338 lapua 300gr SMK too fast?

[Beale338]

Was doing a load development today with 300gr SMK's and Retumbo and found at only 92gr of retumbo I was pushing 2860fps.
Is this too fast? I have a 28" 1/10 twist barrel and the only pressure signs I can see are slight ejector rings on the brass.
Thanks for your input.

Beale.

 

[Beale338]

Re: 338 lapua 300gr SMK too fast?

Ya sorry! It is a kmw sentinel with a PGW timberwolf action, the barrel is a krieger and I am using Lapua brass and GM215M primers.

 

[Cinch]

Re: 338 lapua 300gr SMK too fast?

I don't think so. I'm shooting a 28" Rock 10 twist. 91gr H1000, 300SMK, CCI 250 right at 2800. No pressure signs at all.

 

[Beale338]

Re: 338 lapua 300gr SMK too fast?

Thanks for the input

Beale

 

[ChrisGarrett]

Re: 338 lapua 300gr SMK too fast?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Beale338</div><div class="ubbcode-body"> Was doing a load development today with 300gr SMK's and Retumbo and found at only 92gr of retumbo I was pushing 2860fps.
Is this too fast? I have a 28" 1/10 twist barrel and the only pressure signs I can see are slight ejector rings on the brass.
Thanks for your input.

Beale.

</div></div>

I think that the original spec for the 338LM out of a 27" tube was 2950 for a 250gr tip and 2800 fps for the 300gr tip. This was years back, so with the advent of better powders and out of a 28" tube, 2860 fps isn't 'oh my God, what are you doing' type territory.

Chris

 

[Beale338]

Re: 338 lapua 300gr SMK too fast?

The reason I thought this was getting in the danger zone is that any more powder than 92gr my velocity starts to drop. Is this a sign of over pressure? Should I back it off a few more grains?

 

[bohem]

Re: 338 lapua 300gr SMK too fast?

That is a sign that the efficiency of the case is dropping off and you're approaching overpressure signs.

 

[Beale338]

Re: 338 lapua 300gr SMK too fast?

Thanks bohem, That is what I was thinking but just wasn't sure.

 

[psinclair]

Re: 338 lapua 300gr SMK too fast?

I'm getting 2860fps with 300gr scenars and Retumbo without any pressure problems..28" Bartlein 1-9.7" 5R.

Your load doesnt sound out of the ordinary..

 

[Fred_C_Dobbs]

Re: 338 lapua 300gr SMK too fast?

What kind of chrono? I ask because I had a Shooting Chrony Beta that read about 5% too fast at any velocity. All three of the calibers I load for were suspiciously fast so I rented a CED from a LGS, which confirmed my suspicions.

 

[Wild_Bill]

Re: 338 lapua 300gr SMK too fast?

if you are getting ejector rings then consider ti max in your rifle you might want to drop it doen .5 to a grain to make sure it s OK. if it is dropping off in velocity with an increase in powder you have hit MAX if you ad powder and dont get more velocity in that barrel you are realy approaching a dnagerous situation going higher that is how rifles show they have achieve dhter max burn rate for load combo and it is always wise to stay a bit below the max pressure i would just drop it a little and se how it shoots but with a 28" barrel you should be around the right velocity and Retumbo is one of the best powders for the 300gr projectiles.

 

[Beale338]

Re: 338 lapua 300gr SMK too fast?

I am using a Beta Master for a chrony. I will have to compare it to another and see if it is off. Thanks for the info.

Beale