Factory tolerances?

spclPatrolGroup · August 6, 2011, 12:21 PM

I picked up a bullet comporater for my caliper, i wanted to test it out, and get a measurement from some factory ammo compare my reloads to. I measured 7 federal fusion .270 130gr cartridges. I was supprised to see the variance, they measured x.670 to x.709 almost a .04 differance, this suprised me since I thought the ogive measurement was suposed to be more exact. Is this normal? Does it matter? I know the reason for measuring the ogive is to place the bullets so far off the lands, but I haven't made it that far yet, I still need to tools for measuring the chamber (still a noob).

GURU1911 · August 6, 2011, 01:41 PM

What i suspect you are concerned with is "the overall length & how deep to seat the bullet into the case" ???? Am i correct in my assumption?

Make up a dummy round of ammo (no primer & no powder) using a properly sized case & trimmed to the proper length. Raise the height of the bullet seating stem in the die. Place bullet over the mouth of the case & guide into the case mouth, while slowly lowering the press handle. If the bullet did not enter the case, then turn the seating die several turns until the bullet is held in place by the tension of the case neck.

Now take that dummy round & gently attempt to chamber the round--don't force it---be gentle---withdraw the round & look at the scratches on the bullet. Reseat the bullet a little deeper in the case. Paint the bullet with a black marking pin & rechamber again. Do this repeatedly until the scratch marks finally disappear.

Congratulations---you have reached the proper seating depth for that particular brand of bullet & weight. If you change brands or weights, you will have to repeat the process using another prepared case. Thus, you are making a dummy round for each & every rifle caliber & bullet brand that you use.

Guru1911

Ideal Tool · August 6, 2011, 03:18 PM

Hello, spclPatrol. Your title says it all...What you most likly have is bullets from more than one press. The bullet forming dies all have tolerances, and as they wear & are re-polished by the die-maker, shapes change..but still are within fac. specs. If you want tighter tolerance..might have to go with match quality or custom bullet.

August 6, 2011, 12:21 PM	#1
spclPatrolGroup Senior Member Join Date: August 19, 2010 Location: North Dakota Posts: 349	Factory tolerances? I picked up a bullet comporater for my caliper, i wanted to test it out, and get a measurement from some factory ammo compare my reloads to. I measured 7 federal fusion .270 130gr cartridges. I was supprised to see the variance, they measured x.670 to x.709 almost a .04 differance, this suprised me since I thought the ogive measurement was suposed to be more exact. Is this normal? Does it matter? I know the reason for measuring the ogive is to place the bullets so far off the lands, but I haven't made it that far yet, I still need to tools for measuring the chamber (still a noob).

August 6, 2011, 01:41 PM	#2
GURU1911 Senior Member Join Date: December 22, 2010 Location: SEALY, THE REPUBLIC OF TEXAS Posts: 501	What i suspect you are concerned with is "the overall length & how deep to seat the bullet into the case" ???? Am i correct in my assumption? Make up a dummy round of ammo (no primer & no powder) using a properly sized case & trimmed to the proper length. Raise the height of the bullet seating stem in the die. Place bullet over the mouth of the case & guide into the case mouth, while slowly lowering the press handle. If the bullet did not enter the case, then turn the seating die several turns until the bullet is held in place by the tension of the case neck. Now take that dummy round & gently attempt to chamber the round--don't force it---be gentle---withdraw the round & look at the scratches on the bullet. Reseat the bullet a little deeper in the case. Paint the bullet with a black marking pin & rechamber again. Do this repeatedly until the scratch marks finally disappear. Congratulations---you have reached the proper seating depth for that particular brand of bullet & weight. If you change brands or weights, you will have to repeat the process using another prepared case. Thus, you are making a dummy round for each & every rifle caliber & bullet brand that you use. Guru1911 __________________ NRA LIFE MEMBER (1984) & PRESIDENT: S.W. LA. R&P CLUB, LAKE CHARLES, LOUISIANA (1994-1999) METALLIC CARTRIDGE RELOADER (1977) & GENTILE CHRISTIAN ZIONIST INFIDEL !!! "THERE AIN'T TOO MANY THINGS THAT YOU CAN'T FIX, WITH $500 DOLLARS OR A .30-06"

August 6, 2011, 03:18 PM	#3
Ideal Tool Junior member Join Date: October 6, 2010 Location: Michigan Posts: 1,080	Hello, spclPatrol. Your title says it all...What you most likly have is bullets from more than one press. The bullet forming dies all have tolerances, and as they wear & are re-polished by the die-maker, shapes change..but still are within fac. specs. If you want tighter tolerance..might have to go with match quality or custom bullet.