AR 15 6.8 SPC built and review

[Glock357]

Bolt carrier group and firing pin

These are YHM bolt carrier and stag arms bolt. They are both phosphate coated. They have perfect tolerances but the phosphate coating made things tighter and by hand it was hard to move the bolt in and out and the bolt cam pin would catch on the bolt carrier and it also scratched the upper on its way rearwards to open the breach. Also the firing pin would catch and not rotate freely. After close inspection the firing pin was a little bit bent and that's why it would catch. The polishing compound helped to resolve this issue as well.

I applied flitz on the firing pin and used my electric drill to polish it against the bolt. I used flitz on the bolt and carrier and the carrier and bolt cam pin and polished all the surfaces that touch each other and now everything is squeaky smooth and moves freely.

Since I was in a polishing mood I also polished the trigger at the interface spots and managed to remove the grittiness.

Probably all the polishing wasn't 100% necessary as things would smooth out with use but I wanted to tune it to my standards earlier than later.

 

[Glock357]

UTG bipod

For an el cheapo bipod I am pretty happy with it. Its pretty sturdy constructed with steel base, aluminum legs, brass bushings and strong springs. The cheapness shows in that the picatinny mount doesn't fit flash on the picatinny rail. The result is that when its fully extended or not extended at all the rifle is not level. I fix this by adjusting the length of one of the bipods legs. I can live with this.

 

[Glock357]

Glock357 this is a great write up and thank you for answering so many questions!

I am glad Engage armament introduced me to this forum, lots of good people and useful information.

 

[Glock357]

Nikon Prostaff scope

I am very satisfied with this scope as it is serving its purpose. I need it for 50-250 yard shots for deer hunting. I ll also try it for varmint if I get the chance.

My requirements were

• low light performance for early morning and late evening shots,
• large field of view for moving targets,
• good eye relief range so that the highest mag view position is the same as the lowest mag position with some room for hasty positioning,
• large exit pupil so that I can acquire the target fast and still see the target even if I don't position my cheek perfectly
• large range and ease for elevation adjustment
• markings for hold up or down
• good ballistics calculator for different loads

The Nikon scope mounted with a Burris PEPR meets almost all the requirements at varying degrees of satisfaction.

The good
The scope is very bright with 98% light transmission. It has a large 50 mm objective lens to collect light as well as to allow for a large field of view at each magnification. It is very sharp, I can easily read 14 point font print at 200 yards at 9 mag. At 3x it is focused from about 2 yards to infinity and at 9x it is focused from about 30 yards to infinity. The BDC reticle parallax is set at 100 yards. The magnification is OK for bench shooting at 200 yards. At 300 yards it would probably be quite difficult to aim with only 9x. You can also zero the turrets after you sight in. It is light and it is compact.

The bad:
The turrets are plastic and they don't align with the zero line properly. The BDC reticle doesn't have hold-under degradations so for under 200 yards I have to estimate or turn the turret. The reticle doesn't have windage degradations for left right hold when its windy or the target is moving.The reticle doesn't move with the magnification adjustment, therefore at lower magnifications the holdover degradations are at different distances than at higher magnifications making it difficult to remember where to hold over at each magnification making the hold over functionality almost useless unless you stick with one magnification or you have a chart with you and the time to look at it.

The ugly
Not bad for $160 I paid for it. I am realizing that for bench shooting you need a different type of scope. Large field of view is not as important as high magnification. However I wouldn't sacrifice large eye relief. For over 200 yards I would say the limiting factor will not be the rifle accuracy/precision but the scope and the shooter. If I get good at shooting I might get a better scope in the future, but it might be difficult to meet all the requirements at the same time as typically large exit pupil and high mag are not found together.

 

[Glock357]

Range report

After braking-in (lapping) the barrel and zeroing in 3 different brand ammo I tried some target practice last Saturday: Federal Gold dot 90 gr, Hornady 110 gr V max and Sellier and Bellot 110 gr FMJ. I printed the targets myself and each circle is 1 inch larger that the smaller one, so the numbers are inches. The 3 inch target is for 100 yards and the 5 inch target is for 200 yards. I am showing the Sellier and Bellot at 100 and Hornady at 200 yards. Both bullets are 110 grains and have ballistic coefficient 0.37. Both rounds have the same nominal velocity of 2550 fps from a 16 inch barrel, but based on my calculations (based on the drop from 100 to 200 yards, not a chronograph) I was getting about 2550 fps from the 20 inch barrel. The S&B is full metal jacket while the Hornady is a polymer tip. It looks like I was getting about an inch at 100 yards and 2 inches at 200 yards. Each target has 3 bullet holes. The hole outside of the target for the 200 yard target is from the stapler.

As I mentioned earlier I am saving brass to reload. I paid $17 for the S&B, $18 for Hornady and Federal per box of 20 before shipping. The federal brass seemed to be the lowest quality from all three. It is very soft as the bolt extractor effectively scratched the writing off of the case head and the case throat of a good number of rounds got bend as you can see in the pics below. The Hornady and S&B brass seemed pretty nice. Hornady is redder than S&B so it must have more copper. This also makes it easier to tell them apart. Federal is also distinct as it is fire formed. All cases are small primer.

Many thanks to the shooter I met at the range that donated his 6.8 spc hornady brass for my future reloading endeavors!

 

[amoebicmagician]

Magazines

I was going to go for the cheapest ones I could find, as for some reason 6.8 SPC mags are quite expensive, but then I read a few reviews and when I discovered my favorite round (SSA 140 Grain Berger) they also recommend the Precision Reflex Inc. (PRI) mags. Unfortunately my indecision between 6.5 Grendel and 6.8 SPC pushed me beyond Oct. 1st so when I decided on the 6.8 SPC caliber I could only get the 10 round mags. I got two mags from Brownells for $80 (ouch!). As it is, they barely protrude below the mag well – they are tiny.

I keep telling myself that it doesn’t matter since the rounds are so expensive I won’t be shooting for quantity. In any case I can only load 8 rounds when I go hunting.
But why can’t I have 15 or 20 round mags which I think it’s the reasonable size mag one should carry on this platform. I am so glad I have 5 15-round mags for my Glock. The other day I participated at the Gilbert's range Hogan Alley event and I needed every bullet in the mag for the course without wasting ammo. I wonder for people that participate in shooting matches if there is any exception to the 10-round-mag rule, or if the event organizers give people from Maryland a handicap… Anyway, enough of my rambling, I wanted to put my complain out there…

Back to the PRI 6.8 SPC mags I got. They are very well and carefully made. PRI’s QA/QC works well. They are steel construction from 0.033 inch thick sheet. They have a waffle pattern as well as two vertical indentations for protection against bulging. Effectively they are made by stamping the two halves of the mag with a tool and welding them together at the locations where the primer and the tip of the bullet sit. The seams are very clean and smooth without any indentations giving a total length from primer to bullet tip 2.320 inch and 2.460 inch total length. Effectively the manufacturing technique allows them to achieve this large tolerance and that is why SSA recommends them since their rounds are 2.300 inch overall length. The mags have the PRI logo as well as 6.8 mm written on them. The plastic follower is olive green and has 6.8 inscribed near the bullet tip. The bottom of the magazine has the following stamped: "WWW.PRI-MOUNTS.COM, USA, NEW BREMEN, OH". When I am done with the rifle all the components will have the MADE IN USA logo on them (except for the scope...)


Regarding fit and function in the lower receiver: the mags insert effortlessly and catch on the mag catch.
When you press the mag release button the bolt catch spring shoots them out of the mag-well as expected. I haven’t loaded them with ammo yet to see how they do.

uhm, two things:

One, you can use Pmags with 6.8SPC. I use 5.56 pmags all the time with no problem. You can't get but a little less than 2/3s the capacity, but they work fine.

Secondly- you can get 30 round mags out of state and bring them home with you. You just can't buy them in MD.

 

[amoebicmagician]

Hi all,
its been a while since my last post. It took a while to get the upper back from Bison Armory. Because of the hunting season and Christmas they shipped the rifle early February. Since then I shot it 3 times, once at the NRA range right after attending the Chantilly gun show, and the past 2 weekends at the Carol County shooting range.

After some hand lapping with Fritz polishing compound and the JB cleaning paste and me getting used to shooting further than 50 yards after more than 15 years without a rifle I managed to get 1 inch groups at 100 yards and 2 inch groups at 200 yards. I tried the cheapest ammo I could get online, Hornady 110 gr v-max, Sellier and Bellot 110 gr FMJ, and Federal Gold Dot 90 gr soft top and they are all consistent and accurate.

Here are some pics of the rifle and I will give a more detailed review below:

I generally prefer stainless when going for accuracy, and chrome or melonite for longevity and dependability.

I came late to this thread.

But my God, that gun is beautiful.

6.8 is wonderful, you will be happy with this gun for a long time.

 

[photoracer]

uhm, two things:

One, you can use Pmags with 6.8SPC. I use 5.56 pmags all the time with no problem. You can't get but a little less than 2/3s the capacity, but they work fine.

Secondly- you can get 30 round mags out of state and bring them home with you. You just can't buy them in MD.

The Berger 140g has a longer OAL than normal 6.8 SPC II rounds. Only the PRI mags will cycle the longer 140g rounds, none of the others including the Pmags will feed them. The main difference between 6.8 mags and 5.56 mags is the shape of the follower. I personally don't trust that even a good 5.56 mag like a Lancer will feed my 6.8 rounds forever.

 

[amoebicmagician]

The Berger 140g has a longer OAL than normal 6.8 SPC II rounds. Only the PRI mags will cycle the longer 140g rounds, none of the others including the Pmags will feed them. The main difference between 6.8 mags and 5.56 mags is the shape of the follower. I personally don't trust that even a good 5.56 mag like a Lancer will feed my 6.8 rounds forever.

Haven't had a problem so far with any of my Pmags or Emags. They work better than the purpose built el cheapo 6.8 mags I got.

That said, Tapcos don't seem to feed the 6.8 in any kind of reliable fashion.

The Tavor mags I have are working so far, so good.

I've never fired anything heavier than 115 grain ammo, though.

 

[Glock357]

Haven't had a problem so far with any of my Pmags or Emags. They work better than the purpose built el cheapo 6.8 mags I got.

That said, Tapcos don't seem to feed the 6.8 in any kind of reliable fashion.

The Tavor mags I have are working so far, so good.

I've never fired anything heavier than 115 grain ammo, though.

That's good to know. I read some place that when using the plastic pmags with 6.8 SPC the bulge. I ll try them out. I plan to load 2 types of loads: 115 gr for plinking and varmint loaded at standard length and 130 gr for hunting loaded at PRI mag length. The pmags appear to be good options for standard length ammo.

 

[Glock357]

The Berger 140g has a longer OAL than normal 6.8 SPC II rounds. Only the PRI mags will cycle the longer 140g rounds, none of the others including the Pmags will feed them. The main difference between 6.8 mags and 5.56 mags is the shape of the follower. I personally don't trust that even a good 5.56 mag like a Lancer will feed my 6.8 rounds forever.

Unfortunately it seems that SSA stopped producing their 140 gr Berger load. Its not listed in their 2014 catalog. I d love to know their load data.

 

[jimbobborg]

That's good to know. I read some place that when using the plastic pmags with 6.8 SPC the bulge. I ll try them out. I plan to load 2 types of loads: 115 gr for plinking and varmint loaded at standard length and 130 gr for hunting loaded at PRI mag length. The pmags appear to be good options for standard length ammo.

PMAGs bulge, according to Magpul, the manufacturer. That's why they didn't make a 6.8 magazine. As for hunting bullets, 130gr bullets were made for .270 Winchester speeds, you won't get the expansion you want with them. You're better off getting 110gr Accubonds and SSA brass, with the proper load you can get to 2700+ fps which makes this a 200 yard deer round. 90gr VMAX bullets are better (and cheaper) for varmints, as that's what they're designed for.

 

[photoracer]

PMAGs bulge, according to Magpul, the manufacturer. That's why they didn't make a 6.8 magazine. As for hunting bullets, 130gr bullets were made for .270 Winchester speeds, you won't get the expansion you want with them. You're better off getting 110gr Accubonds and SSA brass, with the proper load you can get to 2700+ fps which makes this a 200 yard deer round. 90gr VMAX bullets are better (and cheaper) for varmints, as that's what they're designed for.

I tend to use the 120g SST as they group tight enough to be used as match ammo in some cases. I tried every 6.8 round from 90g-120g. I also wanted the Berger 140g for match purposes because the bullet stays supersonic past 1000 yards, making it the only round in 6.8 that could be used in 1000y competition.
I have 2 BCGs in 6.8. One is the old Stag 3G bolt carrier from my 3-gun AR with a 6.8 bolt from PSA in it and the other is an RGUNs NiB one. Both seem to work just as well.

 

[Glock357]

PMAGs bulge, according to Magpul, the manufacturer. That's why they didn't make a 6.8 magazine. As for hunting bullets, 130gr bullets were made for .270 Winchester speeds, you won't get the expansion you want with them. You're better off getting 110gr Accubonds and SSA brass, with the proper load you can get to 2700+ fps which makes this a 200 yard deer round. 90gr VMAX bullets are better (and cheaper) for varmints, as that's what they're designed for.

Thanks for this suggestion. 2700 gps is impressive. Regarding the v-max did you mean 110 gr? Hornady doesn't have a 90 gr 270 cal.

 

[jimbobborg]

Thanks for this suggestion. 2700 gps is impressive. Regarding the v-max did you mean 110 gr? Hornady doesn't have a 90 gr 270 cal.

Jeez, I stocked up on this stuff a few years ago. Looks like they stopped making the light ones. And after checking with MidwayUSA, the Remington FMJs are the cheapest per bullet, with the Hornady match 110gr bullets a close second. Don't expect great accuracy with the Remingtons, based on my experience and that of others on the 6.8 Forums.

 

[bman940]

Nikon PROSTAFF 3-9 BDC

If you are using this scope without using Nikon's Spot On Ballistic Program you are cheating yourself out of some very solid long range accuracy. YOu have quite a bit of information on your round already, now enter it along with the correct sight height ( mid barrel to mid scope,usually around 2.5 inches for AR ) and you should get the distnaces that correlate to each BDC circle. Spot On is free to use and now that it is not Java based it will work on iPhones/pads and is also Android friendly. Check it and let me know what you think. If you have any question's about it drop me a note and I'll do my best to get you answers.

Here's an idea of the info you can get.

http://i1216.photobucket.com/albums/dd363/bman940/Spot%20On/300blkinfo.png

 

[Glock357]

If you are using this scope without using Nikon's Spot On Ballistic Program you are cheating yourself out of some very solid long range accuracy. YOu have quite a bit of information on your round already, now enter it along with the correct sight height ( mid barrel to mid scope,usually around 2.5 inches for AR ) and you should get the distnaces that correlate to each BDC circle. Spot On is free to use and now that it is not Java based it will work on iPhones/pads and is also Android friendly. Check it and let me know what you think. If you have any question's about it drop me a note and I'll do my best to get you answers.

Here's an idea of the info you can get.

http://i1216.photobucket.com/albums/dd363/bman940/Spot%20On/300blkinfo.png

Thanks,
I already have the app on my android phone. I have to do a little bit of guesswork as I don't have a chronograph and my barrel is 20 inches instead of the typical 16 inches factory loads are tested on.

I used the app on my phone to estimate the ammo velocity based on the known environmental conditions, the bullet bc and the drop between 50 100 and 200 yards.

I think the Nikon app is one of the better ones out there and is well updated with the latest ammo.

Now it can't help much with the federal gold dot 90 gr soft point because there is no published data on bc nor fps ... I ll probably pull a bulet and compare with others.

Here is a feature I would love to see in the app: pull location, elevation, compass readings from the cell phone, weather data from the internet and automatically populate environmental data. Also it would be nice to save shooting and environmental conditions in addition to load data for each shooting session.

 

[bman940]

?

I'll see what I can do about getting that 90 gr. Gold Dot SP into the Spot On Program. I am getting roughly 300 fps less out of my 18 in. AR barrel then the stated MV of 3240 fps. From what I have been told MV are done from a cold 26 in. special barrel that isn't really even a rifle. My .223 bolt action 26 in. bull barrel clocked 3180 fps average.

 

[Glock357]

I'll see what I can do about getting that 90 gr. Gold Dot SP into the Spot On Program. I am getting roughly 300 fps less out of my 18 in. AR barrel then the stated MV of 3240 fps. From what I have been told MV are done from a cold 26 in. special barrel that isn't really even a rifle. My .223 bolt action 26 in. bull barrel clocked 3180 fps average.

Just to confirm the round in question is a Federal Gold Dot 90 gr 6.8 SPC Remington

 

[Glock357]

Range report continued

its been a while, but I was busy shooting, learning how to reload, reloading, shooting some more, and scouting in the woods for next deer season.

I wanted to post a picture of my crown after I shot about 50 rounds. They say the smog pattern on the crown is an indication of crown's health. It looks symmetric enough to me, any thoughts or comments?