AR-15 Variants

[Tactical30]

I have a Vltor MUR upper I had ordered for a new AR build but cant really decide what to cal. to put on it.
I have built already (2) .223 AR's: (1) 6.5mm Grendel AR
(1) 6.8 SPC AR.
I dont want to put a 22lr, 9mm or any pistol cals on it but im not sure what im left with.
<span style="font-weight: bold">Any ideas on what caliber to build</span>?
<span style="font-style: italic">Anyone have a list of what calibers you could build on a regular AR upper?</span>
I seen a .260 AR in a magazine but couldnt remember who built it. Thats maybe my next one-.260. You never see anyone with a .260 AR, Maybe there is a good reason tho.

 

[steelcomp]

Re: AR-15 Variants

5.45 x (i think) 75. Fun little round and ammo is dirt cheap. Uppers are available and you can modify a .223 mag pretty easily.

 

[exhogflyer]

Re: AR-15 Variants

.204 for varmints
another 6.5 'cuz it's a multipurpose round
.458 socom for close in hunting

 

[Tactical30]

Re: AR-15 Variants

6.5 Creedmoor or 6.5x47 Lapua would be sweeeeeeet.

 

[DBrace]

Re: AR-15 Variants

tag.... i asked myself the same question a couple days back. any more cal's that will work with a standard AR upper/lower? Thanks gentlemen! -brace

 

[squirrel_slayer]

Re: AR-15 Variants

.260, 6.5 creedmore, and 6.5x47 would all have to be on a ar10 platform.

if your looking for a nice 6.5mm ar loading look into the 6.5wssm ar. or .243wssm, 25wssm

here are a few I'd like to build.
7.62x25mm tokarev (you can use surplus ammo for plinking with 32 round ppsh43 magazines) or you can use a modified ar15 magazine and load them up to 200gr .308 subsonic loads with the same setup. (near 300 wisper performance with subsonic loads)

6.5 grendel (which you have already)

.458 socom as stated above

7mm wssm

300 OSSM (basically a 30 cal wssm)

 

[DBrace]

Re: AR-15 Variants

Sorry to hijak the thread.....not my intention longrange30. I don't know if you are planning on using a reg. lower or the ar-10 lower. I have a couple reg. .556 lowers and was wondering what cal's I could throw on top of them.

Thanks for the info Squirrel. Never thought of the diff wssm's...how would barrel life....reloading/ammo expense....overall ballistics differ between the 6.5 grendal & the 7mm wssm. What about a .243 or is that a ar-10 lower? Thanks Guys, and Longrange30 if I am crampin' your thread let me know and I will start my own. -brace

 

[squirrel_slayer]

Re: AR-15 Variants

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: D Brace</div><div class="ubbcode-body">Sorry to hijak the thread.....not my intention longrange30. I don't know if you are planning on using a reg. lower or the ar-10 lower. I have a couple reg. .556 lowers and was wondering what cal's I could throw on top of them.

Thanks for the info Squirrel. Never thought of the diff wssm's...how would barrel life....reloading/ammo expense....overall ballistics differ between the 6.5 grendal & the 7mm wssm. What about a .243 or is that a ar-10 lower? Thanks Guys, and Longrange30 if I am crampin' your thread let me know and I will start my own. -brace </div></div>

I haven't seen any hard data on the 7mm wssm. the 6.5mm wssm is about 500fps faster than the grendel in all bullet weights. you do however lose magazine capicity compared to the grendel. barrel life should be good as most loads will be below 3000ft/sec.

.243 Winchester would be on ar10 platform. however the .243 wssm is on the ar15 platform. that one could be a barrel burner with lighter bullets. I would opt for a faster twist barrel and heavier bullets (100-115gr) if I went the .243wssm route.

as for reloading the wssm's. brass is slightly more expensive than other calibers. about .50-.60 cents per piece. so that would be a costly investment up front. after that it would be about the same price as any other .243,.308 round. I have a 25wssm and using 100gr smk's its about $.41 cpr. and the berger 115vld's run about $.50 cpr. (re-using brass of course)

wssm brass is very thick and some people have had better luck turning the necks down and using a sinclair/forster bushing die and annealing every 3-4 loadings. I have yet to try this but definitly plan on it in the future.

 

[Tactical30]

Re: AR-15 Variants

The thing is, where in the hell would you find bolt assemblies for those calibers? Have to have them made? Somebody has to make them. I see Remington makes a camo .30 cal AR for hunting. Thats a caliber I might keep in mind for my next AR build. Anyone ever build one in .30cal? Im just wondering how a .30cal fits a
AR-15 upper/lower, wouldnt you need a AR-10 upper/lower?

 

[gbp]

Re: AR-15 Variants

For ar15
http://www.accuracysystemsinc.com/ar15_conversion.php
For ar10
http://www.ar-10-rifles.com/index.php

I have no experience with them at all but they do have quite an offering.

 

[sobrbiker883]

Re: AR-15 Variants

LR30-with the MUR upper aren't you limited to AR15-compatible cartridges?

The bolt for the AR15 variants is usually a 7.62x39 like your grendel or spc.

I've been looking into 6mm AR15 variants lately, but really don't see many that offer better long range ballistic than the 233. Its hard to drive the good 6mm bullets fast enough to take advantage of high BC bullets and be mag length. In my opinion, if I can't run out of a mag, I may as well be shooting a boltgun.

 

[JL]

Re: AR-15 Variants

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: longrange30</div><div class="ubbcode-body">
<span style="font-weight: bold">Any ideas on what caliber to build</span>?
</div></div>

Thats easy. 7.62x39.
http://www.ar15.com/forums/topic.html?b=3&f=121&t=373257

Ballistically:
did some calculations while ago, comparing cartridges based on 223 Rem case vs. Grendel.

All trajectorys are calculated with Quick Target Unlimited, based on true MV:s that I was able to find. 20" - 22" barrels. My Idea was that 22" starts to be max for practical/tactical rifle.

Used only Lapua bullets, because I had radar-based Cd values for them.
Therefore trajectory matches real life nicely, or is very close at worst. Weather is typical summer condition here, except 1000HPa / mbar pressure which is below standard sea level.
Wind from 9, 4m/s = 9mph. 1000HPa = 29,5 Hgin

Some MV:s are from rifles I know, some from google.
Naturally cant check sources. Still, should be in ballpark easily.

Biggest surprise to me was that Grendel drops didnt differ from 6.5 MPC too much. Grendel bucks wind better though -but still.
<span style="font-weight: bold">
Both elevation and wind "clicks" in charts are milliradians or "mils".
Range in meters.</span>


According to http://www.sskindustries.com/6_5mpc.htm
<span style="color: #FF0000"><span style="font-weight: bold">6.5MPC</span></span>, Lapua 108gr/7g 2731fps / 831m/s , 20"

Based on Corbon factory loads, 77gr MV 2800fps/855m/s. 20"
<span style="color: #FF0000"><span style="font-weight: bold">Lapua 223</span></span>,
77gr/5g Scenar with same MV:s:

223Rem/69gr/4.5g Scenar, MV = based on my own 20" bushy I used to have, 2920fps / 890m/s:

<span style="color: #FF0000"><span style="font-weight: bold">6x45</span></span>,
Lapua 77gr bullet.
Here:
http://www.reloadbench.com/cartridges/w6x45mm.html
is 2900fps / 885m/s 75gr bullet. Perhaps tad high for 20-22" barrel comparsion but anyways:

True measured loads, 22" <span style="color: #FF0000"><span style="font-weight: bold">Grendel</span></span>
123gr/8g Scenar. 2600fps / 792m/s.
8gram Scenar seemed to be better for Grdl that 7 gram.
At least in that rifle. Its L-W SS bull barrel.

 

[sobrbiker883]

Re: AR-15 Variants

I'm sure there's some great info there, but can;t read any of it on my 17" monitor.......

 

[squirrel_slayer]

Re: AR-15 Variants

d-tech and olympic arms make a wssm bolt/carrier assembly with a nice heavy duty bolt. he's actually built it up to .358 caliber in a wssm with great results.

olympic arms is actually releasing their 300 OSSM (300 olypic super short mag) which is making better than 30-06 power out of a magazine fed ar15! the new IMR 8208xbr powder is supposed to be great for this cartridge.(powder to be relased to public jan 2010)

 

[Norwiscutter]

Re: AR-15 Variants

6mm woa, which I believe is also known as the 6/6.8 spc would be one I would look into as well.

 

[JL]

Re: AR-15 Variants

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">I'm sure there's some great info there, but can;t read any of it on my 17" monitor....... </div></div>

Strange.
Mozzilla firefox shows original size with doubleclick.
Internet explorer 6.0 shows hi-res versions straight away.

But IE8.0 doesent, and wont allow to "open pic in new window".

But if you right-click, and "save picture as", You´ll see it full size.
Ranges are in meters btw, 1yd = 0.9144meters.