7RUM load development, need advice

[sambo3006]

I loaded up some rounds for my new (to me) 700 LSS LH 7RUM 26" bbl and did some shooting Monday. The temp was upper 70's. I let the barrel cool to just warm to touch between shots and alternated between the two powders with each shot. Bullet was moly coated 140 BT, primer was Fed 215GM and brass was new full length sized Rem. Bullets were seated just short enough to cycle through magazine. Here is what I got:

Hogdon H1000

1. 93 gr 3284 fps
2. 94 gr 3308 fps
3. 95 gr 3341 fps
4. 96 gr 3367 fps
5. 97 gr 3427 fps

Hogdon Retumbo

1. 94 gr 3259 fps
2. 95 gr 3276 fps
3. 96 gr 3367 fps
4. 97 gr 3392 fps
5. 98 gr 3418 fps

Extraction was easy on all shots. #5 on both powders showed s slight ring on the case head. There was no cratering of primer. Pimers were slightly flattened on #5.

These loads are about 2 grains over max for the Hogdon website, but I am shooting moly coated bullets. I would think that 3500 fps would be attainable with this bullet weight.

Should I increase powder charge some more? I am thinking that the H1000 is the better powder--seemed to be more uniform velocity gain. Should I go up by .5 gr increments?

Should I try a faster powder? The next fastest I have on hand is IMR 7828 followed by RL22.

I have some 150 gr BT's coming, and will develop a load with them. That is probably what I will hunt deer with. I would like to get 3400 fps with them. I will moly coat them as well. Would the same powder work well with this bullet, or slightly slower?

I really have never exceeded listed max by more than a grain before and am unsure. I have heard that moly coating reduces pressure and requires more powder to achieve the same pressure as uncoated bullets. It looks like I would be 3 to 4 gr over listed max to get 3500 fps with the 140. I just don't know what to think.
Thanks in advance,
Sam

 

[mrultramag]

I would try the IMR 7828 and RL 25, Then the RL22 and maybe AA8700 in that order. You will have to find the max for your gun. Your chamber and barrel dimensions differ somewhat from that of the pressure barrel that most manufacturers use for pressure testing. They have pressure barrels that usually have minimum spec chambers etc. Sometimes that gives the handloader a little bit of leeway on how much powder he can use. So.. sometimes you can get away with using some more powder than book. Sometimes not. Read the pressure signs that your gun will give you, IE case head expansion, extractor marks, flattened primers, hard case ejection, and expanded primer pockets. In my experience with the 300 and 7mm rum using RL25 is that primer pocket expansion is the most noticable when you need to back down some. You can feel the difference when reloading the case that you fired and the primer just goes in too easy for your comfort when using a hand primer such as Rcbs. You get a feel for what new brass feels like to prime. That brass is too spendy to only get one shot from. I like to get 3-4 at least. Also, some guns are faster than others. But... I think you should be able to get to 3500 with 140's. Your gun will be the deciding factor and what it tells you if you look for it.

 

[Fotis]

Amazing isn't it? I thought I can easily break 3600 fps with the 140's in the RUM. After all my STW did 3500 fps no problem. Anyway some RUM's just will not do it with a 140. I just use 94 gr Retumbo and 160 Accubonds at 3200 fps --mild load-- and accuracy is in the 1/2" from my SAKO 75. Do the math---heavies pay out dividends as range increases.

 

[sambo3006]

Pop,
I shot the 140's as they are what I have on hand. I have some 150 BT's coming as I got them super cheap. I also plan on trying the 160 AB. I do not plan on shooting over 500 yds or so with this rifle. It will be used for north MO farm country deer hunting. If I can get some more long range practice, I might extend that some.

You are right on the 160 taking over at long range. I am mainly looking at the 140 or 150 for a significant PBR since a deer may pop out at the far end of a 40 acre field after being pushed by hunters on another farm and they don't always offer a long window of opportunity. If the deer stops for 5 or 10 seconds, I need to be able to do a quick eyeball range check (which isn't too hard on a square 40 acres). If the deer looks to be over 250 yds or so, I know I can put the crosshairs on the shoulder blade and hit out to 400 yds.

I am hoping the H1000 works a little better with the 150. I still have hopes of 3400 fps with this bullet and 3300 fps with the 160 AB. If I get high pressure signs, I will stop.
I have a 24" 7STW Savage Tactical (rechambered) that comfortably does 3300 fps with the 140 BT and shoots bugholes at 100 yds. I would hope that with nearly 20 gr more powder and 2" more barrel I can get another 200 fps with the 7RUM.

Thanks for the input guys, and keep it coming!
Sam

 

[bailey1474]

Pop wrote:
[ QUOTE ]
Do the math---heavies pay out dividends as range increases.

[/ QUOTE ]

He is 100% correct. If your just going to shoot those 140s, sell the RUM and get a 7 Rem Mag. Shoot the 160 gr + bullets and that RUM will start to separate itself.

 

[mrultramag]

I do see that accuratepowder.com has data for the 7 rum that exceeds 3500 with 140 and 3400 with 150. Its using AA8700. use the selection by caliber to get to the 7 rum data if you're interested.

 

[Fotis]

[ QUOTE ]
Pop,
I shot the 140's as they are what I have on hand. I have some 150 BT's coming as I got them super cheap. I also plan on trying the 160 AB. I do not plan on shooting over 500 yds or so with this rifle. It will be used for north MO farm country deer hunting. If I can get some more long range practice, I might extend that some.

You are right on the 160 taking over at long range. I am mainly looking at the 140 or 150 for a significant PBR since a deer may pop out at the far end of a 40 acre field after being pushed by hunters on another farm and they don't always offer a long window of opportunity. If the deer stops for 5 or 10 seconds, I need to be able to do a quick eyeball range check (which isn't too hard on a square 40 acres). If the deer looks to be over 250 yds or so, I know I can put the crosshairs on the shoulder blade and hit out to 400 yds.

I am hoping the H1000 works a little better with the 150. I still have hopes of 3400 fps with this bullet and 3300 fps with the 160 AB. If I get high pressure signs, I will stop.
I have a 24" 7STW Savage Tactical (rechambered) that comfortably does 3300 fps with the 140 BT and shoots bugholes at 100 yds. I would hope that with nearly 20 gr more powder and 2" more barrel I can get another 200 fps with the 7RUM.

Thanks for the input guys, and keep it coming!
Sam

[/ QUOTE ]

As i did not play with the 140 gr I can not offer much help-sorry. Your speculation of 3300 fps with the 160 is totally obtainable. Retumbo will do it easily. My rifle just liked 3200 fps better so I left it there. It more than covers my needs as of now anyway.

 

[duckinalaska]

Try the 168 grn smk's, the remmy's love that round. Also, use 94 grns of retumbo and work up slowly. The remmy 9 1/2 primers go good also. The 94.2 grns shoots the best in mine, right around 3312 fps.
Brandon
Here is a 300 yard group with the load listed above, not too bad for a hunting rifle.