The Firing Line Forums

Go Back   The Firing Line Forums > The Skunkworks > Handloading, Reloading, and Bullet Casting

Reply
 
Thread Tools Search this Thread
Old February 11, 2011, 07:44 AM   #1
gregjc9
Senior Member
 
Join Date: June 30, 2008
Location: Northern Va
Posts: 501
RCBS Precision Mic vs Hornady OAL Gauge (for AR)

I've been reloading for my pistols for about 2 yrs, and decided it was time to start reloading for my AR in 223. To help ensure I was sizing correctly, I ordered an RCBS PM as I had read a LOT of positive comments on this tool.

Using the supplied dummy round in my AR was impossible. I tried everything, from removing the BCG completely and trying to ease it into the chamber, to removing the extractor. Spent hours on this thing, and absolutely nothing I tried yielded anything that was close to consistent measurements.

Measurements on the Land nut are also disappointing. The instructions give the impression you read the lines like you would a normal mic. Trying to do so drove me nuts and added to my frustration significantly. I first called RCBS tech support about how the Land nut does not zero, and I was told it wasnt zeroed correctly and to send it back. Which I did, and the new kit was the same. During this time, I sent RCBS a question on this, and they replied with a different set of instructions that basically says to just use the line on the base as a reference line, and to only note the value on the Land nut - this number is only a reference.

The Headspace nut does zero and seems to work well. However I think it would be a little easier now to have a mic to be able to have to complete datum to base reading.

I received my Hornady OAL Gauge (straight model) and Bullet Comparator bushing and mic adapter yesterday afternoon. Within minutes last night I had a consistent value for the distance to the lands, and was able to get exact measurements for my reloads, which made it very easy to compare against the two. My next order will include the case bushing so I get get exact datum to base measurements with my digital mic.

I know a lot of folks use and like the PM, as I had researched the product extensively, here and on the web, prior to purchase. However if you are thinking about getting one to use primarily on an AR, I think there may be better options. YEMV, but this is mine.
__________________
ΜΟΛΩΝ ΛΑΒΕ

Greg
gregjc9 is offline  
Old February 11, 2011, 11:18 AM   #2
GWS
Senior Member
 
Join Date: September 8, 2010
Location: New Mexico
Posts: 688
I pretty much went through the same thing with my Remington/DPMS .308 AR clone. First I tried the RCBS product, then the Hornady product.

My conclusion was this:

1. The magazine on an AR was the limiting factor as far as settling an OAL to go with. Getting it anywhere near the lands was impossible, and still feed out of the magazine. Therefore neither tool is that helpful for OAL, except to verify that you aren't going to have a round reloaded too long for the chamber. The Hornady tool is easiest to use and reliable for that.

2. The RCBS mic works very well to determine and execute the proper shoulder bump achieved with your sizer. But even that is a different need than say a bolt action. For example: In my gun, using a regular RCBS sizer, the shoulder could be bumped, but the base was not sized small enough to cycle trouble free.

Two possible fixes: 1. grind the base of the sizer enough to push the case in far enough until it chambers easily. Problem with that is if you do that you bump the shoulder even more....that means it'll work, but you work the brass too much as the shoulder is forced back and forth. Not great for case longevity.

Fix #2: Just use RCBS's small base sizer, setting it using the RCBS mic to bump the shoulder back .002 further than the chamber....for that the RCBS tool is excellent. The small base die has been accused of over-working the brass. It's minuscule compared with fix #1.

P.S. RCBS states in the instructions that that tool isn't for semi-autos. And they are right for the OAL side for sure.

Last edited by GWS; February 11, 2011 at 11:24 AM.
GWS is offline  
Old February 11, 2011, 11:28 AM   #3
mehavey
Senior Member
 
Join Date: June 17, 2010
Location: Virginia
Posts: 6,869
Quote:
Therefore neither tool is that helpful for OAL, except to verify that you aren't going to have a round reloaded too long for the chamber.
Double check that, however, when going from bullet to bullet due to shape changes. My 77SMK at magazine length is 20-thou off the lands. A 52SMK, however is 15-thou into the lands at that same magazine length. The Hornaday OAL tool is the most reliable way to determine that relationship.

Quote:
ordered an RCBS PM ...To help ensure I was sizing correctly,
The RCBS PM is very good for that operation as it will tell you precisely how much shoulder bump you're imparting. How much you need is another story altogther. If you are lucky, a fired case won't go back without some interference (no extractor/no ejector) and you can then gradually adjust the sizer 0.002" past "just fit" and lock it down.

Last edited by mehavey; February 11, 2011 at 06:37 PM.
mehavey is offline  
Old February 11, 2011, 12:12 PM   #4
Jim243
Senior Member
 
Join Date: January 5, 2009
Location: Just off Route 66
Posts: 5,067
I use the Honady LNL curved gauge and 223 case, works out well and is simple to use.

Jim
__________________
Si vis pacem, para bellum
Jim243 is offline  
Old February 11, 2011, 12:24 PM   #5
Jim243
Senior Member
 
Join Date: January 5, 2009
Location: Just off Route 66
Posts: 5,067
CWS,

I use the RCBS X-Small base FL resizing die in 223 for all my cases and works out well. Also use the LE Wilson case length gauge to make sure the die is set to get the right bump on the shoulder and headspace.




Jim
__________________
Si vis pacem, para bellum
Jim243 is offline  
Old February 11, 2011, 06:27 PM   #6
GWS
Senior Member
 
Join Date: September 8, 2010
Location: New Mexico
Posts: 688
Quote:
If you are lucky, a fired case won't go back without some interference (no extractor/no ejector) and you can then gradually adjust the sizer 0.002" past "just fit" and lock it down.
Speer actually recommends (as per their manual) .004" for autoloaders. Not sure why the extra .002", but probably to make up for the powder residue inside a typical AR chamber after shooting 20 or so, due to the direct gas blowback design.
GWS is offline  
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:22 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2021 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Page generated in 0.04502 seconds with 10 queries