Highpower 600 yard load for 80gr SMK and N-140?

[bigbossman]

I bought a match-prepped AR from a fellow getting out of the game, and he gave me all the accoutrements - N-140 powder, 69 and 80gr SMK bullets, brass, etc. I've tried his load of 24.5gr with the 69gr bullet at the local range, and it is good to go at 200 yards. Unfortunately, that is as far as the range goes, 200 yards.

There is a "across the course" match going off this weekend at a range about an hour away, and I thought I'd give it a go. The problem is I don't have time to test shoot some 600 yard loads with the 80gr bullets and N-140. Having shot service rifle with a M1A in the distant past, I know there are "well-known" loads for service rifle. However, I've searched the internet and, while I've found "well-known" established loads for this bullet and other powders, I have not found one for N-140. The book says 23.0gr is the max load, but it also lists the COL at 2.551 inch, which will barely seat the bullet into the case (typo, maybe? Every other bullet is around COL of 2.3). I was thinking of just backing off the max load to 22gr and see how it does.

Anyone shooting this combination?

[divingin]

Length could be for single loaders in bolt rifles.

Gordon's Reloading Tool shows an 80 gr (with a .4" seating depth) at 25 gr is below max working pressure (but it's close - do not start your load testing there.) 2711 fps predicted.

69gr is closer to 27ish grains. 2912 fps.

Use this as a reference point and work your loads up safely.

22 gr N140 with a 80 SMK sounds pretty feeble. Below 40K psi (62K allowable) at 2395 fps.

[bigbossman]

Length could be for single loaders in bolt rifles.

Gordon's Reloading Tool shows an 80 gr (with a .4" seating depth) at 25 gr is below max working pressure (but it's close - do not start your load testing there.) 2711 fps predicted.

69gr is closer to 27ish grains. 2912 fps.

Use this as a reference point and work your loads up safely.

22 gr N140 with a 80 SMK sounds pretty feeble. Below 40K psi (62K allowable) at 2395 fps.

Thanks for giving me a starting point. Yeah, I thought 22gr might be a bit low, but didn't want to blow things up.

[smoothy8500]

The book lists the COL at 2.551 inch, which will barely seat the bullet into the case (typo, maybe?)

Anyone shooting this combination?

[bigbossman]

Interesting, thanks for that. I'll put together a dummy load at 2.550" and make sure it chambers and the bolt closes on my AR. I'll be shooting slow fire with a SLED, so magazine length isn't an issue (as I'm sure you know ).

I also have H4895, H335, and BLC-2 on-hand, and will test those out over a chrono for groups as soon as I can get them together and out to the range. I really wanna burn up the rest of the N-140 first, as I have far too many partial cans of powder laying about. My guess is that the H4895 is going to do the best, based on it's performance in my .308 match loads as well as the .223 loads I use in my Savage with Hornady V-Max 50gr bullets. That load in the Savage varmint rifle is producing one-hole groups at 100 yards.

[ar15barrels]

I bought a match-prepped AR from a fellow getting out of the game, and he gave me all the accoutrements - N-140 powder, 69 and 80gr SMK bullets, brass, etc. I've tried his load of 24.5gr with the 69gr bullet at the local range, and it is good to go at 200 yards. Unfortunately, that is as far as the range goes, 200 yards.

There is a "across the course" match going off this weekend at a range about an hour away, and I thought I'd give it a go. The problem is I don't have time to test shoot some 600 yard loads with the 80gr bullets and N-140. Having shot service rifle with a M1A in the distant past, I know there are "well-known" loads for service rifle. However, I've searched the internet and, while I've found "well-known" established loads for this bullet and other powders, I have not found one for N-140. The book says 23.0gr is the max load, but it also lists the COL at 2.551 inch, which will barely seat the bullet into the case (typo, maybe? Every other bullet is around COL of 2.3). I was thinking of just backing off the max load to 22gr and see how it does.

Anyone shooting this combination?

2.551" OAL is not a typo.
You can not load 80's to magazine length.
80's get single-fed using a sled to make the bolt lock open after each shot.

[bigbossman]

2.551" OAL is not a typo.
You can not load 80's to magazine length.
80's get single-fed using a sled to make the bolt lock open after each shot.

Yes, as I said in the post right above yours:

I'll be shooting slow fire with a SLED, so magazine length isn't an issue

Here's the interesting thing - the Vihtavuori chart shows the OAL as 2.551 using the Sierra 80gr bullet, but shows all the other brand heavy bullets in the COAL range of around 2.30 give or take. Also, looking up load data for the Sierra 80gr MK on Hodgdon's site reveals a uniform COAL of 2.380 across the three powders I looked up.

Hence my question.

[smoothy8500]

Sierra 80gr MK on Hodgdon's site reveals a uniform COAL of 2.380 across the three powders I looked up.

Hence my question.

Since you mentioned that info on Hodgdon's site, I took a look. Yes, that is odd since the 80-ish grain offerings from Sierra, Nosler, and Berger all require the longer (approximately) 2.550" COAL. Compared to the typical 77 or 75gr, the 80's are almost a quarter inch longer in total projectile length.

As for dummy round and checking chambers: The 2.550" generally has no issues with almost all AR service rifle match barrels done with the Wylde reamer. Good idea to check first.

However, I have heard from other competitors that the CLE (Compass Lake Engineering) reamer has a slightly shorter leade/throat and the 2.550 length may end up as a "soft jam" and show increased pressure. Those CLE chambers require 10-20 thou less length. You didn't mention your upper MFR, but the typical White Oak/Rock River Arms/Fulton Armory/etc are Wylde chamber and good to go.

Good luck and good shooting.
IMG_1063.jpg

[smoothy8500]

And a throw-back in case you miss the M14 days....
M14.jpg

[bigbossman]

As for dummy round and checking chambers: The 2.550" generally has no issues with almost all AR service rifle match barrels done with the Wylde reamer. Good idea to check first.

However, I have heard from other competitors that the CLE (Compass Lake Engineering) reamer has a slightly shorter leade/throat and the 2.550 length may end up as a "soft jam" and show increased pressure. Those CLE chambers require 10-20 thou less length. You didn't mention your upper MFR, but the typical White Oak/Rock River Arms/Fulton Armory/etc are Wylde chamber and good to go.

I bought the rifle from a fellow that was getting out o the game, and do not recall what match upper he said he bought. I can pull the hand-guards to see if there are any identifying marks, but the barrel will be shrouded with the free float tube so I'm not sure if I can glean any info from doing that. I do know that he said he bought a complte upper, I just don't know from who.

I'll do the dummy round and report back.

[bigbossman]

OK, dummy round with 80gr SMK seated to 2.550 chambers fine. I used a black sharpie to mark the bullet, and saw no rifling marks upon extraction. The cartridge mic'ed out to the same length, so apparently it is not touching the lands. Bearing surface of the bullet in the case is only the length of the neck mouth to just above the beginning of the shoulder, so not very much but appears to be enough as the bullet is firmly seated.

I pulled the hand-guards, and as anticipated saw no identifying markings.

[smoothy8500]

Good to go!

[jimmykan]

According to QuickLOAD, for an 80 grain bullet seated to 2.550" COL, you cannot fit enough N140 into a 5.56 case to exceed 5.56 maximum chamber pressure (62,000 PSI).

It would take 25.0 grains of N140 to reach 62,000 PSI and that's a 109% filled compressed load.

[bigbossman]

According to QuickLOAD, for an 80 grain bullet seated to 2.550" COL, you cannot fit enough N140 into a 5.56 case to exceed 5.56 maximum chamber pressure (62,000 PSI).

It would take 25.0 grains of N140 to reach 62,000 PSI and that's a 109% filled compressed load.

Interesting. The VV site lists 23gr as the max charge for that bullet, seated to 2.551.

As an aside, I was able to get to the range and shoot some test loads over a chrono. The 24.5gr load of N-140 under a 69gr SMK was in the high 2800's. The 22gr of N-140 under an 80gr SMK was only making 2400fps 15' in front of the muzzle. I also shot a few test loads using H335, BLC-2, and H4895 with the 80gr bullet. The latter two showed a lot of promise, with the H4895 clocking just over 2800fps and the other two in the mid to high 2700's. BLC-2 had a SD in the single digits, and the 4895 showed a SD of 14.

Based on this (and the fact that I don't have a lot of N-140 left), I'm thinking of using up the N-140 for the 69gr load, and using either BLC-2 or H4895 for the 80gr load. I should note that I used the Hodgdon specified COAL of 2.380, but the next test loads will be at 2.550.

[smoothy8500]

Your 2400 is a tad slow to take the full wind-bucking advantage of the 80's, but will still work ok. Generally 2500 fps muzzle velocity is considered a good spot for using the 80gr at 600yds with the NM AR.

I don't worry too much about SD's even at 600yds, but if you find an accurate node with stable speeds then it's a bonus. Since I use a progressive press I find a load that has minimal vertical dispersion and same point of impact over a half-grain interval at 200 or 300yds. That way if the meter is +/- 0.1gr on each drop I'm well within the accuracy node at 600 yds.

Here's a link to Sierra's loading manual for some more info: https://accurateshooter.net/Downloads/sierra223ar.pdf