Wanted Hornady OAL Gauge

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gunnybedford
Posts: 164
Joined: 27 Jan 2018, 15:00
Location: Lympne Kent

Wanted Hornady OAL Gauge

Post by gunnybedford » 23 May 2020, 21:06

Hi

Dont suppose anyone has got one of these OAL gauges they want to move on ?also need some of the cases for one, .223 and .308
thanks
Neil

Miki
Posts: 87
Joined: 10 Nov 2017, 22:41
Location: Lanark way

Re: Wanted Hornady OAL Gauge

Post by Miki » 24 May 2020, 09:50

If you were closer and this virus wasn't you could pop round and we could have a measure over a coffee. I see you are in th Southern Shires and I am North of the Wall.

You can measure the COAL by sizing a neck so that the bullet doesn't fall in. Use a black marker pen to put stripes from the top to the base of the bullet, seat it by approx 3 to 4mm and 'gently' load it into the chamber. Open and close the bolt (without drawing it back) and then gently extract the cartridge. Watch out that the ejectors don't fling it across the room. If everything goes to plan the bullet will be seated 'to the lands' and you can set your jump accordingly.
If the neck tension is too tight you can stick the bullet in the lands, use a cleaning rod to poke it out.
If its too loose you can often see the max depth where the pen marking are scratched. You can work our what the seating depth 'should be' by looking at the SAAMi specs and making up a dummy round as a reference.

Chasing the lands can be (and often is) a bit of a waste of time - what are you tring to achieve ?
Miki

Things that go bang, day or night.
That satisfying thwack,
be it bright, dark or misty.
Returning home to the warmth of a good cask whisky.


gunnybedford
Posts: 164
Joined: 27 Jan 2018, 15:00
Location: Lympne Kent

Re: Wanted Hornady OAL Gauge

Post by gunnybedford » 25 May 2020, 01:14

Thanks tried that method and got inconsistent results, think the bullet was being dragged out and catching so being pulled slightly out of the case. Just trying to get the optimum seating length for the rounds, to improve accuracy a bit, however will probably end up having to buy new mags as the Pmags that i have are unlikely to be able to take the resulting length of round

phoenix
BRUCE ALMIGHTY
Posts: 6922
Joined: 09 May 2012, 14:40
Location: Aberdeen

Re: Wanted Hornady OAL Gauge

Post by phoenix » 25 May 2020, 07:01

Just load them to SAAMI spec and shoot!
Unless you're really into long range target shooting, a few thou difference in OAL won't make the difference between a hit and a miss on live quarry

Cheers

Bruce
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blueeyes
Posts: 1002
Joined: 22 Oct 2012, 11:39
Location: Bonny Scotland

Re: Wanted Hornady OAL Gauge

Post by blueeyes » 25 May 2020, 07:12

This is what I did , removed the firing pin on my Rem 700 .223 https://www.youtube.com/watch?v=TWmIwPwLyyg but there is a few other vids on this subject :thumbup:

Miki
Posts: 87
Joined: 10 Nov 2017, 22:41
Location: Lanark way

Re: Wanted Hornady OAL Gauge

Post by Miki » 25 May 2020, 12:22

It's not neccasarily going to give you any advantage. Some bullets like a jump, others don't. The key here is to get the bullet to exit the case smoothly and to arrive at the dangerous end of the barrel just as the reflex harmonic is at the null, ie the barrel isn't pointing away from the PoA.
To get that consistent first you need to take care of a whole other raft of things.
The pressure spike needs to be consistent, this is effected by the burn rate of the powder, the volume of the case and and the force needed to initially get the bullet moving, the length of the pressure spike (in seconds), the neck tension as the bullet leaves the case also effects the spike as will the resistance encountered as the lands grab the bullet and start to impart spin.

That initial pressure spike creates a shock wave which travels through the rifle and arrives both at your shoulder and the muzzle, the muzzle flexes and the bullet exits in approximately 0.0011 seconds (slower bullets and longer barrels take longer but it's 'typically less than 0.0018 seconds).

Finding the barrels harmonic null is the key to tight groups and with reloading we do that by (in simple terms) altering the characteristics of the shockwave. We develop a load using different charges of powder. We load to a consistent case volume by accurately measuring the seating depth/COAL and sizing the cases. We provide a consistent neck tension so that it takes the same pressure to get the bullet moving each time.
This should all get you a sub-MOA accuracy, lets say 0.5MOA or repeadedly inside 1" @ 200yds - BANG - Ding - BANG - Ding

You may still get flyers, a bullet that lands outside that 1" which is not caused by you pulling or flinching or moving the rifle or holding it differently. Or you may find that the rifle doesn't meet that expected 1". At this point, you can try moving the bullet forwards, reducing the jump which will make the bullet exit the barrel at a different point (in time) of the harmonic wave, the accuracy could get worse (open) or it may improve (close).

So back at square 1 what are you trying the achieve ?
You said :
gunnybedford wrote:
25 May 2020, 01:14
Just trying to get the optimum seating length for the rounds, to improve accuracy a bit,
The engineer in me shudders at the "a bit" measurement .... the physicist in me sighs.
You might possibly, if you have everything else consitent and the barrel harmincs at its minimum deflection, be able to tighten the group by up to 1" @ 300yds (not to 1", but improve the accuracy by up to 1") by reducing the jump so that the bullet arrives at the barrel slightly eralier than it did when the COAL was @ SAMMi.

Rabbits @ 150yds and Deer @ 400yds would never know the difference between .05MOA and 1.5MOA
At 2MOA you will miss the rabbits head and the deers heart, @ 1.5MOA or less it's a kill shot.
Miki

Things that go bang, day or night.
That satisfying thwack,
be it bright, dark or misty.
Returning home to the warmth of a good cask whisky.


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