Learning is never over

cdoc42 · October 24, 2014, 08:15 PM

I've been reloading for 38 years. I just learned something new tonight.

I had a box of Hornady 140gr SST in .270 that I was using to find the best load in a new Remington Model 700. The box was probably 5 or more years old. I established a seated length of 2.875" from ogive to base was 0.015" from the leade. I got a 100-yd 5-shot group of less than 1 inch (0.973") with 58 grains of H4831sc with a CCI 250 LR Magnum primer.

I was running out of bullets so I bought the last box on the shelf at Cabelas. They looked exactly like the bullets in the old box. No change in position of the cannelure. I had experienced that about 20 years ago with 175gr Hornady bullets in 7mm Rem Mag, which alerted me to remeasure my seating depth.

I had previously loaded 10 rounds with the new bullets, seated to 2.875" but they chambered with a bit of difficulty. I got the same good group so I thought little of it until tonight.

I loaded 10 rounds and decided to chamber one. Hard to chamber and even harder to get the bolt open. Knocked the bolt open with a rubber mallet.
Chambered empty brass no problem. Measured the ogive to base of the extracted round = 2.857" meaning it jammed into the leade at that length. My dummy round with the old bullet measured 2.890"to the leade = a difference of 0.033".

My chamber difficulty was because the new bullets had a different ogive position which was completely invisible to the naked eye. The new box of bullets had to be seated to 2.842" to be 0.015" from the leade!!

Now I have to go back out to the range to see if this will still give the same group.

I have NEVER experienced this before. A new box of the same bullet from the same manufacturer seated to the same measurement as the previous box always fired the same group. Learning is never over.

Snyper · October 24, 2014, 08:59 PM

When I find something that works well, I try to stockpile as much of it as I can from the same lots, or at least the same production time frame.

It sounds like their swaging dies have changed just enough to cause you a problem, but still likely within their tolerance range

tangolima · October 24, 2014, 09:04 PM

It was not the leade the bullet jammed into. It was the riflings. The leade is section of the chamber before the rifling starts. Sometimes it is called free bore, or throat. Your original load must has zero or little bullet jump, which is the clearance between the ogive and the rifling. When the manufacturer made minor change to the ogive, it jammed.

Now you know the col for zero bullet jump from the extracted round. I like to have 0.03" to 0.05" bullet jump myself. I would adjust the seater die to shorten the round accordingly.

-TL

Mike / Tx · October 25, 2014, 04:19 AM

I have run across that before where the manufacturer changes things up just enough to blow a good load or worse like you experienced jam up the works.

I picked up one of the comparator sets which have the different caliber inserts and they lock onto one side of your calipers. They work just fine for checking these little things. You can measure not only just the bullets, but also the loaded rounds as well to see if perhaps things have changed.

cdoc42 · October 25, 2014, 06:42 PM

Tagolima, thanks for the clarification. What I actually meant was the ogive distance from the rifling.
Mike, I use a Stoney Point comparator set attached to a digital vernier caliper. The original bullet from the old box compared to the new lot number apparently had the ogive 0.033" further away and when I seated the new lot number to the same length it was that much closer and jammed into the rifling.

I went to the range today and I had seated the new lot number at 0.015" and 0.020" AFTER I re-established the overall length to the rifling with the new lot. I got a 3-shot spread with a maximum distance between 2 shots of 2 inches with the 0.015" load and 0.598 inches with 3 shots at 0.02".
Amazing how sensitive accuracy can be.

zeke · October 26, 2014, 07:37 AM

some companies have annoying habit of changing their bullet profiles, hornady being one of em. In some rifle bullets, they changed over from the rounded ogee to the angular ogee several years ago. They did this to some of their pistol bullets years ago, and have now changed the 45 230 xtp's.

Jimro · October 26, 2014, 07:54 AM

The bullet forming dies get changed out from time to time as they wear. You can't expect perfect dimensional stability between lots.

Odds are they will shoot as good as the earlier lot, accuracy being more about consistency within the lot than BC differences caused by ogive. Even in match grade bullets you can have a few percentage difference in BC between bullets of the same lot, which is why some shooters tip their bullets. It reduces the BC a little, but creates more uniformity as a result.

Jimro

October 24, 2014, 08:15 PM	#1
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	Learning is never over I've been reloading for 38 years. I just learned something new tonight. I had a box of Hornady 140gr SST in .270 that I was using to find the best load in a new Remington Model 700. The box was probably 5 or more years old. I established a seated length of 2.875" from ogive to base was 0.015" from the leade. I got a 100-yd 5-shot group of less than 1 inch (0.973") with 58 grains of H4831sc with a CCI 250 LR Magnum primer. I was running out of bullets so I bought the last box on the shelf at Cabelas. They looked exactly like the bullets in the old box. No change in position of the cannelure. I had experienced that about 20 years ago with 175gr Hornady bullets in 7mm Rem Mag, which alerted me to remeasure my seating depth. I had previously loaded 10 rounds with the new bullets, seated to 2.875" but they chambered with a bit of difficulty. I got the same good group so I thought little of it until tonight. I loaded 10 rounds and decided to chamber one. Hard to chamber and even harder to get the bolt open. Knocked the bolt open with a rubber mallet. Chambered empty brass no problem. Measured the ogive to base of the extracted round = 2.857" meaning it jammed into the leade at that length. My dummy round with the old bullet measured 2.890"to the leade = a difference of 0.033". My chamber difficulty was because the new bullets had a different ogive position which was completely invisible to the naked eye. The new box of bullets had to be seated to 2.842" to be 0.015" from the leade!! Now I have to go back out to the range to see if this will still give the same group. I have NEVER experienced this before. A new box of the same bullet from the same manufacturer seated to the same measurement as the previous box always fired the same group. Learning is never over.

October 24, 2014, 08:59 PM	#2
Snyper Senior Member Join Date: December 16, 2013 Location: Eastern NC Posts: 3,047	When I find something that works well, I try to stockpile as much of it as I can from the same lots, or at least the same production time frame. It sounds like their swaging dies have changed just enough to cause you a problem, but still likely within their tolerance range __________________ One shot, one kill

October 25, 2014, 04:19 AM	#4
Mike / Tx Senior Member Join Date: April 8, 2000 Posts: 2,101	I have run across that before where the manufacturer changes things up just enough to blow a good load or worse like you experienced jam up the works. I picked up one of the comparator sets which have the different caliber inserts and they lock onto one side of your calipers. They work just fine for checking these little things. You can measure not only just the bullets, but also the loaded rounds as well to see if perhaps things have changed. __________________ LAter, Mike / TX

October 26, 2014, 07:54 AM	#7
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	The bullet forming dies get changed out from time to time as they wear. You can't expect perfect dimensional stability between lots. Odds are they will shoot as good as the earlier lot, accuracy being more about consistency within the lot than BC differences caused by ogive. Even in match grade bullets you can have a few percentage difference in BC between bullets of the same lot, which is why some shooters tip their bullets. It reduces the BC a little, but creates more uniformity as a result. Jimro __________________ Machine guns are awesome until you have to carry one.

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October 24, 2014, 09:04 PM	#3
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,813	It was not the leade the bullet jammed into. It was the riflings. The leade is section of the chamber before the rifling starts. Sometimes it is called free bore, or throat. Your original load must has zero or little bullet jump, which is the clearance between the ogive and the rifling. When the manufacturer made minor change to the ogive, it jammed. Now you know the col for zero bullet jump from the extracted round. I like to have 0.03" to 0.05" bullet jump myself. I would adjust the seater die to shorten the round accordingly. -TL

October 25, 2014, 06:42 PM	#5
cdoc42 Senior Member Join Date: March 13, 2005 Location: Pennsylvania Posts: 1,687	Tagolima, thanks for the clarification. What I actually meant was the ogive distance from the rifling. Mike, I use a Stoney Point comparator set attached to a digital vernier caliper. The original bullet from the old box compared to the new lot number apparently had the ogive 0.033" further away and when I seated the new lot number to the same length it was that much closer and jammed into the rifling. I went to the range today and I had seated the new lot number at 0.015" and 0.020" AFTER I re-established the overall length to the rifling with the new lot. I got a 3-shot spread with a maximum distance between 2 shots of 2 inches with the 0.015" load and 0.598 inches with 3 shots at 0.02". Amazing how sensitive accuracy can be.

October 26, 2014, 07:37 AM	#6
zeke Senior Member Join Date: November 17, 1999 Location: NW Wi Posts: 1,671	some companies have annoying habit of changing their bullet profiles, hornady being one of em. In some rifle bullets, they changed over from the rounded ogee to the angular ogee several years ago. They did this to some of their pistol bullets years ago, and have now changed the 45 230 xtp's.