Case Trimming Questions

[Spike A]

I am just curious on if most of you use the suggested trim lengths, or what your process is for determining your trim lengths. Also how often do you end up actually trimming cases? I have always went from the book suggested max and trim lengths, but i just got my first aftermarket barrel and now am wondering if there is a different process for which i should be doing this to help with brass life?

 

[Nude nut]

My advice stick with the K.I.S.S method nothing wrong with sticking with sammi case length some like a little more neck length.
You can buy a chamber length gauge plug from sinclairs, brownells or whoever sells them if you wish you will need to size the neck down on a case a little so the plug has a snug fit then cut some of the neck off to allow plug to slide into case when chambering case then measure form case base and plug will give chamber length.
Some trim 20 thou 15 thou 10 thou less than overall length but beware if you dont leave enough room for pressure spikes you will have a projectile stuck in the neck and get yourself injured or worse.
At the least you will have to keep extra attention to your case length which would probably mean trimming everytime hope this helps with your question.

Cheers Trev.

 

[fguffey]

I have always went from the book suggested max and trim lengths,

There is a lot of that, to do otherwise would require thinking. Again, I have a long chamber, it is not my fault, I did not build the rifle and there are many rifles of the same model that share the perceived problem. The chamber from the shoulder to the bolt face is .016” longer than a minimum length full length sized case when measured from the shoulder of the case to the case head.


The book suggests trimming the length of the case from the end of the neck to the case head to 2.494”. I could totally disregard the long chamber and follow the instructions. And then it gets complicated for most; mo0st case trimmers are designed to trim the length of the case from the mouth of the case to the case head, others are designed to set up on the shoulder of the case with total disregard for the length of the case from the shoulder to the case head. I want to cover the chamber with the case, for that reason when trimming cases for that chamber I add .014” to the length of the case. I do not want to add the .014” to the length of the neck, I want to add the .014” to the length of the case body from, the shoulder to the case head.


Trimming cases for that chamber to 2.494” would be mindless.


F. Guffey

 

[Spike A]

Sounds like it might be better to just keep doing things the way I have been and go with sammi specs ? I mean will I really gain much by changing ?

 

[ireload2]

If your chamber is longer than your case with cast bullets, the bullet metal will often expand into the gap leaving lead shavings stuck to the case mouth. With jacketed bullets you do not see that issue.

I like to measure the chamber and make the brass fit the chamber length. If the brass is shorter than the chamber from the factory I avoid trimming as much as I can until the brass either gets too long for the chamber or the brass gets uneven lengths from firing and sizing. It can also get uneven across the mouth of a single case. When I find uneven cases I try to do a minimum clean up on the longest offenders. That might be 10% or it might be 50% but I rarely trim 100% of my cases at the same time.

Sounds like it might be better to just keep doing things the way I have been and go with sammi specs ? I mean will I really gain much by changing ?

 

[DHD]

I use the plugs from Sinclair Intl. They aren't expensive and you will "know" what your max OAL case length is. I modify a case per caliber and keep it for the next barrel. FWIW, I trim my cases for my specific chamber length. In other words, I trim .010" short of the number I get from the modified case and plug. I write this number down along with headspace and jam on specific bullets I may use for that barrel.

 

[NorCalMikie]

Most chambers are about .020 longer then the suggested trim length. Get the plugs from Sinclair, measure your chamber, write it down, refer to that measurement before you do any trimming. Depends a lot on which type of die you use as to how often you need to trim. Shoulder bump dies don't let the brass grow that much. I have BR brass that's been resized 25+ times and still doesn't need trimming. YMMV.

 

[Preacher]

The new Lyman bore cam will let you know where it is..
So will the Hawkeye..
If you don't have either, use the Sinclair plugs..

 

[Shaggy357]

Multiple schools of thought on this subject. Many apply in their own variant with the person and cartridge being discussed. I make a lot of "wildcat" brass from parent cases. 223s make several of the TCU family, 221 fireball, 300 Whisper, etc. 30-30 makes the Herrett Wildcats, the Ultimate Silhouette cases, Donaldson Wasp, etc. When I make the initial brass for each of these wildcats I make sure they are all made to the same length. After their initial "fireforming" in the chamber of my gun, I trim them again to ensure they are the same exact length. In these situations, that length seems to have most effect on working up consistent handloads.

I shoot a lot of straight wall handgun cartridges. I have put 1000s of 357s down range without ever trimming a brass. Often times a ring of brass would come out of the crimp die with the loaded round. Didn't make a difference to me.....then things got real....mediocre was no long acceptable to me. Yes, I was a good shot, I had decent scores, but then I shot against the best. What differences were there between me and the best? Quite a few really, but one of the main difference, was their consistency in shot to shot accuracy. I didn't think there was a lot to it until I trimmed some Starline 41 Mag brass for the first time. I was astonished at the difference in length and how much easier they loaded after being trimmed to same length. A few thousandths of an inch did not seem important until that crimp die was adjusted properly and perfectly sealed that bullet in place. Made a huge difference in how that revolver load worked for me after that. I have been trimming my straight wall pistol cases for competition ever since.

I have a lot of hunting rifles and they suit me well out to about 300 yards. Many have fired ammo reloaded 5+ times without the brass ever being trimmed. They neck size fine, shoot in the same gun, and keep that minute of squirrel head all day so why spend the extra time? I have a couple that I like for long range. The brass on them gets checked after sizing every time the box is headed for the reloader.

So, I have typed a lot of words, about trimming and the only mention of length had to do with being "the same". The loading books and SAAMI Specs are reference resources. Your gun, dies, press, brass, bullets, etc dictate if you trim, and the length you trim. I have one old 30-30 that I load for that has necks quite a bit shorter than normal. Trim length is to crimp perfect in the cannelure on the bullet that gun likes. She'll shoot into one hole at 100 yards if I do my part, and seating that bullet exactly the same in every RP case is my part in that particular gun.

Your choice on how much time you invest in getting the accuracy out of your gun and ammo.