Home Forums Reloading Big Game Rifles 7mm rem mag and Retumbo questions

So I finally took my 26" shillen barrel 7mm Rem Mag to the range to test my handloads with 160 Accubonds and Retumbo. I am pleased to say that I am finally seeing the velocities I expect of a long barreled 7mm. 69 grains was good velocity t just over 3000 fps, but accuracy was not there. I then went to the 69.5 charge and hit about 3070 fps. And saw better accuracy. When I stepped it up to 70 grains, accuracy improved, but velocity did not change at all. I am new to the chronograph game, but I am led to believe that most likely I hit my max pressures and need to back off. Is that true?

If so, I am sad as I would like to see the better accuracy of the 70 grain charge, but want to be safe. Slight cratering on the primer, but good bolt lift.

Very high pressure signs using IMR7828 and this bullet at below max charges and only low 2900 fps ranges, so I have had to rule out that powder. Just hoping to get the most out of my rifle.

What would you do?

Reloading for me is accuracy first then velocity! I had a 30.06 that shot a 165 at a slow 2680 fps but it was accurate and killed everything I needed it too.

Yes you are starting to get pressure which means that it would be wise to reduce your load slightly so you don't have any issues or change your powder/bullet combo or both?

Not sure what you are trying to attempt?

7RM brass varies widely in capacity. It would help to know what brass you are using.

If you check those 160 Accubonds I think you'll find they have a very long bearing surface compared to other 160's.

Jason, this was with R/P brass, cci 250 primers.

Esox, you ask what I am trying to accomplish. In a nutshell, I want a 160 bullet at about 3000 fps plus or minus a few and stellar accuracy. This is the reason I have a 7mm rem mag. Every manual on the planet suggests it possible. When I had the rifle rebarreled a couple of years ago, I decided to go 26" so that I would have a better chance of hitting those "magic" numbers. I am not trying to "hot rod" my rifle. I just want it to be a magnum.

I already have a 7-08 that easily pushes 140 grain pills at 2850fps. I want my magnum to act like a magnum, not a .280 rem or powder hungry 7-08.

I had never used a chronograph until a few months ago. In the past, I always watched for signs of pressure and shot for accuracy. Now, I have pre conceived ideas of what my rifles should do velocity wise and I am not interested in shooting a rifle that isn't reaching its potential. I figured that I could approach my loads with caution and try to maximize both velocity and accuracy while remaining safe. Am I wrong to do this?

FH

You definitely should be able to get 3000+ fps with 160's and Retumbo from a 26" barrel. Assuming your chronograph is accurate, your load is a good one. Hodgdon lists 69.5 grains or Retumbo as maximum with 160 Nosler Partitions, and Partitions create more pressure than AccuBonds.

Contrary to popular opinion, primer appearance means nothing. (However, primer disappearance does.)

If it shoots better at 70 I'd run 70 unless your getting difficult extraction or other pressure signs.

Bb

FH: No you aren't wrong and I feel exactly the same way. We have to remember that when we check several sources and see a certain range of max velocities from a cartridge, they will generally only be acquired at the top velocity potential for that case,and the only way we will get it is to use maximum,but safe, loads.

I figure, if I want a 280, I will buy a 280;and I will not try to make it a 7 mag....most people who try do this are confused;they simply bought the wrong cartridge for what they were trying to accomplish.

When I have a rifle chambered for a given cartridge that only shows great accuracy at loads that develop sub standard velocities for that cartridge, I generally suspect that something in the system is out of whack;that the rifle is not well nor properly assembled....I fix it or get rid of it.

Not all rifles will respond the same way to a given bullet/powder combination.I had one 7 REM MAG years back that doted on 7828 and 160 Partitions and would give about 3100 fps with no problems and I hunted that rifle everywhere until the barrel wore out....but over the years I have learned a couple of things about the cartridge,and one is that when I see a 160 gr bullet hit about 3050 or so with good accruacy, I stop right there as the case is not really capable of safely providing much more.

It is not unusual for a magnum capacity case to deliver better accuracy at max pressures and velocity than with lighter charges....sometimes they will deliver better accuracy when the charges are TOO hot for steady use, which might be where you are....but like Mule Deer say, hitting your velocity objectives is entirely within reach; if 7828 does not do it for you, we have a wealth of new slower burners that work well and will give you those velocities you want very safely....Retumbo is among them;today the first powder I reach for in the 7 RM is RL 25,which is an ongoing experiment but has delivered fine accuracy and good velocities for me so far.

I would do more testing with the retumbo at 3070 fps;get off the 100 yard line and shoot from at least 300 yards,because 100 yard groups frequently do not tell the whole story.

I've done more than a little playing with the 7 RM and 160's. 3000 ft/sec is doable in a 24" barrel with the slower powders. I have a 26" M70 and have run Retumbo under a 160 Partition. I ran my loads to 71.5 under the Partition - which I think was a bit too warm. I averaged 3095 with 71.5, 3014 with 70.5, and 3009 with 69.5 but the accuracy I was looking for wasn't there.

If you're looking for velocity, try Ramshot Magnum and H1000. 7828, as Bob mentions, is also in the top tier. My gun likes Magnum and H1000 and averages 3060 with Magnum and decent groups - this gun has been a struggle and won't win any contests with Partitions.

I also have a 7 WSM and it really likes Magnum under a 160 Partition. I get right at 3000 ft/sec with 72.5 gr and 1.25" groups. I need to play with seating depth a bit on this load. some days it'll shoot 3 touching but most days it groups 2-4 touching with 1 that opens the group to 1.25 or so. I call it 1.25" although I've shot more than a handful of 3 shot groups under an inch. Sometimes I hate JB suggestions - the 4-5 shot group is one of them. The combination of statistics and 4-5 shot groups makes most of my guns 1.25" guns - but I have some pretty 3 shot groups from all of them.

Thank you everyone. I feel better about the Retumbo. I do like h1000 and have shot quite a lot of it, before the rebarrel project. I intend to continue trying. That said, I am very pleased to get the velocities I am getting with Retumbo. Like I mentioned above, I was shooting IMR7828 and my rifle liked it, but I couldn't safely hit 2950 let alone 3000 fps with the 160 accubonds. Most accurate loads were safe below 2900 fps which is too slow for this boy. I was also getting to pressure well before my older books suggested I should, but match up closer to today's load data and max charges.

So my concern was really, whether the lack of velocity increase was a sure sign of pressure. I did see a definite accuracy improvement between 69.5 and 70 grain charge. I will play a little more at that point and adjust seating depth etc. til I find the right loads. I just wanted to feel okay about the lack of Velocity increase. I never would have noticed that before I had the chronograph. Those things can be a curse or a blessing I am beginning to think.

FH

I like the Retumbo too for my 7mags, but for some reason they both like RL22 better, for 140's and 160's. Working up to 66.5 g of RL22 with 160 AB's gets me superb accuracy and 3050'ish fps. It's probably due to the fact that my rifles seem to tighten up groups near max pressures.

A lot of rifles do, primarily because most of today's slower powders burn more consistently at 62,000+ psi, since that's what they were designed for.

The Ramshot rifle powders are particularly prone to this. I've seen a lot of posts where somebody gave up on a Ramshot powder because the starting load didn't shoot very well. If they'd kept on adding powder the groups would have shrunk, unless there was something wrong with the rifle or scope. I know this because I've seen it hundreds of times.