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338 twist rate, what are your thoughts?

 
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  #8  
Old 01-18-2008, 01:01 AM
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Join Date: Jul 2006
Location: Mill Bay BC Canada
Posts: 35
Thanks Gentlemen, just the kind of info I was looking for. 1:9.5 it is.
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  #9  
Old 01-18-2008, 11:27 AM
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Join Date: Sep 2002
Location: calgary alberta canada
Posts: 113
Quote:
Originally Posted by J E Custom View Post
Fozzy

I would think a 1 in 9.5 or 1 in 10 twist would be fine.

If you intend to load hard (max) with the 338 Edge I
would go with the 1 in 10 but if you load below max
then the 1 in 9,5 would probably be the best choice
for the 300gr SMK.

250gr or 225gr bullets would need the 1 in 10 twist.

J E CUSTOM
I don't understand the "load hard" relationship with twist rate.
I run 111.5 grs of US869 under 300 gr SMKs in my 338LAI, which propells them out the muzzle at 3065 fps and the rifle consistantly delivers 1/4 moa groupings. This is very close to the begiining of pressure signs.
I am using a 9.4 twist barrel, which now has just over 1000 rnds through it with just the very slightest bit of firecracking starting to show up, which given the round count, to me seems pretty fair.
Am I missing something? I am simply a custom rifle builder, NOT a barrel maker, so any insight here would be great.
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  #10  
Old 01-18-2008, 09:25 PM
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Join Date: Jul 2004
Location: Texas
Posts: 5,381
Ranger

You did not miss anything .

What I call hard loads are normaly over max saame pressure.

These can be from hard bolt lift to blown primers,Even though
not recomended there are a lot of people that do load (HARD).

I once owned a 1000 k rifle that loved velocity (The faster I
pushed the bullet the better it shot) so I loaded so hard that I
could only get two loadings out of the brass .

As far as Twist the velocity of a bullet normaly sets the rate of
twist.(the faster the bullet the slower the twist) .
The fact that the 300gr in .338 is slower than a 225gr or a 250gr
in the same chambering was the reason for the recomendations.

The 1 in 9.5 twist would be my choice if I knew that I intended
to use the 300gr bullet and lighter with out over rotating the
bullet.

On my 338 rum I load a 225gr accubond to just over 3300ft/sec
so I chose the 1 in 10 twist in case I wanted to shoot 200gr or
210gr to 34 or 3500ft/sec.

I think you chose the right twist (1 in 9.4) for your velocity with
the 300gr SMK , But if you tryed to shoot say a 160gr at 36 to
3700ft/sec (very possible in your LAI) you might have a problem
with over roation.

So I try to pick a rate of twist that is the MOST likely to to work
within the range of bullets to be used.This is not to say that a
slower or faster rate of twist can not be made to work.

I always talk to my customers about what the intended use of
the rifle is (hunting or target) and the range of bullet weights
to be used so I can make recomendations as to barrel Type,
weight,length and twist for optimum performance .

Sorry if my term LOAD HARD threw you off . Just one of
many terms learned at the jeff foxworthy school of english.

J E CUSTOM
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  #11  
Old 01-18-2008, 10:18 PM
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Join Date: Mar 2006
Location: polson MT.
Posts: 654
Quote:
Originally Posted by long ranger View Post
I don't understand the "load hard" relationship with twist rate.
I run 111.5 grs of US869 under 300 gr SMKs in my 338LAI, which propells them out the muzzle at 3065 fps and the rifle consistantly delivers 1/4 moa groupings. This is very close to the begiining of pressure signs.
I am using a 9.4 twist barrel, which now has just over 1000 rnds through it with just the very slightest bit of firecracking starting to show up, which given the round count, to me seems pretty fair.
Am I missing something? I am simply a custom rifle builder, NOT a barrel maker, so any insight here would be great.
What barrel length is your 338LAI? The reason i am asking is i am thinking of going with basicly the same only a 338 ax kirbys. I have been working on a 338am for 13 months we finally got all the components but janison brass is not very good; 4 to 5 loadings will be it at reduced loads say 3250 instead of 3400.I am not real thrilled about having to firefourm after 4-5 rounds plus this rifile was to be under 16 pounds now its not going to make it. KIRBY is a great guy he is giving me a choice to build something different since the brass sucks.The 16 pound weight is for Idaho i live only one hour away.It sounds like you have had alot of trigger time with this calibur. How many firings do you get from your brass? I hear this calibur is quite accurate.Thanks for your input. joe
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  #12  
Old 01-18-2008, 10:54 PM
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Join Date: Sep 2002
Location: calgary alberta canada
Posts: 113
JE Thanks I thought maybe I had slept through something in class when learning the trade many years ago in Trinidad.

I am a firm believer in heavy bullets being the answer to all long range issues, but agree with you twist rate like 9.4 would most likely sheer the jackets right off of lighter bullets. And know this happens with thin jacketed bullets.
The reason I tend to opt for heavy bullets is simple, at real distance weight rules. Selecting the right twist rate is paramount. The good folks at Pacnor thought I was nuts asking for 9.5 twist 338 barrels.

If my exbal program is to be believed the 300 gr SMKs I shoot are still supersonic at 2500 yards, yet the 250s are sonic only to 1950 yards.
Energy is another issue for me , the 300s have 1000 ftlbs left at 2700 yards, the 250s only have the 1000 ftlbs at 1900 yards. For many this is not an issue, for me it IS.

New Shooter
I started with a 34" barrel and chronoed it with the best accuracy load I could build, then started cutting the barrel back 1 inch at a time to see where I really started to see a decrease in velocity. I found not much changed until the 30" mark, so finished my 1st barrell at 29.5".
I still have and shoot this rifle, it has as posted just over 1000 rounds through it, I am still using the original box of Lapua brass, which has all been loaded 11 times if you count fire forming. I have not trimmed any of it, but have bumped the shoulder back 1 thou, every 2nd loading.
This is without a doubt in my mind the most accurate large caliber rifle combination I have ever built. I have built quite a few of these and have many more on the build board again this year, I think there will be alot more to come on this caliber as time goes on I believe it will enjoy a well deserved repuation for being a very hard hitting, flat shooting cartridge. Whether it is ever adopted as mainstream is doubtful, but we can hope..
The 338EdgeAI is also showing me great promise, but at the moment I still prefer the Lapua, strictly on the count of the Lapua brass being about the best there is.
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  #13  
Old 02-08-2008, 01:56 PM
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Join Date: Mar 2006
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Posts: 654
Quote:
Originally Posted by long ranger View Post
JE Thanks I thought maybe I had slept through something in class when learning the trade many years ago in Trinidad.

I am a firm believer in heavy bullets being the answer to all long range issues, but agree with you twist rate like 9.4 would most likely sheer the jackets right off of lighter bullets. And know this happens with thin jacketed bullets.
The reason I tend to opt for heavy bullets is simple, at real distance weight rules. Selecting the right twist rate is paramount. The good folks at Pacnor thought I was nuts asking for 9.5 twist 338 barrels.

If my exbal program is to be believed the 300 gr SMKs I shoot are still supersonic at 2500 yards, yet the 250s are sonic only to 1950 yards.
Energy is another issue for me , the 300s have 1000 ftlbs left at 2700 yards, the 250s only have the 1000 ftlbs at 1900 yards. For many this is not an issue, for me it IS.

New Shooter
I started with a 34" barrel and chronoed it with the best accuracy load I could build, then started cutting the barrel back 1 inch at a time to see where I really started to see a decrease in velocity. I found not much changed until the 30" mark, so finished my 1st barrell at 29.5".
I still have and shoot this rifle, it has as posted just over 1000 rounds through it, I am still using the original box of Lapua brass, which has all been loaded 11 times if you count fire forming. I have not trimmed any of it, but have bumped the shoulder back 1 thou, every 2nd loading.
This is without a doubt in my mind the most accurate large caliber rifle combination I have ever built. I have built quite a few of these and have many more on the build board again this year, I think there will be alot more to come on this caliber as time goes on I believe it will enjoy a well deserved repuation for being a very hard hitting, flat shooting cartridge. Whether it is ever adopted as mainstream is doubtful, but we can hope..
The 338EdgeAI is also showing me great promise, but at the moment I still prefer the Lapua, strictly on the count of the Lapua brass being about the best there is.
THANKS alot. Have you every tried Retumbo powder? Why did you go with us 869 does it burn cleaner? thamks joe
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  #14  
Old 02-08-2008, 02:51 PM
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Join Date: Sep 2002
Location: calgary alberta canada
Posts: 113
I have not found the best success with Retumbo, it may work well in other calibers, but my experience has not been that good with it in Lapuas and Edges.
The US869 I burn by the ton in my 50s and 20mms, and figured to give it a try in the big 338s and was surprised at how well it worked out.
Ball powder like the 869 meters easily and fills the case easier than large granular powder, so makes loading cases easy, it burns clean as well unlike 870 did, and any time I can save a few $$ on powder , thats a good thing too.
So all in all for me the US869 wins in all areas for me.
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