7x47 lapua

[GSPV]

Hey guys, another 7x47 Lapua installment. This is in my T3 action, Broughton 1:8, .3156 neck, .138 freebore chamber. Sorry, forgot the tripod for the LabRadar, so no velocity this time. I'll get it done, I promise.

All loads with the same lot of IMR 8208 XBR, Lapua brass, 205M primer. Since I found the spot with the 160 grain TMKs last time, I only worked with Speer 110 TNT, and the Nosler 120 Ballistic tip this session.

110 Speer TNT:
Last session, the 40.0 grain charges were too light and velocity was all over the place. So, this time. I started at 41.0 grains and went up in 0.3 grain increments. Accuracy was much better immediately. Pressure feeling pretty good. The 41.3 grain set looked and felt good too. The 41.6 was starting to feel a hair sticky and the 41.9 was definitely warmer than I liked. I left the 42.2 grains unshot. But, groups kept on getting better. I know what I need to know and will, perhaps, resume when I have the 284 Shehane rechambered.

120 NBT:
The 120 NBTs felt better last go round at 40.0 grains. Groups were pretty good, but velocity was a bit inconsistent. So, this session, I started at 40.3 and again went up in 0.3 grain increments. Groups were good right away, but quickly went to heck in a hand basket. Pressure was ok, accuracy sucked, so I abandoned the series after the 40.9 set.

I have a batch of 150 grain SMKs on the way. My next workup will be with them. More at that time.

 

[RangaNZ]

Hey guys, another 7x47 Lapua installment. This is in my T3 action, Broughton 1:8, .3156 neck, .156 freebore chamber. Sorry, forgot the tripod for the LabRadar, so no velocity this time. I'll get it done, I promise.

All loads with the same lot of IMR 8208 XBR, Lapua brass, 205M primer. Since I found the spot with the 160 grain TMKs last time, I only worked with Speer 110 TNT, and the Nosler 120 Ballistic tip this session.

110 Speer TNT:
Last session, the 40.0 grain charges were too light and velocity was all over the place. So, this time. I started at 41.0 grains and went up in 0.3 grain increments. Accuracy was much better immediately. Pressure feeling pretty good. The 41.3 grain set looked and felt good too. The 41.6 was starting to feel a hair sticky and the 41.9 was definitely warmer than I liked. I left the 42.2 grains unshot. But, groups kept on getting better. I know what I need to know and will, perhaps, resume when I have the 284 Shehane rechambered.

120 NBT:
The 120 NBTs felt better last go round at 40.0 grains. Groups were pretty good, but velocity was a bit inconsistent. So, this session, I started at 40.3 and again went up in 0.3 grain increments. Groups were good right away, but quickly went to heck in a hand basket. Pressure was ok, accuracy sucked, so I abandoned the series after the 40.9 set.

I have a batch of 150 grain SMKs on the way. My next workup will be with them. More at that time.

Hey guys, another 7x47 Lapua installment. This is in my T3 action, Broughton 1:8, .3156 neck, .156 freebore chamber. Sorry, forgot the tripod for the LabRadar, so no velocity this time. I'll get it done, I promise.

All loads with the same lot of IMR 8208 XBR, Lapua brass, 205M primer. Since I found the spot with the 160 grain TMKs last time, I only worked with Speer 110 TNT, and the Nosler 120 Ballistic tip this session.

110 Speer TNT:
Last session, the 40.0 grain charges were too light and velocity was all over the place. So, this time. I started at 41.0 grains and went up in 0.3 grain increments. Accuracy was much better immediately. Pressure feeling pretty good. The 41.3 grain set looked and felt good too. The 41.6 was starting to feel a hair sticky and the 41.9 was definitely warmer than I liked. I left the 42.2 grains unshot. But, groups kept on getting better. I know what I need to know and will, perhaps, resume when I have the 284 Shehane rechambered.

120 NBT:
The 120 NBTs felt better last go round at 40.0 grains. Groups were pretty good, but velocity was a bit inconsistent. So, this session, I started at 40.3 and again went up in 0.3 grain increments. Groups were good right away, but quickly went to heck in a hand basket. Pressure was ok, accuracy sucked, so I abandoned the series after the 40.9 set.

I have a batch of 150 grain SMKs on the way. My next workup will be with them. More at that time.

Great stuff GSPV, thanks for taking the time to put this info up.
What barrel length are you running?

 

[GSPV]

25". It's a Broughton 5C. No brake.

 

[GSPV]

Addendum...three shot group. 110 TNT, 41.6 grains of 8208 XBR. Warning: this was pretty hot in my Tikka. No primer issues, or extractor Mark, but bolt was sticky. YMMV, but approach with caution.

 

[Jason Boersma]

Have you tried any 180's yet?

 

[GSPV]

Hi Jason,

I haven't. I have a buttload of them as I'm coming from a 284 Shehane, but really hadn't thought about it.

I didn't think that there was enough freebore. If the cartridge pulls me that way, though, I have a throating reamer....

What are your thoughts?

 

[Jason Boersma]

I'm thinking more for benchrest but with as a single shot hunting rifle it would probably work also but with a 30" barrel and about .220 freebore you should be able to push a 180 around 2850fps Which would be great for targets and long range hunting

 

[gunsandgunsmithing]

Not bad for a...what 8 lb hunting rifle, with a factory action(I did true the action face only..had to to get rid of that taper on the front receiver ring of a Tikka), trigger and stock?--Mike

 

[GSPV]

Thanks, Mike. You did a great job on it. It's an interesting project.

I have a better trigger spring that I'm about to put in that should greatly improve the trigger. Then, I need to put a scope on it with more magnification and finer crosshairs. The danged hunting scope covers up the entire bull and I can't aim small.

If the cartridge shows in what was my 284 Shehane like I expect it to, I might try out some 180's at some point. I have several barrels.

My loaded rounds are showing 6 thou total neck clearance. I might just get it reground to be tighter or get another reamer and keep this one for hunting chambers. We'll see.

 

[CTK]

I'm thinking more for benchrest but with as a single shot hunting rifle it would probably work also but with a 30" barrel and about .220 freebore you should be able to push a 180 around 2850fps Which would be great for targets and long range hunting

I am still a rookie compared to most in this forum. My knowledge base is still very small. I cannot understand how you can get a 180g bullet safely to 2850 fps out of a 47L case. I am hoping to average that out of my 6.5x47 23" barrel with 130's. I do not think that i can get anywhere near that velocity with a 180 out of my 280AI with a 24" barrel. Is barrel length everything or are these super hot loads? Shouldn't an "efficient" cartridge like the 47L have a diminishing return with much longer barrels? Know the 47L brass can take a great deal more pressure than Nosler 280AI brass.

 

[Jason Boersma]

The OP is already pushing 160's at 2750fps so more freebore and a longer barrel should make it happen easy, if not with h4350 then with R16 or R17

 

[CTK]

The OP is already pushing 160's at 2750fps so more freebore and a longer barrel should make it happen easy, if not with h4350 then with R16 or R17

I am looking forward to trying RL16.

 

[GSPV]

I don't think that 2850 is doable with the 180. At least not with the 8208. I was surprised that the 160 TMK chrono-ed where it did.

Check here:
http://www.accurateshooter.com/guns-of-week/7x47-lapua-wildcat-cartridge/
http://accurateshooter.net/Downloads/7x47chronographresults.xls

I personally conceived this to shoot the varmint matches that we shoot around here rather than Benchrest or F-Open (at 1,000). My secondary goal was as a medium game (think whitetai) cartridge.

Can't wait to try the 150 SMK this weekend!

 

[boltfluter]

The OP is already pushing 160's at 2750fps so more freebore and a longer barrel should make it happen easy, if not with h4350 then with R16 or R17

No offense, but I think 2850 fps with a 180 gn. Is a pipe dream.

Paul

www.boltfluting.com

 

[Jason Boersma]

None taken Paul, was looking at his results and figured it might be possible, looks like a fun project

 

[CacheCropp]

Digging this interesting thread back up. Wondering if anyone has any more to report on the 7x47 cartridge.

 

[GSPV]

Hey guys,

I finally got out with the 7x47 and the chronograph. So, some more data.

All Lapua brass, and Wolf SRM primer. I was fire forming new brass, so I didn’t get the greatest ES on the velocities.

Magnetospeed chrony. I was using a LabRadar previously. I have not checked this chrony against another for sanity.

All out of my 27” 1:9 Brux.


43.0 grains of H43 pushed a 150 SMK at 2850-ish. No pressure signs. This load has promise. Good case fill. Some room to speed it up a bit.

I went from 38.4 grains of R16 up to 39.0. This pushed the 168 SMK at only 2450. Super mild. I had had high hopes for R16, but I’m now feeling a little negative. The problem is getting enough of it in the case to get it up to a competitive velocity. I hope to play with a long drop tube to get enough in the case. I’ll report back.

 

[joshb]

Bump!

 

[GSPV]

Went back out with the 7x47L. Shooting my varmint match rifle. Borden BRM, Tracker stock, NF Competition 15-55. Lapua brass, obviously. Wolf SRM primer. 43 gr H4350, Berger 168 gr VLD just a bit jammed. I’d already shot another load, took one sighter, then shot for effect. 5 shots. 200 yards. Came in at 2800-ish FPS.

 

[GSPV]

I’ll keep posting on this every so often. The bottom line, though, is that if have a 284 Win for 1,000 yard games and want something more comfortable and cheaper for 300-600, the 7x47 or a, I’m ashamed to say it, 7 Creedmoor, would be a very nice option.