7mm RM Load Development ?

sveltri

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I am trying to work up a load for my 7mm Rem Mag with 8133, Berger 175 Elite Hunters, virgin Hornady brass and Win LRM primers. I copied a gentleman on here and used the data from Hodgdon for the Berger 180 VLD. I started at 68 grains and worked up to 72 shooting 3 round groups round robin style. I did start to see some pretty good primer splash from 71-72 so I'd probably want to drop down a little from there?? This gun will only be used for hunting and sparingly at that. The scope on the gun (which I will replace with a Leupold VH5 today) was just a cheap Nikon 3-9 with no parallax adjustment. I conducted the test at 100 yds, can't imagine a shot on game past 500 assuming I can get this load verified and high level of confidence. What say you guys, based on the target and velocities recorded
with the lab radar?

7 mag 8133 175 EOL Velocities.JPG
 

sveltri

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I know it's not the best group or fastest but if I shot 3 in a row at 70gn with 0 ES and SD I would have to try that again. Seating adjustment could tighten the group up if you could repeat those velocity numbers. Just a thought.
That's what I was thinking, but I guess just looking for confirmation. I don't have enough experience to know if seating depth will have enough impact on group size to make it hunt worthy, again 500 yds would likely be the longest shot I'd have. Thanks 74honker!!
 

74honker

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Every rifle is different in how it reacts to any kind of changes and some just will not follow the norm but yes seating depth can be everything lol. In my 7mag the seating depth changed my now "pet load" from 1"+ group to a consistent bugholer if I do my part. Good luck on the search, just take your time and maybe go .01 at a time. Do you have a way to measure your jump?
 

MagnumManiac

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I don’t think your gun likes that powder.
I don’t think seating depth will tune it much at all. It may tighten it some, but it doesn’t look promising to me.
If I were you, I would take a case, cut two slits in the neck down to where the neck meets the shoulder, clean off any burrs, size it and place a bullet in the neck and carefully chamber it and remove it. This will tell you where your jam is. Do it a few times, once you get the hang of the feel as it chambers without sticking in the throat, it will be a very accurate measurement.
Work off this number to get your amount of jump.

Cheers.
 

Shane Lindsey

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Take the center of the groups in relation to the targets from 69.5-70.5. They are very close (node). I would like you test seating depth at 70 as it looks like it is right in the middle of the node.

I am finding that I am starting my load development touching the lands, assuming my magazines allow for it. Then tweek it as I need to.
 

sveltri

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Thanks for the replies everyone. I am fairly new to reloading, but being taught by my dad who has a few decades of reloading, now mostly for benchrest, who is helping me. We did check distance to touch 2 different ways, each providing the exact same measurement. One with a split neck and one with a fired case that he slightly tapped the neck to get it to hold the bullet in place. What I didn't have initially was a comparator to measure base to ojive and typical of other Berger bullets I've loaded the OAL of the bullets have pretty big variations. All I recorded the other night was COAL, but I did pick up a comparator for .284 today so will now be able to get more reliable data. I do know that we were backed way off from touching and I have plenty of room to go in either direction. I am probably in the .040 jump range now, I'm thinking I'll see exactly where I'm at now and go +&- .010 at 70 grains to see if that gives me a clear direction that I should proceed. Sound like a decent plan?

Magnum Maniac - is there something specifically that makes you say that? After all this is a fairly inexpensive rifle with a grossly less expensive optic on it.
 

MagnumManiac

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Magnum Maniac - is there something specifically that makes you say that? After all this is a fairly inexpensive rifle with a grossly less expensive optic on it.
I say that because there is no form to the groups, they do not have a circular pattern.
You see, unlike most, I do not look at ES/SD numbers during development nor do I use virgin brass for development. There is too much ‘noise’ when using virgin brass because not all cases expand at the same rate. This changes internal ballistics quite a bit.

Cheers.
 

Shane Lindsey

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I say that because there is no form to the groups, they do not have a circular pattern.
You see, unlike most, I do not look at ES/SD numbers during development nor do I use virgin brass for development. There is too much ‘noise’ when using virgin brass because not all cases expand at the same rate. This changes internal ballistics quite a bit.

Cheers.
Agree with the virgin case white noise. I use virgin cases, but only as the starting point. If I have 200 of them, I can develop a load with them and once they are all fireformed I will address tweaking the load. I have found I need to slightly decrease the charge on fireformed vs virgin as the pressure seems to increase if using the same charge weights. This is with my charges as I typically work in the upper end of pressure/node.

Also kind of agree with the ES/SD. I typically do not chrono a load until I am done finding what I think is an acceptable group...OR...I do it in the beginning trying to find max pressure. I kind of use the velocity as a guide telling me the flat spots, but do not use that as gospel.
 

74honker

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^^^This^^^. But I chrono everything. Sometimes it might be meaningless information but its still information. ES/SD isn't always everything if the POI doesn't change, I have one like that. But IMO the tighter you can keep those spreads the better and you can't get much better than his zero. Why I would have to try to repeat that to see if it was a fluke or not. Never know, this gun might just really like new brass. All part of the journey and learning proccess.
 

DesertBoy

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I am working up a load for my T3x 7mm Rem Mag with these same bullets. Using virgin Norma brass and WLRM primers. Not sure exactly where my lands are, but with my comparator on, I was jamming at 3.793”, and started backing out .01”at a time until I couldn’t see land marks on the bullet or feel jam. I am pretty sure the lands are around 3.773”. Set bullets to 3.768”. I ended up with 2900fps average with 76.5gr RL33, and 2953fps average with RL26. They are shooting around 1/2MOA
 
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