schoolcraft

Ok, so I'm looking at Federal Premium's website.

They're showing the 160gr. Nosler Partition at a muzzle velocity of apx. 2950 fps

I'm wondering 2 things........

1. Most published velocities come from a 24" test barrel. My Browning A Bolt has a 26".
How much of an increase should I expect from the extra 2" of barrel.

AND.......

2. How close are the "published" velocities to what you actually get through a chrono?
Anyone ever had factory ammo that EXCEEDED it's published velocity?

DeerandbearhoG

I always thought ammo co.s used 30" barrels to test loads.

gregrn43

If I remember correctly for every inch more in barrel length you gain 50fps in most rifles and I believe that most ammo companies use 24 and 26 inch barrels for there velocity tests.

stubblejumper

Most tests are done with 24" or 26" barrels.Some low velocity rounds may only gain 10fps per inch,while some large capacity.high velocity cartridges may gain 40-50fps per inch.Then again a rifle with a tight chamber and a 24" barrel may produce more velocity than another rifle with a 26" barrel.Most test barrels have minimum spec barrels which normally produce more velocity than a standard factory barrel of the same length.

schoolcraft

Could some of you 7mm. Rem. Mag users post what kind of velocity you're getting from your factory or handloads?

I would like to find a 150gr. or 160gr. load that gives me the best possible velocity while still keeping the groups small so I can fully utilize the rounds capability.

DM

I agree... I think the old days of using 30" and longer test bbls is over...

DM

eldeguello

You may get no increase at all from the extra 2" of barrel length. You will have to chronograph it to know.

My 7mm Rem Mag. with 26" barrel gets 3070 FPS from my 175-grain Nosler Partition handload, and 3350 from a hot 140-grain load. This is with handloads, not factory ammo. Factory figures are dismal. IF I wanted to shoot 7X57mm ammo, I'd not use a 7MM Rem Mag to do it with!

DeerandbearhoG

I had some notes written in my loading manual, in the 7mag data, from last summer when I bought a 700 sps SS, 7mag 26" barrel. Load was a 160gr hot cor, over 58.5grs(max load) of imr4350, col 3.295"(on the lands) avg velocity was 2900(cronied). Got a little over 1" groups, not bad out of the box w/ the crappy x pro trigger, set at about 4.5lbs(lowest i could get it[:'(]). Recoil was not bad either.

LEE manual gives reloder 22 as giving the highest velocity for a 160 which I think is perfect for a 7mag (3075)

I also ran some winchester silver box 150s, got about 3050fps which surprised me!

As far as factory test barrels I couldnt find much on thge subject but I believe hornady use 30" barrel to test ssst slugs which is the only way you can get those things to do 2000fps I just figuerd all ammo co.s did the same.

Ron Duval

removed by RD

skeeter 7MM

160gr AB with RL22 or IMR7828 - 3050 - 3100
150gr NBT with RL22 - 3200
140gr AB & Barnes TSX with RL22 - 3300 - 3350& 3275 (not the warmest load but the most accurate with the barnes).

All these loads are safe and sub MOA shooters from a 25" barrel.