Tight neck in my 6x284 . After firing new brass zero extraction problems. Upon 2nd firing with same load major extraction problems. Custom chamber I turn necks . With bullet neck diameter is .2745 after firing neck diameter is .274 ? Now I'm going to neck size in Redding type s bushing neck sizer . Bushing is .273 and trimmed cases to 2.160 .
Extraction problems
- Thread starter Worker
- Start date
Boyd Allen
Active member
Cut your necks so that the loaded round neck has .003 clearance in your chamber. Do the shanks of your seated bullets extend to where a doughnut might form? If they do, you may have an interference fit, in your chamber at the neck shoulder junction. Also, if your bullets' shanks are in the doughnut area, you can have your barrel's throat cut longer so that they do not.
Cleaning up the necks isn't good enough ?
The inside diameter of neck that I just fired measures .2405 the out side is .2745 so wall thickness is .034. I guess I need to buy a ball Micrometer,and turn necks down to .031 ? I just shot 6 rounds that I trimmed to 2.160 and were neck sized. Out of clean bbl it took 2 rounds to fowl and remaining 4 produced .272 at 100 yds. Load was 52grs of Retumbo behind Berger 105 Hybrid just touching the lands. Rounds 1 and 6 extracted hard but rounds 2-5 were fine ! Why ? No shinny ejector marks.
The inside diameter of neck that I just fired measures .2405 the out side is .2745 so wall thickness is .034. I guess I need to buy a ball Micrometer,and turn necks down to .031 ? I just shot 6 rounds that I trimmed to 2.160 and were neck sized. Out of clean bbl it took 2 rounds to fowl and remaining 4 produced .272 at 100 yds. Load was 52grs of Retumbo behind Berger 105 Hybrid just touching the lands. Rounds 1 and 6 extracted hard but rounds 2-5 were fine ! Why ? No shinny ejector marks.
Dusty Stevens
Hollow Point Dispenser
whats the trim length?
Boyd Allen
Active member
Worker, first of all we need a little math work. From your figures, your neck thickness should be calculated by taking half of the result of OD minus ID. Secondly, how are you measuring ID and OD, with what tools? If you want to get an accurate fix with a 1" mic. that reads to .0001, measure a bullet at its largest diameter, and then seat it in a sized neck. Then measure the OD of the loaded neck over the largest diameter of the bullet, then subtract the bullet diameter, and divide that by two. That is your neck thickness.
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Need another tool
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Digital caliper ,is all I have now. I 'll buy one of these .RCBS® Vernier Ball Micrometer at Cabela's
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Dave Tooley
Active member
Do you have a reamer print? Tell me about the rest of the chamber in particular the diameter .200" ahead of the case head.
Dave Tooley
Active member
If you don't have enough clearance between the case and the chamber this can happen because there isn't enough room for the brass to expand and then spring back. It just gets tighter with each firing.
Boyd Allen
Active member
Get yourself a regular 1" micrometer that reads to .0001 for making accurate OD measurements. Everyone who plays with close tolerance chambers needs one. I really think that there are a whole lot of shooters out there that do not realize that their calipers are simply not accurate enough for some critical measurements, not matter what the brand, or how many places they display to.
Additional Neck turning
Interesting, so additional neck turning might not fix the problem ? Could my gunsmith of used the wrong reamer ?He did tell me he prefers a tight chamber and to FL size my brass. What would be the fix ?
Interesting, so additional neck turning might not fix the problem ? Could my gunsmith of used the wrong reamer ?He did tell me he prefers a tight chamber and to FL size my brass. What would be the fix ?
Doughnut
There doesn't appear to be a " Doughnut " in the case neck. The bevel on the berger bullet is even with the base of the neck.
Butch Lambert
Active member
Dave, I don't think he gets it. I think Dave is talking about the body and not the neck. If you have a die that is a .002-.003 smaller than the reamer spec. at the base, it will eliminate this problem. You need to have accurate measuring equip. for anybody to help you.
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This has nothing to do with the neck
This has nothing to do with the neck!
This has nothing to do with the neck!!!!
Necks do not hang up in the chamber.
THE ONLY way the neck can factor in is if it's actually crimping down tightly on the bullets, thereby raising pressure. IF THIS HAPPENS you will definitely be seeing ejector marks. Tight cases, no ejector marks means hangup at the base, lissen to Tooley
This has nothing to do with the neck!
This has nothing to do with the neck!!!!
Necks do not hang up in the chamber.
THE ONLY way the neck can factor in is if it's actually crimping down tightly on the bullets, thereby raising pressure. IF THIS HAPPENS you will definitely be seeing ejector marks. Tight cases, no ejector marks means hangup at the base, lissen to Tooley
Dave Tooley
Active member
Butch I think your right but if the chamber doesn't have enough clearance to start with a small base die won't help.
Worker
If you don't have enough clearance in the chamber and neck for the brass to expand and spring back you will have problems. There is no sizing die that works when the chamber body is too tight. You can't size the brass smaller than it was when manufactured because at that point it has work hardened and has a memory.
Redding small base body die
Can some one provide a link to the specific measuring tool I need to purchase ? The neck isn't expanding in the neck area of chamber with or with out a bullet, its the same size before and after firing .2745. Ok worst case scenario is the fix having a gunsmith run a new reamer in existing chamber to open it up ? Also Redding makes a small base body die ,another shooter on 6mmBR said he had that same problem in his 6x284 and die solved the problem . Really appreciate time and effort for diagnosing problem.
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Bold above
Dave Tooley
Active member
Worker,
In regards to the neck. Take a fired piece of brass. A bullet should go in and out of the neck with no resistance. If it drags at all or it is a very very close fit your necks are too thick. In regards to the body if you had a 1" micrometer you could measure a virgin piece of brass just ahead of the extractor groove and compare that with a fired case and a sized case. If there is a problem with chamber dimensions that is how you diagnose it.
If your chamber is too tight have your smith polish out the chamber. I have reamers that just a tad too tight and do it frequently. It's no big deal if you know what you're doing.
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