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CVC
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In the manuals it list the trim to length for the brass. Why is this important? As a novice it would seem that the overall length would be the important length, but obviously it is not the only important length.

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Brass expands (lengthens) with use, especially with hot loads. Over time, the cases may become hard to chamber and cause dangerously high pressures.
Perodic checks on case length with a maximum case length gage will tell you if cases need trimmed. I like the Foster case trimmer for trimming cases,

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Depending on what you are using for cases, sometimes you can avoid the case length issue.30.06 cases can be used for 270 reloads, are shorter in length, so trimming is not an issue. Saves a lot of time too.
What cal are you reloading ?

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30.06 and .243

The manual lists a maximum case length and a trim to length? If the case is less than max, but greater than trim to length do you need to trim?

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Anywhere between the two measurements should be fine.Semi autos can be a little fussy at times, but trimming to length fixes problem.
Difference in Trim Length and Maximum Length is almost always .010 " so there is a lot to play with if you want to try different lengths.
And it is safe. I don't usually like using the words "PLAY WITH" in The Reloading Section but not a problem with case trimming

Big smile 243 & The 06 Big smile great choices Thumbs up

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unfortunately with rifle rounds, especially high pressure cartidges the brass will grow with each firing and resize. Always trim the case to the specified trim length or you may end up with the brass unintensionally crimping your bullet when you chamber it, causing high pressure when you fire. As Hammer1 said it is always .010 inches less than max.

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Most important is max case length, don't exceed that. What happens is that the case length has grown to where the mouth of the case actually intrudes into the barrel. As a result, the mouth is crimped down a bit and pressure is raised because it take more to drive the bullet out of a mouth that hasn't expanded.

After trimming the case back to min case length, be sure and champher the inside and outside of the mouth. That will bevel it just a bit and help get the bullet started seating it. Don't champher to much. If you take to much it'll sharpen the mouth and you'll lose case life due to splitting the necks.

A big cause of case streach is pulling the neck back down over the expander button in the sizing die. I use Hornady one shot case lube and spray inside the neck of each case. Spray in at about a 45 degree angle. I used to use STP and I put it in with a Q-tip with a small amount of it on but, you have to clean it out after re-sizing, oil is not a good friend of primers. It was the best I ever used. I also spray One Shot inside the die body every 20 rds too.

Probally the easiest way to keep the cases the right length is the Lee trim tool. I haven't used one but I understand that it's a pin on the end of a specific cal rod that you insert into the case. The pin enters the flash hole and the rod fits the re-sized case neck. There's a knob the rod goes into that is a cutter on one end and smooth ont the other. Only drawnack, if it is, is you have to order one for each cartridge. The rod is a specific length for each.

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I learned the hard way about case triming when I was a novice reloader. Loaded up 40 rounds of 264 Win Mag's and about 75% of them would not chamber. Bolt would only go half way down when you tried to lock it. I had to pull a lot of lead and resize the casings and then reload them again with new lead.

One thing that has not been mentioned here is you trim the casings after you resize them. Some of the casing growth happens during the resizing process. I have also learned that you need to ensure the casings go all the way into the resizing die. I reload both the 264 and 7MM and they are vertually the same case except the case mouth. (264 = 6.5 MM) If you do not get them all the way into the die some may not chamber even though the case lenght is at the case trim length.

Took a long time to figure that one out. I had shells within tolerance, but they would chamber hard, the bold scraped the bottom of the case and brass shavings were always on the bolt face. A gun smith finally got me looking in the right direction when he told me that the casing belt had over expanded. I started looking hard at my process and when I thought I had run the case all the way up into the resizing die I put a flash light beind the die and sure enough, there was a sliver of light between the die and the shell holder. When I closed that gap, the casings loaded as smooth as ever. (Devil is in the details)

Lightly deburing the inside and outside of the case mouth to ensure a smooth bullet seating is also good advice.

Good luck to all HMG

SJ
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The Lyman Universal Trimmer is really nice and comes with about every pilot you'll need. Once you get one casing trimmed in each caliber you plan on reloading to the recommended trim length mark it as a pattern so when you change the settings on your trimmer to do other calibers when you go back to that caliber you can set the trimmer back to the pattern case.

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Hitmgood wrote:
I learned the hard way about case triming when I was a novice reloader. Loaded up 40 rounds of 264 Win Mag's and about 75% of them would not chamber. Bolt would only go half way down when you tried to lock it. I had to pull a lot of lead and resize the casings and then reload them again with new lead.

One thing that has not been mentioned here is you trim the casings after you resize them. Some of the casing growth happens during the resizing process. I have also learned that you need to ensure the casings go all the way into the resizing die. I reload both the 264 and 7MM and they are vertually the same case except the case mouth. (264 = 6.5 MM) If you do not get them all the way into the die some may not chamber even though the case lenght is at the case trim length.

Took a long time to figure that one out. I had shells within tolerance, but they would chamber hard, the bold scraped the bottom of the case and brass shavings were always on the bolt face. A gun smith finally got me looking in the right direction when he told me that the casing belt had over expanded. I started looking hard at my process and when I thought I had run the case all the way up into the resizing die I put a flash light beind the die and sure enough, there was a sliver of light between the die and the shell holder. When I closed that gap, the casings loaded as smooth as ever. (Devil is in the details)

Lightly deburing the inside and outside of the case mouth to ensure a smooth bullet seating is also good advice.

Good luck to all HMG

Some lesson's are hard learned aren't they. Sounds like a couple things happened with that 264. First it sounds like you might have been partial re-sizing and rather than the neck going into the throat, the case had actually expanded to where the shoulder wouldn't allow it in. The neck would have to be very long to do that and you mentioned that you pulled the bullet's and re-sized the cases. Actually with the belted magnums, you can partial re-size and make the case better fit the chamber. The advantage is that you eliminate a lot of case streach. With the cases headspacing on the belt, the case is sloppy in the chamber. You'll notice after several normal loads a bright ring form just in front of the belt. What happens is everytime you full length re-size the shoulder get's pushed way back. On the next firing, the case re-expands to fill the chamber. The bright ring that forms is a thin spot in the case and is looking to split right there. By re-adjusting to die a bit, you actually take out a lot of the slop in the chamber so the streach is greatly eliminated. Nobody in including the invernors know why the belt was put on those cartridges.

As for the brass rubbed on the bolt face, that is one super pressure sign if in fact the belt had expanded that much. When you test a new load, there should be no measureable increase in the belt. Of course if what was happening was that you were partial re-sizing, it's possible that the shoulder didn't have enought clearence. That will be indicated by your first problem. If you had looked on the bolt face then, you'd likely have found brass. Not from pressure necessairly, but lack of clearence between the case shoulder and the chamber. That seem's likely as you said you pulled the bullets and re-sized the cases. Seems that then they worked.

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I have been loading 7MM shells for over 25 years and have never had to trim a case yet.

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