Ogive Question

[Thumb]

I went to the range today and was shooting at the 600 yard range and got some really good results using Nosler 77gr HPBT Match ammo. So in trying to duplicate everything I measured the ogive of the Nosler ammo which was 1.866" and then the ogive of my AR-15 rifle and got 1.962". That I believe is telling me that I have roughly .096" of space to the rifling. That sounds a little to close but then I'm no expert. The only thing that might be in error is that I have no idea what bullet Nolser is using and it may be different than the bullet I'm using to measure the ogive in the rifle which is a Sierra 77gr HPBT bullet.

Any comments or suggestions would be appreciated since I just started loading rifle ammo and am learning as I go.

 

[pacificman]

In AR-15 seems you would have to make sure all your ammo would fit the magazine. I would try both bullets but you would probably still have to adjust seating depth differently with each bullet as length and ogive of each bullet would probably still be a slight difference. I think you would always have a bit of a jump to the lands because of magazine limitations. I would try loading the Sierra to just fit the magazine and close to the same C.O.L. of the Nosler ammo and see what they do down range then play with depth from there. Just an idea.

 

[Thumb]

That's what I was thinking but wanted some input on it to make sure I was thinking right. I'm sure that I'll have to play with the powder also and start out at the low end and work up.

 

[pacificman]

I believe the newer loading manuals (Hornady ,Sierra for sure) have starting loads for the AR type rifles. These reloading manuals are the best reference for all of us that reload as you definitely want to start low and work up to see what your rifle likes. I wouldn't be too concerned with the seating depth until you find a good bullet powder combo as again you are limited by the magazine length. Hope ya find a good load for your rifle!

 

[BoydAllen]

I understand your post, but would point out one thing for future reference, no rifle has an ogive. I believe that you probably used a tool to determine the loaded length of a round that touched the rifling, as measured off of a bullet's ogive. In any case, I do think that it is interesting that your rifle performs well with that much bullet jump. I believe that that is useful information for anyone who is worried about the difference between their chamber and what magazine length will allow.

 

[stool]

he does not say, but typical 600yd shooting is single loaded..so mag length is not an issue.
again , not enough info in the original post.

 

[Thumb]

Yes, I didn't know what they call it, maybe chamber length to the lands? I am using a magazine so I am limited in COAL.

How I determined the "Chamber/Land" length was by using the Horandy gauge with a special 223 case. Put a bullet into the case and then insert the tool with the case into the chamber and then push the bullet in until it lightly touches the land, then lock the rod down and pull the tool out with the bullet. Then measure the ogive and that gives you the max measurement. At least that's what I think I'm doing. Then I measured the Nosler 77gr rounds ogive and that gave me the distance from the lands.

Forgive me if I'm naming things wrong, I'm just starting out on rifle reloading so I may be confused. ;D

 

[BoydAllen]

With a fine attitude such as yours, you will learn fast. As it is, I think that you are showing great aptitude.

 

[Turbulent Turtle]

Edited to remove crap written during an Oracle trigger debugging session. Bad timing.



The ogive (a French word) is the name of the bullet section that starts at the meplat (the tip of the bullet) and goes to where maximum diameter, or bearing surface, begins. Essentially the bullet nose. The bearing surface is the area of maximum diameter from the ogive to the boat tail or the base of the bullet, if it's a flat base.

Talk about being a pedant. :grin:

 

[Turbulent Turtle]

Here's a hair, start splitting.

8)

Or as the pin said to the oncoming bowling ball, spare me.

;D

 

[jonbearman]

Pedantic,one of my favorite words to use describing handloaders, me included.It is a badge of knowledge.

 

[BoydAllen]

If the OP can manage to pull a bullet from one of his factory rounds without damaging it (inertial puller), he can use it with his Hornady tool, and come up with a relatively accurate bullet jump measurement.

 

[Thumb]

Yes, I was thinking about pulling one of the bullets out of the Nosler's and using it because the bullet I'm using is a Sierra bullet and I do not think it's the same.

What gets me is that in most of the load data books they say to trim the case to 1.750 but if you measure the Nosler case before it's spent, it is 1.737 to 1.740 in case length and I believe most other brands are the same.

Anyway, I'll pull a bullet tonight from one of the Nosler's and use it to get the correct measurements and then report back.

 

[Thumb]

I was thinking the same thing and I just ordered some Nosler 77gr bullets.

 

[Turbulent Turtle]

I believe you mean pedantic. It's Italian in origin: 1580–90; < Italian pedante teacher, pedant; apparently akin to pedagogue .

In any event, I don't think he was reporting COAL; 1.866" is a little short to be a COAL when the case itself is ~1.750". His COAL should something greater than ~2.150" with that bullet.

Thank goodness there are people like you in this forum who will quickly point out the errors committed by people like me.

Yesterday was a difficult day as I was locked into a day-long argumentative phone session debugging a customer inflicted Oracle trigger that was tripping on a constraint. The insufferable twerpish Brit at the other end of the line simply could not fathom the difference between a unique constraint and a foreign constraint and I was slowly losing my temper. After a while, I just decided to go into "dictation mode" and simply reel off the differences using the Oracle documentation, word for word. His brilliant reply was to simply call me "pedant," for making that fine distinction. Yes, I know, it didn't really apply but I had had enough.

So while he was preparing and then conducting the test with the now fixed trigger, I decided to take a break and come to my favorite site to calm down, and of course missed a great opportunity to avoid a mistake as I conflated various concepts in the same paragraph. I posted and got back on the phone to get the final results. A little while later, I saw the reply and posted some quick exasperated reply.

Then I decided it was time to call it a day and slip into a gin and bitter lemon, made with the best gin on the planet, Citadele. After the first sip, I realized that my original post was simply a mixture of crap and worse. Using my Note 3, I removed the bad information and returned to my gin and bitter lemon, making a mental note to return here in the morning and thank gstaylorg for catching that mistake.