Hornady OAL Gauge, what good is it for AR-15?

[Mike in CT]

So I continue to work my way towards a 'go to' load for my AR.

I picked up the Hornady OAL gauge and bullet comparator to see if I can gain any accuracy with these tools and measurements.

So my OAL from base of case to bullet hitting lands is 2.299. When I measure my OAL (case base to bullet tip) with that same set up it is 2.305 base to tip.

Since I am limited to a 2.260 max with the AR Magazines, what have I gained?

If I drop my OAL down to say 2.50 or even 2.55 I am still looking at a 'jump' to the lands of .050 or .055.

This seems to be much more than desired.

Granted I am getting sub 2" groups at 100 yards with my 1x4 scope, can I gain anything with the OAL gauge or bullet comparator or did I just blow some cash?

I should add that in order to have my resized cases fit the Lyman case gauge I am having to bottom out the die and even cam over a bit. with that set up 9 out of 10 cases will drop right into the gauge, the other 1 might need a slight finger push to slip all the way in the gauge. Test firing shows no problems with fit for any cases. (RCBS small base FL sizer, and Dillon RT trimmer FL sizer).

Thanks

Mike

Edited April 9, 2012 by Mike in CT

[Doc Hunter]

Its a tool. It gives you information and some numbers to work with. You have to know what those numbers mean and if changing them matters to you. Knowledge is power. By the way, oal is not what you need to be measuring. Measure to the bullet ogive. That's what you want to know. And yes you can change it dramatically with a different bullet profile. Its bullet jump you are measuring. OAL may/will not change but jump will. Some bullets are "mag length" bullets they will take the jump better loaded for the mag. Other styles need to be single loaded long to work well - VLDs for example.

Edited April 10, 2012 by Doc Hunter

[jkrispies]

Some folks shoot precision rifle events with AR's (I think it's called NRA High Powered Service Rifle... or something like that...) and use two different bullets depending on the distance. For closer ranges that require the shots to be fired faster they'll use bullets loaded to magazine length. For longer range slow fire shots (600 yards, etc.) they'll go with heavier 80+ grain bullets that are OAL'ed to the lands (or just off) and load them one-by-one. These would be the VLD's previously mentioned. AR's are getting more and more popular with 1000 yard shooters, and those would definitely be heavier and loaded to the lands. For most of the shooters on this site, who only shoot out of the magazine, I would say that the OAL gauge is not very useful for an AR.

Edited April 10, 2012 by jkrispies

[Mike in CT]

Thanks for the both the replies. A different bullet profile makes sense and then they could be loaded to limit the 'jump' to the lands.

I will do some research on the VLD bullets mentioned. My club has targets out to 440 yards. My eyes and hands will likely be tested at that range so maybe I will not ever need to load 'match' bullets. It is fun to see how tight of groups I can shoot at 100 yards and I still have some practice to do as I am now just shooting sub 2" groups at 100 yards bench rest.

As always this is a great place to get info and learn more about the sport.

Mike

[jkrispies]

Make sure you check the twist rate in your barrel before you start playing with VLD's and match appropriately.

[Doc Hunter]

Mike if you are shooting to only 440yds, a VLD will likely be more trouble than its worth. I'd stick to something that comes in a green box - they shoot great for a reason.

[anachronism]

It suddenly struck me that there are different leade profiles in ARs, depending on who made the reamer, and the exact chamber design (.223, 5.56, Wylde, etc). With the myriad of bullet profile options, the length gauge could be really helpful in identifying throat length, perhaps not to set minimum bullet jump, but to keep things from getting too short.