View Full Version : Test Loads for .300 Win Mag question

In God We Trust
06-30-2013, 09:33 PM
I tested 4 different loads in my 300 Win Mag today. I shot 5 rounds of each load. I let my rifle cool down and cleaned it between each load variation. I noticed my gun didn't group well until rounds 3-5 after it had some fouling and warmed up a bit. I am going to try a couple of other "recipes" and my question is should I put a few through the barrel to foul it before testing. I am shooting a Remington model .700 XCR with a HS Precision aluminum bedder stock and a weaver 3X15 tactical scope with 3 bolt weaver rings and weaver pica tiny rail. The barrel is a factory Remington barrel. It just seems to group better when the barrel is fowled. this is my first semi custom expensive rig so I am learning as I go.

06-30-2013, 10:43 PM
It might be worth your time to separate the temperature effect from the fouling effect.

For what it's worth, I try to tune my loads to shoot a cold bore group. It takes forever to shoot and gets boring as heck at the range, but I set a timer to make sure I have at least three minutes between shots. Obviously the first shot is the one that counts while hunting. The bore will always be cold. A load that tightens as a barrel warms is of no interest to me.

In regards to fouling, I usually scrub the crap out of the bore before load development. I use a nylon brush and a cordless screwdriver to get the carbon ring out of the end of the chamber just ahead of where the case neck ends. JB's bore paste to eliminate fouling from the barrel, especially the "tight spot" that forms from the throat into the first few inches of rifling. (I can share more on how to detect this if you don't already know) I always want a clean barrel as a baseline starting point.

After the major scrubbing, the first clean and cold bore shot is invariably at a different POI from subsequent shots. If the cold bore shots do not group well after that, I move on to a different powder, bullet or primer until I find a match up that works.

If fouling creates a sweet spot, you probably ought to run with it as long as it is consistent. If I can track a consistent fouling pattern that promotes accuracy I will scrub the bore before hunting season, then shoot the predetermined amount of foulers, then dry patch the bore a few times and hunt with it.

Hope that helps. I also hope I did not insult your intelligence by stating things you already know. Good luck with it. I'd be curious to hear your progress.

BTW, what bullet and powder combos are you trying?

Colorado Cowboy
07-01-2013, 07:00 AM
After cleaning the bore, I always shoot a round or 2 (depending on which gun I am using) to get the POI back to where it normally is. Every one of my hunting rifles are different. I always bore scrub at the range and reshoot before I leave, that way I'm ready to go hunting.

In God We Trust
07-01-2013, 05:45 PM
I am using Nosler Accubond and Nossler Partition 180 grain bullet with H1000 and Win Supreme 780 Powder. Thanks for the help guys.

07-02-2013, 01:29 PM
I only clean my rifle once a year and that is after hunting season. I used to clean it a lot more, but I noticed my groups not being very pleasant the first 3-4 rounds. If you use bore scrub or some other liquid, I would always shoot a few rounds to clear the residue of the liquids before testing your hand loads. If you are not using any liquids, I would say you wouldn't see as much of a difference, but will always see some. Just make sure to "clear" the barrel after cleaning it with the same loads you are about to shoot. That way you are comparing apples to apples. After all, you will be shooting all the same ammo when you settle on a load, so why not make sure everything is going to be as close to hunting season as possible?

The way I look at it is like this: When I am hunting, I am never hunting with a clean bore. I have shot my rifle just before leaving to go hunt, shoot it a few times when I get there, and don't touch it. If its on, I don't clean it or mess with it in any way.

I'm not so picky about my smaller caliber rifles like my .223. I load those rounds and will start shooting with a clean or dirty barrel. Its just a coyote and prairie dog gun so I don't worry about having as tight of groups with it... sometimes missing and having them run is the fun part!

Good luck with finding/building your load! I have a .300 that I haven't gotten any loads built for so I will be working on the same thing soon.

07-02-2013, 02:58 PM
I agree with with the cold bore group. I always wait until I can grab and hold onto my barrel for a good amount of time 10-15 seconds. This some times takes awhile. I try and go early morning if it's going to be a hot day as it only adds to the wait. I am shooting a max load "according to Berger" of H1000 with 185gr Bergers. My 5 shot group at 100 yds was .9", but hard to read because I had a piece of particle board that was holding my target and it exploded on impact.


12-28-2013, 11:46 PM
I load a .300 mag pre 64 Winchester I used 150 sierra then 180,s and now 165. the 150 seemed to tumble and the 180 dropped to fast and now I am real happy with the 165 sierra bt and I can keep a nice tight 2 inch consistently I use IMR 4831. I used IMR 4350 with the 150's at the range I always clean my gun with a clean dry patch between a 3 shot set. and not to get bored I take my .45 Henry Golden Boy and my backup hunting rifle .270 win. also my .45 long colt Rugger to shot filled milk jugs at 30 and 40 yards away that's what I do at the range

Musket Man
12-29-2013, 09:32 PM
It just seems to group better when the barrel is fowled.

Not something I have ever really experimented with. Other then my muzzle loader I usually just clean my guns after hunting when I put them away. But I think you answered your own question:)