Needing some numbers on some boolits

[TaylorS]

I’m looking for Length of a Lyman 356637 HP and a rcbs 9mm-124-CN bullet my Lyman book has both of those in it but I’m using a Lee 356-125 2R and I’m trying to make my OAL match any of the numbers in the book.


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[Burnt Fingers]

Make your OAL for YOUR firearm. Don't try for some number in a book. As long as they plunk and drop you're fine. Longer is better in 9mm.

[mdi]

You can use an OAL for a similar weight and shape bullet for starters. Plunk test to make sure they fit and tweek as necessary...

[Conditor22]

As previously stated you need to match the OAL to the gun.
IF you go "1 size fits all" you boolit will be a long way from the lands on some of the firearms.

You notice that most factory ammo is either sort of has pointy bullets ---"1 size fits all"

[kmw1954]

I am interpreting this as he is looking for measurements to compare two similar weight bullets to find the actual length of the bullet. Two bullets the same weight but of different lengths because of profile is not going to load to the same length and then develop the same same pressures.

If load data lists one particular bullet at a certain length to develop a listed pressure and then one uses a same weight bullet of a different profile one has to adjust for length to achieve the same pressure. NO? In nother words if one takes a published load and then loads it longer or shorter than published to "fit" a certain gun it is not going to produce the same pressures or velocities.

[Gus Youmans]

KMW1954,

The four attributes of a bullet that affect pressure are the amount of bearing surface that is engraved by the rifling, the volume of the bullet that intrudes into the case, bullet weight, and hardness. Therefore, loads using two bullets that are identical in all of those attributes and use the same primer, case, powder, and powder weight, but are of different profiles should have the same pressure. I am sure it is possible to calculate each of those bullet variables and to calculate the effect changing any of those variables has on pressure but most of us don't have the expertise to do so. Also, most of us do not have the ability to pressure test our ammo, so we begin load development using the starting load or some other load that is safely below the maximum listed load. And, since we want the ammunition to function in the gun we are going to be shooting it in, we use the plunk test.

We should be more concerned with comparing the volume that each bullet intrudes into the case than with the COAL because that is a better way to estimate (guess) if two bullets of similar weight but dissimilar OAL are going to have similar pressure. If the OP wants to compare case intrusion of two bullets he can use the COAL listed in the manual, subtract case length, and determine how much of the bullet protrudes from the case. He can then determine case intrusion by subtracting protrusion from bullet OAL. However, even knowing that information is no guarantee that the load will be safe because there are too many other variables in the reloaded round that affect pressure, including case capacity, primer, powder lot, scale accuracy, etc.

Gus Youmans

[kmw1954]

KMW1954,

We should be more concerned with comparing the volume that each bullet intrudes into the case than with the COAL because that is a better way to estimate (guess) if two bullets of similar weight but dissimilar OAL are going to have similar pressure. Gus Youmans

I cannot agree more and basically this is the point I was trying to get across. It is the volume of the case under the seated bullet that determines pressure not how long or short a measured finished round is. I have seen in many cases a Round Nose bullet of the same caliber and weight have completely different profiles with different ogives that loaded to different lengths create the same pressures. Have seen the exact same thing with TC bullets.

As with the above were I was trying to explain If a known published load is loaded longer than published the pressure will decrease and the opposite will happen if reversed and loaded shorter. I Don't believe anyone will disagree with that.

So again it is my belief that TaylorS is looking for the actual length of two different bullets that he has load data information for and want to know how a third bullet compares against those two others so he can adjust length and powder charge to equal each other.