trim length ???

toad67

Loading for my 6.5x55 and want to try some IMR 4451 with some Hornady SST's. In doing so the trim length is different by .010" between the 2 different load data's. Which one should I follow? Thanks.

iceracerx

In the world of automotive engineering two extremes in measurement become a 'tolerance' and adding the numbers and dividing by two gives the 'nominal' measurement.

If I were you, I'd look for a 3rd source of info (like SAAMI) or do some simple math.

I believe it is the shoulder dimension/location and bullet seating depth that are more important than trimmed length.

It will be interesting to read other opinions.

SAAMI case length is 2.165" - 0.020" (54.991 - 0.51)

http://www.saami.org/pubresources/cc_drawings/Rifle/6_5x55 Swedish.pdf

Edit: Thanks Bob.

charliemeyer007

What is your chamber length? A chamber cast would tell you.

My newer Lyman book says the trim to length is 2.155", the older Lyman cast bullet only book says 2.150"

A shorter can work just fine; 38 Special in a 357 Mag. Build up needs to be cleaned before going back to longer cases.

Hornady Leverevolution in 45-70 ammo uses a shorter case to work with the cannelure and OAL for repeaters.

Tailgunner1954

As a rule of thumb, there is a 0.020 difference between "maximum allowed" and "minimum allowed", with the "trim to" being 1/2 way between the 2 (IOW a +/- 0.010 tolerance on the trim dimension).
There are a couple exceptions to this rule, where the "trim to" is equal to the "minimum allowed" dimension (IE: both being 0.020 below max).

I think Iceracerx means 2.165 on the max dim for the 6.5x55 Sweed "Max length". [:D]

There is also the "copyright infringement test", where a simple and minor error is inserted as a check as to if another publisher is using your data (this used to be common in the old paper road maps). IE: Hodgdon #23 shows in the case drawing section a maximum of 2.165", but in the data section shows 2.160 as the maximum length (with 2.150 as the trim length).

nononsense

toad67,

For $6.00 you can determine the length of your chamber then trim to the length you need rather than trying to get someone else to make that decision without any information.

http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx

There is a short video demonstrating the proper use.

Be sure your chamber is clean especially the neck and transition angle.

Two observations:

Most, if not all, new current brass is made shorter than the lengths written in the reloading manuals. All you need to do is check the chamber length with the gauge then trim the case mouths to be concentric.

The worse case scenario is if the cases have grown to be longer than the chamber allows, the mouth of the case will be pushed into the transition angle and the bullet will be crimped tighter creating higher pressure.

Best.

toad67

quote:Originally posted by nononsense
toad67,

For $6.00 you can determine the length of your chamber then trim to the length you need rather than trying to get someone else to make that decision without any information.

http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx

There is a short video demonstrating the proper use.

Be sure your chamber is clean especially the neck and transition angle.

Two observations:

Most, if not all, new current brass is made shorter than the lengths written in the reloading manuals. All you need to do is check the chamber length with the gauge then trim the case mouths to be concentric.

The worse case scenario is if the cases have grown to be longer than the chamber allows, the mouth of the case will be pushed into the transition angle and the bullet will be crimped tighter creating higher pressure.

Best.





Very helpful, thanks NN.