Cuffing a 308 load - the outcome to date

[brown dog]

Finally and at last - got out to fire the AW for the first time ever last night.

Started with 12 rounds of Blaser hunting ammo to blow the cobwebs away. Grouped like sh1t. Got to the last 3 shot group and had that nagging new-gun doubt

- what if this ammo's actually great and the rifle's sh1t ??!!

 

Changed to some old Sako 168 factory match that I had sitting on shelf

- first group a one holer 0.15MOA

the best thing possible for morale after the blaser pap.

 

Next two groups came in at gnat's nadger under 0.5MOA

 

I'd forgotten how much an unsuppressed/unbraked 308 kicks !

 

 

Swapped to my old 46gr N140 155 scenar load - 1st shot the primer was flatter than an extremely flat thing. Fired 2 more and ended up with another 0.5moa group.

 

So.....that left me with a QUESTION:

 

46gr of N140 gave 0.5moa but high pressure. What next?

 

With insufficient time to mess around I asked a couple of pals:

 

Based on a 46gr load being OTT pressure-wise and grouping at 0.5MOA;

Calibrated intuition; what charge weight will be top-end safe?

Calibrated intuition; what charge weight will be the node?

 

I know those questions sound a little mad at first glance; but I'm a big believer in recognitive decision making.

 

…that is recognitive decision making based on years of tinkering with 308.

 

Anyway; my SWAG reasoning went like this:

 

 

I reckon 0.5MOA at 46gr put me between nodes - based on nothing but been there done that 'feel'.

 

I reckon the antinode to node space is something like 0.6gr on a 308 again based on nothing but been there done that 'feel';

 

so if that reasoning had any merit 45.4grain would be a winner.

 

If the reasoning was wrong and I've actually put myself onto an antinode then I need to jump 0.3 in either direction.

 

45.7 is too near 46 (ie pressure) so I reckon 45.1gr.

 

So, I SWAGed 2 loads to try next: 45.4 and 45.1; and then added one more SWAG half node jump to 44.8gr

 

Outcome - just out tonight:

 

Well, this is the outcome; difficult to read -not comfy and not feeling steady so I think the variance in here could be as much me as the loads; firing on downward inclined lumpy ground with feet at the same height as my head'

 

also still re-adjusting to unbraked 308 kick

 

tried 44.8; 45 and 45.4 (did 45 rather than 45.1 because I found some old stuff ready loaded at that)

 

44.8 was another half nodeSWAG below reckon it hit an antinode:

both around 0.56MOA

 

45 gr hit 0.386MOA -node strike?

 

45.4gr 0.46MOA -opening out again?

 

 

Not a lot of data (!) , and undermined by not shooting well enough to be confident what was 'me' and what was the 'load'.

 

Intuition suggests that the node lies at or close to 45gr; and sits between 45gr and 45.4gr

 

- enough to run with 45gr for Sat I think?

 

 

[This rifle needs a brake!!]

[Scotch_egg]

I like 45gr varget under 155gr SMK's out of my sako. You know "the one with the dodgy trigger" lol

 

The brake makes a hell of a difference though. Plus you have been shooting a mouse gun for the last 24 months

[brown dog]

I like 45gr varget under 155gr SMK's out of my sako. You know "the one with the dodgy trigger" lol

 

Dave, what sort of MV is that giving you? (26" tube?)

 

The brake makes a hell of a difference though. Plus you have been shooting a mouse gun for the last 24 months

 

You're not wrong - I don't think I'll manage 120rds on Saturday without a nosebleed

[Scotch_egg]

I only got 2740fps from my 26" tube. However it was pure magic. Infact I regret shooting the 175gr smk in the Czech comp.

 

I shot the comp last year and only shot 108 rounds. I took 105 (5 left over from load development, I got the rifle like you in the weeks before) and borrowed 3 rounds from a very nice chap I can't recall the name of. I had my brake but only in ear protection. Wow that was an eye opener. 120 no brake or mod will hurt.

 

After cz it'll be a piece of cake. Wish I

Could make it. Blooming lympics...

[John MH]

Shooting Thursday with the rifle I shot last year for the first time in a year, same load as last year so hopefully should be not too far off.

 

Groups look ok Matt, and I think you may be shooting in the same detail as me so game on.

[Scotch_egg]

John, your xc makes me cry.

 

How can anything change in 12 months when you already achieved perfection. I will pop £10 on you wining open class. All for HFH of course. Wish I was there.

 

On a seperate note John, the high power rifle club haven't been great in email contact recently. Actually they haven't at all. Can you pm me contact details.

[John MH]

Not using the 6XC its the .260 for me this weekend.

[brown dog]

Groups look ok Matt, and I think you may be shooting in the same detail as me so game on.

 

Great.

 

I'm disappointed with the groups really; I'd like to be turning up with greater confidence but haven't got time to fanny around with it any further. Fingers crossed (for me, that is )

[c18rch]

What sort of velocities are you getting with that short barrel BD?

 

Rich

[gun nut]

Matt your groups are all 2in 1 out sort of shape. The bullet's too close to the lands, step the 45grn load back in 10thou increments from where it is now and pretty soon you'll hit the sweet spot. The beauty of this is if you have a portable press you can load 20 rounds the same and just keep pushing the bullet in in increments till you get the desired results instead of having to load different powder weights which is a pain in the ars1.

 

Mike

[AckImp]

Matt your groups are all 2in 1 out sort of shape. The bullet's too close to the lands, step the 45grn load back in 10thou increments from where it is now and pretty soon you'll hit the sweet spot. The beauty of this is if you have a portable press you can load 20 rounds the same and just keep pushing the bullet in in increments till you get the desired results instead of having to load different powder weights which is a pain in the ars1.

 

Mike

 

I concur. Get the all the speed you can get and then play with the length. We've found that in .308" the further we got from the lands the better it grouped, up to a point obviously. The node was pretty easy to find. For the record we also used 46grn of 140 but decided it wasn't worth it for the hard time the brass was getting (loose primer pockets) and the "what if?" factor of using the load on a really hot day. We settled on 45grn and ended up with a 155 Scenar about 30 thou off the lands. These were doing around 2950 out of our 28" and if memory serves the 46grn load only gave us about 40-50fps more.

[forbie]

I have a 20" Styer CISM with a 20" barrel and find it uncomfy for string shooting really snappy Got a past recoil pad one of the thicker ones makes a great difference to the felt recoil . Feels less than a 223.

[brown dog]

Matt your groups are all 2in 1 out sort of shape. The bullet's too close to the lands, step the 45grn load back in 10thou increments from where it is now and pretty soon you'll hit the sweet spot. The beauty of this is if you have a portable press you can load 20 rounds the same and just keep pushing the bullet in in increments till you get the desired results instead of having to load different powder weights which is a pain in the ars1.

 

Mike

I concur. Get the all the speed you can get and then play with the length. We've found that in .308" the further we got from the lands the better it grouped, up to a point obviously. The node was pretty easy to find. For the record we also used 46grn of 140 but decided it wasn't worth it for the hard time the brass was getting (loose primer pockets) and the "what if?" factor of using the load on a really hot day. We settled on 45grn and ended up with a 155 Scenar about 30 thou off the lands. These were doing around 2950 out of our 28" and if memory serves the 46grn load only gave us about 40-50fps more.

 

Fellows, I'm loving this advice - I was thinking through what could cause me to have to drop my standard load in 2 x AWP barrels by a whole grain due to pressure; my reasoning came up with the commencement of the rifling being nearer the chamber on this barrel.

Your observations fit that reasoning so I'll run with that and see what happens; won't have time before the comp. Got a SWAG recommendation? When you've had a target with a spread and group size like my 45gr target what have you found the average move to sweet spot tends to be? 10 thou? 15 etc

[gun nut]

Hi Matt,

I'd bet money it will be between 20-40 thou. In your shoes with no prep time i'd go middle of the road. Seat them 30thou deeper and the nut behind the butt will drop you points not your group size.If you get a shot spread that forms an equilateral triangle you're slightly too far off and you go 10thou closer to the lands.

Confidence in your equipment is worth more v bulls than another .2" group wise.(Assuming you're shooting at normal size targets and not tryin to shoot the knackers off a fly at 600yds) Happy huntin'.

 

Mike

[brown dog]

Excellent - thanks Mike!

[John MH]

Well, my home loads have not changed and last year's zero hasn't either, shot 5 rounds at 200, 300, 400, 500 & 600 this morning all spot on for elevation. Then spent the rest of the afternoon pasting targets.

[gun nut]

How'd it go BD?

 

Mike