I've been told that manufacturers make their guns that way to avoid liability issues with factory ammo. It's certainly more dangerous to have the bullet jammed into the lands than have to jump to reach them. I ran into two guys at my range, both shooting a Begara in 6.5 CM and they were loading and shooting just about the same length I was because the throat on both their guns were long too. They were using VHT N555 which I will give a try eventually.Originally Posted by Mr.Snerdly
Ernest T,
I think part of the reason is that calibers like .223 and .22-250 and even 6.5mm CM and .308 can shoot bullets over a fairly wide weight range.
My .223s have shot bullets from 35 grains to 77 grains for example and even my 6.5mm CMs have shot bullets from 123 grains to 147 grains.
Just for grins, measure the bullet lengths of a .35 or 40 grain .223 and a 77 grain .223. The light bullets would fall out of the neck if you tried to seat them for a short jump.
In my rifles, the 77 grain bullets can be seated into the lands but if I tried that with a 52 grain bullet it falls out of the neck.
By the way, my rifles shoot the light bullets very accurately, even if the jump is incredibly long.
But if the chamber was short enough to seat a 52 grain bullet near the lands, the 77 grain bullets would have to be seated back so far into the case that the pressure would be much higher.
The weight range of 6.5mm CM bullets is not as severe, but there is still quite a difference between the length of a 123 ELD-M and a 147 ELD-M.
I suspect that the manufacturers are trying to accommodate all of us, those who shoot light bullets and those who shoot heavy bullets.
That article gave me the confidence that I could go shorter, maybe much shorter, and find a length that would shoot well.
For two of my rifles that shoot best in the just under 0.020 jump range, one of them shoots almost as accurately with a jump of 0.060.
The 0.060 jump is supported by almost 20 groups of data.
Maybe that will help.
I can't explain why, but the numbers say it does.
It is .200" jump to the lands on my Axis with a 69 grain Sierra with an OAL length of 2.26". Savage rifles seem to have a very long throat. I know it was less than this since it has had a fair number of rounds through it but it should not be close to being worn out. My 783 Remington is almost .100" less to the throat than the Axis. However, the Axis does seem to shoot well even with this long jump. I do seat them a little longer than 2.26, which is supposed to be the maximum length for a 223 but it feeds and chambers well at a considerably longer length. It might shoot as good at 2.26 but I feel more confident if it doesn't have such a huge jump.
Mr.Snerdly,
Where did you get the impression that the maximum length of a .223 69 gr SMK is 2.260?
The recommended OAL for the 69 SMK is based upon the OAL limit of an AR Mag not on the chamber length.
The Savage mags and the AICS mags have a lot more OAL available than that.
My AICS mag allows up to 2.500 OAL.
I even asked Sierra about their recommendation, and they admitted that the AR mag length was a consideration.
I find you can load those 69 SMKs out as long as you have enough bullet body in the neck to maintain consistent neck tension.
Some say you need a length equivalent to the caliber in the neck. I find it is more like half that. Remember the 69 SMKs have a boat tail and that doesn't touch the neck.
I generally shoot my Savage 12 FV with 69 grain Sierra SMKs around 2.300 but I have loaded them out to as long as 2.340 as the barrel has eroded (4,000 rounds) and got good results.
They shoot great with those OALs.
I load the TMKs about 0.070 longer than the SMKs.
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