M14 Forum

Phil McGrath

Here's how it went down, A shooting buddy lent me his chrono for the weekend, so I was making some ammo when I bent the decaper pin. At 10pm the fun store is closed and I'm kicking myself in the @## for not having any spares, then a idea popped into my head? See that 30.06 die just pull the depriming pin and swap it into the .308 die, no luck there both the same brand but the .308 die used a pin and the 30.06 uses a nailhead style so I'm out of luck. Then I get the idea to swap the whole stem both are .30 cal, It should work right?

Everything swapped over without any drama, things are looking up and I'm back at it, for some odd reason I kept the loads I made with the first stem(.308) seperate from the batch made with the loaner stem(30.06).

At the range I get everything set up and start my chrono work, nothing special normal day at the range I thought everything was running good I had made my target velocity but my SD/ES was all over the map up/down even sideways, accuracy was where I thought I wanted it but there were a few loose flyers with the first batch, at the time I thought this is as good as its going to get, oh well thats the nature of the beast live with it. I looked at the second batch they're both the same load so how/why would there be any differance, but for some unexplained reason in my mind what if there was? I wasn't expecting any, I just wanted too see what if?.

Batch #2 was a suprise my M/V picked up a few FPS and leveled out not much but some, the SD/ES also took a big drop, the few flyers that I had before had now melted away, my groupings were now nice, round, and tight. But why?

After I got home I started to think(DANGER!! Will Robinson)and pulled out my dial caliper and start measuring stuff.
Fired cases measured at the mouth
Outside .343-344
Inside .310-3.12
Unfired cases necks measure .340

Resized case with out the expander
Outside .333-.334
Inside .302

I then measured the .308 dies expander ball and the resized case, expander dia came in at .307
New outside .336
New inside .306
This was the #1 batch of ammo that I fired over the chrono, everything felt good and looked good or so I thought at the time. I had been using this set up as is for about a year, because thats the way it came from the factory.

The loaner 30.06 depriming stem and expander ball used in the .308 resizing die, it measured in at .305
New outside .335
New inside .304
This is how batch #2 was resized, my M/V leveled out and the SD/ES droped heres why I think it has worked for better, when the bullet is seated there is now .004 neck tension holding the bullet just a bit longer and building a little more pressure before the bullet is released starting its run down the bore. This slight extra tension on the bullet is now more consistent time/pressure/release for each round.

If you think your SD/ES is out of line and your rifle kicks out a loose flyer that you know/call good, take a look at your expander ball and the brass.

82nd ABN

Wow that small amount made a big difference. I have to ask, as you know Phil I am just getting started in the reloading realm of things and I don't know what SD/ES stands for. I do have plans to at one point get a chronograph but it will be one of the last pieces of the puzzle. I am going to purchase the redding NM dies sets to start with. I also plan on swapping out the expander to the carbide style. I will have to take some measurements and do what you did when working up some loads by trying both the one that comes with the die and the carbide one to see if there is a difference in results. I often wondered why only some people neck size for the 14 and most don't. I wonder if at some point I might want to give it a try. Thanks for the post!!

Bamban

I know a guy in Alabama that swears by the Lee Factory Crimp die to fine tune his gas gun loads. I guess you got there using a different route. Forgot, his technique shows beneficial changes on lower density charges. I never explored his approach to accurate loads though.

Bamban

SD - standard deviation
ES - extreme spread

Neck sizing for gas guns is an invitation for trouble on the firing line, like failure to load and even extract.

Phil McGrath

Sorry for the confusion, I full lenth resize for all my rifles. I use the RCBS comp dies for my .308 they work great, the depriming stem and expander are shared with both resizing dies 30.06/.308

Yes, the difference maybe small but its effect was large.

RAMMAC

This is why I switched to the Redding S bushing die, I can adjust the neck tension by changing the bushing.