270 Help needed

[mappleman]

Inherited a custom 270. Mauser action, 21 1/2" barrel, 1:12 twist..I'm trying to get 140 grn BTSP into a sub 1" group @ 100yds. I've tried Imr 4831, and H4831sc. Federal 210 , Rem 9 1/2, and win mag, primers. velocites of 2600fps to 3100fps. Barrel is full floating. I'm not sure if the 1:12 twist is compatable with the 140 grn. I've tried to understand barrel twist info but I've given up, can someone just tell me if I need to go heavier or lighter on the bullets

 

[BamaBob]

My ballistic knowledge is propably not comparble to yours but 130 grain has always been the most accurate for me.

 

[rcmodel]

.270's are normally 1/10 twist.

Your 1/12 would do better with lighter bullets then 140 boat-tails maybe.

A flat-base bullet would be shorter for the weight, or a lighter B-T would stabilize in a slower twist barrel better.

rc

 

[mappleman]

thanks for the tip. I'll try the bt 130s instead of the flat base 140s

 

[loadedround]

You can take to the bank the information RCmodel gave you....try a nosler or Sierra(my favorite) 120 gr spitzer.

 

[GooseGestapo]

Do you know for a fact that it's a 1/12" twist ?

I'd check it to be sure.

Either way, It'll still most likely shoot either the Sierra or Speer 130gr Spt flat-based bullets. It might also shoot the 150gr flat-based bullets as well as the Nosler 130gr Partitions, which only have a small heel to facilitate bullet seating due to the process of jacket formation that Nosler uses to close the heel on the rear bullet core.

You also didn't say what kind of results you're getting. It might be acceptable or as good as you'll pobably see. You also didn't say what kind of barrel......... Who did the work ?? Why a 1/12" twist ??.

Could it be that the barrel is pitted, or has a damaged crown, or, If it really is a 1/12" twist, my best guess is that it was used with 90-110gr bullets for some type of varmint shooting and the throat is "washed out" from large quantity shooting with large quantities of slow burning powders or--- "shot out".

Have you tried a really, really good cleaning of the bore with a good Cu removing solvent ??? I've got a M98 Mauser in .257Roberts that if kept clean will shoot near 1/2moa, but after 30-40rds will start "throwing" patterns due to Cu build up in some pitting it has mid-bore. (long story- - -).
Questions, questions, questions........

 

[jim147]

You might try the Sierra 90 grain hollow point if you can find it. With some IMR 4350. I have one .270 that just doesn't like heavy bullets. But it loves that load.
Some of the 115 grain 6.8 bullets might be another choice to look into.

jim

 

[ants]

My rifle is just a plain Rem 700, but it favors 130 grain plain base with IMR 4350 powder. Standard LR primer.
I don't even have to load it close to the lands, but you experiment with it as necesasry to work up your own load.

 

[mappleman]

thanks for all the info... This gun was built for my pap, who shot it very little, the ammo that I got with the gun was all heavy factory stuff (165.grn-170. grn) this might explain why he only ever shot one deer with it. I checked the twist myself with a cleaning rod and jag, the throat and barrel look good. As to my group size thus far... the tightest group is in the 3" neighborhood

 

[dakotasin]

is the action bedded?

what bullet weights have you tried?

i would suggest dropping to a 130 grain hornady, running h-4831, and a magnum primer of your choice.

how is your case prep routine? typically there is a lot of accuracy in case prep alone.

i enjoy problem rifles like this that don't want to behave. i always start by troubleshooting it... start by pulling the rifle out of the stock, make sure all looks ok. confirm the barrel is floating, switch ammo... when you're doing load work ups, find the tightest grouping load you can, then analyze the groups. can you find patterns in the groups, such as vertical stringing...

good luck!

 

[NCsmitty]

This gun was built for my pap, who shot it very little, the ammo that I got with the gun was all heavy factory stuff (165.grn-170. grn)

Inherited a custom 270. Mauser action, 21 1/2" barrel, 1:12 twist..

I'm surprised that you're getting as good as 3" groups with those heavy bullets with the 1in12 twist.
I would try nothing over 130gr, as that's the usual standard for 270 Win.
You should see a dramatic reduction in group size using the lighter bullets, if everything else is good.

NCsmitty

 

[Shoney]

Barrel maker Lilja lists the 1/12 as ideal for 100 gr bullets. Although the 130's may group,they may not group less than 1".

The 120 gr bullets would stand a better chance of good groups than the 130's.