Headspace Question

[jiml]

I bought a Wilson headspace gauge to check the headspace on my rifle to tune on the reloads. The rifle has had no issues at all and will shoot .406. I had checked the head diameter just above the extractor groove on factory ammo and on my fired factory ammo and it was .436 and .438. When I resized the bass it was .437. I don't know how much that should be because I have never checked it before. I put a fired factory case in the gauge and it is .005 over the top of the of the max surface of the gauge as best as I can measure with a caliper. The factory ammo is .001 below the top max surface. When I resize the brass it is .002 below the max surface of the gauge. That is with the sizing die bumping the shell holder. I pondered on it a lot and at first I thought maybe I had an oversized chamber. If the factory load was only .001 below max length it seems a lot of folks would be having chambering issues with factory ammo so I have been thinking the gauge might be out of specs. So what do you think? Thanks for any input.

[LRRPF52]

This has been covered quite a few times, and the short answer is that unless the gauge was cut with the same reamer before or after your chamber was cut, preferably by the same machinist, you can end up with results like you are seeing.

Another thing with your sizing die set-up is that you don't necessarily need to touch the shell holder to the die, and you can find your optimum sizing zone by testing sized brass in your chamber. If you are sizing it too much, you work-harden the brass in areas that lead to shorter case life, so there is a happy space when sizing.

With gas guns, we want a little bit of wiggle room since we are relying on the action to chamber and lock the bolt. If we run the ragged edge of precision, we can run into issues with failure to fully go into battery, and I have had this happen on rare occasions with a load that I had to re-look at before heading to the range.

At the end of the day, my chambers are the final judge on whether or not I sized my brass correctly, and they don't care what any other gauge or instrument told me.

LR1955 has some really good advice in this respect, having been reloading for gas guns since the 1970's.

[lwminton]

I bought a Wilson headspace gauge to check the headspace on my rifle to tune on the reloads. The rifle has had no issues at all and will shoot .406. I had checked the head diameter just above the extractor groove on factory ammo and on my fired factory ammo and it was .436 and .438. When I resized the bass it was .437. I don't know how much that should be because I have never checked it before. I put a fired factory case in the gauge and it is .005 over the top of the of the max surface of the gauge as best as I can measure with a caliper. The factory ammo is .001 below the top max surface. When I resize the brass it is .002 below the max surface of the gauge. That is with the sizing die bumping the shell holder. I pondered on it a lot and at first I thought maybe I had an oversized chamber. If the factory load was only .001 below max length it seems a lot of folks would be having chambering issues with factory ammo so I have been thinking the gauge might be out of specs. So what do you think? Thanks for any input.

http://www.redding-reloading.com/online-catalog/37-instant-indicator-headspace-and-bullet-comparator

Get one of these and measure fired cases which are a template for your chamber. Then use the tool to set your sizing die. They say to set back AR cases 3-5 thousandths from a fired case which can be done with ease with this tool. Over time the fired cases will change a bit so you keep up with that in a matter of seconds.

It is also useful to compare your fired cases to new brass. You will use this tool all the time.

[jiml]

I didn't see a Grendel listed----what do you use or are they special order?

[lwminton]

I didn't see a Grendel listed----what do you use or are they special order?

It has been a long time since I bought mine, but what you do is call Redding and they will tell you what to use with a Grendel. There are cases that are close enough to work because the die just hits the shoulder and the Grendel is not different enough from other cases to matter. You are just looking for a number that says "my chamber" Then set up your die to = "my number - 3-5 thousandths". I was shooting the 6mm AR at the time and they sent me the 6 PPC die. It works fine. It may fit the Grendel (same case, different neck) but you need to ask.. Redding will tell you what to use. It just hits the shoulder more or less in the middle but exactly where don't matter. You just need a number. I have mine in my T7 and use it ALL the time. Set up once and use forever - no touching no fiddling.

[Dentite]

I'm no expert, but I use the Sinclair bump gauges to measure shoulder setback. This is the type where you connect the bump gauge body and the appropriate shoulder insert onto your calipers. This allows you to measure changes in dimension from the head of the case to the shoulder. As mentioned above, the inserts are not caliber specific, but I generally match the shoulder angle. For example, with the 6.5 Grendel, you want an insert that has a 30 degree "shoulder" portion and at least 6.5 caliber hole to allow the neck to come through. I think this is the right part number if you decide on the caliber mounted bump gauge type: 749-011-481WS

See here: http://www.sinclairintl.com/reloadin...prod35265.aspx

[jiml]

Ok. Thanks guys

[lwminton]

I'm no expert, but I use the Sinclair bump gauges to measure shoulder setback. This is the type where you connect the bump gauge body and the appropriate shoulder insert onto your calipers. This allows you to measure changes in dimension from the head of the case to the shoulder. As mentioned above, the inserts are not caliber specific, but I generally match the shoulder angle. For example, with the 6.5 Grendel, you want an insert that has a 30 degree "shoulder" portion and at least 6.5 caliber hole to allow the neck to come through. I think this is the right part number if you decide on the caliber mounted bump gauge type: 749-011-481WS

See here: http://www.sinclairintl.com/reloadin...prod35265.aspx

Dentite is correct on the issues about die size for Grendel. The reason I chose the Instant Indicator is that you set it up once and the resulting measurements are repeatable. I worried about repeatability with the caliper tools because you take them off and put them back on, over and over. Since you are looking only for a few thousandths, I thought that the set up could change by that much and you would never know. I use a T7 so the II is always there with 1 setup. The 6PPC die is .35 so it will slide over the neck ok.

[Dentite]

Dentite is correct on the issues about die size for Grendel. The reason I chose the Instant Indicator is that you set it up once and the resulting measurements are repeatable. I worried about repeatability with the caliper tools because you take them off and put them back on, over and over. Since you are looking only for a few thousandths, I thought that the set up could change by that much and you would never know. I use a T7 so the II is always there with 1 setup. The 6PPC die is .35 so it will slide over the neck ok.

That instant indicator looks like a slick piece of equipment. Thanks for info, I'll have to look into them.

[LR1955]

Man, how come we were able to load for many cartridges without all these expensive, problematic, and totally unnecessary gadgets?

Take a piece of fired brass, size it down according to the die makers recommendations on setting the sizing die, insert it into the chamber, ride the bolt forward about half way and let the bolt go. If the brass chambers, you got half of it right.

Next, pull back the charging handle. The brass should extract without any problems. Sometimes it chambers but is hard to extract. This means you need to bump it a bit more. So bump the shoulder back and try again. May have to do this two or three times, each time screwing the sizing die down just a little bit. You will find a setting where the brass chambers and extracts easily. Now you are set.'

Another thing technocrats do is freak out if the real overall length is different than something in a loading manual. Most of the time the published OAL is fine. Some of the time it isn't. Technocrats then lose sleep and hours of their life trying to figure out if their chamber has been cut right or if they made a mistake in their loading process. How about seating the bullet a bit deeper? Of course, start with a OAL that a manufacturer recommends. Drop the cartridge into the chamber, ride the bolt half way and let it go. The cartridge should chamber and extract without sticking. If it sticks, look at the ogive of the bullet and you will probably find rifling marks. OAL is too long so seat the bullet deeper until the cartridge chambers and extracts easily.

Finally, make sure the cartridge fits the magazine. Have some stand off from the tip of the cartridge and the inside front of the mag well to ensure the cartridge feeds reliably.

I will definitely question a chamber if I have to seat a bullet so deep that the neck goes over the curve of the ogive. In that case, something is wrong with the chamber.

LR55

[wfa17332]

I believe you are addressing the old, but still true, "KISS" principle; I couldn't agree with you more. Yes, accurate, SAFE, ammunition is necessary, but really inaccurate loads are easy to identify, and there is a reasonable expectation that loading data from reputable sources are safe.

I have no problem with anyone attempting to become the best shot you can become, but it's all too easy to get totally involved in "perfection" in a very imperfect sport. If you are not in the top 1% of the shooters, or have aspirations to become one, then 1/8" (or more) difference in group size means little. Time would be better spent in "dry firing" and learning to "call your shots" under actual "field conditions".

Just my opinion.

[lwminton]

"The cartridge should chamber and extract without sticking. If it sticks, look at the ogive of the bullet and you will probably find rifling marks. OAL is too long so seat the bullet deeper until the cartridge chambers and extracts easily."
The Stoney Point does this with a tad more precision. "Probably find" doesn't get it for me.

[Dentite]

Man, how come we were able to load for many cartridges without all these expensive, problematic, and totally unnecessary gadgets?

Take a piece of fired brass, size it down according to the die makers recommendations on setting the sizing die, insert it into the chamber, ride the bolt forward about half way and let the bolt go. If the brass chambers, you got half of it right.

Next, pull back the charging handle. The brass should extract without any problems. Sometimes it chambers but is hard to extract. This means you need to bump it a bit more. So bump the shoulder back and try again. May have to do this two or three times, each time screwing the sizing die down just a little bit. You will find a setting where the brass chambers and extracts easily. Now you are set.'

Another thing technocrats do is freak out if the real overall length is different than something in a loading manual. Most of the time the published OAL is fine. Some of the time it isn't. Technocrats then lose sleep and hours of their life trying to figure out if their chamber has been cut right or if they made a mistake in their loading process. How about seating the bullet a bit deeper? Of course, start with a OAL that a manufacturer recommends. Drop the cartridge into the chamber, ride the bolt half way and let it go. The cartridge should chamber and extract without sticking. If it sticks, look at the ogive of the bullet and you will probably find rifling marks. OAL is too long so seat the bullet deeper until the cartridge chambers and extracts easily.

Finally, make sure the cartridge fits the magazine. Have some stand off from the tip of the cartridge and the inside front of the mag well to ensure the cartridge feeds reliably.

I will definitely question a chamber if I have to seat a bullet so deep that the neck goes over the curve of the ogive. In that case, something is wrong with the chamber.

LR55

Good points, we all have to find our level of detail, time, and cost we want to put into reloading. Some like to keep it as simple as possible, others want to try to control and measure every variable in the quest for ultimate accuracy. Neither is a wrong approach. When I'm at my Dillon, I just want to make reliable handgun ammo as quickly as safely possible. When I'm at my Rockchucker I'm trying to craft precision rifle ammo.

Someone might disagree with the level of detail you put in and suggest something like: "Why do people bother with buying all this expensive reloading stuff like presses and dies. Not to mention spending time seeing if rounds will chamber, adjust as necessary, seat the bullet deeper, making sure it fits in the magazine, etc? Why not just buy ammo off the shelf and keep it simple?"

It's like the analogy of driving on the freeway. Some people think that everyone driving slower than them is an idiot and everyone driving faster than them is crazy.

There is more than one "right" way to do things.

[jiml]

I'm With You Dentite

I like wringing all I can out of a rifle. I'm too old and gone to compete much except with myself and what I can afford. Its just a hobby I enjoy and I don't have to beat my chest and blow anymore. I don't give a crap about being the biggest, baddest, or best. I just want to enjoy it. I guess the old slam it in there and crank it off is ok but I've seen folks blow there butts off so I like to see numbers that helps prevent that. I get more careful as I get older. I was super smart and bulletproof once myself but I don't heal like I used too so I take a little more care. I read on this forum just lately about someone blowing his gun up and I don't have any desire to be the next. Technocrat isn't the worst thing I've been called. So it's a free country(barely) so rave on just don't stand by me when you set it off if you are just going guess on what is really going on in the chamber. Best 'o luck to you Bubba

[NugginFutz]

It's like the analogy of driving on the freeway. Some people think that everyone driving slower than them is an idiot and everyone driving faster than them is crazy.

One of my favorite quotes by the late, great comedian George Carlin.