I assembled a 20" barreled rifle length gas AR. I wanted a dedicated iron sight version and topped this one with a carry handle sight. I have a good supply of 55 grain FMJ factory ammo. I also have a couple of boxes of 55 gr FMJ to reload, which I bought for a plinking load in a different rifle. Should I be looking for a heavier bullet for this length and twist rate like a 62 or 68 grain? I don't think I'm a good enough shot with iron sights to go to match bullets unless it would make a huge difference.
Bullet Weight for 20" Barrel w/ 1:7 Twist
- Thread starter DMW1116
- Start date
- Status
glockgod
Member
Should do okay with 55s- I'll bet it does better with heavier bullets
redbullitt
Member
55s should shoot fine, as well as the heavier AR suitable stuff.
77 class bullets, 62 or 69 should all will do just fine for any kind ir practical style shooting. I've shot plenty of 55s in 7 twist with no issue. Doubt twist will be an issue for you unless you go very light and thin thin jacketed flying fast.
77 class bullets, 62 or 69 should all will do just fine for any kind ir practical style shooting. I've shot plenty of 55s in 7 twist with no issue. Doubt twist will be an issue for you unless you go very light and thin thin jacketed flying fast.
My 1-8 twist likes 40-55 gr bullets as well as 77s.
It does mediocre with 62's.
Try what you got. You may be surprised. Twist rate isn't everything unless you're shooting long bullets or running fast.
Like redbullit said. Don't try for warp speed with light bullets and fast twist.
It does mediocre with 62's.
Try what you got. You may be surprised. Twist rate isn't everything unless you're shooting long bullets or running fast.
Like redbullit said. Don't try for warp speed with light bullets and fast twist.
Generally speaking a slow twist won't handle heavier, longer bullets. While a fast twist like a 1:7 will handle heavier, longer bullets they also handle lighter bullets too. Within reason. I think the individual bullet is more important than the weight. I've shot a lot of 50-55 gr bullets in my 1:7 rifles.
How will you know?
My 7 twist 5.56s shot 55s ok, they shoot 69-77 better, most everything I shoot anymore is 77SMK.
rdnktrkr
Member
I have a 20" 1in7 and with irons I don't think you will notice the difference between 55gr and 62gr, with optics and a bench vise maybe.
In the words of Henry Ford
"Whether you think you can, or you think you can't--you're right."
Charlie98
Member
I have a Colt H-bar... 20" 1:7... it pretty much hates anything 55grn, we are talking 4MOA. I've loaded 69grn SMK's... it likes those a lot. I'm trying something this week... I have some cheapo 62grn BTHP's I found, I'm hoping they will work well enough in the 1:7 barrel where I can use them instead of the more expensive SMK's. I should know by Thursday.
One of the problems with 55grn accuracy, at least in my case, is the bullet itself. Most of the 55grn I've loaded are inexpensive FMJ bullets... which quality can be sketchy at times, even with name brand bullets. They are not a target bullet, for sure, but I also believe it's partially the barrel twist, too. YMMV
One of the problems with 55grn accuracy, at least in my case, is the bullet itself. Most of the 55grn I've loaded are inexpensive FMJ bullets... which quality can be sketchy at times, even with name brand bullets. They are not a target bullet, for sure, but I also believe it's partially the barrel twist, too. YMMV
Random 8
Member
It should do well with any weight 50 grains and heavier. Depends on what you're trying to do. If just target plinking, 55s and 62s will be cheap, likely accurate enough fodder. If you wish to push it a bit longer and tighter, give the Hornady 75 BTHP a look. This bullet has been extremely accurate for me in a 1:8, and is sometimes priced comparably to the less expensive bullets. It would at the very least be worth trying 100 of these.
Blue68f100
Member
Sounds like a Wydle Chamber. I had one and it did the same thing, 65 gr up just fine. This chamber is designed to shoot the heavier longer bullets.
Skeptic13
Member
Really every gun and every barrel shoot differently. The only way to truly tell is to shoot a bunch of different loads through your guns. As mentioned in other posts the general rule is that faster twists do better with heavier bullets but you won't know until you try a load with your gun.
jebova2301
Member
- Joined
- Sep 4, 2013
- Messages
- 182
This. Every barrel is different. Even two barrels made by the same manufacturer from the same blanks will have some variability between them. Whether that is enough to be noticeable or not is another story, but no two barrels are the EXACT same. The only way to find what YOUR barrel likes is to do testing, and that may mean quite a bit of testing. It isn't just a bullet weight that it may not like, but a whole combination of all parts. For example, I tried the 55gr vmax with wc-844, and it wasn't that great(about 2moa, or roughly the same as my bulk 55gr fmj blasting ammo). I tried it with H335, and got the same results. I tried it with imr 3031, and the groups got down to about 1moa. I finally tried it with imr 8208 xbr, and that was the magic ticket. Even with the "magic powder" for the rifle, you can see the early groups were leaving a lot to be desired(worked my way from left to right on each row, then down to the next row). Yes, it is certainly possible there may be some bullets your barrel just doesn't like. However, you won't really be able to be sure with just one simple combination of components. A prime example is the barrel on my precision AR. With bulk Hornady 55gr fmj, it works great with wc-844, h335, and imr 3031. With Hornady's 55gr soft point, it works best with wc-844 and won't really behave with imr 3031. With the 55gr vmax, the only real stellar performer was 8208 xbr. All three of those are 55 grain bullets, all from the same manufacturer, but they all react differently in the barrel depending on the powder. If I were to just use h335, I would think it has some issues with the other bullets, where the reality is that it was the entire combination rather than the bullet itself.
Next, the idea that a wylde chamber will inherently be inaccurate with lighter bullets is pure speculation(and I don't believe it to have any grounding in reality). I personally have a wylde chamber in my White Oak Precision barrel. It is a 1:7.7 Krieger barrel, and will shoot lights out with 55gr vmax(0.5 moa). It will shoot lights out with 52gr SMK(0.7 moa). It will shoot MOA with 60gr TMK, it will shoot sub-moa with 69gr SMK.
It all comes down to developing the right load for the barrel itself. Using any "it worked for me" loads you find on the internet is never a guarantee of accuracy or precision(which is why I always put a disclaimer with my load data that just because it works for me, it doesn't mean it will for you).
For example, here are some of the groups doing load development for my 55gr vmax round for pest control(coyotes, groundhogs, raccoons, and the occasional squirrels when I don't feel like grabbing the 22lr). Based on these results, I find it hard to say that a wylde chamber won't accurately shoot lighter bullets.
Charlie98
Member
I don't think so... it's a gen-u-wine Colt, and the barrel is marked 5.56mm. I just don't think it likes 55grn bullets...
Last edited:
Well, for the foreseeable future, it will get 55 grain bullets. I'll try some heavier ones as they become available. Economy has a lot to do with the choice of 55 grain FMJ loads. Heavier FMJ bullets would be ok. I'd have to show myself I can really shoot this rifle well to justify the cost of match grade bullets.
AJC1
Member
I don't understand at all why people get 7 twist barrels on ar platforms. An 8 twist is about the maximum you need unless your shooting heavies in a bolt gun. The 77smk was optimal in guns that fast with mag restrictions. When you get to 90s then the entire setup needs to be optimized to that special purpose. Some lite varmint bullets may vaporize on you due to syntrifical forces. Most bullets dont like 300+ thousand rpm.
GooseGestapo
Member
- Joined
- Jan 6, 2003
- Messages
- 6,153
55gr FMJ’s aren’t known for accuracy.
I have a Palmetto Arms 20” A2 Upper that I acquired to use for practice to save the match barrel on my RRA National Match gun.
It has a 1/7” FN barrel. TackDriver. Almost as accurate as my match upper w/free float hand guard and match barrel.
It shoots 1.5-2” with 55gr FMJ. 53gr Hornady Amax, 55gr Nosler Ballistic Tips, or Hornady 75gr HPBT match bullets shoot under 1” with a scope mounted.
It’s probably the bullets, not the barrel...
I shoot mostly Hornady 62gr BTHP’s in bulk from MidSouth as they are only slightly more than 55gr FMJ’s. Vastly more accurate however.
I have a Palmetto Arms 20” A2 Upper that I acquired to use for practice to save the match barrel on my RRA National Match gun.
It has a 1/7” FN barrel. TackDriver. Almost as accurate as my match upper w/free float hand guard and match barrel.
It shoots 1.5-2” with 55gr FMJ. 53gr Hornady Amax, 55gr Nosler Ballistic Tips, or Hornady 75gr HPBT match bullets shoot under 1” with a scope mounted.
It’s probably the bullets, not the barrel...
I shoot mostly Hornady 62gr BTHP’s in bulk from MidSouth as they are only slightly more than 55gr FMJ’s. Vastly more accurate however.
Swampman
Old Fart
Last edited:
Whenever components come available again I may switch to a 62 grain load. 55 grain is more available locally, though not easily. This is an FN barreled PSA kit. Between rain and holiday range closings I still haven't gotten to shoot it.
I lucked into a good load in my 16" PSA upper using the 75 grain Hornady BTHPs. As this 20" is intended for irons only, I'll be pretty happy if I can hold 3" or less at 100 yards. With a developed load, I can do that with my factory sighted Marlin 336, though I hope to do a little better with the aperature sights on the carry handle.
I lucked into a good load in my 16" PSA upper using the 75 grain Hornady BTHPs. As this 20" is intended for irons only, I'll be pretty happy if I can hold 3" or less at 100 yards. With a developed load, I can do that with my factory sighted Marlin 336, though I hope to do a little better with the aperature sights on the carry handle.
- Status
Similar threads
