6x47 Lapua Load Development Questions

[dstoenner]

I am new to the 6x47 Lapua. This will be my new caliber for 1000 F-Class once my current 260 barrel is more used up. So for this winter I have been fire forming my 6X47 brass and doing a look at load development. My action is a Remington 700 in an Eliseo RTS chassis. While it is an F-Open rig, I shot off of an Accushot Bipod and rear bunny ear sandbag. My new 6x47 barrel is a McGowen 30 inch med palma Remage style. I have the headspace set so that the GO gauge closes smooth and one layer of scotch tape you feel some resistance and with 2 layers it will not close at all.

I now have 280 rounds down range so for this last range session I started looking at H4350 vs 105 Hybrid, 105 RDF and 110 SMK. Since the bullet I am most familiar with is the 105 Hybrid, I loaded 5 each at 38.0, 38.2, 38.4, 38.6, 38.8 and 39.0. I shot them across my magnetospeed and I shot for groups with the magnetospeed attached.

What came out was some perplexing results. So I am looking for some of you that havce more experience with this caliber to give me some hints at where to go next.

Lets first look at the 105 Hybrid's

Here are the statistical data

charge weight, ave velocity, ES, SD group size
38.0, 3000, 34, 17, .461
38.2, 3013, 29, 12, .550
38.4, 3037, 34, 13, .465
38.6, 3052, 15, 6, .930
38.8, 3053, 9, 4, .712
39.0, 3053, 17, 6, .519

So to me it looks like I hit a good wide valley of charge vs velocity with good ES and SD. BUT group size was not as good as lower charge weight with much higher numbers.

My thought is that since at 39.0 I was not experiencing any pressure signs, like hard bolt lift or blanked primers or primers that looked really flat, load 5 of 39.0, 39.2 and 39.4 to see if ES and SD still stay low and group size looks better. Or the other thought is load 20 of 38.8 and 20 of 39.0 and shoot 4 5 shot groups without the magnetospeed to see what the individual and the average group size looks like.

For sure H4350 and 105 Hybrids have a pretty close go to load. And at first blush the 6x47 is turning out to be as stable as my 6BR i have been shooting for the last 4 years.

Now for the horror story - 105 RDF

SD and ES were very good at all levels with 39.0 having an ES of 8 and SD of 3, yet all groups were huge horizontal spreads with groups sizes from 1.180 to 1.390. It just seems that my gun/barrel doesn't like these at all.

Last was the 110 SMK. Since I have no experience on these bullets, I just wanted to see what I might get for velocity etc. My first group was .650 but I have no idea of the statistics because my magnetospeed slipped forward and the sensor fell lower and didn't register anything.

38.0 was Ave of 2952 with an ES of 15 and SD of 5. Group size was bad but they had called the line cold just as I finished firing the first set of 5 of my first group and when we went hot, I fired 2 shots that were touching then the 3 through 5th shot jumped up about .5 inch and were nice and close but had a group size of .615 almost all horizontal.

3rd group for the 110 was an ES of 23 and SD of 9 with a group size of .780

Here my thought is to load up 20 at 38.0 and see how they average out. With an average velocity of 2950 this load would do better in wind than the 105 hybrid at 3050.

Overall I am really happy that, at least for me, the 6x47 has not shown itself to be so finicky as some have said. I am getting the extra velocity over shooting a 6BR and have 2 pretty good looking loads, even better than the 260 Remington I am shooting today.

Thanks in advance for any extra things I might look at or where would you go if you had seen these results.

David

 

[mgunderson]

David, were you using the magneto for all of the group testing? My experience.... the magneto will influence the barrel vibes. Some of my rifles don not care , but most do not like it.

Do you mention the barrel twist rate?

 

[dstoenner]

David, were you using the magneto for all of the group testing? My experience.... the magneto will influence the barrel vibes. Some of my rifles don not care , but most do not like it.

Do you mention the barrel twist rate?

Yes I was using the magnetospeed for all groups because I was really more interested in the velocity numbers than groups directly. Yes I know it could impact barrel harmonics but this barrel seems to be really stiff in that the MS didn’t appreciably change POI from no MS.

My barrel is 1:7 twist.

 

[Willow]

With H4350 I'd consider looking for a node between 39 and 40 grains. 39.2 worked well for me with the original 6.5x47 and I'll be playing carefully between this range when I get a couple of 6x47s chambered up in the new year. The other thing you didn't mention is whether you jammed or jumped your bullets? Obviously the Hybrids like a little bit of a jump, but how much? If you consider some of the loads where your SD is tight, then your seating depth could make quite a difference in shrinking some of those group sizes.

I have briefly (and only briefly) tried the RDFs in a 6BRAI. Jumped them about .030 and they weren't great, but not shocking either. It may be worth trying them touching the lands if it is a bullet you are keen to get working. The one bullet I have never had an issue to get working is the Berger 108gr BT, if you can get your hands on some, I'd try that too, .010 in the lands.

 

[dstoenner]

Willow

I was jumping all of the loads as a measure of caution since I have no experience to go on. The hybrids were jumping about .025 right now. I don’t have all of my documention with me right now to tell you what the others were being jumped.

What kind of velocity were you getting at 39.2 with the 105 hybrids?


The RDFs were just a look and see. I have shot the 6.5 140s in my 260 and they did as well as 140 hybrids at a lower price point. I was hoping the 105s might do the same. I may play with them a little more but if they don’t start performing I will drop them. I have 600 hybrids right now so I am set for a couple of years even if they dry up

Thanks for the thoughts you proposed. I will have to factor them into my work ups

David

 

[woodnut]

Hum, I'm also new at the 6x47L. I did see the potential in it a while back and had an AR10 upper build for it with an 8 twist barrel. The builder said to stay away from the 105s, thinking at the time only Berger made them and they would not feed. He was partially right; the Bergers won't feed in the AR10, but 105 AMAXs and 108 ELDs do!
Fast forward to now and I have a bolt gun in it. Same twist. 26" tube. It is loving H4350 but I have seen a big velocity change because of temps. My 4R barrel is liking only 37.5 gr. in hot (85-90') weather. Have not done a lot of testing, but that seems to be where I will wind up. Have gone to 38.5 gr, but heat says to stay at 37.0 to 37.5. As a good friend and smart guy says, so what if you don't get 3000? You got a scope so use it to compensate.
Bad news is that I recently tried the 108s with 37.5 gr of H4350 and blew all the primers! Haven't got a clue why that happened,but until I do, will go back to lighter 95s or less in the AR10. which gave very good accuracy.
This round is excellent for 1000 yard shooting! Using 108s, since I think Hornady is quitting the fine 105s, it a flat shooting and hard hitting round way out there.
I know I have jumped around, sorry! But if it helps, I'm glad. I hope someone can tell me why the AR10 punches primers, too.

 

[steve123]

6x47L is my favorite cartridge.

I've been loading for it for 11 years now. I'm on my 7th barrel if I include a rifle I sold.

I decided right away I'd have the reamer done for a long free bore, .208", for the 115's. This works out well for stuffing more powder in the case and getting more fps and the COAL of 2.755" with 105's runs in a AI mag nicely. I can't remember the length with 115's but it was around .30 longer.

Back when the 115DTACS ran dry and the 105 hybrids had just come out I switched over to the 105's.

So I have a pretty big jump going on which suits the hybrids just fine. I'm not a benchrest shooter but off a bipod it's common when I'm confirming my 100Y zero to get sub 1/2" groups and had a mid .2" last time out.

I used H4350 a few times, like two 8 pound jugs, it's okay but I like H4831SC better, my SD is 6-7, and fps is 3172 out of a 28" 8 twist. 43.2 grains which is slightly compressed.

On the 22" barrel I had, 39.9 grains of H4350/105 was the sweet spot, but as I mentioned my free bore is longer than most.

I use CCI450 exclusively.

About 35 firings on my old brass, most still going strong, all with warm loads.

 

[dstoenner]

6x47L is my favorite cartridge.

I've been loading for it for 11 years now. I'm on my 7th barrel if I include a rifle I sold.

I decided right away I'd have the reamer done for a long free bore, .208", for the 115's. This works out well for stuffing more powder in the case and getting more fps and the COAL of 2.755" with 105's runs in a AI mag nicely. I can't remember the length with 115's but it was around .30 longer.

Back when the 115DTACS ran dry and the 105 hybrids had just come out I switched over to the 105's.

So I have a pretty big jump going on which suits the hybrids just fine. I'm not a benchrest shooter but off a bipod it's common when I'm confirming my 100Y zero to get sub 1/2" groups and had a mid .2" last time out.

I used H4350 a few times, like two 8 pound jugs, it's okay but I like H4831SC better, my SD is 6-7, and fps is 3172 fps out of a 28" 8 twist. 43.2 grains which is slightly compressed.

On the 22" barrel I had, 39.9 grains of H4350/105 was the sweet spot, but as I mentioned my free bore is longer than most.

I use CCI450 exclusively.

About 35 firings on my old brass, most still going strong, all with warm loads.

Thanks for your thoughts. I have 3 lbs of H4831SC in my closet without any cartridge I use it in. Guess I will have to give it a try.

My next range trip I am going to do a full test on IMR 4451 with the 105 hybrids just to see if I can find any correlation between it and H4350. Then I guess H4831SC might be the trip to the range after 4451 is concluded.

David

 

[4xforfun]

I ended up at 39 g H 4350 with both the 108 Berger BT and the 105 Hybrid. 10 firings on my brass and it is as new. In fact, when this BBL is done i will use the same brass on my next tube if at all possible.

LOVE the 6-47L,
Tod

 

[JBT47]

Viht N550 also works very well in the 6x47 Lapua. Great velocity and a generally wide node.

 

[reubenski]

I am new to the 6x47 Lapua.

Lets first look at the 105 Hybrid's

Here are the statistical data

charge weight, ave velocity, ES, SD group size
38.0, 3000, 34, 17, .461
38.2, 3013, 29, 12, .550
38.4, 3037, 34, 13, .465
38.6, 3052, 15, 6, .930
38.8, 3053, 9, 4, .712
39.0, 3053, 17, 6, .519

So to me it looks like I hit a good wide valley of charge vs velocity with good ES and SD. BUT group size was not as good as lower charge weight with much higher numbers.

My thought is that since at 39.0 I was not experiencing any pressure signs, like hard bolt lift or blanked primers or primers that looked really flat, load 5 of 39.0, 39.2 and 39.4 to see if ES and SD still stay low and group size looks better. Or the other thought is load 20 of 38.8 and 20 of 39.0 and shoot 4 5 shot groups without the magnetospeed to see what the individual and the average group size looks like.

For sure H4350 and 105 Hybrids have a pretty close go to load. And at first blush the 6x47 is turning out to be as stable as my 6BR i have been shooting for the last 4 years.

Thanks in advance for any extra things I might look at or where would you go if you had seen these results.

David

Looks pretty straight forward to me. Looks like 38.8 is the middle of your node. Flat velocity increase with low SD's. Take the Magneto off, load up a seating depth test, and shoot for groups at 300yds. Try .005" jump increments starting 5 thou off up to .035 off. That will tune your accy and inform you of how much jump tolerance your load has before you need to start chasing the lands. Don't do it with your MS on.

Also, record your initial cartridge base to Ogive (to the throat) and save the bullet you used to measure it with so you can periodically measure your throat and compare to new. When switching lots of bullets re-measure the throat with the new lot and continue to use the jump the rifle showed you that it liked. To track your total throat erosion, only the original lot of bullets will be relevant so keep and use a bullet for that purpose.

 

[dstoenner]

Looks pretty straight forward to me. Looks like 38.8 is the middle of your node. Flat velocity increase with low SD's. Take the Magneto off, load up a seating depth test, and shoot for groups at 300yds. Try .005" jump increments starting 5 thou off up to .035 off. That will tune your accy and inform you of how much jump tolerance your load has before you need to start chasing the lands. Don't do it with your MS on.

Also, record your initial cartridge base to Ogive (to the throat) and save the bullet you used to measure it with so you can periodically measure your throat and compare to new. When switching lots of bullets re-measure the throat with the new lot and continue to use the jump the rifle showed you that it liked. To track your total throat erosion, only the original lot of bullets will be relevant so keep and use a bullet for that purpose.

I agree that on the surface the 38.8 would be the choice to test as it is in the middle of the flat velocity spot. What I was maybe looking for from someone with experience in this cartridge is "yes but..." So far nobody has said that. I can only shoot for groups at 100 yards as that is my only test range I have access to. I wish I had access to a 300 yard range. The good news for me is that the 100 yard range is indoors so I never have a wind factor influencing my results. Mirage, yes.

I have the stoneypoint (now Hornandy) COL measurement system and have made a 6x47 L modified case. I have a group of 6mm bullets that I do all of the measurements with for my 6BR and now 6X47 so I can be sure that I am comparing apples to apples.

Thanks

David

 

[basshusker]

38.8 is about the center of your node. Magnetospeed changes the harmonics of the barrel whip. Great for getting speed close but bad for groups. Got my Labradar and never looked back. Saves rounds in load development and time in setup and takedown. I can run QL to verify if you want. 38.8 sounds about right for 30" barrel.
Justin@shootbb.com

 

[dstoenner]

38.8 is about the center of your node. Magnetospeed changes the harmonics of the barrel whip. Great for getting speed close but bad for groups. Got my Labradar and never looked back. Saves rounds in load development and time in setup and takedown. I can run QL to verify if you want. 38.8 sounds about right for 30" barrel.
Justin@shootbb.com

Yes I know that my magnetospeed can change barrel vibrations and hence may help or hurt group size. When I bought my magnetospeed the labradar was being rummored. I agree it does let you do 2 things at once accurately but at a cost. At this point I am 69 and I hopefully have a few more years of long range shooting left in me. I might even wear a few barrels out but I found in my 260, that once I had a good load it was a good load for my next barrel or very close.

I have been thinking about all of the responses so far and yours reflects what the conciseness is and and my thoughts. Since I am shooting known distance matches, absolute highest verlocity is not needed nor maybe even wanted for barrel life.

So I think my plan is to load 15 more up at 39.0, 39.2 and 39.4 just to see where the center of this node is. Load 15 up at 38.8 and shoot 3 groups to see if I get better groups without the magnetospeed. Then regroup with an extended set of data.

For me the good news is that I am at a point with this barrel that it took me 800 or more rounds on my 260 to get to. I attribute my speed with this new caliber to this forum.

Thanks to all

David

 

[basshusker]

39.5 is around the node for 26" barrel. Might be high pressure in 30" tube

 

[JigStick]

I did my load development just like you did for my 6x47. Using 105 Hybrids and H4350 and Varget. After my barrel settled in H4350 gave me the most consistent velocity. However accuracy was very dependent on seating depth with the Hybrids. 10thou back and it bug holes. If I deviate by as little as 3thou the groups open up.

 

[lee1982]

However accuracy was very dependent on seating depth with the Hybrids. 10thou back and it bug holes. If I deviate by as little as 3thou the groups open up.

Have you tried the 108 bthp? Jump, jam, it never really mattered in my 6 brx.

 

[pat fulghum]

FWIW,

I had a load of 39.9 H4350 at 3250 (30" Bartlien) with Berger 105s. This was a hotter lot of powder. Bullet was seated well ahead of the neck shoulder and jump .015.
I saw pressure at 40.5 ... so I was really close to the top end.

It was a very accurate laser for about 800 rounds

Edit: 39.9 gives me 3150 not 3250

 

[Adlew]

You need to push it to the next higher node with 105 gr pills. At 3050 you might as well shoot a Dasher ;-) The reason for the 6x47 is case capacity. Use it. Sweet spot at/near 3150 for the berger bullets.
My rifle likes the 110 smk and 4955 enduron, bug holes.