Seating "short" bullets in a long freebore chamber

[MichalS]

On my quest to find a suitable 308 Win long range load I decieded to try lighter bullets and encountered an interesting problem. I wanted to do a depth seating test, but for 2 of the bullets I decieded to try (Berger 155.5 and new Sierra Palma) the max COAL is so long the bullet almost "falls out" of the case. For example the 155.5 Berger leaves the case @3.05" COAL, while I measured 2.975 COAL to the lands. It's similar with Sierra. The only 155gr I can comfortably use with short jump (0.010") is Lapua Scenar with COAL of 2.90".

How would You proceed in such situation? Would You try to make Sierra and Berger wprk wint a long jump or pass on them?

TIA,

Michal

[That bald headed Geordie]

Many years ago I bought a Remington VSSF in .308 and started to handload.    I selected the 155 grain Sierra but found that if seated to touch the rifling,  it was only held in the case mouth by about 1/10th of an inch (or less).   

To overcome this issue I bought the Sierra 190grain HPBT and this solved the problem by allowing the bullet to just touch the rifling and leaving quite a bit still in the case mouth and held in with enough retention.    Problem solved and I used the bullet out to 1000 yards at Diggle with reasonable accuracy for a factory rifle.

 

 

[Laurie]

There are two factors / ways forward here. One is that you actually need very little shank seated in the neck for single-loading range shooting. I've many times used less than a half-calibre seating depth and got good results. However, for a semi-auto/straight-pull with pretty violent bolt pick-up and feed or a tactical / sporting bolt-action set-up in magazine use and rapid bolt operation, I'd prefer a full calibre depth of seating. With barely seated bullets transport, handle and chamber the ammunition with care to keep the bullet concentric. If this is acceptable, a mere tenth of an inch shank held in the neck is adequate for 30-calibre.

Second is the bullet design and how jump tolerant that makes it. The 155.5gn Berger is a very jump tolerant design indeed and if you simply seat it at 2.800" COAL or (if appropriate) whatever COAL the magazine will handle and still feed reliably, the odds are that you will see good results despite horrendous amounts of jump. With any given charge weight, you do lose a bit of MV though.

Partially related to this, I've just started load development of 260 Rem in a rebarreled (opriginally 308 Win) FN SPR with a lot of freebore designed to see 140gn VLDs seated optimally. One bullet I'll try is the Berger 6.5mm 130gn AR-Hybrid designed for AR-10 type rifles (or AR-15s in 6.5 Grendel) and which allegedly is very jump tolerant in long-throated (or worn barrel) versions of same. The COAL at around 20 thou' off the lands is 2.927" in this 260 Rem chamber in newly cut form. The rifle's magazine won't hold/feed rounds at the 308's 2.800" COAL, max being something in the high 2.7s (bit remiss for a police / LEA repeating rifle I'd have thought, although the original US FBI spec was for use with Federal 168gn GMM which is under 2.8"). I'll work a load up for the full 2.927" COAL to see what it's capable of then try it again at whatever the magazine accepts and see what that does to groups, MVs and spreads. That'll be around 160 thou' jump - a good test for Berger's claims for this rather (!!) pricey model. As I normally single-feed rounds in this rifle, COAL and magazine OAL mismatches aren't normally an issue for me.

[Andrew]

Load to whatever the data recommends. It's not a random number pulled out of thin air. Usually the load in question was found to perform best at that seating depth. When the bullet maker is not supplying the data, use the bullet maker's OAL anyhow. You can't be far off. JMHO~Andrew

[The Gun Pimp]

2 hours ago, That bald headed Geordie said:

Many years ago I bought a Remington VSSF in .308 and started to handload.    I selected the 155 grain Sierra but found that if seated to touch the rifling,  it was only held in the case mouth by about 1/10th of an inch (or less).   

To overcome this issue I bought the Sierra 190grain HPBT and this solved the problem by allowing the bullet to just touch the rifling and leaving quite a bit still in the case mouth and held in with enough retention.    Problem solved and I used the bullet out to 1000 yards at Diggle with reasonable accuracy for a factory rifle.

 

 

I remember that gun matey - a 'one in a million' Remington!  Didn't you get a five-inch group with it?

[That bald headed Geordie]

6 minutes ago, The Gun Pimp said:

I remember that gun matey - a 'one in a million' Remington!  Didn't you get a five-inch group with it?

Not sure of the smallest group I got with it Vince but using the 190gr Sierra it has quite a bit of a kick to it.

But I was over at Al Maughan's workshop and was taking a look at George Balfour's rifles which are stored there awaiting disposal and handled the Remmy again after a long time (I sold it to George many years ago) and it brought back some memories.

Will be happy to get a 5 inch group on Sunday or hopefully smaller.

 

[Laurie]

32 minutes ago, The Gun Pimp said:

I remember that gun matey - a 'one in a million' Remington!  Didn't you get a five-inch group with it?

Ha! Ha! I always said our Leslie is a jammy Geordie b*gg*r!