[351 WINCHESTER]

I've been loading for the .303 for a short time now. I've got cases that I've shot 4 or 5 times and haven't trimmed them (haven't measured them either).

I think the oal for the .303 is 2.22". I shoot a no. 5 mk 1 and neck size only.

What effect or problem can I run into by not keep oal at 2.22"?

Keep in mind that it's a military chamber so it's a little generous, but not bad really.

[Linear Thinker]

351 -
303 is one of the odd case designs that does not seem to stretch a lot.
I also fired 4-5 loads without trimming, the brass did not seem to elongate enough to warrant trimming. I use HXP (Greek military) brass, it has been excellent so far. Their annealing seems to prevent the brass flow.
Mild loads of 4895 under heavy .308 bullets work well for me.
I've never bothered with .311 bullets.
LT

[koja48]

does not seem to stretch a lot.

Be that the case, I'd still make it a point to measure them. As for OAL, it depends on the dimensions of the chamber in your particular rifle. I measure and inspect, clean & prep EVERY case, regardless of caliber or how many times it's been reloaded, record manufacturer, lot, times loaded, how it was resized, number of trims, pistol/rifle it was fired from (assuming I may have more than one in that caliber), powder, charge, bullet & weight, primer, OAL & COL. Measuring, inspecting. & record-keeping are judicious insurance . . .

[The Bushmaster]

If the case gets too long the case mouth will enter the mouth of the barrel and engage the lands. You will notice a slight difficulty in closing the bolt. Thus chambered and fired chamber pressures will exceed safe limits because the case mouth is being forced tighter on the bullet...Hence the need to measure and trim all cases...