Seating depth with crimp groove

[Gawp]

Hey!

It's me again trying to do my first batch of .30-30 Win cartridges.

At first I didn't think too much about the seating depth for my .30-30: I was thinking "oh well there is a crimp groove so I'll just seat the bullet according to the groove".

Well... turns out it still leaves quite some space...

Below are 3 of the manufactured .30-30 Win bullets I usually buy. You can see that:
1. On the first (top) bullet, we don't see the crimp groove at all
2. On the second (middle) bullet, we see the crimp groove very slightly
3. On the third (bottom) bullet, we see the crimp groove pretty clearly

What's the right way to seat the bullet? No crimp groove visible at all? Half of it visible?

Will this have any noticeable effect in the accuracy of the cartridge?

Thanks!

 

[ligonierbill]

First, cast bullets have an actual groove, or two, for the crimp. That ribbed band on your jacketed bullets is referred to as a cannelure. As long as your bullet is seated so as to allow crimping into the cannelure, at least half in the case, and you do it the same every time, you are unlikely to impact accuracy. I do find that seating a bullet to the maker's spec in a properly sized case usually puts most or all of the cannelure below the rim.

Your 30-30 needs a uniform crimp because it probably has a tube mag, and you need to prevent bullet setback. There are other good reasons to crimp rifle rounds, but most often I just seat for best accuracy and ignore it. Read that front section of your load manual. Most are well written and contain lots of valuable advice.

 

[Shadow9mm]

My understanding is that the cannalure is to make space for brass from the neck to fold in without deforming the bullet. If you cant see it it might be too high and not lock into the cannalure. based on my understanding the first if bad, the second 2 are both fine.

 

[Bart B.]

Knurling or canneluring bullets unbalances them. They shoot less accurate. Especially when crimped in place.

It's a compromise for heavy recoiling cartridges in sporting rifle ammo with crimped in bullets.

 

[Gawp]

First, cast bullets have an actual groove, or two, for the crimp. That ribbed band on your jacketed bullets is referred to as a cannelure. As long as your bullet is seated so as to allow crimping into the cannelure, at least half in the case, and you do it the same every time, you are unlikely to impact accuracy. I do find that seating a bullet to the maker's spec in a properly sized case usually puts most or all of the cannelure below the rim.

Thank you, I didn't know these 2 words couldn't be used interchangeably. I get it now! Thank you for your answer!

Your 30-30 needs a uniform crimp

Can this "uniform crimp" be achieved with the Lee Factory Crimp?

My understanding is that the cannalure is to make space for brass from the neck to fold in without deforming the bullet. If you cant see it it might be too high and not lock into the cannalure. based on my understanding the first if bad, the second 2 are both fine.

Makes sense, thank you!

Knurling or canneluring bullets unbalances them. They shoot less accurate. Especially when crimped in place.

It's a compromise for heavy recoiling cartridges in sporting rifle ammo with crimped in bullets.

What do you mean by crimped "in place"? I guess I still need to crimp my bullets right? Because they will go into a tubular magazine (Marlin 336 XLR).

 

[Bart B.]

"Crimped in place" means the bullet is seated and crimped wherein the case mouth is folded into the bullet's knurle or cannelure.

You may need to crimp them for use in tubular magazine rifles. Depends on how tight case neck grips the seated bullet. The difference may be masked by the number of cartridge's weight in the magazine that changes the barrel's vibration vertically. I would test each load with the magazine half full of live ammo.

There's seldom, if ever, uniform enough grip on bullets when crimped in place that enables uniform push force on bullets to move them out of the case neck. Never seen any data specs on 30-30 cartridge bullet pull or push force minimums. If crimped in bullets really produced best accuracy, it would be common in benchrest matches.

 

[big al hunter]

It has been my experience with that lever guns are not prone to showing much difference between crimped and not. But the only way for you to know what your rifle is capable of you need to test it. Load 20 or 30 rounds. Seat all to the same depth. Only crimp half of them. When you shoot them for groups single load them in the rifle. If your groups are the same....makes no difference. If you groups are smaller with one....by how much? Is it enough to matter with the purpose for the load?

 

[44 AMP]

Knurling or canneluring bullets unbalances them. They shoot less accurate. Especially when crimped in place.

while probably technically true, I think "less accurate" is a highly situational matter. Losing a 1/4 moa ( or whatever) potential because crimped bullets are "less accurate" is a different matter of concern to the guy shooting matches/small varmints at long range, and the guy shooting a deer at 70yds with open sights on a win 94 .30-30.

My understanding is that the cannalure is to make space for brass from the neck to fold in without deforming the bullet. If you cant see it it might be too high and not lock into the cannalure. based on my understanding the first if bad, the second 2 are both fine.

The second 2 are not fine. A roll crimp, outside of the cannelure or crimp groove can not only distort the bullet, it can distort the brass. This can happen to the point of the case buckling, and not being able to be chambered. The .30-30 can wrinkle the case neck and even bulge the shoulder out if the crimp isn't done right.

Your 30-30 needs a uniform crimp
Can this "uniform crimp" be achieved with the Lee Factory Crimp?

IT can be done with any crimp, Lee die or just the crimp shoulder in your regular seating die.

The way you make it "uniform" is to have all your brass a uniform length. A couple thousandths difference in case length MATTERS when crimping.

Adjust your die so that finished rounds come out looking like the bottom round in the picture. You want to be able to see the top edge of the cannelure above the finished crimp. This small amount allows for "stacking tolerances" that didn't get uniformed when you trimmed your brass to uniform length keeping them from turning a good crimp into a bad one.

Usually.

 

[Gawp]

"Crimped in place" means the bullet is seated and crimped wherein the case mouth is folded into the bullet's knurle or cannelure.

You may need to crimp them for use in tubular magazine rifles. Depends on how tight case neck grips the seated bullet. The difference may be masked by the number of cartridge's weight in the magazine that changes the barrel's vibration vertically. I would test each load with the magazine half full of live ammo.

There's seldom, if ever, uniform enough grip on bullets when crimped in place that enables uniform push force on bullets to move them out of the case neck. Never seen any data specs on 30-30 cartridge bullet pull or push force minimums. If crimped in bullets really produced best accuracy, it would be common in benchrest matches.

Thank you for the explanation!

It has been my experience with that lever guns are not prone to showing much difference between crimped and not. But the only way for you to know what your rifle is capable of you need to test it. Load 20 or 30 rounds. Seat all to the same depth. Only crimp half of them. When you shoot them for groups single load them in the rifle. If your groups are the same....makes no difference. If you groups are smaller with one....by how much? Is it enough to matter with the purpose for the load?

Makes sense, I will do the test, thanks.

IT can be done with any crimp, Lee die or just the crimp shoulder in your regular seating die.

The way you make it "uniform" is to have all your brass a uniform length. A couple thousandths difference in case length MATTERS when crimping.

Adjust your die so that finished rounds come out looking like the bottom round in the picture. You want to be able to see the top edge of the cannelure above the finished crimp. This small amount allows for "stacking tolerances" that didn't get uniformed when you trimmed your brass to uniform length keeping them from turning a good crimp into a bad one.

Thank you for making it clear that "uniform" is about the case length, I didn't have it.

I will try and do my best to make it look like the bottom round then. Thank you so much for taking the time to explain all this!

 

[pete2]

The cannelure on your 30-30 bullet IS the crimp groove in this case and you do need to crimp rounds for tube magazine rifles. You need to trim all cases to the same length, roll the crimp into the center of the cannelure/crimp groove. You should also crimp rounds for machine guns and revolvers. The 30-30 brass is thin so be careful to not over crimp or you will damage the brass.