Worlds Finest Trimmer test

S

Shadow9mm

New member
so, I have been using the worlds Finest Trimmer for 223 for a while. I set it bellow max length at a roughly the hornaday recommended 1.750 trim length

Well I got a set of RCBS X-dies because trimming is not fun, especially in large batches and this die is supposed to keep your trim length after the first trim.

The die says to set trim length to 0.020 below max and I spent over 2 hours and wasted about 15 casings trying to dial in the trim length and gave up.

Today I had an Idea. Trim some casings and see how consistent it was. I grabbed some range brass and resized it all in the die. picked the shortest casing, at 1.743 and set the tool to that casing and trimmed them 19 of them, 1 got wasted. Here are the results

First test
1.7439 average, Hi 1.7500, Low 1.740, ES 0.0100

I reset and tested again and I'm leaving it there
1.7396 Average, Hi 1.7415, Low 1.738, ES .0035

Not sure why the ES varied so much from the first group to the 2nd. I hope you find this helpful. I knew this trimmer would not be as precise as bench type, but it was faster and I did not anticipate needing to trim to a specific length when I bought it.

First group
1.7455
1.7445
1.7440
1.7445
1.7430
1.7450
1.7440
1.7430
1.7440
1.7450
1.7455
1.7455
1.7440
1.7425
1.7430
1.7415
1.7405
1.7435
1.7410
 
I copied and pasted your numbers into Excel and got an ES of 0.005", with a standard deviation of 0.001491. Unless you copied incorrectly, I have your largest at 1.7455" and smallest at 1.7405".

It has to be remembered that this trimmer registers on the case shoulder, so the trim length will only be as consistent as your shoulder distances are from the head. This measurement can vary some for any of several reasons:

The brass didn't spring back the same amount upon withdrawal from the resizing die because of:
  1. Different headstamps
  2. Different load histories
  3. Different firing histories (fired in different chambers)
  4. Cases from different sets of tooling have slightly different wall thickness and uniformity
Or, if your gun tends to bend the rims on extraction, the cases can have that bend sometimes over the insertion slot in your shell holder and sometimes over a solid area, varying exactly how far the shoulder is pushed up into the sizing die.

If you use a case comparator, like the Hornady, or even just a spacer that rests on the case shoulders, you can measure how consistent shoulder position is, select some identical ones and see how close they come in trimming.
 
Unclenick said:
I copied and pasted your numbers into Excel and got an ES of 0.005", with a standard deviation of 0.001491. Unless you copied incorrectly, I have your largest at 1.7455" and smallest at 1.7405".

It has to be remembered that this trimmer registers on the case shoulder, so the trim length will only be as consistent as your shoulder distances are from the head. This measurement can vary some for any of several reasons:

The brass didn't spring back the same amount upon withdrawal from the resizing die because of:
  1. Different headstamps
  2. Different load histories
  3. Different firing histories (fired in different chambers)
  4. Cases from different sets of tooling have slightly different wall thickness and uniformity
Or, if your gun tends to bend the rims on extraction, the cases can have that bend sometimes over the insertion slot in your shell holder and sometimes over a solid area, varying exactly how far the shoulder is pushed up into the sizing die.

If you use a case comparator, like the Hornady, or even just a spacer that rests on the case shoulders, you can measure how consistent shoulder position is, select some identical ones and see how close they come in trimming.
Click to expand...
there should have been a 1.750 in there. with the 1.740 ES is0.010...

Yes, it does register on the shoulder, however they have all been through the same sizing die prior to trimming, so the shoulder should be fairly consistent.

I need to get the case comparator tool eventually, I have bought so much new tuff recently, im trying to reign it in a bit.
 
Sometimes brass shaving build up inside the trimmer at the shoulder and doesn’t allow the case to be fully trimmed and thus affects the length.
 
The 4 items Uncle Nick posted would be the primary reasons for the variances you list. If the brass you are dealing with is range p/u, you have NO way of knowing the complete history of that piece of brass. Even if the brass is brand new out of the bag/box, there still will variances within that particular lot/bag of brass. If you are wanting brass that is more consistent from one firing to the next, get some Lapua brass or other high $$ brass. You pay for that consistency.
 
Yes there is some variance on the shoulder trimmers.

I would go with a Geraud Tri Trimmer or even the Trim It II (though it is a pain to setup). They both chamfer and deburr saving steps.

I also over trim so I don't have to do it as often.

I have cartridges the Tri Trimmer does not come in so am moving over to the Giraud Power unit that has the adapters for everything. I will sell off the two Tri Trimmers and maybe the Trim It II (may be limited market due to the cartridge I got it in)
 
Were the cases sized before trimming ? I think everyone here knows I am a Wilson fan so there is no need to beat that drum again. I have a WFT in .223 I bought used several years ago used once or twice and decided no more shoulder indexed trimmers. I need to send it back to Ebay.

If I wanted to save time I would buy my ammo preloaded
 
Last edited:
Perhaps I'm just not educated enough, but why should anyone get excited about a 10 thousandths difference in trim length? The only thing that changes is the amount if neck holding onto the bullet.
 
I’ll bet the variation is shoulder to base, not shoulder to case mouth.

FL sizing can vary 0.003” pretty easy.
 
I see a .005 difference in that list between min and max, 1.7455 maximum and 1.7405 minimum

@ Nathan you are probably correct. That is why I prefer trimmers that index off the case head. I measure case length with my calipers with one jaw on the case head and the other one the case mouth, not from the datum on the shoulder to the mouth. You can get shoulder springback if the shoulders is work hardened.

No big deal for hunting ammo, probably not for long range ammo either but when you try and make everything as identical as possible five thousandths might as well be five inches.

I am down too weighing primers to try and get that last couple of points in a match. Something I swore I would never do.
 
Shadow9mm said:
Yes, it does register on the shoulder, however they have all been through the same sizing die prior to trimming, so the shoulder should be fairly consistent.
Click to expand...

I've seen two sets of 30-06 brass out of two Garand chambers coming out of the same sizing die with a difference of 0.005" from head to shoulder datum according to an RCBS Precision Mic. The more brass is stretched, the springier it is, so the more it tries to pop back to shape after being withdraw from the sizing die. Same for gradual work-hardening. That is, a piece that has been resized more times without annealing, especially if it is coming out of a chamber that is on the long side, can be springier.

The other thing that can happen is softer brass that isn't springy can be pulled forward a little by the expander in a conventional rifle die set. You need to be sure to be using adequate inside neck lube to avoid that. I find the small, nearly spherical carbide expanders put significantly less drag on the brass. To check if you have this problem, select about thirty cases and resize half with the expander and half without and see if the head-to-shoulder measurement is the same.

If you have a caliper, you have the basic tool you need for head-to-shoulder measurements. The comparators just make it a little less fumbly to do. You just need to take a case with you to the hardware and find a drawer of steel spacers and find one that, when you insert the case neck into it, seems to land on the shoulder the right size. One with a 5/16" hole would probably do. Then it may be used as shown below with a larger space on a .308 case.

attachment.php
 
totaldla said:
Perhaps I'm just not educated enough, but why should anyone get excited about a 10 thousandths difference in trim length? The only thing that changes is the amount if neck holding onto the bullet.
Click to expand...
2 reasons.

1, I am using the RCBS x-dies. After the first trim they use a mandrel in the die to stop the necks from growing (I never have to trim that batch again) but the cases need to be relatively uniform, and they specify 0.020 below max.

2 it makes it a royal pain to line up with the cannelures for crimping
 
You must log in or register to reply here.
Back
Top