30br neck clearance

S

skeetlee

Active member
I have asked about this a bit in different forms a couple times, but i am still unclear, if there is any one set neck clearance for the 30br that works better than most. My Bartlein 30br barrel is shooting real average at best. Big 2's low 3's. I have tried just about everything i know to do to get the groups down, and i feel confident that i am done with load development. Im thinking i have a average barrel or my brass needs something. Possibly another make of powder, but i cant find what i want. Im am using 4198 and my rifle likes the powder right around 33gr give or take a little. The brady knight 118 bullets are shooting the best. the long 10 ogive 118 bib are not shooting all that well. the bib 112 does ok. the Brady knight bullets have a 8 ogive i think? I am thinking i dont have enough neck clearance. My smith told me to take a fired case and see if i could drop a bullet back down the neck without any resistance. Well i cant. I dont know what else to try! Maybe my barrel is just average. I assume thats a real possibility. I dont ever get any big groups, but i dont ever get any small ones either. Big 2's low 3's is a common occurrence!! any ideas? I have another 30cal barrel on the way, so i will soon know if its the hole set up or the barrel. Thanks. I am heading out this am for a little more testing and i will report back this afternoon. Lee
 
Lee, how much neck clearance do you have now? You need to know that before doing anything else. With a micrometer, measure the neck diameter (with a seated bullet) across the pressure ring of the bullet. Also, measure the diameter of a fired neck....the actual chamber neck diameter will generally be .001 larger than a fired case..provided you have some clearance. Reamers have tolerances and things can happen. A .330 reamer that actually measures .329.... and you've turned necks for .0015 based on a .330 neck...and you'll have problems.

If neither of those two BIB's shoot better than big .2's and little .3's, there are other issues. If you have a decent amt. of jam, neck tension and no other component issues (like scope, bedding), round... but large... groups in these .30's are a classic sign of too little neck clearance or a ho-hum barrel. Ho-hum .30 cal barrels are rare, but possible. Insufficient neck clearance is more common than most think.

Don't be fooled by the ability to drop a bullet down a fired case neck as a sign of insufficient neck clearance, though. Depending on many factors, this may or may not be a true indication.

The bottom line is to find out where you are before moving forward.

Hope this helps. -Al
 
I set mine up with .002 clearance as a loaded round measured at the point of the gas ring.

As was said before, do not rely on other methods in an attempt to acsertain the clerance., use a good set of micrometers. .........jackie
 
Last edited:
Lee,
I had the same problem with my 30BRs’. I reworked my load, started with a load at 33.5 grs. of 4198, (118 gr. 8 ogive bullet) and worked up to 34.7 in .3grs. steps. I found that I had a small group at 33.5 and 34.4. Neck clearance of .002”. I used these weights and started with seating depth, when I completed my load test I found that both guns liked the high end load. My 100 yd. rifle grouped at about .075” and my 200yd gun was about .350”. Check the length of your brass, make them all the same. I do my load testing when there is no wind.
 
Well i had a better day with this barrel today. Last night i really paid close attention to my brass work and also trimmed to all the exact same lengths. I also used a smaller neck bushing a .323 instead of the .325 i had been using. My groups today were much better. I had a .095 .105 .264 .191 .291 and a 3 shot .040 . I figured out several rounds ago that the rifle likes the bullets about 10-15 off jull jam. My powder was were i thought it needed to be right around 33.0 to 33.5 grains 4198. I have been getting my best results with Brady knight 118gr 8 ogive (i think) bullets, so thats what i shot today. I also shot some 115gr Berger bullets, not to bad either. It seems the shorter jackets on these two bullets help with this 18 twist barrel??
I do have a micrometer but it only measures .000, i need one with a fourth decimal point. That brings up another thing i noticed. While measuring these two bullets that i used today compared to the bib bullets i had been using i noticed the pressure ring to be a tad bit smaller on the knight and Berger bullets, and that seems to shoot better in this barrel?? Again i am only measuring the best i can without having a fourth decimal point to know for sure. I cant help but wonder if the tighter neck bushing made the difference today? I would like to think so, but i really dont have enough evidence yet to know for sure. Anyway we made an improvement this morning and thats a good thing. Fellas i really enjoy talking shop with all of you i just hope i am not wearing out my welcome. I just really enjoy learning all there is to learn about short range benchrest. the 30br 6ppc and 22ppc are fantastic chamberings and i enjoy them all very much! I will try to shoot some more of these knight bullets but i am going to have to find some more, as i am out!! Bummer!! thanks Lee
 
Is there any way that you can get a print of that chamber?
Or do a chamber cast with cerrosafe ?

Good tools are a great investment that will last a long time.
Ask a few questions and buy a quality mike soon.

Glenn
 
You must log in or register to reply here.
Back
Top