7mm Mashburn Fireform load

[SJB358]

So usually I use 65.0 grain of IMR4350 with a 139/140 grain bullet for fireforming. It usually runs about 3180-3220 depending on the bullet I am using. Really easy shooting load and accurate. I actually have a couple of 140 hunting loads that I'd tackle just about anything with (140 AB and 140 Swift)..



Well, everyone was trying the new IMR4451 and from all I have heard it is a great powder which mimics H4350 and IMR4350 speed wise. Well, I used 65.0 grains after looking at a few manuals online and knew I wouldn't be hurting anything, but I was surprised..



I kinda thought it would have been much closer to the IMR4350 speeds, but it wasn't the case. Accuracy was still pretty danged good, but the speed had a good drop off. When I get a chance I will rechrono my IMR4350 loads too, just to get an idea as well and keep stuff fair..

 

[JD338]

That is a pretty good drop, at least for FF loads.
Max loads might prove to be different results.

JD338

 

[SJB358]

I was thinking that myself. 65 grains is a pretty minimally case filling load, so I am sure it acts different than a 30-06 with a 180 where it is close to full to the brim.. I was just surprised as folks said it acted very similar to IMR/H4350.. Could just be the lot I have.

 

[FOTIS]

closer to H4831 I would say

 

[SJB358]

closer to H4831 I would say

Could be Fotis. Not really complaining as it's just a FF load. Cases still came out perfect and really it's even less pressure on it than before. It'll be nice when QL gets a few of the new IMR powders in there. I keep holding out for that update.

 

[DrMike]

That is quite a difference in velocity. Remember that charge weight alone doesn't determine burn rate. Case volume and bullet weight factor into determining burn rate.