Looking for guidance for crimping in the crimp groove of a cast bullet

[greenjoytj]

Looking for guidance for crimping in the crimp groove of a cast bullet.

During bullet seating where do I park the bullets “sharp edge of the crimp groove” in relation to the edge of the case mouth?
Is there a rule like make the two edges evenly aligned or some number of thousands of an inch short of being evenly aligned?

A classic roll crimp or a Redding Profile crimp will be applied to finish the cartridge.

The wide flat cannelure band on jacketed bullets doesn’t give me bullet seating concerns as it easy to stop bullet insertion ¾ up the wide cannelure band, so after crimping just a thin band of cannelure knurling is still visible.

I have cast bullets from 20:1 Rotometal alloy in a SAECO #955 mold.
Sized at .452” and lubed with homemade Emmerts.

The annealed Starline 45 Colt case mouth is slightly belled to accept ~ ½ the length of the base drive band (.060”) so I can set the bullets into the cases.

I’m not using a publish load recipe, as the Starline (and others) cases new out of the bag(s) are always, always too short by one to several thou and I haven’t found a recipe that uses the SAECO #955 bullet. Therefore my load manuals published COL data is useless to me.

[tazman]

I assume, from your description, you are seating and crimping in separate steps. I park my boolits that I am going to crimp, just below the farthest edge of the groove, so that the case doesn't quite cover the crimp groove. This way, you have the entire crimp groove to work with.

I also , don't pay too much attention to published COL data. I work with whatever the cases dictate.
If I were doing long range pinpoint work with my handguns, I would worry about every tiny detail. That isn't what I do with my handguns.

[WHITETAIL]

If I were making these I would put the OAL first
to the reloading book rec.
And see where the shells mouth is.
If it falls in the cannelure crimp it there.
If not, I reduce the OAL just to catch the cannelure.
provided you are not shooting top end loads.

[DougGuy]

If you have a load with the same (or close) boolit weight, and the distance from the crimp groove to the base of the boolit is close, you can use the data for that load. Meaning if you find a load where the base of the boolit is at the same depth in the case as the 955, and the weight is close, you can use that data.

For your question, I would seat until the case is even with the top of the crimp groove, so the case mouth crimps right under the sharp edge.

[9.3X62AL]

If you have a load with the same (or close) boolit weight, and the distance from the crimp groove to the base of the boolit is close, you can use the data for that load. Meaning if you find a load where the base of the boolit is at the same depth in the case as the 955, and the weight is close, you can use that data.

For your question, I would seat until the case is even with the top of the crimp groove, so the case mouth crimps right under the sharp edge.

This is my practice as well.

[reddog81]

I don't believe there's any definitive rule. As long as the rounds chamber and shoot with acceptable results you're doing it right. You can have light crimps, moderate crimps and heavy crimps. Any one of them could be correct depending on the load.

If making full strength Magnum loads a heavy crimp all the way to the "sharp edge" is generally advised. This helps powder burn and makes sure the bullets don't jump crimp under heavy recoil. With low recoil target loads a light crimp that only minimally turns the brass inward will work as good as anything else with less working of the brass.

I usually pay no attention to OAL length with revolver loads. My biggest concern is the amount of bullet buried inside the case. This is what determines the pressure inside the case. I have a Lee 358-140 grain SWC that when seated properly has as much of the bullet seated inside the case as a 158 RN bullet. I use the lower powder charges of the 158 grain bullet as my reference material rather than anything closer to 140 grains.

[mdi]

As a new reloader, crimping is important, but don't over think the process. Find a factory cartridge and use that as a "standard", just copy it...

I started reloading 38 Specials in '69, and always seated the bullet to the crimp groove and disregarded the book OAL. Still do (I reload 4 revolver cartridges)...

[dwtim]

Short answer: It doesn't matter, so long as the round is in spec based on the load data. If the bullet design is not published, compare it to one that is published, and has the same dimensions....especially in regard to seating depth.

The crimp groove is just a suggestion. Seating depth is more important in terms of pressure and safety, because that dimension directly affects remaining case volume. Unless you're shooting pistol bullets long-range, where the it might pass under the super-sonic "barrier", a little deformity from unorthodox crimping probably isn't going to make a big difference in accuracy.

I also want to point out that the SAECO #955 is very similar to the Lyman #452664.

Edit: Oops, Reddog81 already posted the same response.

[Rcmaveric]

I prioritize my fire arms COL over crimps and published COL. They get a light crimp where they are. Neck tension is way more important that the crimp.

Sent from my SM-G950U using Tapatalk

[popper]

bullets “sharp edge of the crimp groove” in relation to the edge of the case mouth

The edge of the crimped case mouth is supposed to push against that sharp edge of the crimp groove to prevent setback. As others have pointed out, it is not mandatory.

[mdi]

I have always thought the bullet designers did not just randomly place a crimp groove on their bullets. They took into consideration how much of the bullet extends into the case and powder capacity relative to pressures. I'm sure there are other factors, like bearing surface., center of gravity, etc. but none are a WAG or random, or a "suggestion"...

[tazman]

I have always thought the bullet designers did not just randomly place a crimp groove on their bullets. They took into consideration how much of the bullet extends into the case and powder capacity relative to pressures. I'm sure there are other factors, like bearing surface., center of gravity, etc. but none are a WAG or random, or a "suggestion"...

I agree. When using boolits in my 38/357 that have a crimp groove, I use that groove. I figure it is there for a reason.
This habit has never steered me wrong.

[MostlyLeverGuns]

If you are crimping for revolvers, the inertia of the bullet tries to pull the bullet forward. If you loading for semi-automatic pistols or tube feed rifles, the bullet is being pushed deeper into the case. For tube feed rifles I try to set the case neck forward to the 'front' of the crimp groove. For revolvers I crimp to the 'rear' of the crimp groove. Heavy recoil and certain powders call for more crimp. In .45 ACP, 9mm, and .40 I taper crimp just enough to remove the 'bell'. Less crimp is USUALLY better and MOST crimp grooves are in the right place. The length and depth of the crimp groove, actual case length, and overall length can also complicate this.

[popper]

Assuming the 45 (long) Colt, revolver rimmed cases with heavy boolits tend to pull the case back off the boolit (inertia of the heavy). Tube mags, recoil tends to compress all the rnds forward, possibly moving the boolit deeper. Rifle rnds often don't fit the desired 'jam' or 'jump' to rifling, seating depth is done to accommodate the particular rifle and crimp happens where it is needed. Slam (hard as you can) some dummy rnds case head on a hard surface and remeasure length, if it moved, crimp tighter.

[Mk42gunner]

I assume, from your description, you are seating and crimping in separate steps. I park my boolits that I am going to crimp, just below the farthest edge of the groove, so that the case doesn't quite cover the crimp groove. This way, you have the entire crimp groove to work with.

I also , don't pay too much attention to published COL data. I work with whatever the cases dictate.
If I were doing long range pinpoint work with my handguns, I would worry about every tiny detail. That isn't what I do with my handguns.

This technique works for me.

I normally seat and crimp in one step, unless it gives me problems, then I explore seating and crimping or different crimping styles.

Robert