300 RUM Issues...

[cohunter14]

I finally had the opportunity to get out and verify my drops this weekend on my 300 RUM. I am loading up 92.5 grains of Retumbo for a 200gr Accubond, COL of 3.587" (to fit my magazine). I initially got pressure signs at 93 grains when loading these up (half moon on the case head), so I backed off a half grain.

My issue after shooting this weekend is that it looks like this load is only pushing approximately 2,860 fps. According to Hodgdon, their minimum load of 89 grains produced over 2,900 fps (with a COL of 3.60") and the majority of load data I have seen get people well over 3,000 fps when going over 91-92 grains.

Is there something I could be missing here? Should I just try loading up some other powder? I could stick with this load as is, but I don't really feel like it is taking advantage of the RUM's capability. By the way, I was able to shoot at 700 and 900 yards to verify these drops. Any advice is appreciated!

 

[BEEMAN]

That seems slow. I am shooting the 215 Berger Hybrid with 91 gr H-1000 @ 2985. No pressure signs in my rifle. How Long is your barrel? My friend just got a Sendero with a factory 26". He is loading 94 gr Retumbo with the 215 hybrid and getting 3140 fps. Not sure about your speed. I think we need LOOONGER BARRELS. These loads are safe in our rifles. Work up carefully.

 

[cohunter14]

I have a 26" barrel. Those numbers that you are getting seem to be typical, which is why I am a bit confused...

 

[D.Camilleri]

I am shooting 93 grains of Retumbo with 215 bergers, however, my oal is around 3.670 (max that will fit in my magazine) By extending the bullet out the pressure changes. My chrono numbers are 3075 from my old pro chrono and 3163 from the new chrony. My drops at 700 say 3003. My next shots will be at 1000 to verify the drops again.

When you said you have verified your drops, what was your zero and what were your come up amounts at the distance you shot at?

 

[cohunter14]

I sighted it in at 2" high at 100 yards. Came up 20 MOA at 900 yards (80 clicks with 1/4 MOA scope) and 13.25 MOA at 700 yards (53 clicks). My COL of 3.587 couldn't be responsible for that much loss of velocity could it?

Edit: temps were approximately 55 degrees, altitude was 4,150. Don't know if that helps as well.

 

[BEEMAN]

We are using different bullets but this is what I get for drops at my location with the 215's. Elevation of 1450 ft, temp 35. Rifle is zeroed at 200 yds. Drops according to SHOOTER APP.

700 yds 11.5 moa
800 yds 14.5 moa
900 yds 17.7 moa
1000 yds 21.1 moa

 

[cohunter14]

Yeah, as an example if I were getting 3,000 fps, I would need only 45 clicks at 700 and 71 clicks at 900, so there are some pretty big differences there.

 

[BEEMAN]

There are differences. Not sure what the BC of the AccuBond is. But the Berger is .696 I believe with not a lot of bearing surface. My COAL is 3.843" and my friends is 3.9xx. Can't remember exactly. Every gun is different, and so is every barrel. How far off the lands are you? I am 50 thou off and my friend is 22 thou off.

 

[cohunter14]

I meant a big difference from what I was seeing at what 3,000 fps provides in mine, but yeah I know there will be differences in your loads as well. I am not sure how far off of the lands I am in mine, haven't checked.

 

[D.Camilleri]

Cohunter14,

I ran your numbers and your calculations seem correct. I came up with 12.75 moa @ 700 and 20moa @ 900 using 2860 and a 231 yard Zero which exbal says is 2 inches high at 100. Can you seat your bullets a little longer and still fit the magazine? By extending the bullet, you create more case capacity and thus reduce pressure, so you would have to add more powder. It could be possible that you have a tight barrel. How are your velocities with other bullets?

 

[cohunter14]

There is not much at all left as far as length goes to fit the magazine. This is the first bullet I have loaded in this gun, so I cannot really judge the velocity difference. One of the things I am contemplating would be to try loading up another bullet (maybe 215 hybrids, although I am not sure how well they would work with my short case length). The other would be to try another powder like RL-25 or H1000, but it seems like everyone gets better velocity than I am getting out of Retumbo, so I wanted to make sure I wasn't doing something wrong first.

 

[BEEMAN]

I just shoot mine as a single shot. Lots of time for a follow up shot if you need it. Might want to try some R33. Supposed to work good. Being in Canada I probably won't see any for about a year!

 

[cohunter14]

I want to keep the rounds so they can fit in the magazine as I use this for all hunting, long range and short range.

The only two things I have come up with as a possibility for the low velocity at this point is my scope being off or my powder being bad. But my scope would have to be almost an inch low at 100 yards to get anywhere close to 3,000 fps, so that would be a pretty drastic change from when I sighted it in. Either that or the scope doesn't track correct, but it seems like the differences in clicks between 700 and 900 yards match up pretty close. And if the powder was bad, I wouldn't think I would see pressure signs... Thoughts?

 

[aramarine6]

If you've got access to a chrono I'd double check your velocities with that. What kind of tempuratures are you shooting in? What do the primers look like? Have you tried different primers?