When I was AD and had the need for lights, lasers and other bits the integrated quad rail from KAC (M44 IIRC) was the best you could get as it was a one piece extruded tube, That said it would shred your hands if you didn’t have the rails covered.
Since then I don’t run much of anything other than a sling swivel or possibly a bi pod for group testing on the bench or mat. To that end I am a fair fan of the slim line Key Mod or M-Lock tubes with a single 3" rail on the bottom up front and the integral full length rail on top. I find there is less hand strain after a day of 3 gun or similar endeavors.
1:7 twisted tubes were brought about with the M4 SOCOM barrel length of 14.5" to be able to make 193 (55gr) and 855 (Green Tip 62gr) run out to 500 yards. It also works to good advantage with both on the 10.3" MK18 and civilian 7.5" pistol variants. For 16" to 20" tubes I’m a bigger fan of 1:8 twist and a Wylde chamber as it covers a wide swath of boolets that fit into the mags. I did build a 18" (1:8 twisted, Wylde chambered White Oak tube) SPR ish rifle that I was able coax sub MOA out of at 500 yards with 855 and similar hand loads. It did reasonably well at 1K but obviously had no A$$ for anything but making round holes in paper. 193’s would key hole with it and even with a 20" NM 1:9 twisted tube.
@Jeff-A1 Alas the rifle, loads and dope book were stolen so I’m going off of memory from about 4 years ago.
I want to say that I was using ~25 - 26gr of BLC2 and my chrono data @ 15’ was ~2930 FPS in LC Brass using cheap 62gr BTSP (Spire not Soft Points). I want to say the ES was well within the factory 855 spreads as I don’t recall getting upset about it in comparison. OAL length was the max I could get into the mag as the contact point for the ogive was a bit longer than mag length. I wanted to play with some W748 and H355 but never got the chance.
@Craig6 -Brother, your memory is much better than mine. I can go look at stickers I completed for my 68 gr A-Max. 25 gr of BLC(2) using the Hornady 5.56 NATO Table. The 9th Edition didn’t have A-Max so I guest low on generic BTHP. Thankfully, face/hands/firearm are still intact. Ok grouping with repeatability from a bipod. Guestimate at 2800 FPS out of 16" barrel. With that weight bullet and muzzle velocity at 500 yds (if I could hit the intended recipient) the lead pill would deliver ~450
Foot Lbs Force (FPF) with a 50" drop (yikes-foot shot). Ok, FPF would be similar to .357 Magnum at 50 Yds. Wouldn’t use it as a deer round, or zombie sized animals… well, maybe. Devils Backbone 16 Point was involved in these calculations.
Correction: I was using Hornady Match Boat Tail Hollow Point…not A-Max. No such beast.
I had to go pull my Hornady books as it’s been a minute since I did any FPF look ups. It’s showing for 500YDS for your 68gr pill at 2800 FPS MV would net you ~384 FPF @1595 FPS. If you zero’d at 100 you would be 63.9" low. IIRC most folks go with any velocity north of 750fps to have passable terminal effects on “critters”. Hornady has a calculator that develops a number to see if the intended boolet will be effective on XYZ game critters called HITS but there is a whole world of opinions about terminal velocity/terminal energy vs. terminal effects, opinions being the key word.
Here is a very good chart describing what ammo to use for the twist of your barrel. The top numbers are grains of bullet and the numbers on the left side of the chart are twist of the barrel. A 1:9 twist rate will provide the best performance with a standard 55 gr bullet. I would also think about what kind of barrel you want. A cold hammer forged (chf) barrel will give you a longer barrel life, but not as great accuracy. A button rifled barrel (milled) will provide better accuracy with a shorter barrel life. If selecting a rifle that will be used for defense or a end of the world as we know it prep, I would select a CHF barrel. If you want a gun for shooting longer ranges with superb accuracy then a button rifled barrel might be better for you.
As far as uppers I like, I have a Ballistic Advantage upper. I also like and have heard great things about Daniel Defense, BCM, and Sons Of Liberty Gun Works.
Why do you want a quad rail? I like M-Lok rails because you can buy sections of picatinny rails and have the same modularity and keep the weight down.
I was initially looking into a quad rail because that was what I was used to. I wasn’t sure how difficult it would be to mount accessories on M-LOK, and I wasn’t sure how reliable it would be. From the previous replies, however, I am looking into a M-LOK upper now. I don’t have any experience with either M-LOK or Key Mod.
@Craig6 I think we made James nervous… @James We did veer off target. My apologies. Nice chart. Looks like 1:8 will work in most situations @CDW15. Unless you are going to run-and-gun at night with NVGs, I wouldn’t worry about the strength of mounting points. “Never tell a man his horse is ugly…” I guess the same goes for handguards.
Brother, the Hornady ballistics calculator is really nice:
I had experience in the Army with quad rail and now I prefer MLOK because of weight reduction. USSOCOM did select to use MLOK on their firearms now, so I would trust it myself. God only knows what they are using it on and how many rail systems they replaced.
@Jeff-A1 You didn’t make me nervous! I just wanted to provide that chart as I found it helpful. Honestly, I don’t really notice any real difference with shooting 55 grain out of my 1:7, but generally, I am shooting at closer ranges and doing CQB drills.
@James & @Jeff-A1 I could go a long way down the road of barrels and twist rates as I have studied them extensively in my long range pursuits. One of the things I discovered was that barrel length has a significant bearing on the effectiveness of the given twist rate vs. bullet wight which is why a 1:7 twisted tube throws 55 & 62gr boolets better out of a shorter tube as noted above with the 10.3" & 7.5" tubes. Basic rule of thumb is that you need to twist your tube faster for shorter barrel lengths as the boolet spends less time in the tube and needs that extra spin just to stabilize.
That being said twist rates can and are responsible for boolet stability at different RANGES.for optimum accuracy in precision guns (I don’t consider AR platforms to be precision guns). Similar to @James twist chart optimum accuracy is found in a bell curve based on boolet weight at a certain distance. My 30-06 comp gun throws a 208/210 gr boolet at 2800 fps and will give me a 1" group at 100, a 1.5’ group at 200 and a 1/2" group at 300 due to stability and will maintain that level of accuracy out to about 1400 yards where it begins to open up again and at a mile it is still a sub MOA gun which means ~14" groups. With a different twist rate I could move that accuracy “sweet spot” forward or back to suit the application given the same load.
There is no difference to the mounting of accessories to a quad rail, M-LOK , Key Mod as they are all 1913 Picatinny rails (Pic Rail’s). The difference is only in how they attach to the free float tube and modularity there too. Simply evaluate which option suits your needs better. After that it’s all “Pic Rail” mount.
Does anyone have any experience with Palmetto State Armory? I have heard and read several conflicting opinions about PSA. I know in my first initial post I was looking into a Yankee Hill upper, however, I realized that the upper is a little more out of my budget at the moment. I see that PSA currently has a sale going on and I found one that has decent reviews and for a pretty good price. I will post the link below. I was thinking of getting this upper and dropping a BCM bolt carrier group and charging handle in it. My current rifle setup is just a stock DPMS ar15 with fixed front post sight/gas block. (I know DPMS isn’t a very good brand, I bought this when I just turned 18 and there was the big scare of whether or not we could buy them again after the 2016 election.) I would hope a PSA upper would be a step up, but I wasn’t sure. Figured I would ask here first.
I know that a few people posted prior that they liked Aero Precision uppers. I have heard a lot of good things about them. Would I be better off spending the extra money and getting an Aero Precison upper?
@CDW15 I have no experience with PSA on the range. Some folks I know have had to send kit back to get it repaired or replaced but this is a high volume company and to-be-expected. What suits your price-range? You have to pay your bills and the end of the month so it is your decision. That’s the reason I don’t fall for the high $$$ range-candy. I know Andersen makes a highly functional kit. Forged v. Cast receivers? Got some of each. Been using AP for last few years but I always buy on sale with a military discount to boot. They go through sales parts very quickly. Read all the customer comments on a product. Most are honest. Caveat-Emptor in the long run. Functionally, no diff between auto and semi bolt. Just more mass.
I’d like to not go over about $400 for an upper. But not afraid to go a little over that for quality. I lm doing my research, so I’m just trying to get opinions on here as well. I’ve been kind of torn between an Aero Precision and one of the PSA’s I’ve been looking at.
