Measuring Bullet Bearing Surface Problems

[HAZORD]

So, I just got a supply of Berger 308 diameter 215gr. Hybrids that I wanted to separate by bearing surface length to do some ELR with my 300WM. Some time back, I purchased the Sinclair 30 cal stainless steel inserts and holders to attach to a digital caliper as suggested in the ELR reloading Sticky, and I started sorting, just to find out that the two 308 inserts from Sinclair seem to have small differences in their inside diameters. One insert will allow almost half of the bullets to slip inside to what appears to be 1/8 inch or so past what would appear to be the tangent point between the ogive and the beginning of the bearing surface. The other insert appears to be slightly smaller inside diameter, but it will allow a few bullets to slip inside, but not as far. The bullets measure .308 OD, and I tried some Sierra 168 MK's with the same results. In addition to that, I have a Sinclair 30 Cal stainless steel bullet height measuring base, and the Bergers slide into it also, even further.

I'm not sure what Sinclair's quality control is on the ID measurements of their product, but I'm not very impressed for a tool that is supposed to be precise enough to detect a 308 diameter, and the consistency of multiple copies of that part.

So, I'm wondering about the following:

1. Are you guys that measure bearing surface seeing this same kind of thing, or did I just get a shitty batch of inserts?

2. Are you guys using smaller inserts, like 7mm to keep the bullets from slipping inside?

3. Or are you buying slightly undersize inserts like maybe .307 Diameter?

4. Maybe a guy has to buy 10 inserts to get two tight ones, and return the rest?

5. Does anyone have any better advice?

Thanks in advance.

 

[LR338nut]

Try the Hornady comparator Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Tools & Gauges :: Lock-N-Load Gauges-Formerly Stoney Point :: Bullet Comparators :: Bullet Comparator Kits

 

[KYpatriot]

I believe that the newer comparators from Sinclair were machined with lead angle just like the threads in a rifle barrel, and will measure a little differently than the straight 308 comparators because you can jam the bullet in the lands just like in the rifle. You need to have good consistent technique on the calipers.

Sinclair makes excellent products but everyone is going to have defects, so you won't know what you have without comparing it to something else. Did you measure the ID of each?

Going by eyeball it will be very difficult to gauge at what point you have full width on the bullet by eye...it will almost always be further down the bullet than you think.

To investigate, measure a bullet with both of your comparators on the calipers. Record this measurement ,and then reverse the position of the comparators, and measure the same bullet again. Try and use the same pressure when you "seat" the bullet in the comparators. If using good technique the measurements are off more than 2 or 3 thousandths something is suspect.

 

[HAZORD]

Guys,

Thanks for the advice. I spoke at length on the phone with both Brownells and Sinclair. I was told that they had a consistency problem with a batch of the inserts back around January, which was approximately the time I received mine. I was told they use a chamber reamer to cut the final ID on the gage inserts, but that the surfaces should be smooth. The surfaces on mine look really rough and when I mentioned that, they told me that the manufacturer wasn't properly cleaning the reamer and they were getting rough surfaces from the retained material on the reamer. They are sending me a set of gages to try out and asking for my observations on the inside surface finish and performance of the gages. So, we will see.

 

[zipollini]

I shoot both DTAC 115 and Lapua 105 Scenar-L in 6mm. With the DTACs I have to sort by weight to .1 grain and bearing surface. I use the Sinclair comparator. I tried some of the Scenar-L and the bullet to bullet as well as the lot to lot consistency was so incredible that my comparator is just collecting dust now. I don't even have to weigh sort. Here is the Lapua web page. Might want to try the 220s and save yourself some time and aggravation

Products - Lapua

 

[D_Lamz]

I'm having the same problem with my Sinclair comparators. Bullets would slide in and out with no consistency. I guess I should give them a call.

 

[HAZORD]

I received my new Sinclair comparators in the mail on Saturday, and they are 1000% better than the older ones that I have that were giving me fits. I mounted them on my Mitutoyo digital caliper and tried out some bullets.

No more sliding in and out inconsistently, and the two of them are so close in diameter that I can swap ends with the bullet and get almost the same length as the other direction. Considering the huge gentle radius where the ogive meets the bearing surface, and the tighter radius where the boat tail meets the bearing surface, this pair that I have now are very impressive to be able to pick up the tangent locations.

On another note, I'm also going to take zipollini's advice and try some 220 gr. Scenar-L bullets. Thanks zipollini!
[MENTION=12969]D_Lamz[/MENTION], thanks for seconding my frustrations with the older inserts.