Always One To Tinker... .300RUM w. 230 Hybrids?

[lancetkenyon]

Ok I see it!! Thanks I didn't know anything about that. And that is another bad sign of pressure right??

Definitely a sign of pressure, but these are pretty minor, and the only sign it showed. I have seen far worse from factory loads.

 

These are new brass, so headspace has not been refined to my chamber. The excessive headspace of factory new brass, in this case a .016" short shoulder, definitely causes some pressure too. I doubt I would see the same ejector mark using fire formed brass with a .002" shoulder bump and the same charge weight and seating depth.

 

I also do all of my ladder testing with the bullet touching the lands, which also increases pressure. I do this so I know I am at the absolute max for pressure, with the possible exception of using a powder that is temp sensitive, and doing load development at low ambient temps, then going shooting with a 50 degree higher temp.

 

Basically, stacking a lot of the possible causes of pressure, to ensure once load development is complete, this will not be an issue in the future. But I do want to work in the higher node to wring all the speed I can get out of it. I have a light load for the rifle already using a 210 HVLD @ 2960. So these will be strictly for killing stuff.

 

There are several signs of pressure, from mild to holy crap!

 

Excessive speed, excessive recoil, hard extraction/sticky bolt lift, case head swipes, ejector marks, bent case head rims, flattened or cratered primers, pierced primers, soot around the primer pocket, blown primers, loose primer pockets when re-priming if low round count on brass, and in extreme cases, case head separation, cracked case walls, ruptured cases, ruptured actions, etc.

 

Here are a few examples:

Bad ejector mark with brass flow

 

Case head swipe

 

Various severities of flattened primers

 

Cratered primer

[Zeke-BE]

That is the biggest crater pocket I have ever seen!!!!

[300RUM]

If you are working with a semi-auto you can also watch what the extractor does to the rim. If you see an area of the rim completely bent back or the sharp forward edge of the rim badly rounded off you probably have high pressure. In real bad cases the extractor may tear a section of the rim off and leave the case in the chamber.

[lancetkenyon]

Went out on some other load development, and got my .300RUM some range time this morning with some very promising results.

 

Shooting some charge weight testing loads at 200. Good speeds too. Just a hint of pressure at the top load with the bullet touching the lands. Hoping tonreduce pressure once I get better headspacing with fire formed brass and a bit of jump to lands. Speeds were between 3042 and 3070 across 5 loads.

 

Tough to see through the spotter, but cold bore was dead on, about 1/4" high at 200.

 

 

First 3 shots

 

 

 

 

 

[Zeke-BE]

Wow crazy accurate

[CraigK]

Wow!

[dse]

What's the COAL? I believe I can go to 3.800 and still fit in the Wyatt box on my 300 Rum.

[lancetkenyon]

3.875+/-" COAL. I know I have to back them off at least .0500" to fit in the Wyatt's box I ordered @ 3.825". But I always ladder test on the lands.

[300RUM]

I put a Wyatt's box in my .300 about 4 years ago. It will feed reliably with a 3.835 COAL. I'm sure since it is a stamped part there can be some dimensional variances between magazines but based on my experience your COAL expectation should be accurate.

[gaps]

Awesome thread! I love the 300 RUM and 230gr combo out of my Phoenix Custom Rifle. Below is a little bit of my ladder test with them:

 

http://www.longrangehunting.com/forums/f28/300rum-230-berger-ladder-test-127800/

[300RUM]

I tend to copy / paste interesting information I find on line and hide it all over my computer like a squirrel hiding nuts. During a "clean up" session I just found the following. The test uses a heavy bullet load so this seemed a reasonable place to post it. I thought others may find the results interesting.

 

Testing the 300 Ultra Mag by Charlie Sisk
A few weeks ago I done some testing with shortening barrels with various calibers. I just finished this test with a 300 Ultra.

These loads were EXTREMELY HOT !!!!!!!!!

I will not post the grains here because on the third loading the primer would fall out of the case . I never load this hot , only this time for the test. I used Remington brass, Federal GM215M primers, 220 grain round nose bullets. I used the same procedures as the last test.

length H-4895 H-870
.....27 2740 3107
.....26 2709 3088
.....25 2685 3062
.....24 2663 3046
.....23 2636 3018
.....22 2612 2997

H-4895 lost 128 fps
H-870 lost 110 fps

 

 

No, I do not want a 22" barreled 300 RUM but it is interesting to see what actually happens as the barrel is shortened rather than guess.

[lancetkenyon]

In all honesty, if you want a short, lighter weight rifle, the .300RUM is not tha cartridge for you. I run a 28" barrel on my rifle. I would not want to give up 125+fps to lose 6" of barrel length and maybe 10-12 oz. I built it to reach out and touch something. From a prone or sitting position. If I want to shoot a heavy .308 bullet slower from a lighter gun, I would build a .300WM/.300WSM/.300RSAUM with a lighter taper barrel to carry around.

 

I realize that is not your intent. But you also lose a lot of efficiency by going to a 22" barrel. Powder burn rates come into play and you could probably do better by using a faster powder to match the shorter barrel length. In all reality, the .300RUM was meant to shoot in longer barrels. That is why Remington introduced it with a 26" barrel in the R700.

[300RUM]

No, I was not trying to make a case for short barreled .300 RUM rifles. I would never go under 26" on that round. I just thought the data was interesting. He did the same test with a variety of cartridges. I collected data like that when I was considering a 20" barrel on a 7mm-08AI. It could be projected the other direction for an idea of what a longer barrel may achieve. I have seen a few .300 Rum rifles with 30" plus barrels. I have a 27.5" barrel on my .300. That may sound like an odd dimension but with a lengthened stock and the brake it was the longest barrel I could fit in my pelican 1750. I am so glad I measured and figured that out before I installed the barrel at 28". That would have been a bad day.

 

Did you catch he noted R-P brass with loose primers after 3 loads? Someone else said they had that problem a while back.

[lancetkenyon]

Well, in the midst of several other projects, I had a bit of time today to get the Seating depth test loads ready to test out as soon as I get a chance.

 

Original load testing was all done with the bullet touching the lands, at a CBTO of 3.105". Knowing I have a Wyatt's extended box waiting to go in, and wanting a repeater, I knew I would have a minimum of about a .0500" jump to fit the box. So I started just barely below that COAL max of 3.850" @ 3.846". That puts CBTO @ 3.072".

 

 

 

 

I went down to 3.055" and kept a .020" difference from there on.

 

 

Plenty of space in the Wyatt's box now.

 

 

 

 

 

[firstcoueswas80]

I don't know how you do it Lance. I've been wanting to get out and send some more lead downrange with my 28 Nosler but, maybe it's just my old age creeping up this heat is repulsive to me! I want to do nothing more but sit in my lazy boy drink iced tea and watch the Diamondbacks!