Case reloading measurement variances

[Just Me]

I am new to reloading and confounded on how much in variances between cases may still produce competitive cases. My question is should all the cases have the exact same: Case headspace? Case weight? Case trim OAL? What would be any acceptable variances between any of these measurements? I am currently shooting 100-yard bench rest, and planning on shooting 600-yard bench rest. I am shooting a bolt action rifle and will neck size these cases. I appreciate any guidance you may offer to me. Thank you.

 

[G Liles]

I am using Laupa brass and bump my shoulders.002 or whatever the chamber likes and when I shoot matches all my record rounds shoulders measure the same. I don’t weigh brass because I have found no benefit from doing it, I also try to keep the OAL the same or no more than.003 difference. I’m sure there are some people on here that know a lot more than me that will chime in.

 

[Bill Norris]

Case headspace or Shoulder Bump - Very important to stay uniform
Case weight - Most BR or Competitive shooters say it's a waste of time
Case trim OAL - Most BR or Competitive shooters say trim the cases every time you re-size

 

[L.Sherm]

Keep variables to a minimum the best you can, tolerances stack up.

 

[ronemus]

I did an experiment several years ago to determine just how much effect brass weight has on .223 loads. I used WW brass (sized, trimmed and deburred, primer pockets uniformed, flash holes deburred, and neck turned) , WSR primers, charges of RL-15 or N-550 powder weighed to 0.1 gr, and 75 gr A-Max bullets. Using the lightest and heaviest cases (sorted from 1000 once-fired I had on hand), I had two lots of 10 cases with a 3 gr difference in weight. The average muzzle velocity difference was 16 fps, just a bit more than the 12 fps due to 0.1 gr of powder. I choose to sort 0.5 gr lots of .223 brass for my long range loads, but the effect will only matter at 800-1000 yards - the vertical displacement on the target from such a small velocity change is negligible at shorter distances. Unless you control all other sources of variation, the effect of brass weight is negligible. I also shoot .284, and because the brass is twice as heavy I batch in 1 gr lots.

 

[Mulligan]

Case headspace or Shoulder Bump - Very important to stay uniform
Case weight - Most BR or Competitive shooters say it's a waste of time
Case trim OAL - Most BR or Competitive shooters say trim the cases every time you re-size

Bill,
He says he shoots 100 yards now and plans to start shooting 600.
I know of VERY few 100 yard PPC shooter who trim every time they resize.
What are you seeing?

CW

 

[jackieschmidt]

I don’t trim anything until it gets too long.

But sizing and shoulder bump, which determines consistent headspace, is very important.

I all honesty, if all of the cases are the same age, you should not be able to measure the difference with the proper tools.

Same goes for seating depth.

 

[Straightshooter1]

I am new to reloading and confounded on how much in variances between cases may still produce competitive cases. My question is should all the cases have the exact same: Case headspace? Case weight? Case trim OAL? What would be any acceptable variances between any of these measurements? I am currently shooting 100-yard bench rest, and planning on shooting 600-yard bench rest. I am shooting a bolt action rifle and will neck size these cases. I appreciate any guidance you may offer to me. Thank you.

Am not sure what you mean by "will neck size these cases". . . like in neck sizing only?

I've done a lot of "neck sizing" but also followed up with bumping the shoulder back. Whether you bump the shoulders or not when neck sizing, at some point you're going to need to full length size the case to avoid feeding issues. As other's have pointed out, it's really important to bump the shoulders back and I would say to get measurement variation for that of +/- .0005.

If you're going to compete at a high level, getting consistent ignition is pretty important. And that starts with having uniform primer pockets and seated primers. Always know how deep your primer pockets are and the height of the primers you're using so that you can measure how far the primer is seated and know if they're being properly seated (like, being seated to touch where the anvil is getting some crush). Primer pocket depths can vary and different primers have different primer height.

Sorting cases by weight can help where doing so you can identify the outliers that can produce unexpected "flyers". Or you might identify and mark a particular case that has produced a flyer you can't explain. With quality brass like Lapua, this is less of an issue, but those outliers can still be an issue you don't want to see in competition.

Keeping case OAL's consistent helps with velocity consistency as it interacts with the how the bearing surface releases gases. Also, that OAL can relate to the amount of interior neck surface produces interference having to do with the release of the bullet. Consistent distance from the case mouth to the neck-shoulder junction is what you might want to focus on. Trimming every time you just size necks or FL case the case can remove variation that can be induced by the sizing operation.

How deep you really want to get into all the details is up to you. Whether it's your brass, action, bolt or firing pin. . . it all about the details and controlling what you can control. IMHO

 

[TTE]

I am shooting a bolt action rifle and will neck size these cases.

 

[Bill Norris]

Bill,
He says he shoots 100 yards now and plans to start shooting 600.
I know of VERY few 100 yard PPC shooter who trim every time they resize.
What are you seeing?

CW

Im seeing mine grow not everytime I size but I trim about every third sizing to keep it uniform. Jack Neary @ short range BR sbooter and Erik Cortina @ F-class shooter both say trim at each sizing and some others Ive heard comment say they trim at each sizing.

 

[BoydAllen]

I think that it is important to understand that what may matter a little bit for a top shooter may get lost in the mix for a new shooter. We literally know nothing of the OP's equipment, the rest setup he uses or the quality of the benches he uses. Beyond that I would like to know if he regularly shoots over wind flags, and how he works up his loads, as well as his average level of accuracy, not best group shot, but what he can depend on over a number of groups. Until the big things are well dealt with, worrying about the smaller issues is kind of a waste of time. Finally, no one that I know who shoots short range group benchrest neck sizes. They all use FL dies, usually bushing type, that are designed to just barely size the brass. Buy good brass, shoot it in rotation so that the cases have the same number of firings/sizings, so that the will all work harden together. Don't get sucked in to the primer depth by thousandths of an inch silliness. Virtually all of the top short range group shooter that I know seat by feel. It works. Finally, understand that differences in charge weight that matter at 1K do not at 100 yards. l have shot short range group sanctioned competition, and have had the pleasure of knowing world record holders and Hall of Fame members.

 

[searcher]

Regarding headspace, this is one of your more important measurements for fine accuracy. While some say .002" or more clearance, I follow the lightly "snug" protocol. When you feel slightest resistance with bolt handle down almost all the way - you have optimum headspace. You will tend to see it on target - and sizing your cases to the optimally longest length will result in much less trimming. When I began striving for accuracy long ago, I was first using standard full-length sizing dies (of good make). Then I switched to neck sizing dies and bumping the shoulders. That lead me to having to occasionally resizing with a full-length die. I found that changed the dynamics of the load each time a different routine was introduced. That eventually led me to full-length sizing with a custom (typically oversized) full-length die. I have found that to be the best "all around" method for me. With that, each loading is uniform from the prior loading, yet without as much work-hardening that was introduced by the standard full-length dies. I'm picky about trim length, yet I don't find the need to trim each time when using the latter method. I do measure headspace on each piece of brass after firing and only trim those which exceed a set length that I want them to be. Usually, that will entail cutting when one is beyond .002" of my selected trim length. I used to trim all each time - but don't automatically do that each time, particularly when fireforming new brass the first few firings. This has worked well for me.

 

[JFrank]

Case weight - Most BR or Competitive shooters say it's a waste of time

Normally we are on the same however after trying a few different ways I find that sorting by volume has its challenges, case sorting by speed takes time and components so that leaves weight’ I still have mixed feelings about this but firstly it’s free, secondly you learn something about your cases, and lastly it doesn't hurt or have much of a down side and I certainly prefer to shoot record rounds with cases that are within a few tenths in weight that not.
Just me of course but at 1000 yards I try and consider everything I can.

 

[Bill Norris]

I agree I have mixed feelings about it too but most say it has no value.

 

[JFrank]

I agree I have mixed feelings about it too but most say it has no value.

I guess that puts me one up on them fellas. Lol….

Actually at the end of the day the difference between 1st and 10th can be too close to leave anything in the reloading room.

 

[searcher]

I think a lot of folks, on any such topic, tend to "thumbs down" any technique that didn't show them (or others) definitive or detectable improvement. I think so many of the little things we do really do all add up, as I think most would agree. So, then it becomes a question of time spent doing various procedures that we know to make things more uniform, yet, for which we haven't seen benefit. Some either don't have the time or aren't willing to spend the time. Others have a lot of free time and are willing to do anything that hypothetically should make things more uniform (and might have a reloading disorder of sorts like me). Too bad we can't take a poll from good shooters who are certifiably OCD to compare their results with everyone else. THAT would be interesting. But in the end, it most often comes down to who is the best shooter over who weighs powder to 1/20 gr, who levels pockets, gets brass within 1/2 grain, etc. I still do some of these things - even knowing this...... But I can walk away knowing it was ME. That happens a lot.....

 

[Bill Norris]

I guess that puts me one up on them fellas. Lol….

Actually at the end of the day the difference between 1st and 10th can be too close to leave anything in the reloading room.

Absolutely truth.

 

[M14AMU]

FULL-LENGTH RESIZE ALL CASES!!

 

[Will Henry]

I once watched one competitor (who was plainly a little frustrated) sort his cases by throwing every case which had produced a flier over his shoulder. Wasn't long before he realized he was running low on brass and had to pick some back up. I don't recommend this approach. WH

 

[Just Me]

First, I want to thank all of you for sharing your information with me. I am reading all your responses and trying to digues them. I’m sorry that I did not provide more information, but until I read all of your responses, I did not realize that I should have provided more information. I hope the following will do that.

I purchased Tikka T3x super varmint bolt action 1:8 twist 20-inch barrel. Put a Leupold 4.5x14x40 scope. I just started shooting 100 BR this year. I was told by other shooters to match each case for headspace, case OAL (trim if necessary), case weight and CB-T-O. I created a ladder of loads 3 gr apart. I did well and was satisfied with the grouping for my first time out of the box scoring one relay with a 200 16x’s. I was informed by the march chair master that I should move out of the varmint class into the precision class.

I loaded up 60 Starline cases matching the case weight (within .1gr), headspace and trim (no variances). (A real nebbie). Then I hand loaded with Varget spread out every ten rounds by .3 grs, seated SMK 60 gr with a jump of 0.010 off the lands: Federal 205 primers.

Now the questions: I was informed by other shooters to neck size the cases only, as the 60 fired cases are now sized to my barrel. So, just recheck the headspace and trim length, and reload. Weight should not be a factor at this point since all the cases were originally the same weight. So, if I find variances between the cases say more than .002 what should I do? FL size and start over?

The other question is regarding sorting new cases: how much variation would be acceptable in Headspace? Weight? Case OAL? Should I just fire off a bunch of rounds so they will be formed to my barrel, then sort by matching the cases for Headspace, Weight and Case OAL.

I’m 80, so life is precious, and I want to enjoy it. I am competitive, but also realistic by my age. There is no way that I have the time to put all my energy into learning all that you have learned over the years of your experiences. My goal is to have fun, but to also do the best I can and compete basically with myself.

If I do well with this Tikka, then I would look into acquiring another rifle (say like a 308) to start shooting 600 BR.

Thank you all again for sharing your expertise with me.