Factory Ammo OAL/Head Space?

[bkhartman]

Greetings, Haven't reloaded in 25 years so I don't recall allot of data. I have been using Hornady 204 32gr VMax with no trouble. I purchased several boxes of them all with the same LOT #. I was experiencing the loss of groups. POI would be 2-3 rounds touching and then 1 or 2 way off but a very tight group. I chased bullets for awhile then noticed while chambering some of the round the bolt was hard to lock down.
Sometimes it was just a little tighter and others it was fine.
I decided to check the overall length and found very few matched. The rounds measured anywhere from 2.241 to 2.260.5 Checking some load data I see the OAL should be at 2.225. Question is, is this difference in length causing this? I will have the head space measured and yes I researching researching reloading equipment. Any other suggestions would be great Thanks Brian

[Bill K]

I personally would start by running every one of the cases through my seating die and seat each bullet to the same COL. See if that does not improve the accuracy. I would also check the lenght of the case/measurement from the case base to the shoulder with a caliber. I would imagine the sizing fo the case is not off enough to bother. I think the problem is the COL. Appears quality control is off. Bill K

[Rick in Oregon]

If the bolt closed with resistence on some, and none on other rounds, I'd say the shoulders are not consistent in terms of headspace. The ammo most likely came off of two different presses at the factory, and one was out of spec a few thou in regard to the headspace datum on the shoulder. The bullet is so far from the lands in factory barrels with 204 commercial ammo, it's doubtful that the seating depth is causing any bolt resistence, but it sure could affect that accuracy issue.

If you separate all your ammo by removing the firing pin, and chambering them all, I suspect you'll have two piles of cases, one that chambered with difficulty, the other chambered with no effort whatever. QC problems as Bill mentioned.

[bkhartman]

I also have 2 boxes of the hornady 40 gr and put the calipers to them and found the same thing, this is from round to round out of the same box. I don't know if they all end up in the same bin and then boxed or what. The measurements are close to the 32 gr. Thanks for the info. Brian

[Ol` Joe]

I suspect if you take a bullet "comparator" and measure your cartridges you`ll find they are all very close to the same length from base to ogive, which is the important number if the COL from base to bullet tip allows the cartridge to fit the magazine to start with. Bullet tips are notorious for varying in lenght from the base of the bullet, but the bullet base to ogive seem to be quite consistant.
I wouldn`t worry about the COL on factoiry ammo.

[bkhartman]

I suspect if you take a bullet "comparator" and measure your cartridges you`ll find they are all very close to the same length from base to ogive, which is the important number if the COL from base to bullet tip allows the cartridge to fit the magazine to start with. Bullet tips are notorious for varying in length from the base of the bullet, but the bullet base to ogive seem to be quite consistent.
I would`t worry about the COL on factory ammo.

Well I picked up more Hornady 32 gr and they all were fine no tight ones. Checked the lot numbers and they were not the same as I was having the tight bolt trouble with. Guess it was that run of ammo. Back to 1/2" at 100 yd. Thanks everyone for your int put. Brian