.243 A.I. fireforming

[chino1969]

I have a .243 A.I. 1:10 Douglas barrel that was reamed with a min. SAAMI reamer but not a tight neck. I broke the barrel in using 41.5 gr. of IMR 4895 using 80 gr. Remington factory hollow points touching the lands. Over the past several years I've developed some very accurate pet loads. One of these pet loads is 47.3 gr. of H4350 pushing an 80 gr. Berger MEF,touching the lands) @3550 ft/s. I use the rifle for live varmints and punching paper. I have two new barrels that were made with a reamer that was made to min. SAAMI specs. with a .270 neck diameter. One of these barrels is another 1:10 Douglas and the other is a 1:12 three groove Pac-Nor super match. The rifle is a Savage single shot switch barrel and the barrels are Savage varmint contour.

The questions I have for people who have experience with this caliber are as follows:
1) When I screw one of the new barrels on can I use one of my pet loads to break the barrel in, since some of the pressure is going to go toward blowing the shoulder out? In other words, can I safely load 47.3 gr. of H4350 with an 80 gr. Berger MEF and expect reasonably safe and accurate fire forming loads or should I default to the 41.5 gr. of IMR 4895 with the Remington 80 gr. factory bullets? My goal is to find an accurate load while fire forming and break the barrel,s) in at the same time. Any input would be greatly appreciated.

My assumption is that since some of the pressure will go toward blowing the shoulder out in the case it will be safe, but I may be missing something in assuming that I can use one of my pet loads in a previous barrel to accomplish this with a new barrel.

 

[Bobs243Ackley]

Hello,
The biggest issue that you will have is simply getting a .243AI load into a standard .243 Winchester. I looked in several of the loading manuals, and the heaviest load that I could find is in the Second Edition Lee Manual. The load is shown as a do not exceed charge of 46 grains of H4350 at 56,423 PSI. This is a maximum load for the .243 Winchester shooting an 80 gr. bullet! The 41.5 grain charge of IMR-4895 is also shown as being .5 grain over maximum, according to the Lee Manual. I would highly suggest that you back off of either of these loads and work up to the listed maximums in this load manual.

To paraphrase PO Ackley, "You need a snappy load" for fireforming. This means using at least a factory load, or factory load equivalent, not a .243AI load. There is usually no safe way to put a .243AI load in for fireforming, and you do not need it to form the cases properly.

You still might be able to use your old load data in the new barrels, for the .243AI only, but only after working back up to them as the new rifles that they have become. You are correct in assuming that the pressure is being used to blow the case body, and shoulder, out. But you have to be able to do it safely, and that is always the bottom line. I hope that this will help you in getting the new barrels up and running. Once you get the issues of the new load development under control, you can use the fireform loads for barrel break in as well.

Cordially,
Bob Blaine

 

[chino1969]

Bob and gunamonth,
Thank you for the replies. I agree with not putting a quality Berger downrange when a lower pedigree bullet will do just as well for fire forming purposes. It just seems that if you can fire form new brass and accurately whack varmints, you've made efficient use of your time and equipment. My past endeavors in fire forming in Ackley chambers has been to break the barrel in and fire form a hundred rounds; which is the minimum I use for each barrel. I then begin my load development, etc. with the fire formed brass. In the case of my .243 A.I., I've already developed several pet loads that I will know have a good chance of success in my new barrels. I will of course, back off the load by a safe margin and begin working up to my previous load. I realize that my new loads may differ from my old loads but at least the R & D has been done previously and I should be able to find my new pet loads rather quickly.

The 41.5 gr. of IMR 4895 that I used previously gave me the nice sharp shoulders in new brass that I was looking for. I had tried a lesser charge and the shoulders were rounded; therefore the snappy load of 41.5 gr. I will start with a lesser charge in the new barrels and see what happens and go up if I'm not getting the nice sharp shoulder. Correct me if I'm wrong but I believe the reason why a properly head spaced Ackley chamber is .004 less than a standard chamber is to yield a crush fit on the brass and prevent the firing pin from moving the case forward upon firing and subsequent rearward case head movement. When developing loads in an Ackley I go the the max. load in the parent cartridge and go up in .3 grn. increments from there. For the 6mm's I usually seat the bullets to touch the lands.

 

[Bobs243Ackley]

In my last barrel, I would normally shoot the Sierra 60 grain HP with a good charge of H-414 behind it. This load would pop the brass out sharply, and would still deliver solid .5" MOA performance for me. I have killed many woodchucks in NE Indiana with this load while fireforming. I had a chance to talk to Ferris Pindell, one of the "P's" of the PPC, and he confirmed that the reason that the AI, and PPC, cases were set up to headspace .004" short was to indeed hold them in proper position for fireforming. He went so far as to say that if you chambered a new, unfired .220 Russian case, into a 6PPC chamber and it chambered easily, then the gun was not chambered properly by the gunsmith. He said that the same thing is true with the AI rounds as well. Nothing like hearing this information from one of the "Grand Masters" himself! Before I forget, I use 46.1 grains of H-414 and the 60 gr. Sierra HP. This is a starting load in Hodgdon's load data, and I have used this load for fire forming for years. It chronographs out at 3,530 fps in my .243AI's.

Cordially,
Bob Blaine

 

[chino1969]

Bob,
You mentioned that you would use a good charge of H414 with a Sierra 60 gr. H.P. to fire form your brass. After you had your fire formed brass, did you then start loading from your fire forming load and work your way up to determine your new pet load? If so, how much difference of charge did you observe? What I have found with respect to fire forming A.I. brass is to go to the max. load in the parent cartridge. I've tried starting in the middle of the chart and have been disappointed with rounded shoulders. The max. charge has always provided sharp shoulders and a good starting point for load development after the case has been fire formed.

 

[Bobs243Ackley]

I usually start my load develpment by starting .5 grain to 1 grain below the listed maximum .243 Winchester loads. I will then work with once fireformed cases to start working loads up from this point by checking the expansion. I will not use loads that give me more than .0005" expansion on the case web. If the cases do not have sharply defined shoulders, I usually do not let that bother me too much as long as the shoulder angle, and body, are where they need to be since further firings at .243AI charges will sharpen the shoulders. The other thing that I have noticed is that the slower twist barrels will generally allow heavier charges with a given bullet weight than the faster twist barrels will.

Cordially,
Bob Blaine

 

[chino1969]

Bob,
The measuring of case web expansion has always been an enigma for me in that I haven't been able to take consistent and accurate measurements that inspire confidence. For example, where you place the caliper blades on the case web can yield different dimensions. Placing the thicker portion of the caliper blade directly in front of the extractor groove will give a different dimension than the very tip or thin end of the calipers. The other problem that I have when trying to take this dimension is that you are into the taper of the case. Even though the taper is minimal at the contact points of the calipers, you are still not taking dimensions on a perfect perpendicular surface. This less than ideal contact point can yield differences of several ten thousandths of an inch. Is there some consistent way of taking this measurement that I'm not aware of?

 

[Bobs243Ackley]

I will use a blade micrometer to take these measurements. When I take the measurement, I will mark the location on the case, with a fine point magic marker, before I chamber the round to fire, and then, I will have the same reference for the measurement after I fire the case. Generally, you can see where the expansion web is on a once fire formed case, and that is what I use as my reference for the point of the measurement.

Cordially,
Bob Blaine

 

[chino1969]

Hello,
The biggest issue that you will have is simply getting a .243AI load into a standard .243 Winchester. I looked in several of the loading manuals, and the heaviest load that I could find is in the Second Edition Lee Manual. The load is shown as a do not exceed charge of 46 grains of H4350 at 56,423 PSI. This is a maximum load for the .243 Winchester shooting an 80 gr. bullet! The 41.5 grain charge of IMR-4895 is also shown as being .5 grain over maximum, according to the Lee Manual. I would highly suggest that you back off of either of these loads and work up to the listed maximums in this load manual.

To paraphrase PO Ackley, "You need a snappy load" for fireforming. This means using at least a factory load, or factory load equivalent, not a .243AI load. There is usually no safe way to put a .243AI load in for fireforming, and you do not need it to form the cases properly.

You still might be able to use your old load data in the new barrels, for the .243AI only, but only after working back up to them as the new rifles that they have become. You are correct in assuming that the pressure is being used to blow the case body, and shoulder, out. But you have to be able to do it safely, and that is always the bottom line. I hope that this will help you in getting the new barrels up and running. Once you get the issues of the new load development under control, you can use the fireform loads for barrel break in as well.

Cordially,
Bob Blaine

Bob,
Just a follow up to an earlier thread. I began breaking in my new Pac-Nor 1:12" .243 A.I. barrel recently. I started with 41.0 grn. of IMR 4895 with an 80 grn. Remington factory hollowpoint into the lands. The barrel is on a Savage single shot action that is properly headspaced with a .004 'crush fit'. After fireforming some rounds, the shoulders were not nice and sharp so I bumped the load up to 41.5 grns. and the rounds came out perfect. I've been tracking the throat with a borescope and amazingly there is evidence of fire-cracking in the freebore area after 60 rounds. Nothing major, just small axial firecracks that begin right after the neck juncture ends and the freebore begins.
Chino69

 

[Bobs243Ackley]

He Chino,

I'm glad that everything has been coming along on your .243AI. Seeing a little bit of firecracking, even at this stage, is nothing new for the .243AI. You might try some JB Bore Compound to see if this will allow you to delay the throat erosion that is inevitable with the .243AI.

Cordially,
Bob Blaine

 

[chino1969]

He Chino,

I'm glad that everything has been coming along on your .243AI. Seeing a little bit of firecracking, even at this stage, is nothing new for the .243AI. You might try some JB Bore Compound to see if this will allow you to delay the throat erosion that is inevitable with the .243AI.

Cordially,
Bob Blaine

Hi Bob,
I pretty much have to accept the firecracking with the .243 A.I. and the recent purchase of a borescope has added a new dimension to the whole equation. I've got another 20 rds. to fireform and then I begin load development but I've already got some pet loads that I can start with and with some fine tuning, I should be in business in short order. This new barrel is a Pac-Nor 1:12" that will go up to 80 grn. bullets. I have another 1:10" that I'll use for anything heavier. I've got a fairly good assortment of bullets to try: Hammonds, Starke, and Fowler 68 grn. bullets, Fowler & Berger 80 grn. bullets, and Hornady & Sierra 75 grn. bullets. I've been using the borescope to monitor/modify my cleaning technique and I'm very impressed with Bore Tech's Eliminator. It's as effective as BMG 50 on copper and appears to get the carbon better than BMG 50. It is not as fast as BMG 50 but there are also no fumes to contend with.
Chino69

 

[Ackman]

I have a .243 A.I. 1:10 Douglas barrel that was reamed with a min. SAAMI reamer but not a tight neck. I broke the barrel in using 41.5 gr. of IMR 4895 using 80 gr. Remington factory hollow points touching the lands. Over the past several years I've developed some very accurate pet loads. One of these pet loads is 47.3 gr. of H4350 pushing an 80 gr. Berger MEF,touching the lands) @3550 ft/s. I use the rifle for live varmints and punching paper. I have two new barrels that were made with a reamer that was made to min. SAAMI specs. with a .270 neck diameter. One of these barrels is another 1:10 Douglas and the other is a 1:12 three groove Pac-Nor super match. The rifle is a Savage single shot switch barrel and the barrels are Savage varmint contour.

The questions I have for people who have experience with this caliber are as follows:
1) When I screw one of the new barrels on can I use one of my pet loads to break the barrel in, since some of the pressure is going to go toward blowing the shoulder out? In other words, can I safely load 47.3 gr. of H4350 with an 80 gr. Berger MEF and expect reasonably safe and accurate fire forming loads or should I default to the 41.5 gr. of IMR 4895 with the Remington 80 gr. factory bullets? My goal is to find an accurate load while fire forming and break the barrel,s) in at the same time. Any input would be greatly appreciated.

My assumption is that since some of the pressure will go toward blowing the shoulder out in the case it will be safe, but I may be missing something in assuming that I can use one of my pet loads in a previous barrel to accomplish this with a new barrel.

Actually,.270" is a tight neck. My .243AI reamer cuts a .273" neck....Remington brass is .272" unturned, Winchester is turned to .271. The web on Lapua brass is .004" larger than Win. and .003" larger than Rem. and won't fit the chamber.

To answer your questions:

Don't worry about barrel break in. It's not necessary and won't do anything except use up time and components.

The .243AI isn't like other Improved cartridges. A .243 is already a semi-improved case. The AI version blows the shoulder forward, but it only gets a little larger. Improved cases shoot fine while fireforming anyway and the .243AI is no exception. So don't even worry about special fireforming, just work up an accurate load and go shoot. Accuracy with the right load can be just excellent. Loads with formed cases will be just about the same and get very similar velocity.

My barrels are 13" and 9" twist. They both like 65 and 70gr bullets of one sort or another with W760 or H414 powder. For example.....best fireforming were mid 3700's to mid 3800's depending on bullet/powder/primer, and with good accuracy. For example, fireforming..... 48.3/760/70TNT/BR2 would put some bullets into a ragged hole, and 48.7gr were doing 3858 and .3" group. Very effective hunting loads that zapped a great many prairie dogs and rockchucks.

Again, don't mess with special fireform loads. Just go shoot.

 

[AckleymanII]

My hunting partner and I used the same reamer that we had PTG grind for us, minimum spec, zero freebore, .2435 throat. We use Remington 7/08 brass, turned at 7mm, necked down and re-turned at 6mm. We shoot Hart 1-12 twist, 28-30" unturned blanks with muzzle breaks.

I make a 70g & 75g BT VLD on a .900 jacket with a 9 ojive, .070 Meplat. Fireforming with 47.0-47.8g of Win 780 gives a velocity of 3750-3800 in most barrels. Formed loads are usually 48.0-48.5g of Win 760 @3850. I leave the wax lube on the bullets which dramatically reduces copper fouling and lowers the standard deviation. Copper fouling is 3x as great on an 85g Bullet fired with 45.5g of 760@3550fps...hard to believe I know, but it is true due to much more bearing surface.

My hunting buddy shot 70g TNT's with the same load.

With the 1 1/2* leade angle, it seems that the 70's like a jam of .003-.005 but every rifle will be different.

You were wondering if you could use the same fireforming load in the Douglas 1-10 and the Pac Nor 1-12, I would not think so, but you may get lucky. I would expect to see different pressure spikes from one barrel maker to the next in the same twist, and you are increasing the twist on one barrel.

I think that I would work up a load for each barrel, and I hope that your gunsmith set your barrels up for a "Crush fit" on the cases that you provided him, otherwise you need a HARD jam on the bullet into the rifling and pray,I never trust this method). I have had AI's with as much as 0.050 crush fit, but had to grind off a little off my shell holder to get the Full Length sizer to work properly.

We got extremely long barrel life with the 243 using 760 when shooting the 70's. We usually set back the barrel at least 3-4 times on the unturned blanks, cutting off 3/4"-1 1/4" after 1800-2000 rounds or so...we never let the leade get washed out, we tried to stay in front of excessive throat wear.

Good luck!

We found out early on that stick powders were rough on barrels when shooting 600-1000 rounds per person of centerfire a day on dog towns.

 

[chino1969]

I have a .243 A.I. 1:10 Douglas barrel that was reamed with a min. SAAMI reamer but not a tight neck. I broke the barrel in using 41.5 gr. of IMR 4895 using 80 gr. Remington factory hollow points touching the lands. Over the past several years I've developed some very accurate pet loads. One of these pet loads is 47.3 gr. of H4350 pushing an 80 gr. Berger MEF,touching the lands) @3550 ft/s. I use the rifle for live varmints and punching paper. I have two new barrels that were made with a reamer that was made to min. SAAMI specs. with a .270 neck diameter. One of these barrels is another 1:10 Douglas and the other is a 1:12 three groove Pac-Nor super match. The rifle is a Savage single shot switch barrel and the barrels are Savage varmint contour.

The questions I have for people who have experience with this caliber are as follows:
1) When I screw one of the new barrels on can I use one of my pet loads to break the barrel in, since some of the pressure is going to go toward blowing the shoulder out? In other words, can I safely load 47.3 gr. of H4350 with an 80 gr. Berger MEF and expect reasonably safe and accurate fire forming loads or should I default to the 41.5 gr. of IMR 4895 with the Remington 80 gr. factory bullets? My goal is to find an accurate load while fire forming and break the barrel,s) in at the same time. Any input would be greatly appreciated.

My assumption is that since some of the pressure will go toward blowing the shoulder out in the case it will be safe, but I may be missing something in assuming that I can use one of my pet loads in a previous barrel to accomplish this with a new barrel.

Actually,.270" is a tight neck. My .243AI reamer cuts a .273" neck....Remington brass is .272" unturned, Winchester is turned to .271. The web on Lapua brass is .004" larger than Win. and .003" larger than Rem. and won't fit the chamber.

To answer your questions:

Don't worry about barrel break in. It's not necessary and won't do anything except use up time and components.

The .243AI isn't like other Improved cartridges. A .243 is already a semi-improved case. The AI version blows the shoulder forward, but it only gets a little larger. Improved cases shoot fine while fireforming anyway and the .243AI is no exception. So don't even worry about special fireforming, just work up an accurate load and go shoot. Accuracy with the right load can be just excellent. Loads with formed cases will be just about the same and get very similar velocity.

My barrels are 13" and 9" twist. They both like 65 and 70gr bullets of one sort or another with W760 or H414 powder. For example.....best fireforming were mid 3700's to mid 3800's depending on bullet/powder/primer, and with good accuracy. For example, fireforming..... 48.3/760/70TNT/BR2 would put some bullets into a ragged hole, and 48.7gr were doing 3858 and .3" group. Very effective hunting loads that zapped a great many prairie dogs and rockchucks.

Again, don't mess with special fireform loads. Just go shoot.

Ackman,
Thank you for the info. I've never used either of those powders with the .243 A.I. but I'll try with these new barrels. I've had very good results with H4350 with the 70 & 80 grn. bullets and H4831 sc for the 87 grn. Horn. V-Max in a 1-10" Douglas. I'm not near my notes, but I'll pass them on.
Chino69