Well last night was my first time for reloading and I am still trying to figure everything out. So last night I checked 40 or so fired cases from my 700 SPS Tac 308 and the necks all measured around .343-.344. Well I pulled my new Lapua brass out and before neck turning it was .334-.335. After neck turning and seating a Sierra 168gr TMK it measured .334. So I ordered a .331 .332 and .333 neck bushing for tension adjusting. Now after that little back story my question is if my case necks loaded measure .334 but my chamber is .343 to .344 is this okay or how do I fix this to get it closer? Any help is appreciated.
Case Neck Measuring
- Thread starter Ignotbullet
- Start date
Assuming reasonably accurate measurement, you’ve a cavernous factory done SAAMI chamber and at least .009” to .010” case neck to chamber wall clearance with your neck turned Lapua brass. There’s nutin you can do other than do not turn necks or to turn off no more than necessary to equalize unequal wall thickness or have that barrel set-back and re-chambered using a more suited reamer or use that better suited reamer to cut the chamber into a new “real” barrel.
Ya might wanna buy an intermediate size neck bushing(s) and step down the size of the necks. If you decide to not neck turn then case body to loaded bullet concentricity may well be improved by sizing down the necks just enough more so that dragging them back over an expander ball will shove any wall thickness disparity back to the outside where you’ve a plenty room to spare.
Ya might wanna buy an intermediate size neck bushing(s) and step down the size of the necks. If you decide to not neck turn then case body to loaded bullet concentricity may well be improved by sizing down the necks just enough more so that dragging them back over an expander ball will shove any wall thickness disparity back to the outside where you’ve a plenty room to spare.
Even with no neck turn it's still a big jump. I guess new barrel time
Brians356
Silver $$ Contributor
How does the gun shoot? The generous chamber neck dimension will only increase work hardening of brass when you resize, but shouldn't affect accuracy.
Unless you rechamber, you're stuck with it. But if you periodically anneal the cases, you might expect normal case life.
Unless you rechamber, you're stuck with it. But if you periodically anneal the cases, you might expect normal case life.
I have run into what you have on several occasions. I unscrew the barrel, cut off the threads. Rethread it and rechamber with a min dimension reamer. You will need to make a decision of whether you want to continue with that brass.
I have a reamer with a .336 neck, LC Match won't even start in. If your are going to keep shooting Lapua measure the base of the case .200" up from rim.
I suspect it will be .465 or .468. If it is .465 get a reamer with .467 base dimension. If it measures .468 get a .469 base on the reamer. Have the rifle headspaced to snug on a GO Gage. You will have brass that will last much longer.
A .339 neck will just allow M118 to close.
Humpy Gage: Get a section of 30 cal barrel 1" long. Run reamer in till 1/4" of shoulder is inside. Turn it around and trim the front till you are about .015" from the end of the neck.
Try every round you load in this gage and you will never have a pressure problem.
I have a reamer with a .336 neck, LC Match won't even start in. If your are going to keep shooting Lapua measure the base of the case .200" up from rim.
I suspect it will be .465 or .468. If it is .465 get a reamer with .467 base dimension. If it measures .468 get a .469 base on the reamer. Have the rifle headspaced to snug on a GO Gage. You will have brass that will last much longer.
A .339 neck will just allow M118 to close.
Humpy Gage: Get a section of 30 cal barrel 1" long. Run reamer in till 1/4" of shoulder is inside. Turn it around and trim the front till you are about .015" from the end of the neck.
Try every round you load in this gage and you will never have a pressure problem.
I too have a cavernous win 308 chamber. I bought a tube mike to see what I was doing to the necks with the Forester FL sizing die. My fire-formed neck id is around .313. After sizing without the expander ball it is .298. After dragging the expander ball thru it is .3065. That's really working the brass. Now I anneal every time, not for greater brass life, but to get the smaller groups that show up on the targets. I get 40 plus reloads before I toss the brass for neck fatigue, loose primer pockets, or body wall variation over .005. You would be surprised what works.
If I understand what you are saying: The fired neck sizes are .343-.344 and your saying this is the chamber neck diameter. Not so the brass expands to fill the chamber when fired then springs back a little. The chamber neck diameter should be larger than .344". I am not going to lookup the SAAMI drawing dimension. If the neck measures .334 with a loaded bullet you have the following.
.334 - .308 / 2 = 0.013" neck thickness. I don't see any problem.
Dusty Stevens
Shiner
Dont let that big neck scare you. The necks only expand so far. May not be ideal but i doubt youll ever see a difference.
Get yourself a .338" bushing and size in two steps , run em throught the .338" first and then do your final bumpsize with the .331 , .332 or .333" .
Lots of clearance is a good thing with respect to it not affecting the tune.. It is harder on the brass but can be overcome by sizing in two steps as others have mentioned..
Shooting a .30 cal with only .002" clearance has worked for many but you'd better be sure everything is concentric or you start to run into problems that are hard to diagnose when all that is needed was for the clearance to be opened up to .005"
Good luck , let us know how you make out.
Lots of clearance is a good thing with respect to it not affecting the tune.. It is harder on the brass but can be overcome by sizing in two steps as others have mentioned..
Shooting a .30 cal with only .002" clearance has worked for many but you'd better be sure everything is concentric or you start to run into problems that are hard to diagnose when all that is needed was for the clearance to be opened up to .005"
Good luck , let us know how you make out.
OP, my 2011 fullbore chamber is the same. I 2 step resize just like posted above. It's fine. Don't worry about your set up.
Thank you for all the responses! very informative! I took the gun to the range and with 168Gr TMK I got a low of .204 size group to .510 at 100yards 5 shot groups. When taking it out to 300 yards the gun shot just below 1.5in. I was using 47.3 GR of 2000MR coming out of the barrel around 2650fps. So far I am very happy and might just leave it alone. Oh and the wind was 15 to 20mph at 300.
I suggest measure before and again after. I understand; there is a commercial trap when reloading. Not every question should be answered with purchasing something else.
F. Guffey
A builder of bench rest type rifles called to inform me he sold one of his rifles to someone that accused him of building rifles with loose necked chambers. I asked about accuracy, I wanted to know if the accuracy was up to standard or if the loose? neck was causing problems. Accuracy was not suffering so I agreed to tighten the necks.
F. Guffey
Classic example of reading too much. No disrespect to the OP what so ever as I have been guilty of the same over and over. Its easy to get all tied up around the axle based off what you read about making good quality ammo. Most times we are not shooting Bench Rest...
Good Question though.. I bet it helped a few folks beside yourself.
Sounds like you got a pretty good shooter.
Russel
Good Question though.. I bet it helped a few folks beside yourself.
Sounds like you got a pretty good shooter.
Russel
dmoran
Donovan Moran
Dusty Stevens
Shiner
But every question should be answered with shadowy responses and riddles
BoydAllen
Gold $$ Contributor
I am going to give you some advice that some will deem to be unconventional. With your chamber, and Lapua brass, don't turn. Also, when necks need to be sized down as much as your chamber requires bushings are not going to give you your best result. As an alternative, I suggest that you start using a Lee collet die as your first sizing step, and then take the bushing out of your FL die and use it as a body die, taking care to set it properly for shoulder bump. A precautionary note on the collet die...you should read the instructions carefully and take it apart (and reassemble it) before using it, so that you will understand how it works. Also, with that die, neck tension is increased by using a smaller mandrel, not by setting the die to toggle harder. I have gotten a lot of very favorable feedback on this method of loading, so I can recommend it with confidence for situations like yours. If you have any questions you can PM me.
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