Precision load workup, .308 bolt gun, check my plan please

[Citadelgrad87]

I have a 700 5r 24” that i am playing with. First trip the range, after sighting in with two rounds (i am starting to like the Horus reticle), i settled down and shot a 5 shot group at 100y off a bipod and bag, 175 GMM, that was under an inch, all touching, no fliers.

Stupid me with my pages of notes and working on a new rifle, i took a photo but never measured it. Suffice to say an inch tape circle would have covered it with room to spare.

I chronoed the factory ammo and have that in my notes.

Its a 700 5r, 24” braked barrel, timney 510 with a Grayboe Ridgeback stock and a Bushnell HDMR2 scope, Horus reticle. For now, a Harris with podlock and a rear bag.

My goal is to work up the best load for my intended use, first, just playing with an accurate rifle and trying to eek out more accuracy, secondarily, once i get the drill down i intend on entering some local mid range matches, like they run in Burbank i think. I dont think thats paper matches, i think thats on metal, so whatever difference that makes.

I have a rock chucker for my precision rifle loading, picked up some lapua 1x brass, bought some competition dies, have plenty of 4064 and 175 mk projectiles, a case length gauge with ogive insert for 308, and i am about ready to load some “lets see how THESE work” rounds.

So i used the case length deal and it looks like the 175s touch the lands at 3.320 to the ogive.

I think that means i should start loading at 3.300 to the ogive? Is that correct? Which way do i go with that, +/-, to see if thats the sweet spot?

Its a good deal longer than a factory round, i think i will have mag clearance issues.

How does one deal with that? I have a single shot sled ive used to simplify loading during load development. I dont mind using it but being locked out of magazines seems a pretty hefty trade off.

Do people work up a load that is the best they can run, then another load thats the best the rifle will feed through a magazine? Or just load the same charge weight, but shorter to run in a mag? Am i going to note a difference? Should i load as long as will run in magazines, or find what the gun likes?

I plan to run a ladder test at 300 at angeles, unless i go to the desert, thats as far as i can set up paper that i know about, and its a 3/4 day trip to do that.

I appreciate the input.

[J-cat]

Try 42.2grs if 4064 in the FGMM case at a oal in the 2.830” range. Then adjust up/down in .005” increments until they all shoot under .5”. This should yield a 2600 FPS load with single digit SD that won’t ruin your brass.

[baih777]

Stop and remeasure.
There is no way that measured 3.30 to the ogive for .308
OAL to the lands should be around 2.90
If you have a .308. The mag will only take 2.80 OAL

[Citadelgrad87]

Originally Posted by baih777

Stop and remeasure.
There is no way that measured 3.30 to the ogive for .308
OAL to the lands should be around 2.90
If you have a .308. The mag will only take 2.80 OAL

Its a funky measurement because it includes the holder and ogive insert, so its substantially longer than oal. Like .5” longer or so.

It attaches to a blade on the calipers and is more to transfer the measurement from the insert round to a loaded round.

Edit, here is what i am trying to describe


https://www.1967spud.com/shop/hornad...-gauge-system/

[smoothy8500]

Remingtons generally have very "long" throats and trying to load just off the lands will require long loads meaning single loading. However, The Sierra MK's are very jump tolerant and you can load them to magazine length without any detriment to accuracy. Figure a load and we'll see you at Burbank. It's 600yds on paper, so you get every shot spotted.

[Citadelgrad87]

Just measured OAL of the length i posted sbove.

Its 2.902

[Citadelgrad87]

Originally Posted by smoothy8500

Remingtons generally have very "long" throats and trying to load just off the lands will require long loads meaning single loading. However, The Sierra MK's are very jump tolerant and you can load them to magazine length without any detriment to accuracy. Figure a load and we'll see you at Burbank. It's 600yds on paper, so you get every shot spotted.

Ah. Gotcha.

Do you ladder test? I a, seeing reslly good things about 42-43 of 4064. I like to figure things out for myself, but dont have any interest in reinventing the wheel.

[smoothy8500]

I did an OCW (optimum charge weight) test at 200yds over a chrono. I had three parameters: I needed over 2,650fps along with finding a range where vertical dispersion was minimal and the velocity maintained a plateau. This was for Long Range load when shooting at Santa Margarita Gun Club. We sometimes deal with extremes with a start in the cool of the morning and will finish in the heat of the afternoon.

I don't weigh every load, I just meter. It falls +/- .2gr max. The load I found maintains almost a water-line at 1,000 with wind reading as my major issue.

[boyguan]

Originally Posted by Citadelgrad87

Just measured OAL of the length i posted sbove.

Its 2.902

That’s about what mine is as well. I’m actually loading to 2.92 on the 168grn amax. I took .010 off already for jump

[Citadelgrad87]

Originally Posted by boyguan

That’s about what mine is as well. I’m actually loading to 2.92 on the 168grn amax. I took .010 off already for jump

Do you just forgo mag use?

[baih777]

I have the same guage. But I use digital. I reset the zero with the guages attached.

[boyguan]

Originally Posted by Citadelgrad87

Do you just forgo mag use?

Yep. I single load.

But recently just got a chassis so I will be changing that up a bit now and using max magazine length

[kcstott]

My 308 175gr Nosler RDF's are 3.057" COAL or 2.268 with a comparator.
thats .005 off the land and the only way they shoot out of my rifle.
SMK shoot mag length just fine. single hole five shot group