284 Win Case length problem ?

[ecomeat]

Does anyone have a handful of virgin Lapua 6.5 x 284 brass that they could check the length on for me please ? And hoping for a measurement of length on said Lapua brass, AFTER it is necked up to 284, but before firing ??

Sierra and other reloading manuals give the 284 Win a maximum case length of 2.170", and a "Trim To" length of 2.160".
I have some 300 Lapua necked up cases, fired 1-3 times and until today have been randomly checking case length by dropping into a Wilson Case Guage.......and there is/was no problem. I havent trimmed any.

However, when I put the calipers on a good sample today, i have an overall case length that varies from 2.1465" thru to 2.162".........with an average of probably closer to 2.150 than 2.160 (ten thou shorter than the "trim to length".
Have i got a problem here, or if its shooting well (won an OPM last week, and shot 2 x 60s at 500 & 600 yards) is it a case of "it aint broke so dont try to fix it" ??
I would really appreciate any input on this one. It seems a bit scarey having a case length thats ten thou shorter than a well published "Trim to Length". How much does it matter ??

I use a custom minimal bump FLS bushing die that was made with the same reamer used for the chambering, and bump the shoulder a carefully measured 0.0005"
I am a fair way out of town, and dont have any new or unfired cases to check the "starting length"....hence the plea for some case measurements and comments.
Primer pockets have loosened a bit, but still have a very safe feel when seating, even though the ejector groove is already measuring 0.406 to 0.407" (and Paul Janszo discards his at 0.408") on those with three firings.
Thanks for any input.
Tony

[RAVEN]

Precision reloading requires chamber OAL slug available from sinclairs
RB

[bruce moulds]

or cerrosafe to cast the chamber.
if your primer pockets are safe, measuring things doesn't make them less safe.
bruce.

[IanP]

Ecomeat, I checked my reloading data for the Lapua 6.5x284W cases and a brand new case measures 2.159" and I trim to 2.150" after expanding the necks to 7mm.

Ian

[ecomeat]

Thank you, Ian. Thats exactly the sort of feedback that i was hoping to get. Trimming to 10 thou (0.010") less than the commonly recommended "trim to length" obviously works just fine for you or you would have had some issues well before now.
I will take Raven and Bruce's comments on board as well, and (back) order the Sinclair 7mm Chamber Length Gage , as well as making and keeping a Cerrosafe cast of the chamber for future reference.
Once i know what my Chamber measures, i will go ahead and confidently trim all cases to an even length.

Questions : Are you seeing any lengthening of your cases ? And do you FLS every reload ? Or minimum bump FLS ? Or maybe even Neck size only ?
Thats nearly a question in its own right : Is the 284 Win a cartridge that is suited to Neck Sizing only for mayber 1-3 cycles, or is everyone full length sizing every time ?
I have a 0.313" neck, so turn my brass lightly to 0.013" which gives me 0.003 clearance at the neck with a loaded round.
Tony

[IanP]

Ecomeat, I'll have a go at answering your questions and what I do works for me, but everyone will have a slightly different way to do the same thing.

Firstly, I wouldn't bother with a chamber cast and I would save the money for other things. I use my reamer diagram for reference along with a fired case. If the head space gauges, (go, no-go) either you or your gunsmith use, indicate the chamber has been cut to the right depth, then use the reamer diagram as a guide for the chamber dimensions.

The fired case will give you the chamber head space when measured with the Hornady, (or whatever) head space comparator. When I FLS I set the shoulder back 0.001". I use the obligatory Hornady OAL gauge for bullet seating info.

I have had a lot of success, (accuracy) with neck sizing only, provided I throw the cases away after 3 to 5 firings. In the big matches, Queens, etc I use twice fired brass which is neck sized only. After 5 firings with NS only the cases are still ok to use in club competitions but can start to show some opening up of the group size. After 5 firings the primer pockets are pretty second hand and case head expansion is an issue.

I have now changed my sizing regime over to FLS. I did this along with dropping the load in my cases and settling for a few fps less to extend the case life. I have found that FLS the brass along with lighter loads allows me to keep a tight group longer than before with NS. I now FLS every time and even though its more work it extends the case life out to 10 firings with great accuracy. The compromise is of-course less fps means a little more wind drift out at the longer ranges. The 180gr Bergers still fly pretty damn well at 2900fps out of my 32.5" barrel.

My 284W Shehane reamer was for a no neck turn chamber and I went with a neck dimension of 0.3167" for Lapua brass. I didn't want to neck turn but found it necessary to inside ream the cases to prevent donuts from forming. When expanding the necks to 7mm, thicker brass from the case shoulder is brought up to the bottom of the case neck. I found either inside reaming or taking a very fine skim off the neck and continuing down slightly into the shoulder was needed to prevent donuts.

I have now decided that my Shehane will be my go to rifle out to 600 metres and beyond that I am now in the process of putting together a magnum 30cal to launch the new, (newish) 230gr Berger Hybrids. The ballistics of the 230s launched at conservative fps, (2800fps) exceed that of a 7mm, 180gr Hybrid launched at 3100fps. I'm thinking that the 30cal with the 230gr combination may even have a longer barrel life than that of the pushed hard 7mms. I will know the answer soon enough!

Enjoy your 284W, its a great cartridge and extremely accurate when coupled up with the 180 and 168 grain projectiles.

Ian

[Norm]

Tony,
My fire formed Lapua brass fired in a standard .284 win chamber measures same as yours, so I don't think it is an issue.

[DaveMc]

Another simple chamber gauge - cut ring off old shell, debur both ends and slip over a projectile then chamber.



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Tony - most cases come out well short of SAAMI specs and variable. This seems to have very little effect on neck tension or other variables. But it does effect the weight of the shell more than you would think. If you are inclined to weight sort you should trim to same length first.
I make my own dies so use a custom FL die on every firing but see no issue with Neck sizing and then bumping occasionally. In the Shehane case running at 2800-2840 I get at least a dozen firings from the Lap cases. Occasionally there is one loose primer here or there that I discard. I now discard fairly early as they can act like an oxytorch on your bolt.