[Rmeju]

So I measured the max OAL of my chamber, using some plinking 147 grainers that I've got. I have some loads that are about 0.080" shorter than that, measured with the comparator.

The instructions say that somewhere between -0.040" and -0.020" is desirable, but closer than that, one should use caution...

So, a couple of questions (the rifle in question is an M1A):

1) Is this warning that Hornady gives as a CYA, or is it foolish to get closer than -0.020"?

2) Even if I can get closer, do your sweet spots tend to fall under -0.020"? I understand that my own rifle's sweet spot will be different from everyone elses', but I'd like to hear what's been working for you all so I have a neighborhood of where I might want to start.

3) I've got a batch of about 100 loaded plinking rounds. Being sort of anal, the thought has crossed my mind to reseat these rounds closer to the rifling. The thought would be to tap the rounds partially out using my puller, and then reseat them to something closer to -0.020" (instead of -0.080"). However, I worry that I may be ruining the neck tension using this process, and since the M1A is a semi-auto, I worry about this process making a mockery of my hard work with bullet setback, due to low neck tension (or coming out too far when they get chambered for the same reason).

Given that these rounds are meant basically to zero the iron sights, and use the leftover for iron sights shooting, I'm wondering if any accuracy gains are worth the trouble.

[steve4102]

The warning is there because the closer you get to the lands the higher the pressure. If you start your load development at .050 off the lands and gradually increase OAL (closer to lands) the higher the pressure. It best to start your load development LONG and go shorter. With each decrease in OAL the less the pressure.

[hentown]

I use that same setup and have for years. I start at about .010" off the lands and work out. Works for me. So far, no explosions.

[Craigman]

I dont believe tapping them in/out a few thousandths will ruin the tension at all. If it were me I would load to spec for plinking rounds with good components and then go for accuracy from there. Is accuracy suffering now? What prompts you to seat as far as possible? With open sights I think you are thinking in to it too much.

[USSR]

So, how does you comparator measurement relate to your mag length? You know, the 147gr FMJBT bullets have very little full caliber section to them, so seating depth variation is very little.

Don

[Rmeju]

@Craigman: I'm not trying to seat as long as possible. Myabe a better way of asking my question would be that I'm wondering if my "sweet spot" is longer than -0.020", should I skimp on accuracy for the sake of safety? If my loads are at their most accurate at -0.010", is that ok if I'm not seeing signs of high pressure (i.e. flattened primers, etc.).

I kinda figured I was thinking about it too much for these particular loads.


@USSR: My mags' ID legnthwise is 2.863". Of the rounds I've loaded, the one with the sharpest point is at 2.790". That leaves me with 0.073" (less some allowance for some breathing room in the magazine, variation in bullet shape, and variation in the seating operation) to play with, if that leaves me on the .308" diameter part of the bullet.

I see your point though. Even if I elongated them +0.050" or +0.060" (down to -0.030" or -0.020"), that still wouldn't be under -0.020", so maybe I shouldn't worry about it so much since I'm restricted by my mags, and perhaps my bullets as well.

[USSR]

...maybe I shouldn't worry about it so much since I'm restricted by my mags, and perhaps my bullets as well.

Yep!

Don

[Bad Flynch]

Loads for an M1A should be loaded to service length, ignoring all that other stuff. Your primary concern is the correct lenght for proper feeding and adequate bullet tension to withstand the rigors of semi-auto functioning.

If your bullet will not allow you to attain a standard length (it is short) then load to the bullet's cannelure or be sure to seat deeply enough to have a one-caliber deep gripping area on the bullet.

[YankeeFlyr]

Like BF said...the 147's have a cannalure, yes? Load to it, for the M1A.

If not, load to mil COAL. No way the 147 will have an ogive that hits the lands or is even particularly close.