Jump space.

[MRAD]

I'm new to reloading. Now I have some of the measurements I need but I'm trying to find the jump length of my t3 varmint. I don't think tikka have that sort of data on there PDF from what I've read. Cheers

[Jagged 77]

You won't find any published information on jump to the lands, this is individual to each rifle. To measure jump you can cobble together a home made gauge or splash out on something like a Hornady Lock n Load kit (recommended). This will allow you to accurately measure jump with the bullets you intend to use.

 

Personally if you are new to reloading I would start out with jump tolerant bullets like the 168 or 175 SMK, load to published lengths and get comfortable with the process. The accuracy may surprise you. Once you are in control of the basics move on to looking at accurising your hand loads.FYI all my .260 / .308 / .300WM long range loads are all jumped and loaded to mag length or shorter.

 

We have several new members at our club that have started home loading and are jumping into advanced techniques without understanding the basic principles - this leads to stuck cases in chambers on the firing line and all sorts of other issues. I'm not saying you are one of these guys but it is important to master the basics and understand each process. Good luck and stay safe.

[DaveT]

If you mean the maximum cartridge overall length (COL for a specific bullet) that your chamber will accomodate then you need to get an OAL gauge and dummy brass from Hornady or Shooting shed in order to obtain the maximum possible measure and then decide what 'Jump' (if any) that you want the bullet to make when fired.... this is a big subject in itself so make very sure that you understand the options and pressure / accuracy implications of any decisions made.......happy to help further if required.

[Andrew]

With the rifle empty and the bolt closed and striker cocked, run a cleaning rod with a flat tipped jag down the barrel until it contacts the bolt face. Very carefully make a pencil mark on the rod at the muzzle. Remove the rod, remove the bolt, drop a projectile nose first into the chamber and using a short rod to hold it into the lands, reinsert the cleaning rod into the muzzle and run it up against the bullet nose. Again. carefully mark the rod with a pencil. Remove the rod. Measure between the pencil marks with a caliper. Write the measurement down on a piece of paper. Remember to take the projectile from the chamber.

 

Or......Simply don't worry about it. Manufacturers of the worlds finest match ammunition don't.~Andrew

[MRAD]

Right I have a lock n load OAL and measured with my smk 175 with the comparator giving 2.176". Now after that measured the length from tip to brass bottom and I'm at 1.773" I'm wanting to do things properly and get all the accuracy I can to a certain extent. Brass I'm using Lapua .308

[1967spud]

[MRAD]

I just started to watch that lol, watched your others too.

[DaveT]

Right I have a lock n load OAL and measured with my smk 175 with the comparator giving 2.176". Now after that measured the length from tip to brass bottom and I'm at 1.773" I'm wanting to do things properly and get all the accuracy I can to a certain extent. Brass I'm using Lapua .308

The bullet tip to bottom of the case measure is little or no use to you whatsoever and you will find that it varies (sometimes significantly) from cartridge to cartridge due to the manufacturing inconsistencies at the 'pointy' end of the bullet itself.

 

You have a jump tolerant Sierra bullet so why not start at a Lock & Load comparator measured length between .010 & .020 off of your maximum (bullet 'on the rifling' ) OAL measure and see what accuracy you get.....if not happy you can 'tweak' the length ...(probably a little closer to the rifling.)

 

Hopefully that will fit in your magazine and keep you safely off of the rifling at first given that pressure peaks can arise when starting a cartridge on or jammed into the rifling.

[1967spud]

The bullet tip to bottom of the case measure is little or no use to you whatsoever and you will find that it varies (sometimes significantly) from cartridge to cartridge due to the manufacturing inconsistencies at the 'pointy' end of the bullet itself.

 

You have a jump tolerant Sierra bullet so why not start at a Lock & Load comparator measured length between .010 & .020 off of your maximum (bullet 'on the rifling' ) OAL measure and see what accuracy you get.....if not happy you can 'tweak' the length ...(probably a little closer to the rifling.)

 

Hopefully that will fit in your magazine and keep you safely off of the rifling at first given that pressure peaks can arise when starting a cartridge on or jammed into the rifling.

[MRAD]

Well thanks for all your replies. Tho the mag might have the last say, it's a little smaller than the entire length. May go for single shot. I don't think that it is too bad.

[shooter79]

+1 here. This is what i use.

[Andrew]

Well thanks for all your replies. Tho the mag might have the last say, it's a little smaller than the entire length. May go for single shot. I don't think that it is too bad.

 

Have you tried just seating the parallel sides of the bullet to the base of the neck? I do this when starting a new load, moving outward in increments until I come to magazine length. More than not, I find a good accurate load in that region. This fixation with "distance to the lands" from a factory chamber is a little over done in my opinion.~Andrew

[MRAD]

Well that's why I joined up Andrew. Information is always helpful. Thanks

[kent]

Have you tried just seating the parallel sides of the bullet to the base of the neck? I do this when starting a new load, moving outward in increments until I come to magazine length. More than not, I find a good accurate load in that region. This fixation with "distance to the lands" from a factory chamber is a little over done in my opinion.~Andrew

Andrew,

I couldn't agree more, the manufacturer tries to prevent the occurance of a Jamb into the rifling with the longer bullets pertaining to the calibre, then people think they must load a factory rifle like a bench gun. Try for example getting a 55 grn Nosler to touch the rifling in a .243 win factory gun, the bullet will likely drop out the case before you get there. However they seem to shoot pretty well in most with a large jump

[gbal]

[quote name=MRA

D" post="163382" timestamp="1376655495]Well that's why I joined up Andrew. Information is always helpful. Thanks[/quote

 

As we all were....some of the terminology gets confusing-jump,jam.OAL. It all clicked into place for me when I realised bullets were not the same-the "ogive" or curved bit outside the case,tapering to the bullet tip could vary quite a bit-the point goes a little further up into the barrel,without touching.OAL is really an industry standard -more for magazine length.

Your L&L (again a recent term) guage locates the seating depth of the bullet in the case,at the point where that bullet/ogive just touches the rifling.Generally you don't want to JAM the bullet in further when you are starting to reload-pressure goes up,and most rifles shoot better with the bullet back a little-a slight JUMP from the case before engaging the rifling when fired.You adjust this via the seating die,and measure with a comparator-the ones that screw onto you micrometer seem best.Usually good accuracy come in the region of 5 to 15 thousands of an inch 'jump'( = seated 5-10 thou off the lands),but rifles are to some extent individual in their interaction with bullets,and you need to establish each 'jump' for each different ogive bullet in that rifle.a few thou is really ver fine tuning-hunting rifles eg do pretty well with SAAMI commercial loads.Affictionados understandably fine tune/tinker.

If you have all this,fine-Sinclair International (get their catalog)used to do a very fine little book on advanced handloading,using and explaining all the desirable bits and pieces in the catalog,by Bill Gravatt & Fred Sinclair-'Precision shooting and reloading handbook'-best £20 you will ever spend on reloading-though it won't be the last £20!.

Gbal

[Andrew]

Andrew,

I couldn't agree more, the manufacturer tries to prevent the occurance of a Jamb into the rifling with the longer bullets pertaining to the calibre, then people think they must load a factory rifle like a bench gun. Try for example getting a 55 grn Nosler to touch the rifling in a .243 win factory gun, the bullet will likely drop out the case before you get there. However they seem to shoot pretty well in most with a large jump

 

Funny you should mention that particular combination. In my Winchester 243 it was one of the most accurate varmint loads I had yet I'll bet it crossed 2.5 calibers length before it hit the lands! Unless I'm shooting a custom chamber, specifically made for a particular round, I don't worry about distance from the lands. I have several 308's and several .223's and my goal is to have one .308 load and one .223 load: in other words, build a match grade copy of factory ammunition. Obviously, one rifle will like a load more than the other, but my goal is the highest standards of accuracy from a cartridge that can be used in any of them. It takes the emphasis off of the weapon and places it on the round you're building which is a slight, but important shift in attention. I own many firearms and have loaded for more than I can count over the last 40 years. I used to relish tailoring one load to a particular rifle; finding that sweet spot that made the most out of that rifle. Now I like making really good, effecient, and uniform ammunition. If intelligently thought out and executed it will be good in most rifles. Perhaps not the most accurate load, but hopefully very good nonetheless.~Andrew

[kent]

 

Funny you should mention that particular combination. In my Winchester 243 it was one of the most accurate varmint loads I had yet I'll bet it crossed 2.5 calibers length before it hit the lands! Unless I'm shooting a custom chamber, specifically made for a particular round, I don't worry about distance from the lands. I have several 308's and several .223's and my goal is to have one .308 load and one .223 load: in other words, build a match grade copy of factory ammunition. Obviously, one rifle will like a load more than the other, but my goal is the highest standards of accuracy from a cartridge that can be used in any of them. It takes the emphasis off of the weapon and places it on the round you're building which is a slight, but important shift in attention. I own many firearms and have loaded for more than I can count over the last 40 years. I used to relish tailoring one load to a particular rifle; finding that sweet spot that made the most out of that rifle. Now I like making really good, effecient, and uniform ammunition. If intelligently thought out and executed it will be good in most rifles. Perhaps not the most accurate load, but hopefully very good nonetheless.~Andrew

 

Certainly cant go far wrong with that approach

[Andrew]

 

Certainly cant go far wrong with that approach

Thanks for that. Some of my buddies think I'm crazy... or have just gotten lazy. One friend shares this philosophy and is enjoying the challenges it provides. He has come up with a 308 load that is sub MOA in all but one of his six 308's. He small base FL resizes all his brass and all the finished product put into an ammo can marked "308". when he wants to shoot he simply takes as much ammo as he is going to need. He has one load for target and one for deer. I haven't hit that stride yet but I'm working at it.~Andrew

[sonic]

One mans lazy is another's efficiency.

I am working on one load for Roe or fox rather than the two I used previously. Far less wear on the rifle wasted powder bullets etc. This could be maturity setting in or maybe just being a yorkshireman.

[Andrew]

This could be maturity setting in or maybe just being a yorkshireman.

I believe the former but I'll need to take your word on the latter!!

Good luck with your work.~Andrew

[kent]

One mans lazy is another's efficiency.

I am working on one load for Roe or fox rather than the two I used previously. Far less wear on the rifle wasted powder bullets etc. This could be maturity setting in or maybe just being a yorkshireman.

 

in .243 win look towards the 95 grain Nosler B/T. I have shot deer both far and near with it without undue meat damage, yet have never had it pencil on a fox. Its highly accurate in most .243's and offers good long range ballistics and I run it as fast as I can. Other 95 grn bullets I have tried were not such a great cross over, I have been told the 70grn Nosler is also good on Roe /fox but personally find it too explosive on fox to bother trying it on deer. I wonder about the 87 grn Hornady HPBT varmint bullet I have been using of recent, yet I shoot very few Roe these days

[sonic]

I have a box of 87 vmax but they may get left for foxing when the weather is to much for the 222. If the new (to me) CZ likes that weight then the hpbt may be the round to load.

 

Just going back to the OP when finally retired my old 243 had no throat and very little rifling at the start of the barrel yet still grouped under 3/4" a 100 yds. I found working loads with the parallel sides of the bullet in the neck. Powder weight increases done by percentage rather than .2 or .5 of a grain gave my best loads.

 

Correct me if I'm wrong but when dealing with standard chamber bullet combinations moving the bullet seating depth will have the effect of fine tuning pressure the jump leaving the bullet unsupported in the free bore. Unlike the longer bullet sat closer to the lands where bullet alignment comes into play.

[Andrew]

The amount of bullet in the neck affects alignment (making use of those fancy dies we buy) and pull-weight: the amount of pressure needed to pop the case walls away from the bullet before the gasses send it on it's way. Because it effects pressure, it effects burn rate and over-all ignition qualities of the charge. It's an important consideration. If you are a 'lander' stuck with a short bullet you'd be best served to seat it deep and make the best of your reloading dies and the skill with which you used them. JMHO~Andrew