Gentlemen,

I've gotten my act together in respect of record keeping for my reloading and an interesting pattern seems to have emerged looking at the velocities I'm getting from my 30.06.

I have chronographed three different loads representing light game, heavy game and target shooting loads using different bullets and powders in each case.

In each case they Chrograph at 125-150 fps slower than the book load from a 22.8" barrel. Going by the oft quoted formula of 50fps lost per 2" barrel less than the 24" barrel used by the powder manufacturers my velocity is lower than than expected by 100fps or so.

Is this within the variance to be expected or is the throat excessively worn or something like that?

The accuracy is still there I think but it needs more rounds to "shoot in" after a clean than when I first got it. I have put maybe 400-500 rounds through it in the 2 years I've owned it, I think the previous owner may have put about the same through it before me.

Another bit of information apparent is that the staple load of 51.3gr of H4895 under a 150gr Speer BTSP at 3.180" oal has crept up from half an inch for 5 shots to around an inch.

Is it worth loading the rounds slightly longer and see if it tightens up the groups?

Any and all thoughts appreciated chaps!

A

What reloading manual? and what barrel was used? Some use a pressure barrel some use a pretyt close replica of what we shooters would experience in a real deal rifle.

Sounds like you need a Hornady OAL gage. When I come into a rifle, new or used, take a bullet with the OAL gage, measure it and keep it aside. After each thousand rounds use the same bullet and same gage to see what you get for OAL.

IMHO, depending upon which manual you are using, 100fps isn't a number to be concerned about.

Oh sorry, the data is from Hogdon

H4895 150gr Speer 51.3gr book MV:2975 Chrono MV: 2850

H4895 155gr A-MAX 51.0gr Book MV:2925 Chrono MV: 2780

H4831 180gr Interlock BTSP 60.0gr Book MV:2700 Measured MV: 2560

The data is the same as used on their online database and uses a 24" barrel, I'm not sure whether that's a test barrel or a sporting rifle.

I have access to a OAL gauge now but lacking a baseline from when I first got it I'm not sure what I can do with it now. For some reason I seem to get best accuracy with a considerable jump to the lands in all loadings. The engagement points for each bullet seems different but most loads are somewhere between 30-100 thou off the lands. I've found that best accuracy seems to be when the bullet is seated to at least a calibre in to the neck with whatever that leaves the jump to the lands.

If I load a test batch of the 150 spr load to 3.200" instead of 3.180" and groups tighten, is it reasonable to infer that the throat has eroded 20thou over 500 rounds?

Thank you for your help.

A

First off, loading manuals are notorious for almost unattainable velocities. Don't pay them any attention other than as reference to pressure. Secondly, the 50 fps per inch rule may or may not apply. I have a 12" 30-30 AI Encore and I got 14 fps per inch difference with the same load as another AR member with a 24 inch barrel.

Not being contrary but there are slow and fast barrels. My AR runs between 150 and 200 fps fast. Doesn't matter if it's a Black Hills Match, M262, or ball ammo. Manuals are written from the equipment they use not our equipment.

Velocity without accuracy means nothing. Often you can have a rifle that shoots slower then list velocity, but if it shoots well, why complain??

Take a spent case, put finger pressure on the mouth to "tighten" it just so it holds the bullet. Chamber it slowly and remove it slowly. Take a sharpie or other permanent marker and mark the bullet. This will give you the optimum seating depth. Normally you will have to shorten it by a few 1/100th's. You can add the info on brass length, bullet seating depth and cartridge OAL for reference.

Velocity is also an indication of pressure. So if you are not getting the velocity, you may also not be getting the pressure. Yes you can try a little longer, but perhaps you should consider very slightly increasing the powder charge in several increments and seeing if the accuracy returns.

I am a proponent of optimal barrel time for accuracy, and if the rifle will shoot, a little faster or a little slower should show a major inprovement.

I have a Browning Continental .30-06 over and under, one barrel is faster than the other, has been since day one.

Chamber volume actually varies quite a bit, which changes pressure and velocity. I didn't realize the extent of this until I started measuring it (as a result of using Quickload).

The manuals will be built using the SAAMI minimum chamber volume, which is worst case or highest pressure--and highest velocity from each load as a result. As an example, instead of the expected 82g of H20 volume, my 7mm Rem Mag actually holds 87g in a fired case--which is very close to the SAAMI minimum in the 7mm Weatherby instead.....

Quickload suggests a once fired case, for your 30-06, filled all the way up to the top of the neck with water and weighed, should contain 68.2 grains of water. Try it a couple of times and see what you get.....if it is substantially more with the brass you are using that might be the issue.

There are also other factors: throat wear, barrel dimensions and smoothness, etc.....in general, low velocity and low pressure go together--as do high velocity and high pressure....

I would suggest that the load your rifle shoots best will matter more than the last 100 fps.

Cheers,

Dan

I am experiencing somewhat the same issue with a new Remington sps 7 mag. I have a Savage 24" barrel that shoots about 40fps faster than the 26-inch barrel with the same load. That really has me wondering about the differences in rifles.

A guy told me that he has experienced a drop in velocity when he gets the load too hot. He said that he goes up in increments until he sees the velocity start to drop and then goes with the highest number that has no pressure signs. I had never heard of this before, but it may be something to consider even with your '06.

I am going to play with mine a little and see what I come up with.