Fussy 300 WinMag - can't find a group.

[AD5GB]

Greetings,

I'm having a challenge. I've got a Win model 70 push feed that I had rebarreled - 27" Brux stainless in a heavy sporter taper. It's epoxy bedded in a Boyds laminate stock and fully floated - at least an index card thickness anyway. I've put in a 375 H&H magazine box and bolt stop and a 7MM STW follower to increase the magazine length as well but working up loads for this thing is becoming problematic. I'm afraid I'll burn the barrel out before I find a shooter. My 270 spoiled me I guess - found it within 60 rounds.

Anyway, it'll shoot "OK" groups with a little care - meaning about 3/4" @ 100 using 165 or 180gr SSTs (3202 and 2978 fps respectively) seated .020" off the lands. I've been trying to find groups with 190 SMKs and 200 and 212 ELD-Xs and it's maddening. 3/4" -1" ( or greater ) seems to be about all it'll do. The maddening thing is during the course of inching up the powder charges I find loads where 2 want to share the same hole and one is a "flyer". By flyer I mean it's 1/2" - 1" from the pair. Also I find loads that actually decrease in MV where the powder charge increased only to find that the next incremental increase sort of made up for the 2 if that makes sense. (this could possibly be chrony issues)

For example: Today I went out with 190 SMKs seated .040" back ahead of IMR-7977 in 1/2 grain increments from 71 - 75 grains. Group averages were:

2747, 2765, 2790, 2775, 2815, 2777, 2793, 2871, 2948

None of these were stellar groups but the 72 and 73.5 gr charges had 2 sharing the hole and one 1/2-3/4" off.

I've used IMR4831, IMR7828, H-1000, and just tried Retumbo with the 212s (promising) with various seating depths but that I can't find anything to tell me where to start focusing is maddening.

Cases are sorted, weighed etc with basic prep (not neck turned) and neck sized; Either Rem, Win, Hornady or PPU.
CCI-250, Fed-215, Rem-9 1/2M.

Maybe 3/4 MOA is the best it'll do?

Thoughts?

 

[johnnyk]

I have only tried the 190gn SMK once in my .300WinMag and it was a very accurate bullet. I used H1000 w/CCI 250 primers. This was the "first" time she had the 190SMK's and H1000 and I must say I was well pleased. However, I wanted to shoot heavier bullets and only shot one box of the Sierra's.
I tried from 79.0 to 80.5 in 1/2gn increments. All four of these loads were .522" or less, with 79.5gn being the .522" group.

79.0gn was the most accurate @ .142" and velocity averaged 3078fps with an ES of 7.83 and a SD of 4.12.

80.5gn was the next most accurate @ .4185", 3160fps, ES 31.07, SD 13.63.

I shot these four loads twice through this rifle and results were repeatable. The 190's were seated .010" off the lands with an OAL or 2.9090" (my chamber).

Shortly after shooting these I got a muzzle break for my rifle and never looked back at the 190's. I have shot the 208gn A-Max's for quiet some time now and they are equally as fast and accurate. Pretty soon I plan on running some 212gm ELD-X's and see how they do.

Good luck and hope some of this can benefit you. JohnnyK.

 

[HARPERC]

......Maybe 3/4 MOA is the best it'll do?...Thoughts?

3/4" isn't terrible. It sounds what you really need is it to be more consistent.

Start with examining your shooting technique for places variables may slip in unnoticed.

You don't mention an optic, or how many rounds total you have down it.

A lot of chrony's out there that cause more questions than reveal answers.

 

[fiftybmg]

While you're at it, double check the free floating. With a thin barrel profile, the amount of flex may be greater than the current clearance, especially when things heat up.

If the barrel is fully free floated, which a piece of paper folded in half twice will show you [ not sure how thick an index card is ], then the only thing left is the action bedding.

The action needs to be stress free. If the action was bedded without relieving first, the action bedding may need to be re-done. Torque check the action screws.

My 308 Norma gives me 0.5 MOA now, before action bedding then free floating it was always just over 1", consistently two together and one flyer.

 

[AD5GB]

3/4" isn't terrible. It sounds what you really need is it to be more consistent.

Start with examining your shooting technique for places variables may slip in unnoticed.

You don't mention an optic, or how many rounds total you have down it.

A lot of chrony's out there that cause more questions than reveal answers.

Well, it's possible. When working up loads though I use a Lead Sled. Trigger is a bit heavy - Timney set at 3.5#. I've always been decent with a rifle though and can shoot my .270 into the same hole. That said you bring up a valid possibility.

Optic is a Vortex Viper PST 4-16x50 FFP EBR-1 MRAD. I was playing the parallax game at the range today just to be sure there wasn't something wonky. Doubt it's a scope issue.

Many thanks!

 

[AD5GB]

While you're at it, double check the free floating. With a thin barrel profile, the amount of flex may be greater than the current clearance, especially when things heat up.

If the barrel is fully free floated, which a piece of paper folded in half twice will show you [ not sure how thick an index card is ], then the only thing left is the action bedding.

The action needs to be stress free. If the action was bedded without relieving first, the action bedding may need to be re-done. Torque check the action screws.

My 308 Norma gives me 0.5 MOA now, before action bedding then free floating it was always just over 1", consistently two together and one flyer.

Thanks. It's a heavy sporter/light bull profile, do you consider that thin? #4 Brux or Krieger contour.

An index card is probably the thickness you suggest; 4 paper thicknesses - though this may not be enough. I just watched a video where Randy Boyd was suggesting .020"-.040" clearance. I'll be relieving the barrel channel a bit more I guess.

I spent a great deal of time building the epoxy pillars after reading about the troubles with bedding the Mauser type actions and I believe it came out well. The recommendation being the recoil lug area and the area at the rear mounting screw being the only thing bedded - the remainder of the action fully relieved. Almost dread the thought of re-doing all that.

Many thanks!!

 

[Frank in the Laurels]

Put the old standby in her...H-4350...you loose some velocity but your groups will be better, worth a try anyway...

 

[Mike 338]

Did you test a variety of primers?

 

[fiftybmg]

Thanks. It's a heavy sporter/light bull profile, do you consider that thin? #4 Brux or Krieger contour.

No, that is not thin, but based on the below :

The recommendation being the recoil lug area and the area at the rear mounting screw being the only thing bedded - the remainder of the action fully relieved.

the only thing to look at more closely is how free is your free float.

You need to verify at run-time, so to speak, where the barrel may be contacting the stock, so if you put some removable marking compound on the inlet between the barrel and the stock, and have a piece of white paper taped around the barrel while you shoot, when you remove the paper it should show if there was any contact.

The most likely spot is the fore-end tip.

 

[6mm06guy]

I recently just worked up some sub moa groups using 70gr of h4831sc with 180 nosler and 210 gr noslers, the 210s had an es of 6, might try it.

 

[just country]

morning, Williams 5.5 barrel, timmey trigger, rem 700 LA. H&S stock

glass bedded. 78.5grs MRP 215mFed. Winchester brass 168gr sierra, 180gr

sierra, 200gr sierra. back off 200gr .5 grams. in my opinion this is a very

accurate load. .250-350 groups. lightbulbgun) starting load

 

[BEEMAN]

My 300 WM has a BRUX #3 at 26". Load work up was done in 15 rounds! Would of been less had I started with a higher powder charge. But better to be safe. Between myself and a friend we have a few Brux barrels and all have shot VERY WELL. You really should try some H1000, FED GM215M, and a Berger 215. Start out 30-40 thou off the lands and work up to pressure. This is what I did and have never looked back. It's a very hard combo to beat.

 

[AD5GB]

Did you test a variety of primers?

Well, I've used CCI-250, Fed 215, and Rem 9 1/2M. I sent my last batch of Winchester primers back to Olin earlier this year due to pinholing problems and haven't gotten more. I'm reluctant to actually though there probably is nothing wrong with current production stuff..

215s and 9 1/2Ms seem more consistent and show pressure (to my eye) much better.

 

[Triple BB]

I have a 300 RUM. Went through a boat load of bullet/load combinations after doing all the fab and build work expected with a long range gun. Was ready to chuck the thing. As soon as the 212 ELD-X's came out, I shot them with Retumbo and got it down to a 3/4" group at 100 yards. Then did more loads with the same bullet and RL26. Now its down to 1/2" or slightly less depending on whether I'm doing my job holding it steady, concentrating, breathing right, etc...