7 Backcountry Build, Update 8/7 and 8/25

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I promised myself I wasn’t going to get into seven Back Country until it’s been more proven. But sometimes things change I guess.

After watching all the recent videos on building your own rifle I decided I was going to give it a shot. I place the order for all my components but the barrel I’m going to get from carbon 6 in 280AI it going to show up until sometime next year. Therefore, while I’m waiting I decided to go ahead as I found a place that I could get a 7mm backcountry in Fairly quickly.

The components
Barrel McGowan 7BC 1:8, 18 long and med palma
Action- Zermatt TL3
Chassis MDT LSS G3

My experiences

  1. Assembling the rifle was pretty easy with the right tools. I got a barrel Vice from sac and with an inline fabrication plate I’m able to use it at the same place on my bench as I have my press. Barrel wrench from an online supplier and a torque wrench from Harbor Freight and go / no go gauges and ready to go.

  2. I need to pay more attention to the components in the future. This is a medium Palma Barrel and it is a thick hunk of steel. I’ve had several rifles from Tikka as well as Remington with varmint barrels and this thing makes those look like spaghetti noodles.

With the chassis and the scope and the barrel of action put together this thing weighs roughly 15 lb and that’s with no ammo, no bipod, etc. Not the end of the world in terms of weight but a lot heavier than I was expecting. And I wasn’t really looking for a lightweight Mountain Gun either.

  1. This thing kicks! All that Malarkey that many of the online influences were saying about it’s going to have less recoil than a seven Magnum because of less powder charge is bologna. I was shooting a 7 PRC with similar weight bullets at the same range session as my first outing with this thing and the 7prc was a much easier shooting rifle. Now this MDT chassis does not have the best of recoil pads so maybe putting on a backstop would help.

So, not really sure I want to make it a lighter rifle or not actually.

  1. 1 range session in with 20 rnds 175 Fusion tipped

Reliability was 100%. Perfect feeding and extraction with every single case. None of the problems I’ve heard reported

Velocity 2963 SD 13 ES 56 again out of an 18 inch barrel. Seems about middle of the road in terms of what Factory ammo does for me. Box velocity is 3125 but I don’t know what length barrel that is.

Recoil was definitely more significant than a seven Magnum or 7prc even with using a suppressor on this gun.

After getting it on paper and then getting a close to zero scope adjustment I was able to shoot four three shot groups with the remaining ammo.

1.15 then 0.55 then 0.57 then 0.18 MOA groups. The 0.18 group is probably going the best groups I’ve ever shot in my entire life.

Overall I’m pleased at this early stage. I obviously need to do some more work with seeing what the groups are going to do is the barrel breaks in more. Not sure what I’m going to do about the rifle weight. But I really would love to have something a little lighter close to 10 lb, but I really don’t want to make the recoil any worse. It’s manageable but definitely noticeable right now

Still have mixed feelings on the cartridge, chambering overall. We’re now 6 months or so into this and we still haven’t heard anything about reloading. I appreciate that Federal has a variety of bullets to use but none of them are really my favorite bullet. For a Barnes bullet they picked a 168. They really should have picked the 160 in my opinion. For the Berger they picked the 195 which also would not have been my choice if I could make my own load

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Great write-up. Very instrersting insights, especially on the recoil. I think Velos are either set on a 20" or a 22" barrel, I heard that once or twice but I didn’t commit it to memory other than it wasn’t 24". And .18 is rediculous!!!

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Keep us informed on this. I’m very interested in how this turns out for you down the road.thanks for the info.!

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Nice write up Carter. Sounds like you got it shooting fantastic!

Have you noticed anything from the additional psi? Does it have a harder bolt lift or anything?

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No, bolt lifts were all fine. No obvious pressure signs on the cases either, but wonder if that’s going to be different given the metal alloy.

Thanks

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After range day number one with 20 rounds of 175 tipped Fusion I decided to clean the gun because a. I wanted to shoot some copper rounds and needed a clean bore, as well as b. I wanted to see if 80,000 PSI plus a suppressor led to worsening fouling. I can’t say that I noticed any difference in the amount of fouling that I got with this gun

So today was the 168LRX’s turn. I figured the first 5-9 shots would be fouling and really shouldn’t count. In fact Barnes recently talked about that on their podcast. So fired the first shot on a cold, clean bore and had it hit fairly close to center. When I fired the second shot I looked and it looked like it just enlarged the hole from the first shot. I was very excited thinking that this thing is going to be great and shoot cold and clean well. But when I fired the third shot I noticed it was 6 in low and then, what the heck, there’s another bullet hole about 3 in to the right of both of the others and midway between them.

So maybe it needs to be fouled. I ended up shooting 15 shots and I mentioned in the first post that I think I shot my best group ever with this gun on that day, well today it was time for my worst group ever. This thing was shooting over an 8-in group.

I checked to make sure the suppressor was tight and it was. Didn’t have anything to check tightness of the action screws or scope screws. Went down to the Target and this is what I saw

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Keyholes!!!

This bullet requires an eight twist. It works perfectly beautifully in my 7prc. I actually tried it with a Bergara 28Nos with a 1:9 twist and saw similar results to what I saw today.

I had a few more of the 175s lying around and shot two groups with them. One was 0.9 and the other was 0.6 moa. So at least in the same general ballpark of what I was seeing last week with them.

Came home and did a Quick test with a cleaning rod, tape measure, and a paint marker and I got that this was a slightly faster than 1:8, almost certainly within the error of measurement of This crude technique. It’s kind of difficult to do this with such a short barrel.

I always thought keyholing was due to an inappropriate twist rate. Is there something that can be wrong with the ammo that would lead to that instead?

So needless to say certainly have increased my doubts regarding this chambering. Not sure if I want to try any of the other loads or not. None of them really interest me. I guess I could just stick with the 175s. I’ll need to order some more of them and do some more testing to see what it is truly going to do with them.

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What’s the velocity on those?

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Oops

2916, SD12, ES 45

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Doesn’t seem to be a twist rate issue

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Yeah my PRC loves them at 2860 with a 22 in barrel.

So what’s different? Barrel is shorter, velocity is higher, pressure is significantly higher.

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Higher pressure at the muzzle might be destabilizing the bullet on its way out, especially with incomplete burnout is the only thought I have. Maybe try another box/lot of the same bullets to make sure you didn’t get a bad batch.

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Update #2/ Range Day #3

Took the above advice and purchased another box of 168LRX. Despite the fact that I bought it from a completely different store in a completely different part of the country then the first box, it had exactly the same Lot number as the first box. Figure they’re not selling a ton of this stuff right now.

Not surprisingly, 3 shots with 3 Keyholes.

Also purchased a box of Berger 195 EOL. Shot the first six shots at the center of the target just to make sure my point of impact didn’t make a massive shift as well as foul the barrel with the new load. Then shot four, three shot groups.

MV 2792 SD 13.6, ES 49.9

One group was 1.1 inches at 100yrds. Cannot give you exact measurements on the other three groups. On two of them two shots were relatively close to each other, typically an inch or maybe less but the third shot was completely off the paper. The final one, only had one shot on the paper and two off. That means they were at least two MOA if not more. I’m using the same type of targets that you see Spomer use, I was using the four corner targets as poa’s.

Don’t know if I’m going to try the Terminal Ascent at this point. If I do, it will be after taking some time off from this thing and focusing on some more fun guns.

Can’t wait for that 280AI barrel to get here next Spring!

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Carter,

I found in my 18in barrelled 7 PRC using 168 LRX bullets I had to really work on finding a good powder/charge/seating depth setup to get good groups so maybe this is the case for your gun as well. In the end if worked for 0.75 MOA and 12 in group at 1000 yds. Not sure if the calibur is handloadable?

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Yeah it took me a while to develop my seven PRC handload for that bullet also but it really loves it. In fact I just took it out of the safe the other day to put some fouling shots down the barrel before hunting season gets here. The first three shots on a cold clean bore landed in the same spot at 0.25 in.

But as of right now, the seven Backcountry is not reloadable. You can only use federal ammo. Hopefully they’ll get the hand loading, reloading issues straightened out and get it so you can do that but they’ve been saying that now for six plus months and it doesn’t seem like any progress has been made

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Update #3/Range Day #4

I needed to do some testing with another rifle today and decided to take the backcountry out and shoot it some while I was waiting for the other rifle to cool in between groups.

First thing I did was shoot a three shot group on a cold barrel of the tipped Fusion just to see if there might have been some major change in how the rifle was performing.

A 0.174 MOA group!

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Then came time for the 155 Grain Terminal ascent. Box velocity is 3150. I got 3120 with an SD of 12 and an es of 39.

Group sizes (3 shot, in order)

1.996

1.29

0.526

0.604

1.23

I then tried the 170 terminal assent. Five shots, five key holes in a group about 5 in big.

Takeaways at this point

THE GOOD

  1. Performance exactly as advertised. This thing is slinging 7mm bullets out of an 18-in Barrel at the exact same speeds I get from a 7 PRC with a 26 in Barrel.
  2. 100% perfect feeding, ignition, and ejection/extraction. No need to use my tailgate to open up the action like that one guy on YouTube had to.
  3. Absolutely outstanding accuracy with the 175 tipped Fusion. Worst group was an inch everything else has been well under that with some of the best groups I’ve ever shot in my life. I’ve shot fusions in the distant distant past and thought they were so so.

THE SO-SO

  1. Accuracy with the 155 terminal Ascent was so so. I was thinking maybe this thing just needs to settle in a little bit since the group started shrinking significantly as I proceeded. But then the last group opened up a bit. Perhaps some more testing would be indicated for this particular round.

THE BAD

  1. Significantly more recoil than I was expecting. It wasn’t unmanageable, I don’t have a bruise on my shoulder. But it’s definitely Magnum level. And that’s in a 15 lb rifle and using a suppressor
  2. Horrible accuracy with the Berger bullet. I don’t think I’ve ever said that sentence before in my entire life.
  3. I have experienced key holling before. It was with a custom load of ammo and I wasn’t paying attention to what the bullet manufacturer said the twist rate minimum was. But I have never had a factory rifle, shooting Factory ammo go from sub Moa with one bullet to complete keyholes with two other bullets. This Barrel is made to correct specs. I have done testing as best I can in my garage and it is meeting the twist rate it’s supposed to. But with the lrx and the 170 terminal ascent, it is slinging these things completely sideways. I’m dumbfounded. I know some rifles are said to like some ammo better than others but I’ve never seen anything go from one extreme to the other like this.

Overall what I recommend this thing? No, unless you’re just one who likes to Tinker and play around. And it’s not like you can do that much tinkering since we can’t reload or hand load at this point.

Loaded with the tipped Fusion it would be one heck of a hunting rifle although the form factor isn’t quite right for me. MDT says they’re going to release some more hunting oriented fore ends, but right now they haven’t done that. I’m wondering with something with this type of recoil if a more traditional stock would do better than a chassis.

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Random question:

Does the new casing material cause you any problems at the shooting range? One of my local ranges runs a magnet over ammo to check for steel and I was curious what it would make of the new backcountry case material.

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No troubles for me but we don’t do anything that sophisticated at our range. We’re just in charge of policing our own brass and I just sweep it up and dump it into a little bin I have in the bed of my pickup truck.