7mmRM, 150 TTSX, & Grand - Load Verified

[NYDAN]

I am on a quest to develop and non-lead load for one of my rifles to use on deer here in New York when the state mandates the use of non-lead ammo. It could also be used if I ever hunt elk where non-lead loads are required.

I decided to utilize my LH Win. M70 chambered in 7mm Rem. Mag. since I have great lead bullet loads for all my other rifles.

I started with the 150 gr. Hornady CX bullet and Reloder 26. I had some great targets with that combination that I posted on this forum. However, the velocity was a bit lower than I really wanted and I tried to develop and faster load. When I got to my second (and third) box of bullets I ran into oversize bullets that would not fit in the bullet guide section of my Redding Competition seating guide. I returned those bullets to Hornady and am still waiting for a final resolution.

Next, I turned my attention to Barnes 145 gr. LRX BT. I had some success with one three shot group, but I couldn't seem to duplicate the results on a consistent basis. In one of my trials, I substituted GRAND powder for Reloder 26 and actually had better results, but not as good as I wanted.

One of the Barnes Reps had told me that if my rifle didn't like the 145 LRX BT I could switch to the 150 gr. TTSX BT. Since the LRX BT seemed kind of finicky I decided to try the TTSX BT with some GRAND and see what would happen.

The Hodgden website had load data for GRAND with the 150 TTSX BT in the 7mm RM. Top load was 76.0 gr. delivering an amazing 3223 fps out of a 24" barrel. That was significantly faster than any other load data for any other powder with that bullet. I was a bit skeptical of that but thought that I might be able to reach 3100 fps. The Barnes Rep had told me I could easily reach 3100 fps and had actually referred me to the Hodgden data.

I loaded up 4 cartridges with 72.0 grains of GRAND and with a bullet jump of 0.100" to try to get a feel of the velocities I would get with my rifle which has a 26" barrel.

Here are the results starting with a clean barrel:



The Barnes website instructions said to shoot a few fouling shots first - which I didn't. But I hoped that shots 3 & 4 might be indicative of the accuracy I might get. I was able to extrapolate that 72.3 grains should get me pretty close to my goal of 3100 fps.

Following Barnes instructions on their website, I loaded up 12 rounds. Three each with bullet jumps of 0.050", 0.075", 0.100", and 0.125".

The next four targets show those results:





Target 1 (0.050" jump) was pretty much what I expected - an average of 3100 fps, with a 2 in and 1 out group.

Target 2 (0.075" jump) surprised me with a significant increase in velocity to an average of 3127 fps.

Target 3 (0.100" jump) seems to be an accurate load with a 0.45" group. Like target two, the average velocity was higher than target one, but consistent with target two.

Target 4 (0.125" jump) opened back with a 2 in and 1 out group.

It appears that the load represented in target 3 meets my goal of accuracy and velocity with a readily available powder. I hope to verify this load in the very near future.

This table summarizes the velocities that I recorded.


My big question is does anyone have an idea of why the velocity made such a large shift between shots 3 and 4? I was using a Garmin chronograph, and it did NOT (that I know of) shift position. The powder charges were measured on a RCBS chargemaster at the same time. The brass was annealed and any donut reamed. The necks were NOT turned. Bullet concentricity averaged about 0.001". The largest amount of total runout was 0.002"

Could it be copper build up in the bore? Could it the position in the neck of the relief grooves in the bullet?

Thoughts?

 

[RL338]

For some reason shot #10 is low , had it been within reason of the other 2 you would had a steady climb in your average velocities.

 

[NYDAN]

Yes. You are correct. Perhaps seating the bullets deeper was increasing the pressure. But I am not sure that explains the big jump between 3 and 4. I kept the barrel from getting hot by waiting 4-5 minutes between shots.

 

[jimbires]

just a guess , the clean bore needed fouled . when working with Barnes bullets and Grand powder , foul with Barnes bullets and grand powder .

I was told by a Bench Rest shooter that I should clean and foul between switching powders . the first powder residue can skew the results of the second powder numbers , for a number of shots .

 

[NYDAN]

I have read the same thing and try to follow that guideline.

 

[preacher]

I have played with Barnes since 1989, and for sure, clean between then foul "every time you change powders", Foul with the powder you are testing! BTW, last year, I played with a Fierce 7 mag and settled on 72+ Grand, ADG brass and 175 Partiton for 3050fps, sub MOA! Thats "Mashburn" territory! Love that Grand! Good luck to you sir!

 

[Ralt71]

Yes. You are correct. Perhaps seating the bullets deeper was increasing the pressure. But I am not sure that explains the big jump between 3 and 4. I kept the barrel from getting hot by waiting 4-5 minutes between shots.

Are you single feeding your rounds while doing this test or are they staying in your mag/chamber? If you are single feeding, while doing the test was the ammo or gun sitting in the sun? I just did a pretty extensive test on Grand powder (for temp stability, I hope to get time to post it up soon). One thing I learned about this powder is it's decently stable, until it isn't.. then the speed will take off on you. It handles being cold and staying consistent much better than getting warmed up. Looking at your targets (I assume what the table represents was all shot on 7/31) it was sunny and mid to upper 70's. You mentioned waiting 4-5 minutes between shots. Is it sun baking? The velocity was creeping up then hanging out with a decent consistency except for shot 10. Looking at shot 2 and comparing it to 12 shows the entire spread. Could this be case fill % due to seating depth, or is the ammo and possibly metal on the rifle all heat soaking from the shooting session outside.. I would be curious on these.

 

[NYDAN]

Ralt, yes, I was single feeding the rounds. My shooting bench is under a tent, and therefore my rifle and ammo were in the shade. After shooting today, I came to the conclusion that the things were just heating up a bit on Friday.

 

[NYDAN]

I had a chance to shoot again today and verified (to my satisfaction) that I have a good load with 72.3 gr. of GRAND with a bullet jump of 0.100".

I shot three targets, three shots each, with bullet jumps of 0.090", 0.100" and 0.110".

The first two targets pretty much verified my accuracy from Friday. The group with a bullet jump of 0.090" measures about 0.7" and the group with the bullet jump of 0.100" measures about 0.55". Fridays' group with a 0.100" jump measures about 0.45".



The next target with a bullet jump of 0.110" opened up to about 1.1"



As you can see the velocity increased again when I got to shot 7. I think something was just warming up a bit.

Anyway, I am pleased that I was able to repeat the good group with a 0.100" bullet jump. This level of accuracy for a non-lead bullet at over 3,100 fps meets my goals for this production rifle. I will load up the components I have, clean the rifle, and move on to the next project.