The Firearms Forum banner
Status
Not open for further replies.

Help. I don't get the whole jump, jam with the lands thing...

5K views 25 replies 10 participants last post by  CampingJosh 
#1 · (Edited)
Here is my current understanding (probably totally wrong) and what i have done. Just started reloading 308 and want to get my rounds as precise as possible. I took a case and cut a slit across the case mouth. Put in a 168 SMK bullet at the very tip and shoved it into the barrel. After removing I measured the length: 2.925. Did this 2 more times which the lengths being 2.840 and 2.925 (how is that even possible?). Is it to this that I add/subtract 0.0015 and test?

This is a lot longer than the recommended OAL listed which is 2.750 or so.

So what happens now?
 
#2 ·
Count, please read the pamphlet that came with your dies, and then read your reloading manual. The answers to your question will be found in both of these aids.
 
#3 ·
#5 ·
Well, how about answering the questions if you know about the subject! This is the first time I am getting responses to a question on this forum where I am told to 'go read'....
Count, we get these questions all the time on the forum, and there are some sticky posts on these, but again, you have to read them. I'm not trying to be ugly, or anything, and I hope you don't take it that way. While I don't load rifle rounds, I do understand the process. The reason I do is that I reload, and I read my manuals instructions on reloading, and that included rifle, as well as pistol. Anyone here who answers your questions have also read these same instructions. The good thing about having the process in print is that the instructions are always there for you.
 
#6 · (Edited)
Slitting the neck to find the OAL, is quite common. I've done a few times. You must have just the right tension on the bullet to hold the bullet in the case when you remove it, but not so tight as to push the bullet into the rifling. You will need a light touch/feel to get consistant results, and subtract a few thousandths from this measurement (.010" to .015") Another way is to use a bullet and rod. Drop a bullet into the chamber and hold it lightly against the rifling (I use a pencil). Insert a rod into the barrel from the muzzle and touch the bullet tip w/o moving it. Mark the rod. Remove bullet, close the action and insert the rod again and mark rhe rod as it touches the breech face. Distance between marks is COL with the bullet touching the riflind. Back off 10 thousandths or so and test for accuracy. There is a tool made by Hornady that uses dedicated inserts per caliber http://www.6mmbr.com/catalog/item/1433308/977259.htm but you gotta read this article...
 
G
#7 ·
The better way to measure OAL is to use a gauge to do it like the Hornady one posted above.

Ok first



Your chamber, throat and barrel.

Jump is the distance from the ogive of the bullet to the lands and grooves of the barrel. It is not normal to load a bullet which touches or is jammed into the lands and grooves. The only people I know of that do this with rifles are benchrest shooters.

Many loads will call for a specific amount of jump.

My load for my F-Class load in my 308 win is a 175gr SMK loaded to .018" jump. I take my Horandy oal gauge and measured that bullet to the lands being 2.190" So to get .018" jump I just subtract .018" from 2.190" for a total length of 2.172". I myself never ever load to touching the lands. If you use a higher end load that is close to max it can cause excessive chamber pressure. 99% of the loads for a 308 all require some jump.

With your split case I bet you got the bullet stuck once and it pulled it out of the case slightly.
 
#8 ·
Count,

312Shooter is absolutely correct. You need the proper tool to get a precise measurement. The method you use doesn't hold the bullet securely and it most likely will move in the case when you extract it as you found out by the three different lengths you came up with. Once you get the tool and a good measurement, you subtract from that number. You will get OAL's longer than in the reloading manuals. Rifles are built to accept all the different commercial ammo out there so the throats are cut long enough to do that. You also have to take into consideration the maximum length your magazine will allow. If you're going to shoot single shot then you don't have to worry about that. Different rifles will like different bullet jump. Experiment with different bullets, powders, powder weights and primers. Everything makes a difference. Once you decide you've got the best load then start trying different bullet jump. My Remington 700 in .308 likes the bullet .010 off the lands. Yours' may like something different. BTW, every time you buy a new box of bullets you have to take that measurement again even if it's the same kind of bullet you used last time. For .308, I would suggest bullets in the 168 gr. range, Varget powder and Federal 210M primers. I've done pretty well with that combo. I would also suggest that you read "The Ultimate in Rifle Accuracy" by Glenn Newick. It's about benchrest shooting and the 6PPC cartridge but all the info carries over to any type of round. Good luck to you and good shooting.
 
#9 · (Edited)
Also, you need a comparator to measure the cartrige length to ogive of the bullet and not the tip. The approach to seating a bullet near the lands is relative to the ogive, capttango pretty much sums this up with his post.
 
#10 ·
Hey Count, you are on the right track my friend. It's a good idea to know exactly what the bullet is doing in YOUR chamber. OAL listed in manuals has absolutely nothing to do with your rifle and how it will affect accuracy and pressure.

I have the Stoney Point Thingy, I use it and it works well, but it is not needed to find the Max OAL for your rifle.

Here is what Nosler has to say about finding the proper seating depth in YOUR rifle.


As Nosler stated, find Max OAL then seat .015 deeper into the case. This is the Max OAL with that particular bullet in your rifle. Now you can work up your loads adjusting powder and seating depth to find that magic combo. Remember seating deeper from your Max OAL will reduce pressure not increase it as was once believed.
 
#11 ·
And there it is, right there in the re-loading manual! Imagine that!
 
#13 ·
Steve you beat me to it.. ;)

Count, post #10 is all the info you need..
 
#14 · (Edited by Moderator)
Count, please read the pamphlet that came with your dies, and then read your reloading manual. The answers to your question will be found in both of these aids.
And there it is, right there in the re-loading manual! Imagine that!
Why are you being such an $$$$$$$ He's just another fellow shooter/handloader looking for advice/help and thought maybe he could find some here. Guess he was wrong.
 
#15 · (Edited by Moderator)
Why are you being such an $$$$$$$ He's just another fellow shooter/handloader looking for advice/help and thought maybe he could find some here. Guess he was wrong.
The OP didn't want to hear the answer given. A question was asked, an answer given (a very good answer, but the OP had to do something; READ), OP didn't want to hear answer, original answer proven correct in following post. Perhaps the OP wanted the fastest answer possible without having to do anything...
 
#16 ·
No need for name calling here.
 
G
#17 · (Edited)
I didn't see a decent answer till post #6.

I thought the 2nd post was a tad RUDE and HOSTILE myself.

Did someone maybe stop to think that he may have read the book and still didn't completely understand it? I guess that can't be true right. Don't get me wrong I am all for reading your reloading manual cover to cover. That doesn't mean you understand every single piece of information you read in it.
 
#18 ·
Why are you being such an $$$$$$$ He's just another fellow shooter/handloader looking for advice/help and thought maybe he could find some here. Guess he was wrong.
Another really awful reply.
I guess I must expound..........looks like it to me anyway.
THIS forum is jammed full of friendly, neighborly, courteous,
helpful, and respectful
replies........1000's of them ! :cool:
If you can't see that the fourth post was a 'slam'........
you're....you've....you missed it, period !!
Carver's initial reply said, simply, PLEASE !!!!!!!!!
Maybe emotion got ahead of proper thought process.
My suggestion to anyone with panties wadded up.........
PLEASE re-read the entire thread,
from the start, and read it slowly, without any distraction,
and see where you wandered off the path. :eek::bleh:
P.S. Reloading is a simple process in it's own right, BUT can be
dangerous, even fatal if certain precautions are not taken.
FIRST THING is to CAREFULLY READ AND FOLLOW the warnings,
instructions, etc., LISTED in every reloading manual in the universe,
and they are in print-----TO BE READ !!!!!
 
#19 · (Edited)
"I thought the 2nd post was a tad RUDE and HOSTILE myself."-cpttango30

I don't see it !
I'm old school..........I musta missed the 'new and improved'
version of the use of the word PLEASE.

"Did someone maybe stop to think that he may have read the book and still didn't completely understand it? I guess that can't be true right. Don't get me wrong I am all for reading your reloading manual cover to cover. That doesn't mean you understand every single piece of information you read in it."--cpttango30

Even though........still doesn't warrant any reason to get jacked up and 'slam'.
 
#20 ·
Sam......I think it's time you work on
getting this forum caught up with the 'modern' times
and providing a tab we can use to change languages
when we post a reply........
'cause english ain't workin' Brother. :eek::rolleyes::p
 
G
#21 ·
Never said it did.

Just because a Please is in there doesn't take away from the whole rudeness.

Just like if someone said "Please GO AWAY your an AHOLE"

It is still rude adding Please doesn't make it not rude.

I also never said that post four wasn't a slam either. That is just you putting words in my mouth.
 
#22 ·
How many trolls can we get in one day?
 
#24 ·
C'mon guys. The OP got ALL the info he needed in post #10. I dont want to see this thread locked and members reprimanded because of childish namecalling. Lets agree to disagree and get on with business.
 
#25 ·
Jeez what crap !!!! :mad::mad::mad:
Proof that teaching the grandchildren is simple.........
compared to dealing with today's adults.
Sheeple. Gov't must have put extra in the drinking
supply recently.
Handouts, bailouts, do it for me, gimme-gimme-gimme!
Biggest problem in the US......and beyond ?????????
So many cannot think for themselves.......or even
reason with logic !!! Jeez what crap !:mad::mad::mad:
Lucky Brother Art, he left ! :cool:
Research and education takes time and effort, and a lot of reading.
Let me ask you, you that support the count in this thread........
what is the difference between Carver directing da count to read
the material he should have in his possession and reading a quick-fix,
do-it-for-me reply on this forum???????? DUH! Gotta READ IT !
["tell me to go read......piss me off!] Jeez what crap!
I hope, at this point, [the count] ain't shooting nothing he loaded
anywhere near me !:eek::eek::eek:
My apologies to the dear and wonderful folks that I have enjoyed here
at TFF for letting my opinion 'slip through my fingers'.
See ya.
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top