Pressure signs on 300 Win Mag.

[Steve1]

I did some shooting yesterday, trying to find an accurate load. I know my loads are getting too hot, but my rifle seems to group the best with my hottest load. (At least with that powder and bullet). The temperature is increasing outdoors. Yesterday was like our warmest day all Spring....about 70 degrees. Bolt lift was definitely getting noticeably harder at 72 grains of IMR 4831. I'm shooting 180 grain Accu-bonds. They are loaded slightly back from the lands.

At 73 grains I shot a 1/2 inch four shot group. I like that kind of accuracy but the bolt lift and extraction both were noticeably hard on all four rounds. I didn't really notice any ejector swipe. The primers are very flat.

I'm somewhat worried about barrel life, with too hot of a load.

Do you think this load sound too hot to keep shooting? Or should I try another powder....possibly another bullet.....I appreciate your advice!

It takes a long time to find a good load, but this may be too hot as well.....

 

[witchhunter]

That sounds like a hunting load, do you really want to chance it when hunting? Try IMR7828 or Reloder 25....7828 looks like it is available.

 

[briang7511]

for some reason in my 300wm I reach max load about 3 to4 grains less than book max. FGMM ammo was too hot for it. Same as you describe above. I rebarreled and it seems more normal now, I was able to shoot the FGMM without any issues. I am still working on loads but what I had worked up with previous barrel shoots good and 200fps faster. rifle is a rem 700 sendaro.

 

[InkedIan]

If you are getting close to the same accuracy with your slighty less hot loads you could play with the seating depth to possibly tighten them up. How far from the lands are you currently seating them?

 

[Steve1]

I need to buy a micrometer. I had one, but lost the darn thing someplace.....I took an old case and cut a slice out of the neck with a hack saw. Then I seated a bullet long into the case. I chambered it letting the lands push the bullet deeper into the case. I used that as a guide for my seating depth. I set the seating depth slightly deeper than that. (about a quarter turn on my seating plunger).

I used to use smoke or a magic marker and then looked for rifling marks on the bullet. I hope this new method will work better.....but I know I need to buy a micrometer.

I should seat those bullets slightly deeper. That should make less pressure.....

 

[briang7511]

calipers and hornady oal guage. What bullets u using?

 

[Steve1]

I've been using Nosler Accu-bond bullets.....

 

[Steve1]

Thanks for the tip. I'll look for that Hornady caliper....I learn all kinds of good stuff from you guys....Thanks again!

 

[calico22]

your avatar is a bit distracting sorry guys. my bad.

 

[calico22]

briang7511.your avatar is a bit distracting sorry guys. my bad.

 

[briang7511]

briang7511.your avatar is a bit distracting sorry guys. my bad.

That's my wife, she just doesn't know it yet

 

[witchhunter]

Seating it deeper might raise pressure. So could seating it longer depending on where your lands are. You really need to measure. You can find the lands with your method, you just need to be able to measure to know how far you are off.

 

[ZiaHunter]

Some of the reloading manuals suggest loading the 300WM close to maximum. If they chamber easy but require effort to lift the bolt you are definitely on the hot side. I would check to see if the primers are really flattening as well as cratering around the firing pin hole. Seating depth will definitely impact pressure and would be careful not to seat the bullet any deeper with the same load. IMR powders have a tendency to be temperature sensitive and increased temperature either ambient or the round sitting in a hot chamber will increase pressure. You will also need to keep a close eye on your fired cases.

I was shooting my 300WM this weekend with 208 AMAX with 72 gr. of 7828SSC. As the chamber warmed up while shooting 20 rounds at one minute intervals the FPS went from 2885 to 2911. The rifle shoots very well with the 7828 but the temperature sensitivity is problematic when shooting longer ranges. Had 8 pounds of H1000 show up and will be using that going forward.

 

[Steve1]

I was thinking of trying H1000 or RL22 next, if I can find any. Thanks for your thoughts on this. I am learning a lot from you guys.....

 

[briang7511]

I was thinking of trying H1000 or RL22 next, if I can find any. Thanks for your thoughts on this. I am learning a lot from you guys.....

H1000 has worked very well for me.

I use it with the heavier bullets, 208 amax/bthp 230 bergers. I don't really shoot the lighter stuff.

 

[dallenvance.gunter]

What's is your muzzle velocity when shooting the 208 and 230 grain bullets?


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[briang7511]

well I just had a new barrel installed and I don't have a chrono but on the previous factory barrel 2800-2850 ish with the 208 and 2700-2750 ish with the 230s. I will have better data with the new barrel Saturday with a chrono, but what I did test was about 200 fps faster.

 

[RL15]

I would back that powder charge down. You are get hard bolt lift at 70 deg what do you think it will be like on 90+ deg day.
Also touching the lands increases pressure. some factory rifles like Remmington & Weatherby have excessive long throats to reduce pressure.
Some bullets shoot well off the lands, my AR likes 80gr sierras with a .035 jump. Like stated above play with the seating depth.

 

[Steve1]

Is IMR 4350 powder worth trying? I'd rather use RL-22 or H1000 and some 200 grain bullets, but I may not be able to find any for a few weeks. I do have a can of IMR 4350 and mostly 180 grain bullets stashed away.

I know I can lower the pressure by moving my bullets back, but usually accuracy isn't there in my testing. I think I'll start over with different components. Thanks for the advice on this!

 

[dallenvance.gunter]

That's pretty impressive velocity. Not as much difference from the 300 RUM as I expected.


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