Brass Trim Length?

dcloco

Savage 223, bull barrel...

ALL of the reloading manuals indicate to trim brass to 1.750". I measured the chamber length in my rifle, it is 1.789"...question is...do I try to approach this number for better accuracy?

I did trim one brass to 1.775" and the shell chamber great.

rufe-snow

I can only speak for myself in this matter. As long you have trimmed all the cases to the same length and your positive the mouth of the case won't come in contact with the rifleing, when you have a projectile loaded. Your good to go.

My thinking vis a vis the loading manuals is that their data specifically applies to AR type rifles. The case length/overall length has to be kept in much tighter tolerance to feed through the magazine and action of both semi-automatic and selective fire rifles.

mrbruce

Just remember that all chambers are different, as is the trim length for all chambers.
As long as your not over length your fine.
Any accuracy gains are spotty at best.


Gun control is hitting what your aiming at.

JustC

The Leade is an area where the rifling starts. but not at full height. It is a tapered progression to full rifling height. That area where the lands will be smaller, but can be hit by the case mouth, will cause a crimp when the bolt handle is rotated into battery, and raise pressures as well as throw off accuracy. You only need to be a bit off of that area with the case. If you are say .010" or more, longer than SAAMI spec, you are still a ways away from the leade and have no problems. If you are going to use slow powders which may lend a 100% load density, then a longer neck to get a grip on a bullet seated farther out can be a help, but this area is generally not worked with too much. Just trim them all to the same length, and make sure that they don't hit the leade, and it really is no issue how long they are. Just be sure to keep measuring and trim them when the stretch long enough to be close to the leade (the measurement you took with the chamber length guage).

why chase the game when the bullet can get em from here?....
Got Balistics?

dcloco

Just wondering out loud...because, as rufesnow pointed out, looks like ALL or 95% of the data for 223 is jilted towards the AR15...which is not what I am shooting.

Ok...I will trim to 1.750...and leave well enough alone.

haroldchrismeyer

All the case trim measurements are from manufacturer specs, which will fit all the rifles all of the time. I have not found any accuracy gains by trimming to chamber length or trimming to spec length. The one accuracy gain is by the distance the bullet is set back from the rifling. I have found that .050 setback for the bullet before contacting the rifling works best for accuracy without raising pressures. Split the mouth of one case with a hacksaw, and file it to remove the rough edges, place a bullet barely into the case, and chamber it. Remove it, and measure overall lenght, and then seat your next batch to .050 shorter than that measurement.

nononsense

This might make an explanation a little easier to visualize instead of trying to keep a description in your head and try to match figures to it.

The drawing is of the 7.62 mm KJG (wildcat) chamber but it has all of the areas drawn in that need to be discussed, so ignore the metric dimensions and just think about the .223 Rem.



The standard length of factory .223 brass is usually about 1.760" and the trim to is listed as 1.750". So I'm not sure how you're leaving the brass trimmed at 1.775", none of my brass is this long. The only thing I can think of is 222 Rem. Magnum brass. But then a whole bunch of numbers are wrong. Please let us know how you got brass to be 1.775" long and stamped .223 Rem.

As far as the case portion of the .223 chamber is concerned, SAAMI spec says it is 1.772" @ point H2 in the print. This is the extreme length which includes the neck. Here is where the rub comes in. The next feature in the drawing is an angle which is usually 45 degrees and is termed the 'transition' angle. This reduces the chamber from the neck diameter of 0.255" down to 0.2245" or just a touch over the bullet diameter in the area just in front of the angle. The length from the bolt face to include the transition angle is 1.787". But if your brass is this long it will be crushed into this angle, not the rifling, and act like a crimp which will really raise the chamber pressure. But we still don't know how you got brass that is this long...

The cylindrical area (G1) in front of the transition angle is referred to as the 'freebore' and currently by the reamer makers as the 'leade', well at least 2 of them; PTG and JGS. I didn't check Clymer. This cylinder is usually 1/2 of one thousandth (0.0005") over the size of the bullet diameter and can vary in length according to design or necessity. It is one of the deciding factors in the difference between the 5.56 and the .223 Rem. For the most part, it is used to add length to the chamber to accommodate significantly longer bullets in long range chambers.

The final part of the chamber is in front of the cylinder and it's shaped like a cone. This cone can have varying degrees of side angle, which for the .223 Rem. is 3 degrees 10 minutes. The cone tapers from 0.0005" over groove diameter down to the top of the lands. This is what transitions the bullet to the be fully engraved by the lands.

Let us know about your case length. Then you can cast your chamber and measure the cast to be sure what the chamber really is.

Best.

dcloco

Thanks for the info.

The case lengths were out of some once fired brass...out of a 223. I thought this was odd as well.

To measure my chamber, I used a soft ball of lead, placed on top of a case trimmed to 1.750, and gently chambered this "round".

Removed and measured.

I can actually see the transition angle in the lead.

Personally, I believe it would be next to impossible if the brass grew this much without having major problems.

New to reloading, but definitely a "technical" type of person. Still looking at all of the "angles" to improve the accuracy.

Just kind of dissappointed in ALL of the reloading manuals swaying the 223 reload info towards 1:12/1:14 twist semi automatic rifles (not that I don't like AR15's!!).

THANK YOU for the info!!!

jimbowby

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I'm only wearing Black untill they make something darker

JustC

look at the data on accuratereloading.com in the load data pages. Saeed uses his own rifles for testing as well as MANY custom rigs of his friends. These rifles are bolt guns and will more than likely have similar twists as yours.

For trimming, I pick the shortest case in the lot, and trim them to match the short one. Done deal. And yes, you'll probably seperate a casehead before you grow your brass that much to touch the leade transition angle.

why chase the game when the bullet can get em from here?....
Got Balistics?

dcloco

jimbowby...thanks for the heads up. I will order one this weekend.

JustC...thanks again.