Small Ogive Comparator Don't Work

[CharlieNC]

Got my 6.5x47 a few months ago, but didn't have a .26 fixture for the Hornady comparator. The kit came with a .25 insert so I started using it to measure jamb length, and subsequently seating depth for the loads. Well the first batch of 200 shot great, but the second set using the same ogive spec gave rounds that won't even chamber due to the excess length! Strange because it's the same lot of bullets. I wouldn't have thought that the bullet length would vary so much due to the .01 difference in reference diameter to cause this much of a problem, but don't waste your time and try this shortcut. Lesson learned.

 

[Mike402]

Here's another wrinkle. I've been using the Hornady headspace gauges & bullet comparators for the last year regularly. I recently started getting weird measurements w/ my .308 rounds w/ respect to headspace. After a lot of headscratching & frustration, I finally figured out that the aluminum had worn slightly & was giving incorrect measurements. Solution was to replace all the Hornady aluminum headspace gauges & bullet comparators w/ Sinclair steel ones (that still fit the Hornady bodies)

 

[ducdodgers]

That is really strange that you having that problem. Especially from the same lot of bullets. I see no problem with using a smaller gauge as long as you use the same gauge every time you load that make of bullet it will give a consistent measurement.

BTW I think the gauges are .257 and .264, so there should be a .007 difference in the diameter between the 2 gauges, but I bet they just get them close at .25 and .26 like your saying.

If you still have any loaded rounds from your first batch that chambers, I would measure one of those and then compare it to the one that won't chamber. Unless there is really something seriously wrong with the gauge, like dented or worn heavily.


Then just go over your math again. I've been known to make errors on my math many of times, that's why I usually make a dummy round with a specific bullet make I use and keep it as my reference for later on down the road if need be. I keep it with a small paper with its specs and the bullet manufacturer and weight. (It has no powder or primer) That would also been a good place to note what bullet comparator gauge you used to measure with also.

I'm interested to know if you don't mind just going over you math again and if you has a round that was loaded earlier and checked its numbers.

I have the same gauges and I'll pull both sets out and measure 2 different rounds and see if they give consistent numbers, I don't see why they wouldn't though.

 

[CharlieNC]

Duc unfortunately I do not have any of the first rounds or a reference for comparision. Like you, with the same lot of bullets it is a bit confusing. The length for these is close at .005" off the lands. I have noticed that my old calipers are exhibiting a bit of "slop", so in addition to the proper .26 insert I have ordered a new caliper as well.

 

[ducdodgers]

Charlie,
If you dint keeping this updated, I would appreciate it. Especially with the new caliper and old insert.

Thanks

 

[CharlieNC]

WELL. The simplest answer makes the most sense; dirty throat. New rifle and the builder broke in with about 40 shots. I put 200 rounds (number of Laupa brass I bought) through without cleaning, so ran cleaning patch through the barrel with a little Hoppes and the bore cleaned up beautifully (Bartlein). Checking the jamb length again to compare the old 25 vs new 26 insert; measurements started short (explains the bullet jamb but why shorter) and they rapidly got longer. Ah-ha. Cleaned the throat with a few strokes of the brush with a little carbon cleaner and the rechecks gave the same jamb length as original. So while it doesn't look like the barrel needs cleaning this often, it's clear the throat needs attention too at that time.