I was recently told by a fellow that variable neck tension can cause poor accuracy. I noticed a couple nights ago that when I was seating bullets in my Starline 45 Colt cases that there was some variability in the force required to seat the bullets. I assume this translates to different neck tension as well. My sizer die is a Hornady with the titanium nitride coating. I am guessing that the cause of the varying bullet seating force is a variance in case thickness. I can only figure it being that or a variance in bullet diameter. The bullets are Mt. Baldy 270 SAA cast bullets supposedly sized to 0.453". I am crimping the case after bullet seating with a Redding Profile crimp die. Accuracy is sometimes great and sometimes lousy. Do any of you have any suggestions as to what I can do to make the neck tension more uniform or is this not really that big of a deal so long as the bullets are well crimped?

I measured the outside diameter on some various cases. My fired cases measure 0.479". Sized cases measure 0.470". Loaded rounds measure 0.473 to 0.474". The sizer die measures 0.468" on the inside of the titanium nitride ring. The 45 Colt cases have a case wall thickness of 0.012" and my bullets mostly measure 0.4523". What are others getting for case wall thickness and sized brass outside diameters? Thanks, Bruin.

It is not due to the case thickness but to the variable hardness of the brass. Each case will spring back different due to it's own hardness or softness.
Rifle shooters solve it by annealing but you don't ever want to do that to revolver brass for hot loads. Boolits will pull from recoil.
If you are good enough at feeling the difference in handle feel, try sorting loads.

Ditto on what bfr is trying to tell you. What he's trying to tell you is that you should SORT your brass by make and by how many times they've been fired. By firing loads using various mixed brass, you'll never find an accurate load that way. Rule of thumb, hunting loads(HOT), new brass to only 5-6 times fired. The rest can be relegated to warm and just plinking loads. Hope I've expressed myself to you so's you can have a better time at it.

I am only using Starline cases from the same lot and they have been fired the same number of times which is probably only about 5 times. I think I need more neck tension but am not sure how to achieve it. Bruin.

Use an expander plug from a .44 mag. This will give you enough bell on the case mouth to start the bullets, but is not big enough in diameter to expand the necks out.

I ran into the same problems with the .45 Colt and Winchester brass. My dies are an old Lyman set with a carbide sizer that I think was made for .454 bullets. Now I run the cases through the .45 Colt die, then I run them about half way into a .45 ACP die. I do this by feel. The resistance starts when cases are about half way into the die, so I just stop there. This sizes the brass down enough that it has a good grip on the bullet. Expand the mouth just enough to seat the bullet. Maybe this method will work for you. Good luck.

In a load near max you will be using a slow powder. The case must grip the bullet tightly for the powder to burn properly ! It is not enough just to tightly crimp , in fact too tight a crimp can cause accuracy problems. You must get an expander of the correct diameter to grip the bullet properly. You should not be able to push the bullet back into the case with your thumb before crimping. Proper grip and crimp => accuracy and consistant velocity.

For heavy recoiling ammunition in revolvers, would comibing a taper crimp with roll crimp be a reasonable method to maintain cartrdge OAL?

I use the Redding profile crimp dies for revolvers and have been happy with them. However, the crimp on a revolver should be combined with a good grip of the case on the bullet. I did not have very good luck with using a heavier crimp to compensate for an oversize sizing die. Too much crimp can bulge the case and cause chambering problems. I think the best thing you could do would be to try some of the methods described above to increase neck tension and combine it with a good crimp. Good luck.

I also find this issue when seating bullets for my 475 linebaugh. Some will seat easy, some will seat harder.

Gohip, yes it is a BIG problem and is why I suggest Hornady dies. They have the best measurements. It is hard to explain that how tight the grip is, is not as important as how even the grip is from case to case. As long as there is enough case tension for a good burn, then the very most important thing is to try and get the tension EVEN. Since there is so much difference in brass from case to case, it can't be done so loads must be segregated to shoot groups with or for IHMSA.
I have worked on this for years and years and have a decent way of sorting.
What is needed is a way to actually measure boolit seating pressure that holds the measurement after seating so loads can be sorted. My way is kind of crude but works. I would like an actual measurement in pounds or ounces to make it even better.
I will tell all of you that the crimp will not do a single thing to aid accuracy, stop thinking about it and just use enough to hold boolits under recoil.
If you have decent neck tension to start and take 5 with X amount of seating pressure and shoot a 1/2" group at 50 yd's, then take 5 with Y seating pressure, you will still get a 1/2" group but they might be 10" away from the X group. Mix them and the best group you will shoot will be 10". Enough said?
Some of you do not realize how important it is and keep trying to correct it with crimp changes. IT DOES NOT WORK!
I also experimented with every crimp you can think of from zero to ruining brass---IT DOES NOT CORRECT UNEVEN BOOLIT PULL.
Every single one of you can shoot 1" or smaller groups at 50 yd's with revolvers if the loads meet requirements. I recently shot several 1" groups at 100 yd's with my old SBH .44 that has over 57,650 rounds through it.
Don't blame the gun or your shooting ability, blame uneven neck tension.
You can't even work loads if the tension varies all over the place. You will be rejecting loads that might shoot under 1" at 100 yd's.
This is the reason some swear by fast powders in their revolvers because it eliminates some of the problem but still does not solve it. It is a crutch.

bfrshooter pretty much said it all. Consistency is an absolute requirement for accuracy.

A friend on another site bought a set of Hornady dies that do not size enough. This is the first I heard of and I told him to call Hornady. I have had great luck with them but I guess all makers are not right all the time.
He is also having trouble with boolit size dies from RCBS to Lee that are not right and either don't size enough or too much. Too much can be fixed but I am losing confidence in the factories.
I would like to see Redding make collar dies for revolver cases.

Bruin: How about an update on whether any of these suggestions helped with your problem. Good luck.

Besides case thickness, is trim length going to affect bullet pull as well when crimping?

Different length brass can alter the crimp from case to case and it will effect accuracy a little. Not near as much as tension though.
It is not the brass thickness that causes the problem. It is different hardness and grain structure from case to case, even if all are new of the same brand and lot.
Turning or reaming revolver brass will not help and makes the tension even worse.
Even shooting a bunch of light loads with some brass and heavy loads with others can alter the hardness of those cases so they are more different.
No one notices any of this if plinking or hunting but if you want to shoot real far targets or tight groups, the only way is to measure the boolit seating pressure and sort into piles. Shoot each pile separate. POI will change for each but is of no concern shooting groups but for silhouette or something, try and shoot only the pile the gun is sighted for. You can go a pile on each side of this pile without too much change. Just stay away from the ones near the ends if you are target shooting. Use those for play.