Undersize bullets

[kentucky37]

I expect this doesn't really matter, but it is kinda bugging me. I am new to reloading and am working up a load for a 270Win with Nosler 140g Accubonds. I am using a neck expander mandrel and the imperial dry lube, which has got me thinking and reading this forum about neck tension. For some reason I measured some of the Accubonds with my calipers and kept getting .276. (I don't own a micrometer.) I thought my calipers must be off by .001, but I checked with Mitutoyo gage block, and they are right on the money. I measured my Bergers and Speers--both .277. I measured a few each of Nosler .243 bullets in 55g, 58g, and 90g, and two batches showed .242 and one .2425. I measured .243 Bergers and they were .243. Working up the load will tell me everything I need to know practically, but I am curious--is there any reason that I might want to know if a bullet runs .001 undersize? Or, though my results seem quite consistent, am I getting bad measurements for some reason that I can't see?

 

[105Coues]

Interesting.... I have never measured them until now. My 308 Noslers are .307 and my Hornadys are .3075. I always wondered why when I loaded a 155 AMAX with 1 grain more powder than my 165 Ballistic tip I would still have lower muzzle velocity. More powder and a lighter bullet generally equal higher velocity. I also get much less copper fouling from the Noslers which supports this as well. Maybe the extra friction??
You are correct that it doesn't matter. Don't let it bother you. The Noslers shoot exceptionally well so I am quite certain you will find a load that works for you rifle.
Good luck!

 

[Mach 1]

Your barrel is around 6 thousandths less than your .276 bullets so You will be fine to use them and they should work fine.

 

[Varminator 911]

If they're cup and core my understanding is that the bullet will expand on ignition to fit the bore. The massive pressure from behind combined with the forces of acceleration and friction from the bore will compress the bullet enough to fit the bore. That won't happen with a copper mono metal but I think it does with most cup and core bullets.

Then again I could be dead wrong...lol

 

[ar10ar15man]

get a real micrometer that reads to .0001
calipers DO NOT.
in essence you have NOT measured anything yet.

 

[Azrael]

This is sort related; bullets that arent exactly undersized, but have a taper becoming larger at the base. Its subtle, and you may not be able to measure it with a caliper. In some cases it will cause bullets to fit in the cases necks loosely. The first time it came to my attention was in my TSX phase. I had serveral cartridges where I could sometimes move the seated bullets by hand, or even spot it when checking COL with calipers. At first I wrote it off as a weird TSX thing, and could usually fix it by taking a thou or two off the expander ball. Problem seemed to go away; and I eventyslly moved away from those bullets anyway.

More recently I came up against the same problem in a .312 necked STW. (Another phase). A friend had built it with my reamer and hadnt done much with it. 180 Berger VLDs stubbornly refused to be gripped by necks. I ended up owning it, along with a pile of components he didnt need anymore. I was better equipped this time, having a fist full of bushings and 4 sets of dies.
The first thing I did was go down in bushing size until I was all the way to .303" or .007" under. Didnt help one bit. I was just thinking about setting up the annealler when I noticed another box of 180 VLDs on the bench that Id been loading in my 7-300 Win. I looked those over for a second before deciding Inmight as well just seat one instead of measuring. Bingo; bullets were gripped like a starving dog on a bone. Jeez, that had to be a fluke. Try another and it worked. Try 10 and no problem. Go back to the other box and they were loose. Deeper I seated them the looser they got. Just a bad batch of bullets from the past.

I might try them in another 7mm to see if the problem persists but dont really feel like burning my powder and barrels to
diagnose a single box of old bullets.

 

[Azrael]

If you really want to measure bullets get a blade mictometer. A standard one will just hit the high spots.

 

[johngibbs222]

When you're comparing measurements with the same measuring device and it shows a difference, there is a difference, doesn't matter what you measure it with.
Your noslers are smaller than your bergers and speers.
On the other hand the bergers and speers may be bigger than your nosler, in a perverse way, ie what's the bore of your rifle?
It's probably one of the reasons the smart money tells you to work up to loads rather than pop to at the max on load #1.
FWIW I have mikes that can measure up to 6" (external and internal, acquired them in the 1960s made by Moore & Wright), I bought a vernier calliper about three years ago because it was so cheap and have never used the mikes since, perfectly adequate for day to day use.

 

[bigngreen]

get a real micrometer that reads to .0001
calipers DO NOT.
in essence you have NOT measured anything yet.

When you have a guage block to verify it's accuracy it's not going to be a full thou of with a mic!

 

[kentucky37]

Thank you all for your replies! It is all very helpful, as I am still on the steep part of the learning curve.

 

[ronstone09]

you might try gage pins instead of expander mandrels as they are more precise , i like imperial lube on my bullets before seating !

 

[Pmacc60]

I wonder if miking these bullets can help reduce the time working up loads in the future? What I saying here is your particular barrel likes a undersized bullet , is that your first search in putting together a load for your particular needs ?