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Caliber and Barrel Length for New PD Barrel

 
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  #8  
Old 02-23-2005, 09:46 AM
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Re: Caliber and Barrel Length for New PD Barrel

Varmint hunter & Brian B.

We have had this discussion before several times and I fully agree with out conclusion that the 3 grooves are harder on thin jacketed match bullets sucha s the A-Max and Bergers.

Still I have only had a problem with the 6mm-284 and the like. With this round the Hornady and Berger bullets shot extremely well up to around 3200 to 3250 fps. Generally into around 1" to 1.5" groups at 500 yards. IT was only above this level that accuracy dropped off and since it was a 6mm-284, we simply need all the velocity we can get, well that was my reasoning for using the Sierra 107 anyway [img]/ubbthreads/images/graemlins/smile.gif[/img]!!

I do not think there would be a problem at the 3100 fps and under velocity that the 243 would produce.

One interesting note converning fast twist barrels and the 3 groove rifling. I just finished a V-Block rifle for a customer that used a 1-8" .224", 30" Lilja 3 goove barrel which was chambered in 22-6mmAI. This rifle was designed to use the 80 gr Wildcat ULD bullets but until they arrive I tested some 80 gr Berger and Sierra bullets.

I was not expecting anything out of the Bergers but I tried them anyway. They shot extremely well up to 3300 fps and then simply started not landing on paper at 200 yards. I lengthened the seating depth so they were around 0.020" into the lands and tested again and was able to get them to 3590 fps and groups most would not believe.



This is my personal best three shot group at the 200 yard target. Now I am not saying this rifle will average this but it will average in the 1/4" range at 200 yards and at 500 yards it is printing average groups of right at 1" even with this load which produced 3560 fps, just a tick off max.

Perhaps it is more an issue of the 6mm/3 groove combo then anything else.

Sorry for hyjacking the post for a bit [img]/ubbthreads/images/graemlins/blush.gif[/img].....

Good Shooting!!

Kirby Allen(50)
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  #9  
Old 02-23-2005, 09:52 AM
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Re: Caliber and Barrel Length for New PD Barrel

Dcgauger,

For the 243 with the heavy bullets I would really recommend a 26" barrel at the longest, you just do not need more barrel to get a good powder burn with this cartridge.

The 243 is probably the easiest 6mm to get into. Another easy wildcat would be the 6mm-250 which will only be a 100 to 125 fps behind the 243 with longer barrel life. You can cold form brass as well so no fireforming would be needed.

On the other side, the 6mm Rem is also a great round but a little more powder capacity.

As far as barrel contour, the Savage is going to limit you somewhat as you can not go any larger then a 1.0625" straight cylinder diameter which is plenty heavy for extreme accuracy with this type of round. I would go with something in a #7 contour(.825" muzzle) or a #8 contour(.900) for a heavy profile barrel.

Good Shooting!!

Kirby Allen(50)
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Kirby Allen(50)

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Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

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Web Page: www.apsrifles.com

allenmagnum@gmail.com
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  #10  
Old 02-23-2005, 01:26 PM
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Re: Caliber and Barrel Length for New PD Barrel

Don,

With respect to barrel length I would go as long as you can, or is resonable. My early pd rifles with premium custom barrels, I refused to pay for the extra inches thinking I would never need or use it. Years later I find I should have for several reasons.

First of all, with the longer barrel I find I can develop loads that give excellent speed with very little pressure (and hence throat erosion) thus allowing the barrel to last (in some cases) much longer. Secondly, I am approaching the time (on one of them) that it should be set back. I would really like that extra inch right now. And thirdly, if you are not satisfied, or get bored with the .243 you can have it rechambered to a different choice and still have quite a bit of barrel left.

I now order any pd barrel to finish at a minimum of 28 inches for just those reasons. (works for me anyhow) [img]/ubbthreads/images/graemlins/grin.gif[/img]

Jim
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  #11  
Old 02-23-2005, 10:01 PM
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Re: Caliber and Barrel Length for New PD Barrel

fiftydriver,
I must totaly agree with you I have never seen or heard anyone having problems with a 3 groove barrel blowing up bullets except in a 6-284 1-8" twist (very interesting)
do you have any theroy of why this combination does not work ?????
Thanks B
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  #12  
Old 02-24-2005, 05:46 PM
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Re: Caliber and Barrel Length for New PD Barrel

Fifty, Terrific group with the 80 grain Bergers, and interested to see that you had to jam them .020 into the lands to get it.

Previously I have tried seating as far as .010 into the lands, but never went further as I wanted to avoid the nightmare of having a chamber full of powder if I didn't fire the shot and had to eject.

My last .224 Clark only had about .002 of bullet tension, and with case variation, the above "nightmare" occured until I became better at detecting the cases with less tension. (I full length sized those cases, which gave me .004 of tension)

I note that you are achieving near maximum/maximum pressure at 49.0 grains Reloader 22 and a velocity of 3,590 fps. This load would have been about 3.0 - 3.5 grains less than what I used in my last .224 Clark with similar bullet weight, and seems to be another instance of the 22/6mm with 40 degree shoulder consuming less powder than the 22/257 with 30 degree shoulder.

Usually a case with 40 degree shoulder has a slightly larger capacity than one with a 30 degree shoulder. My current 22/250 AI (some call it RCBS) with 28 degree shoulder is an example of that.

Richard Graves emailed 10 days ago to let me know that my order of 80 and 85 grain ULD .224 bullets (and 130 & 142 257's) had been sent by "snail mail" as it would have cost over $C90.00 to send them airmail.

He said that 85 grains was the heaviest ULD that this .224 jackets and dies would make, and asked if I was interested in some 90 & 100 grain 10 ogive flat base bullets. (I said yes)

Now that I know the bullets are on the way, I will order the barrel, and had intended to order a Krieger 26 inch 1 in 7 twist in number 3 profile which is .630 at the muzzle. The last .224 Clark barrel was 25.5 inches in no 5 profile and about .750 at the muzzle, but this rifle will be primarily used on medium game here in Oz, (with a few varmints) so I am hoping to reduce the weight where I can. This prompts my first question, do you think that the 26 inch number 3 profile would be too whippy to give sub 0.5 moa accuracy?

I am now looking for Rem 700 BDL rifle in 270W, 280R or 30/06 to soure the action. Although I have a Sako L61R action that is currently attached to a worn out 25/06 AI barrel, he does not recommend me using it for the Clark, due to the superior bedding qualities of the Remington.

My next question is what cases would you consider for this Sako L61 action? I had previously intended to rebarrel and chamber for the 280 AI, and use mainly the Nosler 140 grain BT's on medium game, and heavier bullets if the need arose.

However, if Richards's 142 grain ULD's do stabilise in my other 25/06 AI (10 twist) this seems a little pointless, as 142 grain ULD bullet with a BC of .750 or more at about 3,100 fps, should be infinitely better than a 140 grain BT with a BC of .490 at a similar velocity out of the 280 AI.

The L61R magazine length appears to be 3.575 inches, with the follower measuring 3.455 inches. I would prefer to use a rimless case, and would consider having the boltface opened up if it wasn't too expensive and any feeding issues could be overcome. The RUM cases appear to long, and the others such as the Lazzeroni, etc are expensive and difficult to source. Regards, Brian.
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  #13  
Old 02-25-2005, 09:50 AM
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Re: Caliber and Barrel Length for New PD Barrel

Brian Winzor,

I was a bit suprised to with the 0.020" into the lands working this well. The rounds are set up with more neck tension then what I prefer but that is by the customers choice, still it works very well so how can I tell him to change [img]/ubbthreads/images/graemlins/smile.gif[/img]!!

I found Rl-22 to be slightly quick burning for this rifle but groups and velocities were where we wanted them to be so we left it with this powder.

As far as the #3 contour at 26", look at this rifle. I finished this last week for a customer. It wears a Lilja #3 with a 25" finish length in 270 Win. It is built on a fully accurized Rem 700 BDL and pillar bedded to a Lamtek sporter stock.



These are the first two groups out of the rifle. I cleaned the bore, shot a fouler and then three shots, then cleaned, fouling shot and then three shot groups, accuracy testing was finished after these two groups.



I think your #3 will be plenty capable of sub 1/2 moa groups without much of a problem. The 243 will stress the rifle less then the 270 plus the #3 contour will have more mass to it in the 243 bore compared to the 270 so I would not have any problems using this contour.

Any of the '06 based round will work great on the 61. I am particular to the 280 AI and the 6.5-06 AI but they all work well.

I would not recommend jumping to the larger case diameter. It can certainly be done but itis not nearly as easy as with a Rem 700. The 280 AI would be my choice.

Good Shooting!!

Let us know how those Wildcat Bullets look. I received my shippment of 142 ULDs in 257 and 80 gr ULD 224s yesterday, I assume out of the same lots as your bullets. Look very good and I know will shoot at least as good as they look.

Good Shooting!!

Kirby Allen(50)
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Kirby Allen(50)

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Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

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Web Page: www.apsrifles.com

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  #14  
Old 02-25-2005, 09:56 AM
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Re: Caliber and Barrel Length for New PD Barrel

Brian B,

Personally I feel it is a combination of factors that result in the big 6mm rounds being hard on match bullets in 3 groove barrels compared to other calibers.

I think first off it is an initial velocity issue. That meaning that the bullets are still light enough and the cases large enough and the powder quick burning enough to produce some high velocities before the bullet enters the rifling. This increases the engraving stresses on the bullet.

I also feel that we are just getting into bullet weights that will produce alot of stress on the jacket when they are rotated to these high RMP speeds.

The 80 gr 224 bullets have less mass so they are effected less by rotational stresses. The larger calibers often have thicker jackets and use slower burning powders which is less stressful on the bullet as it is engraved by the rifling.

These are all just theories as I really do not know why the big 6mm rounds have so much trouble in fast twist 3 groove barrels.

Good Shooting!!

Kirby Allen(50)
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Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
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