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Posted: 7/22/2008 6:08:04 AM EDT
I checked a few bullets for depth to lands and found that none of them could be loaded in the magazine of my S&W, M&P15PC-1 Talo Exclusive rifle. This is supposed to be a highly accurate rifle. For example, a Hornady, .224 dia, 75 grain BT A-Max in my rifle has a depth to lands of 1.982" giving me a COL of 2.514". The Hornady manual for this load states a COL 2.390". Even this will not likely fit into a magazine. This was the same for the Sierra 69 grain, HPBT and the Berger 70 grain VLD. The VLD was a bit closer though, by about .050". I realize that single feed is the way to go for bullets loaded very close to the lands, especially for bullets such as Berger Bullets, and I have every intension to do so, but, what about those shorter 55 to 60 grain bullets? Won't they be way, way off the lands to be even close to being accurate? With such a large jump, will that erode my barrel? Should I be concerned?
Link Posted: 7/22/2008 6:21:49 AM EDT
[Last Edit: 7/22/2008 6:23:31 AM EDT by slapshot308]
75gr AMAX is a Hornady's answer to the 80gr Sierra MatchKing, its a LR bullet intended to be single loaded. Most likely what you want is the 75gr BTHP which can be loaded to magazine length without killing capacity too much. Mag length is going to the 2.26ish. A 5.56 or Wylde chamber is going to have a longer lead in the throat, its supposed to be that way. Quit chasing the lands and load them (69gr SMK, 55gr and 60gr bullets) to mag length.
Link Posted: 7/22/2008 6:45:55 AM EDT
5.56 chambers have longer lead areas to accomodate for the higher pressures of the 5.56 NATO cartridge.
Link Posted: 7/22/2008 7:10:48 AM EDT
Proof is always on paper.

Load em to mag length and shoot them. Adjust powder to desired power or pick best accuracy.

That said, my wylde chambered RRA uppers haven't been as accurate as my old Colt Hbar with 69 sierras or 77 noslers....but I'm still trying!

I don't load anything beyond mag length, even for my custom barreled .308 "sniper like" rifle. Would I get better accuracy, maybe, but I can live with 1/2 - 1 inch groups.
Link Posted: 7/22/2008 7:28:02 AM EDT
Mark:

You do not need to be overly concerned. Bullets like the 69gr SMK and the lighter bullets seem to do well with a relatively large jump to the rifling. Some of the VLD(s) do not like much of a jump if any. These VLD bullets are not designed for magazine length anyway; they are 600yd (and further) slow fire bullets that are single loaded.

Even with my Wilde chambered WOA (White Oak Armament) upper that supposedly has a minimum throat (it is shorter than any other .223 or 5.56 I've had) still won't allow a magazine length spitzer to come too close to the lands. I've not yet tried a round-nosed cast bullet, however.

Still the accuracy of the barrel is better than I can hold---at least for now.
Link Posted: 7/22/2008 9:57:48 AM EDT
You may want to read this...........

findarticles.com/p/articles/mi_m0BQY/is_9_51/ai_n14816186

Article by Zediker.


Aloha, Mark
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