Sierra 243 Win seating depth question

[Propbndr]

I have a Savage Axis 243 win rifle with a 22” barrel and a twist of 9.25. I am currently loading Sierra 100 grain Spitzer rounds. Both the 5th and 6th editions of Sierra loading manual call for a COAL of 2.650. I finally decided to measure my chamber‘s OAL with that bullet using a Hornady OAL gauge and a Hornady modified case. What I found out is raising major concerns for me. The average OAL (out of 10 measurements) is 2.640. That is .010 shorter than the called for COAL. During the measuring process, I also measured the CBOT and came up with an average of 2.2547. I measured a couple of rounds that have a COAL of exactly 2.650 and came up with a 2.260 CBOT. That is .053 longer than my chamber. I have absolutely no problems closing the bolt when chambering or ejecting the round. Remeasured the “perfect” round after chambering and found no change in its length.

Questions:

Should I increase the seating depth by .010 to .020 to make sure I am not at possible jam?

In case the Hornady modified case is somehow causing a wrong measurement, should I make a modified case using a fire formed case?

 

[Mark W]

Color your bullet with a sharpie and see what kind of marks you’re getting on the bullets after it’s been chambered.

It’s also advisable to use dummy rounds for testing such things. I personally never insert a loaded round into a bolt action rifle unless I’m at a range or out in the field hunting.

 

[Doom]

You may be seeing the bullet hitting prior to the ogive. This sometimes happens because the body of the modified case is resized so it does not fit tightly in the chamber and can get cocked in the chamber. I have found that wiggling the gauge around while lightly pushing on the bullets insures this doesn't happen.

 

[Bill Norris]

I have a Savage Axis 243 win rifle with a 22” barrel and a twist of 9.25. I am currently loading Sierra 100 grain Spitzer rounds. Both the 5th and 6th editions of Sierra loading manual call for a COAL of 2.650. I finally decided to measure my chamber‘s OAL with that bullet using a Hornady OAL gauge and a Hornady modified case. What I found out is raising major concerns for me. The average OAL (out of 10 measurements) is 2.640. That is .010 shorter than the called for COAL. During the measuring process, I also measured the CBOT and came up with an average of 2.2547. I measured a couple of rounds that have a COAL of exactly 2.650 and came up with a 2.260 CBOT. That is .053 longer than my chamber. I have absolutely no problems closing the bolt when chambering or ejecting the round. Remeasured the “perfect” round after chambering and found no change in its length.

Questions:

Should I increase the seating depth by .010 to .020 to make sure I am not at possible jam?

In case the Hornady modified case is somehow causing a wrong measurement, should I make a modified case using a fire formed case?

Apparently you may be in the lands to some degree but not at hard jam. If at hard jam you might be leaving the bullet in the lands and dumping powder into the action.

 

[243winxb]

using a fire formed case

Old school-

Take a case fired in your rifle. Pinch the case mouth with pliers to make it slightly oval.
Place the base of the bullet into case mouth a tiny amount.

Place case head behind extractor. Chamber dummy cartridge.
Extract slowly while not letting the bullet hit the side of the receiver. Use finger to press against the case body. The ejector is working against you. Do 5 or 10 times. Measure COL.

On factory guns, mostly a waste of time, finding maximum COL.
Maximum may not fit magazine.

Start with the base of the bullet at the case neck/shoulder junction.

 

[Propbndr]

Color your bullet with a sharpie and see what kind of marks you’re getting on the bullets after it’s been chambered.

It’s also advisable to use dummy rounds for testing such things. I personally never insert a loaded round into a bolt action rifle unless I’m at a range or out in the field hunting.

I tried the sharpie trick but could not make out any markings.

I have a 50 yard range on my property and have no problems with testing with live ammo.

 

[K22]

This is not unusual in my experience. For, example, using the Sierra 85 BTHP in various 243 Win rifles, I discovered that the Sierra test load COAL 0f 2.650 let alone the max SAMMI COL of 2.710 was too long for these bullets in Tikka and Browning factory rifles but fine in Remington 700's. When I say too long, I mean the bullet would stick in the lands and remain lodge in them when I extracted a live round.

I had to seat these bullets to 2.610 and 2.620 respectively to stay 0.015" off the lands. The accuracy was outstanding in both rifles about 1/2 to 5/8 moa with tuned reloads. For hunting reloads, I like to stay between 0.015 and 0.30 off the lands generally speaking.

I now measure the max base to ogive for every type of bullet / rifle combo. It the first thing I do for a ever new rifle / bullet combo.

I use the Frankfort Arsenal tool method, which is inexpensive, very simple and fairly reliable. It's so simple, you can make you own, all you need is a cleaning rod and two spacers that will lock on to the rod plus a caliper. I like to measure 5 bullets out of each new lot and take the longest measurement as the MAX base to ogive measurement. This method is quick and does not damage a case or bullet.

 

[Propbndr]

This is not unusual in my experience. For, example, using the Sierra 85 BTHP in various 243 Win rifles, I discovered that the Sierra test load COAL 0f 2.650 let alone the max SAMMI COL of 2.710 was too long for these bullets in Tikka and Browning factory rifles but fine in Remington 700's. When I say too long, I mean the bullet would stick in the lands and remain lodge in them when I extracted a live round.

I had to seat these bullets to 2.610 and 2.620 respectively to stay 0.015" off the lands. The accuracy was outstanding in both rifles about 1/2 to 5/8 moa with tuned reloads. For hunting reloads, I like to stay between 0.015 and 0.30 off the lands generally speaking.

I now measure the max base to ogive for every type of bullet / rifle combo. It the first thing I do for a ever new rifle / bullet combo.

I use the Frankfort Arsenal tool method, which is inexpensive, very simple and fairly reliable. It's so simple, you can make you own, all you need is a cleaning rod and two spacers that will lock on to the rod plus a caliper. I like to measure 5 bullets out of each new lot and take the longest measurement as the MAX base to ogive measurement. This method is quick and does not damage a case or bullet.

Which edition and printing of the manual do you have? The 5th edition has 2.650 coal for most of their bullets. The 6th edition 4th printing changed the 85 gr HPBT to 2.590. It looks like Sierra makes, what I consider, major changes with each printing.

As suggested in a couple of posts, my problem may be with the Hornady modified case and or my technique. I have decided to make my own case and redo the measurements. While I have not stuck a bullet, I don’t want to take a chance of that ugly scenario. All I have to do is find a 5/16 - 36 tap.

 

[Todd Earhart]

I have a Savage Axis 243 win rifle with a 22” barrel and a twist of 9.25. I am currently loading Sierra 100 grain Spitzer rounds. Both the 5th and 6th editions of Sierra loading manual call for a COAL of 2.650. I finally decided to measure my chamber‘s OAL with that bullet using a Hornady OAL gauge and a Hornady modified case. What I found out is raising major concerns for me. The average OAL (out of 10 measurements) is 2.640. That is .010 shorter than the called for COAL. During the measuring process, I also measured the CBOT and came up with an average of 2.2547. I measured a couple of rounds that have a COAL of exactly 2.650 and came up with a 2.260 CBOT. That is .053 longer than my chamber. I have absolutely no problems closing the bolt when chambering or ejecting the round. Remeasured the “perfect” round after chambering and found no change in its length.

Questions:

Should I increase the seating depth by .010 to .020 to make sure I am not at possible jam?

In case the Hornady modified case is somehow causing a wrong measurement, should I make a modified case using a fire formed case?

Is the bullet your using the 1540? I came into some of the 1540's a while back and and was not sure they would stabilize in my somewhat factory savage barrel\chamber. I loaded at a 2.650 coal. I test chambered the first round. I loaded 4 more after and went to the range and shot them. I had no issues and they shot very well.
Todd

 

[Propbndr]

Is the bullet your using the 1540? I came into some of the 1540's a while back and and was not sure they would stabilize in my somewhat factory savage barrel\chamber. I loaded at a 2.650 coal. I test chambered the first round. I loaded 4 more after and went to the range and shot them. I had no issues and they shot very well.
Todd

Yes, the bullet is the 1540. I am also loading the 1530 85 gr HPBT. With the newest manual printing, the 1530 is not a jamming concern. As it is coal is 2.590.

 

[Coyotefurharvester]

Strip the bolt and/or use dummy rounds and one of the various methods to find max length with that particular bullet. I made a rod/collars setup with a 1/8 " diameter acrylic rod and 1/8" set screw collars from Amazon for 10$, makes running thru a bunch of different bullets quick/easy for max coal. And checking several different bullets is fast, results are repeatable.

 

[K22]

Which edition and printing of the manual do you have? The 5th edition has 2.650 coal for most of their bullets. The 6th edition 4th printing changed the 85 gr HPBT to 2.590. It looks like Sierra makes, what I consider, major changes with each printing.

As suggested in a couple of posts, my problem may be with the Hornady modified case and or my technique. I have decided to make my own case and redo the measurements. While I have not stuck a bullet, I don’t want to take a chance of that ugly scenario. All I have to do is find a 5/16 - 36 tap.

Like everything I have, mine in old. It's the 4th edition, circa 1995.

I am not a fan of the Hornady tool because it uses an unfired modified case that may or may not provide a good fit to your rifle chamber thus may induce measurement error.

The Frankfort Arensal method does not use any cases. I found it to be reliable enough for most applications. The chief advantage of this method is that it enables one to measure a lot of bullets (ogive touching lands) quickly without damaging or marking them.

I had the ugly scenario your described. I loaded some 243 Win's for my then new Tikka and went to the range to do some dreaded load development. I started with the Sierra test COAL of 2.650 for the 85BTHP. The cartridges would not chamber. When I tried to extract it, the bullet stuck in the lands dumping powder in the action. A mess, a wasted range trip, etc.

I choose the 2.650 because my Rem 700 chambers that quite easily with lots of throat to spare. I assumed it would be the same with the Tikka. I was wrong. It was after that incident I adopted the practice of measuring every new bullet / rifle combo. I often also check new lots and sometimes their is some slight difference in ogives, less so with Nosler bullets, more so with Hornady. I don't use Sierra anymore due to supply and availability issues.

I found that a range of .015 to .030 off the lands provides more than sufficient accuracy for my needs and provides a level of assurance that I will not have a repeat of the ugly scenario mentioned above.

 

[Propbndr]

Like everything I have, mine in old. It's the 4th edition, circa 1995.

I am not a fan of the Hornady tool because it uses an unfired modified case that may or may not provide a good fit to your rifle chamber thus may induce measurement error.

The Frankfort Arensal method does not use any cases. I found it to be reliable enough for most applications. The chief advantage of this method is that it enables one to measure a lot of bullets (ogive touching lands) quickly without damaging or marking them.

I had the ugly scenario your described. I loaded some 243 Win's for my then new Tikka and went to the range to do some dreaded load development. I started with the Sierra test COAL of 2.650 for the 85BTHP. The cartridges would not chamber. When I tried to extract it, the bullet stuck in the lands dumping powder in the action. A mess, a wasted range trip, etc.

I choose the 2.650 because my Rem 700 chambers that quite easily with lots of throat to spare. I assumed it would be the same with the Tikka. I was wrong. It was after that incident I adopted the practice of measuring every new bullet / rifle combo. I often also check new lots and sometimes their is some slight difference in ogives, less so with Nosler bullets, more so with Hornady. I don't use Sierra anymore due to supply and availability issues.

I found that a range of .015 to .030 off the lands provides more than sufficient accuracy for my needs and provides a level of assurance that I will not have a repeat of the ugly scenario mentioned above.

How do you keep the bullet touching the lands? I tried making a dummy round and closing the bolt but, found it sticking to the lands when I extracted it. Plus, my readings were not consistent.

 

[Doom]

Just a thought. I don't know for sure what Savage has done with the chamber of the 243Win when they increased the twist to handle heavier bullet. When designed the bullets were about 85 gr I believe and the SAAMi spec did not include any freebore in the design to accommodate the longer bullets. I suspect that they have not done this based on some of the other calibers I'm familiar with. I suspect that Remington on the other hand has some amount of free bore to accommodate longer bullets. I know that the 308Win has a very long freebore as compared to SAAMI.

 

[Propbndr]

Strip the bolt and/or use dummy rounds and one of the various methods to find max length with that particular bullet. I made a rod/collars setup with a 1/8 " diameter acrylic rod and 1/8" set screw collars from Amazon for 10$, makes running thru a bunch of different bullets quick/easy for max coal. And checking several different bullets is fast, results are repeatable.

What is your method of keeping the bullet in the lands? Or do you actually jam it?

 

[Propbndr]

Just a thought. I don't know for sure what Savage has done with the chamber of the 243Win when they increased the twist to handle heavier bullet. When designed the bullets were about 85 gr I believe and the SAAMi spec did not include any freebore in the design to accommodate the longer bullets. I suspect that they have not done this based on some of the other calibers I'm familiar with. I suspect that Remington on the other hand has some amount of free bore to accommodate longer bullets. I know that the 308Win has a very long freebore as compared to SAAMI.

I don’t have a clue about the freebore in my rifle. I don’t have any way to measure it.

 

[Doom]

I don’t have a clue about the freebore in my rifle. I don’t have any way to measure it.

The only way to know for sure is a chamber cast. You can surmise your free bore by comparing your data to others. I will tell you that may shooters have abandoned trying to set there seating depth as "off the lands" and now use off of "in the lands" because its difficult to determine where the bullet is just touching the lands. They will start at something like 20/1000" from in the lands.

In this case I would follow @Coyotefurharvester advice and determine the COAL with jam.

 

[K22]

How do you keep the bullet touching the lands? I tried making a dummy round and closing the bolt but, found it sticking to the lands when I extracted it. Plus, my readings were not consistent.

The Frankfort Arsenal tool method does not require a dummy round or any case. Furthermore, you can select the amount of bullet contact you desire with the lands from a full jam or just touching it the lands, the latter which I prefer.

If you would like, I will PM you the method, it's quite simple and easy to use. All you need is a cleaning rod, two spacers that can lock on the rod*, and a caliper. You will also need a jag with the pointed tip ground flush.

* You can use tape instead of spacers but it more difficult to obtain a precise reading. Or you can just purchase their kit, it's quite inexpensive. I made my own spacers. I purchased two nylon spacers, 1/4" ID from Home Depot, drilled and tape them with nylon screws. Sinclair use to sale them as "rod stops" which will work also quite well.

 

[Propbndr]

The Frankfort Arsenal tool method does not require a dummy round or any case. Furthermore, you can select the amount of bullet contact you desire with the lands from a full jam or just touching it the lands, the latter which I prefer.

If you would like, I will PM you the method, it's quite simple and easy to use. All you need is a cleaning rod, two spacers that can lock on the rod*, and a caliper. You will also need a jag with the pointed tip ground flush.

* You can use tape instead of spacers but it more difficult to obtain a precise reading. Or you can just purchase their kit, it's quite inexpensive. I made my own spacers. I purchased two nylon spacers, 1/4" ID from Home Depot, drilled and tape them with nylon screws. Sinclair use to sale them as "rod stops" which will work also quite well.

I already have what I need. I have drill stops that I can use for the screw collars / spacers. Please PM your method.

 

[K22]

I already have what I need. I have drill stops that I can use for the screw collars / spacers. Please PM your method.

Will do but it is not my method, it the method used by Frankford Arsenal.