the bullet farther into the case then the tested OAL can and will increase pressure, so always start low and work your way up to max published data

I tested the longest, BT's in the mag at (contact length with lands) and it still fits...I should have included that in the original post. The increase in pressure proportional to increase in OAL is the wisdom needed in my case. I understand a jam situation creating pressure completely but have had trouble comprehending the relationship between increasing OAL and pressure increase.

Thanks for sharing the 10 thou rule of thumb you use. That's the experienced information I am looking for.

Much appreciated post.

Best Regards
Ron

 

[yodave]

as the bullet is seated farther out of the case the case capacity increases and the pressure drops........to a point, when the bullet engages the rifling it hesitates and needs pressure to push it in further, this the point that pressure starts to rise. If you have a long heavy bullet it requires more pressure to get it into the barrel versus a short light bullet, all based on contact area.

when running a small jump the bullet barely moves before engaging the rifling, then it pauses until the pressure is there to force it into the rifling, that same bullet on a longer jump will build the momentum for one but the bullet needs to travel farther allowing more pressure to build behind it, it will hesitate less engaging the rifling and thus lower pressure.........so how much are we talking?? not enough to blow up your rifle, but if you did load development in March you going be blowing primers come August when the temperatures are significantly warmer

 

[RonR]

Treat each bullet as a separate entity... which they are.

TOTALLY Jerry...this exercise proved just that. A different animal I might add...wow...I am learning.

Set the ogive of EACH bullet to be 10 to 20 thou OFF the lands. Assumes that the OAL will still fit in the mag... if not, then the OAL for the mag is the length to go by.

That's the information I am looking for. I should have included that the longest OAL still fit in the mag with no issues.

This is a hunting rifle and jamming can lead to serious problems in the field..

That's what I am having a bit of trouble with. I would have been creating a serious jam by loading the Sierra's at book value length...unless I am wrong. That's pretty serious and should be prevented??? In my case finding some other bullets for fire forming has lead me down this path and without some research on here, and some education/attempt to learn/test further it could have been a terrible situation. I am wondering if any other 7mm-08 users have had this experience and could share?

Yes, each bullet will need a different setting on the seating die..

Yah...this exercise proves it.

Work up loads for each bullet and tune for best performance. Accuracy is likely to be similar but may use quite different loading.

Enjoy...

Jerry

I am coming to realize as time goes on all the nuances of every component change and case tweek. This case is projectiles. It never ends does it? I kind of feel like GGG with his reloading path. I mean this in jest Jerry...but I am starting to think every time you say "enjoy" that you are laughing in the inside knowing the next line of questioning and what post I am going to come up with next. Chess master or Star Wars Jedi...

As always, appreciate the time you take on this and other posts. Yodave...you too.

Regards
Ron

 

[RonR]

as the bullet is seated farther out of the case the case capacity increases and the pressure drops........to a point, when the bullet engages the rifling it hesitates and needs pressure to push it in further, this the point that pressure starts to rise. If you have a long heavy bullet it requires more pressure to get it into the barrel versus a short light bullet, all based on contact area.

when running a small jump the bullet barely moves before engaging the rifling, then it pauses until the pressure is there to force it into the rifling, that same bullet on a longer jump will build the momentum for one but the bullet needs to travel farther allowing more pressure to build behind it, it will hesitate less engaging the rifling and thus lower pressure.........so how much are we talking?? not enough to blow up your rifle, but if you did load development in March you going be blowing primers come August when the temperatures are significantly warmer

Ok...

Less jump = more hesitation = rapid pressure build up? (steep incline in pressure slope?)
More jump = less hesitation, pressure starting to be "consumed" by bullet travel? Less pressure spikes or peaking? (more gradual slope increase in pressure)

I stay on the conservative side of loading. I've never approached more than 75% of max value and found some spots that indicate accuracy improvements that provide the accuracy for hunting we're looking for. (Just want more accuracy ) I'm looking for pressure signs with every range session...One day I will post the photo results of using Hornady Superformance factory rounds in my almost virgin rifle. Scared the living $%^ out of me but I am here in one piece trying to exorcise this occurrence that rattled me. I still have that box and use it as a reminder. And the bill from the gunsmith to repair.

Your time and efforts are sincerely appreciated Yodave.

Best Regards
Ron

 

[hometownhero]

How long is your chamber to the lands? On a factory savage it should be very long. you would need to measure when a bullet contacts the lands to see how much jump is happening. I seat all my hunting rounds to .020 off as long as the mag will allow. I would never suggest jamming on a gun that will be used to hunt with.

In my supergrade these are .020" from the lands.
Hornady 139 interlock 2.232"
Hornady 139 sst 2.200"
Hornady 139 gmx 2.194"
Measured with a bullet comparator.

 

[Ganderite]

One of the worst feelings a shooter can have is to open the bolt and watch the empty case fly out, spraying powder, because the bullet is still stuck in the throat.

Whether he is hunting or in a match, the rifle is out of commission until the powder can be be cleaned out of the bolt, trigger and action.

This is why jamming the bullet is a no-no for hunting.

The OAL in the book means nothing, unless you are borrowing their rifle. 20 thou off the rifling is a good place to start. Most of my match rifles shoot best with that.

Do an initial survey of powder charges of 5 shots each in 0.5 gr increments from the START load up to MAX. Shoot these off a rest, letting the barrel cool between strings.

The survey has two purposes. It will suggest what powder charge is in the range of better accuracy, so you can experiment in that region. And it will tell you where you hit pressure (if you do). A slight increase in initial bolt lift effort is a sign that yourr rifle Max is about 1 gr less than that.

 

[RonR]

How long is your chamber to the lands? On a factory savage it should be very long. you would need to measure when a bullet contacts the lands to see how much jump is happening. I seat all my hunting rounds to .020 off as long as the mag will allow. I would never suggest jamming on a gun that will be used to hunt with.

In my supergrade these are .020" from the lands.
Hornady 139 interlock 2.232"
Hornady 139 sst 2.200"
Hornady 139 gmx 2.194"
Measured with a bullet comparator.

My Savage with SST's 2.227
My sons Savage with SST's 2.220
20 thou...longer than what you measurements are for SST so I guess it's in the ball park regarding the long"ness" of Savages as per post.

Bullets were seated long and the bolt closed to get the measurements, with a comparator, to get the values.

20 thou set back used by yourself is the information I am looking for.

Jamming no good of course and thanks for reiterating for clarity.

Much obliged for your time HTH.

Regards
Ron

 

[RonR]

One of the worst feelings a shooter can have is to open the bolt and watch the empty case fly out, spraying powder, because the bullet is still stuck in the throat..

I'll be honest, the third time reloading something went awry with the collet die setting. Bullets were easily pushed in. I had visions of something like this happening but caught the error of my ways.

Whether he is hunting or in a match, the rifle is out of commission until the powder can be be cleaned out of the bolt, trigger and action..

Thanks for the sobriety of the impact of the situation.

The OAL in the book means nothing, unless you are borrowing their rifle. 20 thou off the rifling is a good place to start. Most of my match rifles shoot best with that..

Exactly the experience I was requesting.

The survey has two purposes. It will suggest what powder charge is in the range of better accuracy, so you can experiment in that region. And it will tell you where you hit pressure (if you do). A slight increase in initial bolt lift effort is a sign that yourr rifle Max is about 1 gr less than that.

I experienced that...at that time I believed it to be the shoulders getting too long cause I was just neck sizing at that time. (bolt close had minor increase in force to close, after firing, a slight bit more increase in force to open. No other signs that I could see of excessive pressure.) Now shoulder bumping a couple of thou to prevent the bolt close increase to close. If there is increased bolt lift force then I know it's from excessive pressure.

Appreciate your wisdom and time Ganderite. Cheers!

Ron