7mm Rem. Mag. load help

[SakoShooterSD]

I've put about 200 Barnes TTSX and MRX bullets down the 24" barrel of my 7mm Rem Mag in the past year, and been very happy with their performance.
All of my hand loads have been MUCH MUCH better than factory ammo I was shooting before. (I was getting ready to get rid of the gun, producing 2" to 3" groups, before my dad did some hand loads for me.)

As for powders, I chose IMR 4831 to begin with, because of the many good things I'd read on the internet about it with respect to the 7mm Rem Mag, and because it appears as the most accurate powder for 3 out of 5 listed bullet weights for this cartridge in the Barnes manual. It has been a very good powder in my gun.

Retumbo has worked very well, and has produced the very best group I've ever shot.
IMR 4350 has been good.
RL-22 has not been as good, though I may have just skipped over the optimum powder charge(s).
I've heard very good things about H1000, but have not tried it.

150 gr TTSX have been very good.
140 gr MRX also worked well, but I did not get to try as many loads with them.

All loads done with CCI LR250M primers, and Nosler brass . . . up until now.
(I just received 100 pieces of Norma brass, and will start load development again. Sigh.)

After having a new stock put on with glass bedding, and having the barrel cryogenically treated, my "optimal" load changed significantly.

Was:
IMR 4831 . . . around 59 grains (1/2" groups @ 100 yds)
behind a 150 gr TTSX

Now:
60.5 gr IMR 4831
behind a 150 gr TTSX (1/2" group)
or
68.9 gr Retumbo
behind a 150 gr TTSX (0.35" group, and very consistent velocities on the chrono, averaging 2964 fps)

69.0 gr of Retumbo also worked very well
behind a 140 gr MRX . . . except for on flier (which was probably my fault):
4 rounds all touching at 100 yds (0.37" group)

Disclaimer: As always, start at the low end of your manual's recipe, and work up.
I go in 0.5 gr increments, and identify one or two good groups. Then do 0.1 gr increments around those points.

The B.C. on the 150 gr Barnes TTSX (0.450) with it's Boattail design and ballistic tip, is better than that on the 160 gr TSX FlatBase (0.392).
It is also has higher gyro stability margin. I think it is plenty big enough Elk, and has excellent terminal ballistics.
(As you probably know, BCs published by different bullet manufacturers are not all equivalent.)

One issue I saw with the Retumbo was a black powder marks on the outside
of the neck and shoulder area. I would be very interested to hear if you see anything like that in your load development.
This could possibly be from too light a powder charge (even though accuracy was very very good), too low a bullet weight, not enough neck tension or cases necks that had been work hardened too much. (Hence my new Norma brass, to see if the problem goes away.) If the new brass, or annealed necks don't fix the problem, I'll go back to IMR-4831, or try the H1000, or maybe some VIT N560 or N160.

 

[Fitch]

I've put about 200 Barnes TTSX and MRX bullets down the 24" barrel of my 7mm Rem Mag in the past year, and been very happy with their performance.
All of my hand loads have been MUCH MUCH better than factory ammo I was shooting before. (I was getting ready to get rid of the gun, producing 2" to 3" groups, before my dad did some hand loads for me.)

As for powders, I chose IMR 4831 to begin with, because of the many good things I'd read on the internet about it with respect to the 7mm Rem Mag, and because it appears as the most accurate powder for 3 out of 5 listed bullet weights for this cartridge in the Barnes manual. It has been a very good powder in my gun.

Retumbo has worked very well, and has produced the very best group I've ever shot.
IMR 4350 has been good.
RL-22 has not been as good, though I may have just skipped over the optimum powder charge(s).
I've heard very good things about H1000, but have not tried it.

150 gr TTSX have been very good.
140 gr MRX also worked well, but I did not get to try as many loads with them.

All loads done with CCI LR250M primers, and Nosler brass . . . up until now.
(I just received 100 pieces of Norma brass, and will start load development again. Sigh.)

After having a new stock put on with glass bedding, and having the barrel cryogenically treated, my "optimal" load changed significantly.

Was:
IMR 4831 . . . around 59 grains (1/2" groups @ 100 yds)
behind a 150 gr TTSX

Now:
60.5 gr IMR 4831
behind a 150 gr TTSX (1/2" group)
or
68.9 gr Retumbo
behind a 150 gr TTSX (0.35" group, and very consistent velocities on the chrono, averaging 2964 fps)

69.0 gr of Retumbo also worked very well
behind a 140 gr MRX . . . except for on flier (which was probably my fault):
4 rounds all touching at 100 yds (0.37" group)

Disclaimer: As always, start at the low end of your manual's recipe, and work up.
I go in 0.5 gr increments, and identify one or two good groups. Then do 0.1 gr increments around those points.

The B.C. on the 150 gr Barnes TTSX (0.450) with it's Boattail design and ballistic tip, is better than that on the 160 gr TSX FlatBase (0.392).
It is also has higher gyro stability margin. I think it is plenty big enough Elk, and has excellent terminal ballistics.
(As you probably know, BCs published by different bullet manufacturers are not all equivalent.)

One issue I saw with the Retumbo was a black powder marks on the outside
of the neck and shoulder area. I would be very interested to hear if you see anything like that in your load development.
This could possibly be from too light a powder charge (even though accuracy was very very good), too low a bullet weight, not enough neck tension or cases necks that had been work hardened too much. (Hence my new Norma brass, to see if the problem goes away.) If the new brass, or annealed necks don't fix the problem, I'll go back to IMR-4831, or try the H1000, or maybe some VIT N560 or N160.

You are getting great accuracy. If I had a load shooting 150g TTSX (great bullets!) into 1/3 MOA groups, I'd stop load development, ignore the black on the necks, get some long range data for the scope table, put the rifle away till hunting season, and save some barrel life for hunting.

Fitch

 

[Terrytf]

Terry this is my last 4 shots out of my Savage 7 mag at 100 yards:

Corey

if I could get groups like that . I would be done. i'm close but just need some fine tuning

 

[Terrytf]

I've put about 200 Barnes TTSX and MRX bullets down the 24" barrel of my 7mm Rem Mag in the past year, and been very happy with their performance.
All of my hand loads have been MUCH MUCH better than factory ammo I was shooting before. (I was getting ready to get rid of the gun, producing 2" to 3" groups, before my dad did some hand loads for me.)

As for powders, I chose IMR 4831 to begin with, because of the many good things I'd read on the internet about it with respect to the 7mm Rem Mag, and because it appears as the most accurate powder for 3 out of 5 listed bullet weights for this cartridge in the Barnes manual. It has been a very good powder in my gun.

Retumbo has worked very well, and has produced the very best group I've ever shot.
IMR 4350 has been good.
RL-22 has not been as good, though I may have just skipped over the optimum powder charge(s).
I've heard very good things about H1000, but have not tried it.

150 gr TTSX have been very good.
140 gr MRX also worked well, but I did not get to try as many loads with them.

All loads done with CCI LR250M primers, and Nosler brass . . . up until now.
(I just received 100 pieces of Norma brass, and will start load development again. Sigh.)

After having a new stock put on with glass bedding, and having the barrel cryogenically treated, my "optimal" load changed significantly.

Was:
IMR 4831 . . . around 59 grains (1/2" groups @ 100 yds)
behind a 150 gr TTSX

Now:
60.5 gr IMR 4831
behind a 150 gr TTSX (1/2" group)
or
68.9 gr Retumbo
behind a 150 gr TTSX (0.35" group, and very consistent velocities on the chrono, averaging 2964 fps)

69.0 gr of Retumbo also worked very well
behind a 140 gr MRX . . . except for on flier (which was probably my fault):
4 rounds all touching at 100 yds (0.37" group)

Disclaimer: As always, start at the low end of your manual's recipe, and work up.
I go in 0.5 gr increments, and identify one or two good groups. Then do 0.1 gr increments around those points.

The B.C. on the 150 gr Barnes TTSX (0.450) with it's Boattail design and ballistic tip, is better than that on the 160 gr TSX FlatBase (0.392).
It is also has higher gyro stability margin. I think it is plenty big enough Elk, and has excellent terminal ballistics.
(As you probably know, BCs published by different bullet manufacturers are not all equivalent.)

One issue I saw with the Retumbo was a black powder marks on the outside
of the neck and shoulder area. I would be very interested to hear if you see anything like that in your load development.
This could possibly be from too light a powder charge (even though accuracy was very very good), too low a bullet weight, not enough neck tension or cases necks that had been work hardened too much. (Hence my new Norma brass, to see if the problem goes away.) If the new brass, or annealed necks don't fix the problem, I'll go back to IMR-4831, or try the H1000, or maybe some VIT N560 or N160.

how far off the lands are you with your loads with your 150 ttsx ? I found that the 140 ttsx held the best group out of the two ttsx 150 and 140 . that was out of a 26" a-bolt but the ruger with a 24" liked the 140's better also . I would of liked to have the 150g shoot the best . but at 400y what the 140g did to a steel target it will take down what I need . next will be out at 800y

 

[SakoShooterSD]

how far off the lands are you with your loads with your 150 ttsx ? I found that the 140 ttsx held the best group out of the two ttsx 150 and 140 . that was out of a 26" a-bolt but the ruger with a 24" liked the 140's better also . I would of liked to have the 150g shoot the best . but at 400y what the 140g did to a steel target it will take down what I need . next will be out at 800y

I have the 150's seated about 0.011" off the lands, according to my RCBS Freebore tool.
I didn't have the freebore/headspace/micrometer tool when I did my very limited C.O.A.L. test; i based my COAL choice on a comparison of just 3 different 4-shot groups. I only tested COAL of 3.300" (over SAAMI spec!), 3.285 and 3.270 . . . and the longest COAL (which I now can calculate as having put the bullet just about on the lands) ended up giving a slightly better group. I decided to stay in SAAMI spec, to allow for a little margin, since this is a hunting/field rifle . . . and so my subsequent loads have been done with COAL of about 3.290, and have produced very good groups. (at 11 / 1000's off the lands)

Regarding the 140 gr bullets vs. 150 gr . . .
I would bet that you can find a powder and charge that will work just as well for the 150's as for the 140's, and save your self a little $ on buying the TTSX (@ 62 cents) instead of the MRX (@ $1.18). -- Oh, I see Barnes now has 140 gr TTSX.

Seat the bullets 10/1000's off the lands, and use your Retumbo to do an Audette/Ladder test with the 150 gr bullets, in 0.2 gr charge increments, shooting at 300 yds.

Then do the same with IMR4831, or another powder of your choice (H1000?)

I bet you will find at least two good loads, with just 30 or 50 shots fired, and can then fine tune from there, and verify drop at different distances.

I am going to try the ladder test for the first time -- it seems like a very efficient way to narrow in on optimum powder charge, without inadvertently skipping over a node. It also seems like it will give you a better idea of the sensitivity of your gun to powder (pressure) variations, and could point you to a more robust solution, as opposed to just the tightest group.
I'll let you know my results, and hope you will post yours! We almost certainly won't get the same optimum load, but one can often learn a little by hearing about other people's development efforts.

Good luck! And let us know what you get.

 

[Terrytf]

will do.. loading tomorrow and might make it out to a 200y range also . I will let you know

 

[Terrytf]

I now have it . but In the barnes loading book it says 3.290 is max length but my best groups where at 3.310 . Is going over the max length OK ??? 70g of retumbo 140g ttsx at 3.310 best group inside a dime ..

 

[moombaskier]

TF, yes it's ok to go longer as long as you work up to it.

 

[CRNA]

subn..

 

[DKA]

I use 160 Gr. Nosler Accubonds & H1000. Very accurate in my Weatherby.

 

[PrecisionRifleBlog]

I have a 7mm Rem Mag, and have a load that has produced 0.18" groups (see photo below). I wrote a series of blog posts that walk through my load development process that I thought might be helpful.

Check it out at: 7mm Rem Mag Load Development Part 1: Bullet Selection & Real-World Velocities | Precision Rifles & Handloading

 

[Bart B]

That's pretty good for a 3-shot group.

What percentage of the rifle and ammo's 3-shot groups are within 10% of that size?

 

[PrecisionRifleBlog]

That is definitely one of my best groups. My average group size is 0.25-0.30" with that load, with 25% being slightly smaller that average (down to the .18" group shown), 50% being within that range, and 25% being slightly larger than average. Here are some of the stats from my groups: mean = 0.274", median = 0.265", standard deviation = 0.062".

The rifle/ammo could probably do better if I was better at doing my part! I definitely can't blame a miss on the rifle anymore. It has to be the nut behind the gun.

What made the group in that photo so impressive to me is that it was my very 1st three shot group I fired out of that rifle with my "match grade" handloads. No joke. I had fired about 25 rounds down the rifle to break-in the barrel, then that was the 1st three shot group when I started doing serious load development. Might have been luck, but I was still proud of it.

I hope that helps answer your question. My barrel has continued to speed up as I've shot it in, and I ended up backing off this load to 69.4gr of Retumbo and still maintained good velocities (3140 fps out a 27" barrel).

 

[Bart B]

That is definitely one of my best groups. My average group size is 0.25-0.30" with that load, with 25% being slightly smaller that average (down to the .18" group shown), 50% being within that range, and 25% being slightly larger than average. Here are some of the stats from my groups: mean = 0.274", median = 0.265", standard deviation = 0.062".

I hope that helps answer your question.

Yes, it does. Thanks.

I asked because I consider rifle/ammo accuracy to be the largest group shot by a given load. That's what one can count on 99% of the time. Rarely is the smallest group ever equalled or bettered. Average group sizes are typically about 2/3rds of the largest ones. Therefore, I consider your rifle and ammo shot by you "pin driver" quality. That's better than just a tack driver. Pins have smaller heads.