I picked up a Model 70 in 300 WSM last fall through which I have put 148 rounds. Out at the range yesterday I was chronographing loads I had worked-up... same powder, bullet, primers, etc., all from the same lots. I noticed a velocity increase of just over 30 fps. for each load I shot.

I've noticed this phenomenon in the past, but always chalked it up to a different powder-lot, etc. All these componants are the exact same I used in early handloads.

Brad

The velocity increase seems to be about 50 fps., but I've had rifles gain as much as 100 fps. after an extended break-in period.

Watch your mailbox!

AD

quote:

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Originally posted by Brad:
Anyone ever notice an increase in velocity over, say, the first 150 or-so rounds out of a new barrel?

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I saw an increase of over 100 fps in a factory .264 remington 700 after 130 rounds. I did clean with jb bore paste frequently so I don't know what exactly gave me the increase.

Interesting... I've never seen a post on this, but it DOES make sense. Possibly factory barrels, being hammer-forged rather than button or cut, tend to have less "stuff" (burrs, etc.) to smooth-out as opposed to "premium" barrels... could also explain wy custom makers tend to stress the importance of barrel-break-in.

Nice to know I'm not having some private fantasy!

BA

What was the temperature on both outings ?

During the past few years I have chronographed a lot of loads and have found that temperature definitely influences velocity.

In your post you say that you bought the rifle in the fall so I would presume that you only developed your loads after that - as it became colder. In your part of the world it is now approaching summer and temperatures should be rising.

When I work up a new load I do it in summer, and I know it will be safe in winter. As the temperature increases, pressure also rises -so a load developed in cold weather may not be safe.

An increase in pressure should also give an increase in velocity - up to a point though.

Something else you could consider is the cartridge cases. New factory cases have a slightly smaller case capacity than fire formed and neck sized cases - so developing a load with an unused case, and then reloading it after only neck sizing it will not yield the same result.

How big the difference in velocity will be due to the above is hard to predict. You don't mention the velocities you are working with at present but the difference is probably less than 1% - and I would'nt loose sleep over that.

Johan

It was definately warmer a few days ago when I got increased velocity readings, however, I was using Hogdon's "Extreme" series of powder which is (supposedly) unafected by temperature. The brass on this last outing was new, unfired brass. Previously I was using re-sized brass, so if anything I should have had slower readings this last time out.

Regardless, I'm not going to lose sleep over gaining velocity!

Thanks,

Brad