Reloading for 600 and 1000 yards

[surfcityred]

I went to the range today to try another half dozen loads in my 24" Grendel. I was pushing them to the high end of the powder charge and did not have satisfactory results. However, one load worked great (target attached) but it is not a "hot" load. Three into one hole but I pulled the last shot 1/2" high. (Each square on these targets is 1/4".)

As you can see, the starting load is 25.5 and I got my best accuracy from a load of only 26.5. I tried pushing all the way up to 28.5 but the hotter loads did not group like I was expecting them to. I also attached the 28.5 target. I have read that some loads do not stabilize at 100-yards but become more accurate at 200+. What is your take on all of this. I am getting a tad frustrated.

For shooting out to 600 and 1000, am I better off with the 28.5 load and attempt to refine it or should I stick with the light, and slower 26.5 load?

[Drifter]

Did you arrive at the 2.263 COL methodically, or is that simply what you used? I ask because ~2.250 has worked best for me in a variety of barrels, and the factory Amax is usually that or slightly shorter.

Be careful with max loads over 28gr of 8208. In some barrels, it's too much pressure for bolts to sustain over numerous firings.

I have read that some loads do not stabilize at 100-yards but become more accurate at 200+. What is your take on all of this.

It's doesn't seem unusual for groups to not open up downrange like might be expected. For example, 1" groups at 100 yards don't necessarily mean 2" groups at 200; they might be 1.25" instead. Might be the initial wobble of a high-BC boattail bullet before if completely stabilizes, but that's just hearsay on my part. I've "wasted" some rounds on steel at 600 yards because they were disappointing at 100 yards, and sometimes the results have been surprisingly good.

Bottom line is that if you plan to shoot at extended distances, it's best to develop loads at extended distances.


ETA- Your group sizes between those charges are not drastically different. Might be an indicator of case prep (runout and / or neck tension) and / or bullet seating depth. If you've tried factory Amax, I would be curious of the results.

[LRRPF52]

Welcome. Before you shoot it again, may I ask what make the barrel is? Did you install it, or did someone else? What about your gas block? What type is it and how was it installed? It often helps to bed these parts during assembly, which is an old Hi-Power Service rifle trick for squeezing out accuracy.

After that is done, I would also consider lapping your bolt to the extension. This will also squeeze out some accuracy, as long as your receiver and action are true.


I would then run a series of pressure/accuracy ladders at 400-600yds. You're probably around 2300fps with your low-end load, and around 2500fps with your 28.5gr load. With a 24" gun, I would personally want to wring out some more velocity in the 2600fps range, which means Accurate 2520 or CFE. There are safe loads that will push the 123gr target pills to 2630fps, using AA2520, from a 24" barrel. My 16" Grendel averages 2460fps with the Hornady 123gr A-MAX box ammo.

Do you have the 6.5 Grendel Reloading Handbook?

[Drifter]

Regarding group sizes near and far, you might find this link interesting:

http://www.appliedballisticsllc.com/epswerve.html

[LR1955]

SCR:

A couple of things that you may want to consider.

First, how many five shot groups did you fire before you determined your load wasn't any good? If you shot five each, five shot groups, then you are probably on to something. Something tells me you probably didn't shoot enough to get a real good statistical measure.

I don't see that much difference between your two loads in terms of vertical and horizontal dispersion. Both are about the same vertically and about the same horizontally. The only real difference is your first load shot four into that cluster and your second, only three.

Given the case capacity of about 30 grains and a gas gun, once you find a load that shoots and is giving you the highest velocity possible within safe limits, you have your load. The notion that it pays to have a short and long range load with a Grendel is kind of negated due to the case capacity.

I would be careful at 28 1/2 grains of 8208 with a 123 A Max. It is safe but I won't make bets that your bolt will last very long before you shear a lug. You may want to look at 2520 or that CFE powder.

Finally, I have never seen a group that open at 100 yards get smaller at farther distances. If your bullets were yawing and pitching that much at 100, the holes would be oblong.

[jawbone]

fascinating article and video. thanks much, Drifter

[Allen]

I usually do load development at 200 yards. I go by the theory that a "good" group is going yo be good enough at 100 yards, but a group that's "good" at 100 doesn't always seem to mean its good enough at 200. I wouldn't like to go out further though, just in case a load walks low or high, you still have plenty of paper to record it, especially if your shooting multiple loads on one piece of paper.

[LRRPF52]

I will say that I have seen a certain company's barrels shoot amazing bug holes with 4 rounds, but then 1 round would open the group horribly. Customers would end up confused why their barrels appeared to be able to group extremely tight in the teens or 20's, then crap the bed well outside of 1.2 MOA, which makes no sense unless some serious residual stress or other metallurgical phenomenon causing inconsistency is.

That company is able to mass-produce barrels for rifle builders, unlike many of the bench rest-grade pipe makers.

[surfcityred]

Thanks so much for all of the replies to my thread. I will attempt to answer all of your questions and perhaps ask a few more.

Drifter: I did not arrive at an OAL by any particular process. I simply loaded a test round into a mag and seated the bullet out as far as I could. It was obviously too far out because the bullets were pretty far into the lands. I figured that out when I had a failure to fire and the round was a bitch to extract. The bullet was bound into the lands. I had to tap on my charging handle with a screwdriver handle to extract the round. Not good. I will seat the next batch to 2.250 and give that a try. Between my hot loads and the added pressure created by the bullet lodged into the lands, I am glad I didn't break my lugs, etc. Great video and info link. Thanks

LRRPF52: I purchased this 24" Grendel upper complete from Accuracy Systems in Colorado. You mention "lapping my bolt to the extension". How is that done? Are there any instructions or videos on line? Regarding the Grendel Reloading Handbook, I do not have one. I have been getting most of my info on line from various forum sources and powder manufacturer tables. I actually called Accuracy Systems and asked who manufactured their barrel but they refused to tell me.

LR1955: The last trip to the range I loaded the following charges: 8208XBR- 28.0, 28.2, 28.4, 28.5, 26.5, 27.5, 27.8 The best of the bunch was the 26.5 load. It is difficult for me to see pressure signs with the AR but I would prefer a load that did not stress my rifle. I would love to make this XBR powder work because I have so much already. The thought of putting more $$$ out for 2520 does not thrill me. However, if ya'll think that is the best choice, I will attempt to find some.

Allen: Where I live in Tennessee it is difficult to find a 200-yard range. I am going to have to though because I agree with you 100%. Plus, I need to measure the drop from 100 to 200 yards. I also need to chrono my loads.

Thanks so much to all of you for your suggestions. A few other things......I do very careful case prep but I do not crimp my cases. I am using Forster dies and they seem to be of good quality. However, I have no way to check bullet run out. I am also 66-years young and not as steady as some of you younger folks out there. I do want to compete in some 600 and 1000 yard competitions though. Two years ago I won a 1000-yard shoot. It was the first one I ever entered. I appreciate any and all advice you fellers can give me soz I can get as good a shooter as possible.

[Bwild97]

SCR, Do you have any other calibers where load data using XBR 8208 is available? I myself purchased an eight pound jug of XBR in preparation for my Grendel. After making several attempts to find a "good" load using XBR in my rifle and only succeeding in ruining brass, I gave up and use it in loads for several of my friends .223s. It is a fantastic powder in long and short barreled .223s and shorter barreled Grendel ARs (other forum members have had experiences similar to mine with 24" barreled Grendels).

Did your rifle cycle reliably with that 26.5g load?

[Drifter]

Drifter: I did not arrive at an OAL by any particular process. I simply loaded a test round into a mag and seated the bullet out as far as I could. It was obviously too far out because the bullets were pretty far into the lands. I figured that out when I had a failure to fire and the round was a bitch to extract. The bullet was bound into the lands. I had to tap on my charging handle with a screwdriver handle to extract the round. Not good. I will seat the next batch to 2.250 and give that a try. Between my hot loads and the added pressure created by the bullet lodged into the lands, I am glad I didn't break my lugs, etc.

I suggest starting over with load work-ups using 8208 with the 123gr Amax. If all previous loads were jamming the lands, I'm just not sure that the previous results are indicative of anything conclusive. You would be best served to check maximum COL with each bullet in your chamber, but you might be okay at 2.245 to 2.250. With the same bullet, 27.7gr of 8208 has been a safe and accurate load in a variety of barrels for me. Good luck going forward.

[Allen]

SCR, Do you have any other calibers where load data using XBR 8208 is available? I myself purchased an eight pound jug of XBR in preparation for my Grendel. After making several attempts to find a "good" load using XBR in my rifle and only succeeding in ruining brass, I gave up and use it in loads for several of my friends .223s. It is a fantastic powder in long and short barreled .223s and shorter barreled Grendel ARs (other forum members have had experiences similar to mine with 24" barreled Grendels).

Did your rifle cycle reliably with that 26.5g load?

So far I haven't been impressed with 8208. I need to pick up a can of CFE and 2520 and test it out though. So far 1 MOA has been unreachable in my 24" barrel, so far.

[surfcityred]

Bwild97, yup, cycling was not an issue. I can certainly use the XBR in my .223 and 204 cases. I guess I will have to hunt down some 2520. Mama Mia!! Yet another powder in the barn.

[LRRPF52]

I would also look at CFE along with the AA2520, and BL-C(2). Anytime I see those powders now, I snatch them.

[Keep The Change]

[QUOTE=surfcityred;67243]Thanks so much for all of the replies to my thread. I will attempt to answer all of your questions and perhaps ask a few more.


LRRPF52: I purchased this 24" Grendel upper complete from Accuracy Systems in Colorado. You mention "lapping my bolt to the extension". How is that done? Are there any instructions or videos on line? Regarding the Grendel Reloading Handbook, I do not have one. I have been getting most of my info on line from various forum sources and powder manufacturer tables. I actually called Accuracy Systems and asked who manufactured their barrel but they refused to tell me.

QUOTE]

I would like some info on lapping bolts to the extension as well.