.338 - 300 RUM pressure problem

[crittergitter]

Been playing with some new loads and I'm having pressure issues. I'm shooting a .338 - 300 RUM with a pretty long lead (.212", lead + throat .4755"). My favorite load has been 107 grains US 869 with a 265 grain Barnes TTSX (LRX, MRX, whatever they decided to call it). Great load but I wanted to try H1000. I extrapolated my starting point on the load based on bullet weight and decided to try 97 grains H1000 with a F215 primer. Resulted in an extractor mark but no sticky bolt or measurable case web expansion. I tryed working it down and even dropping to a standard primer (maybe a mistake) but pressure signs increased. At 93 grains, standard primer, and 30 degree powder temp, the bolt was sticky and I had a case nearly separate. After thinking about it, the only extractor marks I have gotten during hunting situations with my old loads with US 869 and F215 primers or Retumbo and F215 primers have been on days below 30 degrees. Now I wonder if I might be undercharging everything. I have very few guns that shoot loads that can be found in a manual...or even online. I've figured quite a few loads out with a calculator without issue. This one's got me concerned. I'm a little scared to go up or down with the H1000 load without more info. Anyone else with this experience or a known H1000 load for this bullet?

 

[highridge1]

I had nothing but problems with H1000 in my Edge, lot to lot very inconsistent. Go to load was 94 gr with 300 gr bought new powder ended up at 89 grs. Quit using it ,went to RL 25 and everything got better, accuracy, ES velocity.

 

[Chase Curtis]

whats your seating depth?

 

[ZSteinle]

Mine will show pressure at about 93 gr. of h-1000 using lrx 265's

 

[davewilson]

i have 2 guns in that chamber that i've shot 225TTSX,250SMK, 285 HORNADY, and 300SMK gr bullets. i think the 1000 works best with the 285-300 bullets, and pretty good with the 250's. I think the 869 would be a little slow for the 250-265 bullets. someone asked about seating depth. i would think you might be in a double ignition situation with too slow a powder and a light charge as you've already mentioned. i can fill my cases up with 1000 and not have pressure issues with the 250's. Norma MRP for the 225's!
something else you might check is the spring pressure of the firing pin. a weak spring can cause this type of thing.

 

[crittergitter]

As for seating depth, My COAL is 3.930"... give or take a few thousandths. I can't remember exactly off the top of my head. I'm 0.050" off the lands. I get 3216 fps with 107 grains of US869 out of the 34" tube and it shoots .2 MOA groups most of the time. Still, I have had some wacky things happen on 15 or 20 degree days. That's why I tried H1000 to begin with. I may go ahead and try working up from 107 grains with the US869 just to see where excess pressure develops. I may be riding the fence on the undercharged side and getting some detonation issues when the temperature drops a little. My 300 grain load is 105.5 grains of US869 and gives around 3030 fps.

 

[Chase Curtis]

In my experience with my edge or 338/408... 869 will give the highest velocity without pressure, however the ES will kill ya.. especially with a heavier bullet. 869 works well with lighter bullets. I have also found 869 to be pretty temp sensitive.

I would try to make the 1000 work and go about fixing it from other angles rather than changing the load/powder.. with that in mind though....

you might try as crazy as this may sound... H50bmg. I have a friend of mine that shoots a load with it in his edge with the 300 berger.. its a compressed load.. but no pressure.. probably with your seating depth top out around 102ish... BUT WORK UP TO THAT SLOWLY! if you try it.. just a thought.

 

[crittergitter]

Thanks. I had toyed with the H50BMG idea and I don't think it's crazy at all since it is actually a faster burn than 869. What do you mean by make h1000 work but fix it from other angles??? Guess I lost ya there. Are you suggesting 102 grains of 1000 or 50 BMG on a 265 lrx?

 

[Chase Curtis]

I am suggesting you try 50bmg and that it will probably peak out about 102.. but obviously work up to that.. (it will be compressed)

By other angles.. I am referring to the same as said prior.. could be firing pin,brass, primer.. i don't know.. but I don't see why 93 or really even 97 of H1000 would give pressure with that bullet andy your OAL. I don't know what the fix is.. but I do know.. that doesn't sound right.. My edge load is 100gr H1000 @ OAL 4.130 with the 300 berger.. runs right at 2950... NO pressure at all...

 

[crittergitter]

Every gun is different. I was pushing the Berger at 3030 with 105 grains of US869. Once again, low temperature days yielded haywire results and extractor marks. I may have undercharged everything considering your results from such a similar set up. How long's your bbl? Incidentally, I shot a white tail doe at 130 yards (facing me) with a Gen1 300 grain Berger this year. No exit and have never seen a deer drop that fast. I like the Barnes better over all but I must say that was pretty cool.

Thanks for the valuable info. I may give H50BMG a whirl. I'm about to rechamber a shot out 7mm for the last time to 7mm - 300WBY AI. H50BMG may be really good in it too.