Help with overall length back offs

david1976

Well-Known Member
As I am new to reloading, and as the chap who was going to mentor me has passed away I wonder if some of the seasoned reloaders on here could offer me some words of wisdom relating to the following.

I am currently loading 85gr .243 bullets and have been using the C.O.L 2.625" as shown in the manual below:

2cponir.jpg


Groupings are better than factory reloads but I would like to improve on them further.

I recently spoke with my gunsmith who used one of these modified hornady bullet gadgets in the rifle and said that the head of the bullet would touch the barrel if the length was 2.732" which is 0.107" longer than currently used by me.

As I have spent all the money on reloading equipment I would like to get things as accurate as possible. This being the case, how do i decide how much to lengthen.shorten the overall length to?

Hope this makes some sort of sense

cheers

david
 
I'm keeping everything consistent throughout.

Using N160 powder (always same load),
cci primers
same cases (trimmed, cleaned etc)
 
Backing off from the lands / leade, is just a case of moving the bullet back into the case by degrees until you find that your desired point of impact / grouping has degraded or improved, you will probably find that there may be an alternate powder, and or bullet / primer combination that will improve or degrade the results. have you any paper targets with some results on?
 
No but I am hoping to go out tomorrow, weather permitting to try the back off lengths to see how that looks.

If the max size is the 2.732" figure, what should I start at and what increments should I work back on?

Cheers
 
A lot of NON competition reloaders will tend to start at a minimum seating depth of one calibre, & go from there in set increments of your choice, I usually move stuff around a couple of thou', don't make up loads of stuff, you just want a couple of FIVE round groups for starters.
 
Yup!, or any combo you like yourself., just as long as you stay within the min/max dimensions, & your rounds cycle through your mag / action..... an invaluable thing to do is make written notations of all your adjustments, It can be very frustrating to find a great load, & find your records have been mislaid!.
 
Thanks ill give it a go and keep my notes and if I remember take some photos.

It's funny all this length stuff as the factory loads i used to use were 2.553
 
david if you are decreasing the seating distances, ie. oal from 2.553" to 2.730" start off with minimum safe powder charge as having the bullet that close to the rifling will greatly increase the pressure within the chamber, personally I would start 030" from the rifling, then 015", then 010" then reduce in 002" increments if neccessary, 2.732"-2.553"=.179", almost 3/16" or 4.5mm is a helluva jump in one go, with small increments you'll be safe not sorry...callie
 
David

do you use a comparator to measure the cartridge OAL as this will give you a constant length as it measures from the bullets ogive not the tip that sometimes get damaged and are not allways constant.

the black art of reloading has so many variables that it can drive you mad , what groups are you getting with you reloads at this time? i know there are loads of things to try but my Sako got silly accurate when i reduced the neck tension and only sized 1/3rd of the neck length.

keep plenty of detailed records of all reload trials it will help ...neil
 
I won't shoot any load that exceeds magazine length -or the length that allows trouble free feeding. From there I work in in whatever increments seem right (I used to like .005") until I am at a length that leaves the base of the bullet at the neck/shoulder juncture -where I quit.~Muir
 
David

do you use a comparator to measure the cartridge OAL as this will give you a constant length as it measures from the bullets ogive not the tip that sometimes get damaged and are not allways constant.

I just use digital calipers at the moment however I am after a comparator and put an advert in the wanted section so hopefully someone will reply soon.
 
Just to add to this thread. I have reloaded for both my .243 and 22-250 for years. I worked my loadings out by messing around with powder load rather than O.A.L. What is the difference between keeping the powder load, bullet, primer, case consistent and adjusting O.A.L and keeping the O.A.L consistent and adjusting the charge. I use N140 and CCI primers for both rifles. 87gr Hornady SP with 36.6g for the .243 and 55gr Midway SP with 35.2g for the .22-250. Both very accurate using the manual recommendation for O.A.L.
 
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Gazza, there's so many variations that you can accomplish by "changing" different bits to your load, you are setting you're bullet to recommended OAL, that is minimum OAL, you can afford to seat your bullet further forward to-wards the rifling, this usually improves accuracy, with minimum OAL the bullet "jumps" forward, lets say, .050" until it hits the rifling, during this jump the bullet will probably wobble a tiny little fraction, as will the next bullet so that we'll say that you fire five rounds at a target that is 100 yds away, you measure the group of 5 shots and they've landed in a 3" circle, not because you've pulled off, you could have the rifle strapped down and in theory every bullet should go through the same hole, its the little wobble that makes the bullet veer fractionally, now if you move the bullet forwards and have a longer OAL, say .030" from the rifling you will have less jump and less wobble as the bullet enters the rifling, you fire another 5 rounds and measure and this time the group measures 2", you move the OAL to 015" and hopefully the accuracy improves some more, there is one very important point to remember as you make the OAL longer the pressure in the chamber rises much more quickly and can become dangerous so start off with minimum safe recommended powder load, to check OAL to the rifling get a fired case with primer removed but not neck sized so that you can insert a bullet with a little pressure by hand, insert in chamber and close the bolt slowly, withdraw cartridge and measure OAL, do this several times and eventually you will find the dead length to the rifling, you can then set your OAL to the required length to find the "sweet spot" be it .030", .015", .005" or even touching the rifling with the bullet, better still get Hornadys 7th edition and, or, Richard Lee's 2nd edition of hand loading, they're a must buy, hope this helps ...callie
 
Callie, I fully understand and know all that you say but for an example my .22-250 will do sub 1.5" at 100yds with the loading as already said. I know that if I increased/lessened the powder by .5gr it would not be just as accurate. I spent ages increasing/decreasing till I got what I wanted. This is well within what I am looking for to shoot fox and roe. What I am asking is what is the difference between doing what I have done and the original question of sticking with a powder/load/head/primer and adjusting the OAL. Or could I (possibly in theory) having worked out what I believe to be the optimum for this rifle as far as powder/load/head/primer goes now improve on what I have through varying the OAL.
 
Gazza I think that you've answered question yourself, and the only improvement left would be to alter the OAL, having said improve, you might not, and as you say, sub 1.5" at 100yds is plenty good enough, you're happy with the load, bullet and primer, you're not bench resting, punching competition paper so you can now put it in the load book as a finished project, I wish I could say the same, I'm working on a load that I know I can improve and to do that I've got to increase the the OAL and go back to minimum safe load and work it up until, like yourself, I'm happy with the powder load, and if not my next option will be to change powder and start over again, wish me luck, I may need it.... callie
 
Cheers mate. A bit too technical for me, adjusting OAL. As said the .22-250 and .243 are well capable with the loads I do so as they say "if it ain't broken." All the best with your endeavours.
 
just a heads up all factory ammo is short because it has to cycle and load in all guns so your reloading book quotes a standard length that will do the same, [just little info hope it helps]:thumb:
 
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