Barrel length for 300 WM? 220smk to 2900fps

[Coyboy]

I did a quick search and couldn't find the answer. If its been discused please advise.

I've been going over balistic calcs, and this seems like it would make a sweet long range round for me. My current 300WM has 24" factory tube. I know I wouldn't get 2900fps out of it. Is it even possible to get that speed out of a 300WM with the 220gr? If I rebarrel would a 1 in 10 twist be ideal for the 220gr? Any experience you've had with this cartrige and bullet combo would be appreciated.

Thanks in advance.

 

[Brien]

i think you can get that much velocity + out of a 30" tube.. my best accuracy with 30" barrel and 220SMK is at 2860 so far... will be experimenting more with it though...any shorter barrel and i dont know.. we were shooting 190's out of a 28" 11.25twist hart 300winmag and getting 3025 with great accuracy...(that was a friends gun)
i would say most would agree that is probably best twist(10") for 210berger/220SMK
Brien

 

[Guest]

don't think you are gonna get it with a WM... RUM maybe... 30" tube....

 

[Coyboy]

Thanks for the help guys. I loaded a few of the 220smk in my 06IMP Saturday, 24" tube. I was doing a velocity work up and could get to 2525fps safely. I also loaded 175smk to a velocity of 2950fps. 180gr Interbonds to 2900fps. In this gun which would make a better long range whitetail load out to 700 yrds? assuming I get similar accuracy. In my head I guess I narrowed it down to the 175's or 180 IB's. I'm thinking at the speed the 220's are starting at they will drop like pigs. Any suggestions are apreciated.

 

[ricka0]

safe load build up

[ QUOTE ]
I was doing a velocity work up and could get to 2525fps safely.

[/ QUOTE ]
Maybe this needs to be a new topic, but how do you determine a safe maximum? My scout master taught us to begin at the lowest loads in our manuals and work up slowly but never exceed maximum published loads.

I've never had a stuck bolt or loose primer 0r even a split neck, but some guys uses those criteria to establish the upper bound.

 

[Coyboy]

Re: safe load build up

b1g, I had no data on the 220 smk for the 30-06IMP. So the way I worked up the load was to use standard 30-06 data.

I used Rel 22, started one grain below max, and shot through the cronograph. I then check for pressure indicators. If everything looks good I go one grain higher and repeat.

At some point one of two things happens; I start to see pressure indicators. A primer that is noticabley flatter than the rounds fired before it, ejector marks on the case head, and ocasionaly a heavier bolt lift than normal.

If a load shows any of these signs I don't call it my max load. I back them down at least one grain so that the pressure signs are not excessive, this is then my max for that particular firearm. I then note the weather conditions on which the loads were tested. If this load will be used in warm weather I test under those conditions so I know there safe.

The other thing that happens on occasion, is I have a particular cartrige with published data but I find no pressure indications, when I aproach the book max, nor have I aproached book velocity. I then load slowley over max. What I do is work up to the velocity the book lists. Being very careful to watch for pressure indicators, if they appear I stop and back down the charge wieght.

Every barrel is different as is every lot of powder. The manuals list data for one barrel with one lot of powder. There max is not always your max. Like the book says start low and work up. Thats because your barrel may max out before thiers. And on the other hand thier barrel may max out before yours. That is why I have six load manuals, Most do not list the same max charge. They are reference matarial a guide to reloading. Its how you use those guides that determines if your being a safe reloader.

By the way the load I used was 56 gr of REL22 to get to 2525fps in fireformed brass. If memory serves that was 2gr over standard 06 max.