RCBS PRecission Mic

[Yosemite Steve]

The adjustable bullet that comes with the mic is useless.

What is wrong with using it to find the lands?

[hounddawg]

What is wrong with using it to find the lands?

different bullets have different profiles. A bullet with a secant, one with a tangent, and one with a hybrid ogive will all have different lengths for the ogive to the base of the case

http://bulletin.accurateshooter.com/2007/07/283/

[Yosemite Steve]

Interesting. So ogive is not the same from one bullet to the next? I am curious to see what those differences are. I guess that feature was not designed so well. They could have made the test cartridge so that a bullet could be seated into it to test that specific bullet. My existing method of finding the lands is probably more efficient and reliable then.

[USSR]

Yes, the case-base-to-ogive feature on the RCBS Precision Mic is worthless. I use the Stoney Point (now Hornady) O.A.L. Guage for that function. Note: even the Sierra MatchKing bullets will have ogive variances of up to 0.010", since they come off of difference machines at the factory, so don't seat your bullets to an OAL of less than 0.010" for the best accuracy.

Don

[HiBC]

The difference between a RCBS Precision Mic and the Hornady device that clamps on a calipers is precision and consistency. That is not a knock on the Hornady. The Hornady is a practical,economical ,and useful tool.

The RCBS Precision Mic is just a different approach to doing the same job.

Another method is using a bushing gauge,the min/max step,and also measuring over the case in the gauge.
There are preferences and tradeoffs,but its good folks are measuring and controlling.

On the bullet seating feature,agreed that the absolute number may not directly mean too much,but if you simulate the bore dia at the leade with the hole that contacts the bullet,you have a reasonably useful tool to pick up where the ogive will contact the leade. Much more useful,you have a tool to measure an increment of change. "I want .005 deeper" You can measure it.

[Hunter Customs]

Cdoc42, what's the 6 calibers of the Precision Mic's that you have? Are they still for sale?

[Yosemite Steve]

So the difference between the ogive bullet that comes with the tool and the 180SST bullet touching the lands measured with the ogive mic is .113"! I had to check. I will use a 30-30 neck to make an attachment like I did for the shoulder for each bullet I reaload with to determine lands distances.

[cdoc42]

Hunter Customs, sure. I suspect this is the wrong place to engage in this type conversation, but let me just give an overview and you can e-mail me at [email protected] for details:

RCBS Mics: .22-250, 7mm Rem Mag, .270 Win, .223 Remington, .338 Win Mag (only 5 - my error)

RCBS full length die sets: .270 WSM, .17Rem (w/121 cases- 21 once fired; 101 25gr Hornady spire bullets, 7mm STW, .380 auto standard resizer die w/#10 shell holder; .222 Rem

[Hunter Customs]

cdoc42 Thanks but none of those listed will help me.

[30Cal]

Getting repeatable measurements with that dummy ctg that comes with it is extremely frustrating.

I ended up tossing their dummy cartridge and just used a sized case & real bullet. A bullet is short of the lands if it falls out of the chamber when you tip the muzzle up. So start with it seated it out very long, and stuff it into the chamber with your thumb. Seat it deeper in small increments until it drops clear. Then measure.

It's quick, repeatable, and doesn't require a stream of profanity. Plus the seating die is now set for zero jump and adjusting from there is a piece of cake.

[Reloadron]

Yosemite Steve:

So the difference between the ogive bullet that comes with the tool and the 180SST bullet touching the lands measured with the ogive mic is .113"! I had to check. I will use a 30-30 neck to make an attachment like I did for the shoulder for each bullet I reaload with to determine lands distances.

The problem is not all with the tool. The problem is as Don points out is with the bullets. When used correctly the tool will pretty accurately measure the distance from the breech face or breech block face to where the bore diameter is 0.30" in the case of a 30 caliber rifle. That distance is a hard number for your rifle. In the case of a .30 caliber bullet the bullet ogive is where the bullet has a .300" diameter. The problem is the guys making the bullets can't maintain perfect uniformity bullet to bullet and as Don points out, they can vary by 0.010' within a single box of the same bullet. If all the bullets in the box were the same and exactly like the drawing then the tool would work fine.

Discounting the ogive for a moment I have sitting here a box of Sierra 168 grain HPBT Match bullets. Measuring 5 random bullets here is what I get for overall bullet length. 1.219", 1.208", 1.210", 1.214" and 1.220". Now with the same 5 bullets in the same order we will measure bullet base to ogive, base of the bullet to the end of the 0.300" diameter. 0.581", 0.581", 0.588", 0.581" and 0.586". So while 3 of 5 were consistent at 0.581" we still had a few and one of five was 0.007" out from three of the others. This makes seating our bullets consistently a given distance off the lands, in the case of a .308 rifle with a .30 caliber bore diameter a little difficult. Since I don't have a drawing for a Sierra 30 caliber 168 grain HPBT Match bullet I have no clue what nominal numbers should be. I can say out of 5 random bullets I saw a spread of 0.007" in base to ogive measurement.

Ron

[Yosemite Steve]

My method has been to use a fired case with no primer and put a small dent in the neck with a bur facing the bullet so that it leaves a tiny scratch in the mark on the bullet up to where it stopped pushing in. I triple check and measure until it measures the same three times. I think that if I develop this tool to hold a bullet concentric it will be easier to use. I will make a slip on for each bullet I load and recheck the lands every 100 rounds.

[Yosemite Steve]

Ron, my 180 SST bullets have been seating to the same col within .001 95% of the time. My sierra vullets are all over the place.

[Reloadron]

Ron, my 180 SST bullets have been seating to the same col within .001 95% of the time. My sierra vullets are all over the place.

There you go. Finding good consistent bullets is like a Holy Grail thing. This is the sort of thing which can take someone who is OCD right over the edge.

Ron

[Yosemite Steve]

This is the sort of thing which can take someone who is OCD right over the edge.

It's bad. It really really is.

[hounddawg]

This is the sort of thing which can take someone who is OCD right over the edge.

it is easy to get lost in the weeds of this stuff. I got bit by the OCD bug last summer and the more I experimented the more I realized that the answer for me is finding to getting tight groups just meant finding the right powder and load and good basic case prep

This morning I found a .3 wide node for my .223 that produced consistent .3 and .4 groups with cheap GFL(Fiocchi) brass that is on its 5th reload and had no more case prep than the initial trim a quick chamfer on the inside of the neck, cleaned and a quick trip through the annealer. It was shot at SAAMI magazine length. To heck with chasing load lengths , I am just going to skip to load and shoot it.

[Yosemite Steve]

Hounddawg, I would but my Savage shoots big groups if I don't make em just so.

[Reloadron]

Hounddawg, that was pretty much my conclusion. My outdoor range is a place called Kelbly's Shooting Range where I have been shooting at least the last 25 years. The range is home to the annual Super Shoot in the bench rest community which is a pretty cool event. These are the 100 and 200 yard guys. While I am not a true bench rest type I get to meet some interesting people out there all of whom are quick and willing to share their thoughts, formulas and about anything accuracy related.

Heck, anymore beyond bullet, case and charge the biggest thing effecting my groups is my 68 year old body. My case prep is pretty basic also. Most of the tools and gauging I have are a result of having owned a small brick and mortar gun shop back in the early and mid 90s. When my wife and I sold the business the buyer could not afford most of our inventory. Reloading supplies was a niche so I ended up with a small mountain of stuff. Some we sold off at gun shows and the remainder I kept.

Ron

[hounddawg]

@Yosemete - all three of my rifles are Savages or at least that is what they started life as. 1 model 12 FTR and 1 model 10 FP and a pawn shop Stevens 200 with a cracked stock.

@ Reloadron - there is still a lot of things I learned that I still think makes a difference. Making sure primers are seated correctly and bullet runout come to mind. But a lot are just time wasters

[Yosemite Steve]

Since I got my gun 32 years ago everyone always told me how Savages are very accurate. It shot ok early on but never any better than about 2 MOA. Then it got bigger. I have not been reloading very long but getting this old gun to group tight now after all this time is very rewarding.

About 3 years ago I discovered the barrel was bumping the stock. I sanded it out and it warped again this fall when it got really wet hunting and I sanded it out again. I had it at about .75 MOA after I bought some Nosler brass.

After hunting season I came to this site with my poochy primers and the concave bolt face. Since that thread I have learned a lot! While I regret giving my money to the gunsmith I did it turned into a good learning experience. I know not which changes and details made how much difference in many instances. I know that since I got anal with brass preparations finding sweet spots became easier. But there were so many improvements in my ways that happened in a short time that it's really hard to know which ones mattered most.

I don't have much money to buy supplies so if it takes me longer to reload because I'm being a perfectionist that's ok. My last sweet spot was the biggest improvement over my other groups than any I have shot. It was the seating depth, powder charge, brass consistency, bullet consistency, action screw tension and probably less headspace and a new spring. I will continue to add improvements as I learn them. Some day I will get a gun that will appreciate these skills more noticeably.

[cw308]

Savage has that floating bolt face helps in bullet run-out. Once you have your case head space , I seat the unprimed case with the bullet I'm shooting , seat it long test in chamber bolt won't close the slowly lower until you feel a slight resistance , that's zero go another .001 bolt should close with no resistance. Keep your zero measurement so you can jump or jam your bullets. Even with a new lot of the same bullet you still have to test again. Hope I Helped .

Chris

[Yosemite Steve]

How does the floating bolt face help with bullet run-out. I'm not sure what you are talking about. I also do not trust the feel as much as a measurement i do strip down the bolt but using feel gives me +or- .001" for shoulder adjustments.

[hounddawg]

Lee collet neck die is a inexpensive fix for bullet runout. Even when I full length resize I will run them through a Lee before I seat bullets.

Not sure what a floating bolt head does for runout but it does make sure the bolt lines up perpendicular to the chamber so truing the bolt is unnecessary

[Yosemite Steve]

Not sure what a floating bolt head does for runout but it does make sure the bolt lines up perpendicular to the chamber so truing the bolt is unnecessary

On that thought. There is a bit of spring tension on the bolt head by the friction washer that might throw off how much the bullet is onto the lands. Also truing of the bolt might not be necessary but lug to receiver face lapping must be done precisely.

[hounddawg]

the Savage floating bolt head is designed to allow a few thousandths of an inch of movement using that belleville spring you mentioned. Lapping a Savage bolt head is unnecessary. The floating design allows for a perfect fit similar to a custom action or a trued Mauser or Remington