length adjustment of the cases - Trimming

[BruniX]

Is there a probable number of réutilisation of cases before need to adjust in length ...?

When a cartridge is used, the case length increase progressively,
due to the force imposed by the pressure of the gases.

Can we imagine to know approximately the number of reutilization from which it is necessary to trim the case
so that it returns to the nominal length of the 45-70. ?

for the reloading experts, here present , this schema seems correct to you, for the dimensions indicated

cote 45-70.gif (10.81 KiB) Viewed 2550 times

Do you advocate this type of tool ?

Trimmer.jpg (15.73 KiB) Viewed 2548 times

...and to remove burrs, and also clean the primer wells
(lyman multi tool case prep)

lyman multi tool case prep.jpg (17.94 KiB) Viewed 2548 times

[BigAl52]

Straight wall cases dont stretch as much as bottleneck cases do. Both of those tools you have posted should do the job. You will also need a caliper to go along with your tools for measuring. I havent had to trim any 45-70 cases yet and Im almost betting that if one does get to that point of trimming that it may only be done one time. Al

[JEBar]

agree with Al .... once I've set our bullet seating die to where the edge of the case is in the crimp ring, I don't resize cases until they reach a point where the edge is outside of that ring .... if you purchase the trim tool shown in your link, find a case that is the correct link and save it .... use it if/when you need to test or reset the tool .... as Al mentioned, I don't find there to be as big of a need to trim straight wall cases as I have with bottle neck ones

[BruniX]

Good news !
less work and less money ...
thanks !

[Florida_Cracker]

For those who do trim straight wall pistol calibers - do you trim, then size or the other way around. I know most bottle neck cases get trimmed and then sized but I experimented with the reverse order and got much, much more reproducible results using Hornady CamLoc trimmer and Dillon 357 sizing/depriming die. Here were the steps I went through and the results using 10 Starline fired cases for each test.
Test 1.
1) Trim - average size 1.277"
2) Size - average size 1.284" (average gain 0.007" standard deviation = 0.002"

Test 2 - New batch of 10 fired cases (I adjusted trim length 0.003" between #1 and #3).
3) Sized - then trimmed - average length = 1.2742"
4) Re sized - average length = 1.2746" (average gain 0.0004" - standard deviation = 0.0007")
Note that the difference between #3 average and #4 average are less than than the marked divisions (0.001") on a quality Mitutoyo caliper.

Based on my results/data, I will be sizing before trimming. I'm curious if anyone else has experience or thoughts on this.
Florida Cracker

[Flinch]

I've seen rifle cases get shorter after being reloaded multiple times with some of them shrinking shorter than Trim Length, so I trim half way between Max. Length and Trim Length. I decap and resize rifle brass before trimming, because the brass usually gets longer during resizing. If you trim first, then resize, the brass won't be the same length.


I prep bottle neck rifle brass and straight wall brass the same way.

[bdbrown66]

If you are using a roll crimp, a consistent case length is a must. For my .45-70, I trim every time I load a case. And I do my trimming after I have resized the case, so all of the stretching is done.

[Pitchman1968]

I am kind of anal about case trimming, I know it is not necessary, but I trim every case I reload. Got into this practice 20 years ago when I acquired an M1 Garand. As you know, Garands are really tough on .30-06 brass especially at the case mouth. Prior to trimming each case, I would frequently buckle the case neck when seating the .308 bullet. The sequence is: I first f/l resize the case, clean out the primer pocket, trim the case, chamfour the case, and lastly, polish the case with 0000 steel wool. I use Lee equipment to include the drill chock resizing case holder. I careful to apply only slight pressure when holding the cutting tool against the case mouth. Finally, I measure the trimmed case and the C/L's are consistently within .004" of each other. This trimming process results in 4" groups at 100 yards when firing a 5 shot string. After 5 rounds, as the barrel heats up, the grouping will expand to 7 - 8". Interestingly, in firing approx. 2,500 rounds through Garand, I have never had a jam or failure to fire (although I have had 2 M1 Thumbs).. I have 4 other bolt action .30-06 rifles. I neck size their cases, and then follow the same process as I do for Garand cases.

[wingnut]

BruniX-

On your pictured trimmer... there should be an adapter available to replace the handle so that an electric/battery powered drill will do the turning for you. It will save some time and effort.